Ecology, concepts applications 7th ed m molles (mcgraw hill, 2016) 1

His research has covered a wide range of ecological levels, including behavioral ecology, population biology, community ecology, ecosystem ecology, biogeography of stream insects, and th

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ECOLOGY: CONCEPTS AND APPLICATIONS, SEVENTH EDITION

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Manuel C Molles Jr. is an emeritus Professor of Biology at the

University of New Mexico, where he has been a member of the faculty and curator in

the Museum of Southwestern Biology since 1975 and where he continues to write and

conduct ecological research He received his B.S from Humboldt State University and

his Ph.D from the Department of Ecology and Evolutionary Biology at the University

of Arizona Seeking to broaden his geographic perspective, he has taught and conducted

ecological research in Latin America, the Caribbean, and Europe He was awarded a

Fulbright Research Fellowship to conduct research on river ecology in Portugal and has

held visiting professor appointments in the Department of Zoology at the University

of Coimbra, Portugal, in the Laboratory of Hydrology at the Polytechnic University of

Madrid, Spain, and at the University of Montana’s Flathead Lake Biological Station

Originally trained as a marine ecologist and fisheries biologist, the author has worked mainly on river and riparian ecology at the University of New Mexico His

research has covered a wide range of ecological levels, including behavioral ecology,

population biology, community ecology, ecosystem ecology, biogeography of stream

insects, and the influence of a large-scale climate system (El Niño) on the dynamics

of southwestern river and riparian ecosystems His current research concerns the

influ-ence of climate change and climatic variability on the dynamics of populations and

communities along steep gradients of temperature and moisture in the mountains of

the Southwest Throughout his career, Dr Molles has attempted to combine research,

teaching, and service, involving undergraduate as well as graduate students in his

ongo-ing projects At the University of New Mexico, he has taught a broad range of lower

division, upper division, and graduate courses, including Principles of Biology,

Evolu-tion and Ecology, Stream Ecology, Limnology and Oceanography, Marine Biology, and

Community and Ecosystem Ecology He has taught courses in Global Change and River

Ecology at the University of Coimbra, Portugal, and General Ecology and Groundwater

and Riparian Ecology at the Flathead Lake Biological Station Dr Manuel Molles was

named Teacher of the Year by the University of New Mexico for 1995–1996 and Potter

Chair in Plant Ecology in 2000 In 2014, he received the Eugene P Odum Award from

the Ecological Society of America based on his “ability to relate basic ecological

prin-ciples to human affairs through teaching, outreach and mentoring activities.”

About the Author

iii

Dedication

To Mary Anne and Keena

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1 Introduction to Ecology: Historical Foundations and Developing Frontiers 1 Section Natural History and Evolution 11

9 Population Distribution and Abundance 198

10 Population Dynamics 218

11 Population Growth 241

12 Life Histories 258 Section Interactions 282

13 Competition 282

14 Exploitative Interactions: Predation, Herbivory, Parasitism, and Disease 303

15 Mutualism 331 Section Communities and Ecosystems 352

16 Species Abundance and Diversity 352

17 Species Interactions and Community Structure 372

18 Primary and Secondary Production 392

19 Nutrient Cycling and Retention 414

20 Succession and Stability 435 Section Large-Scale Ecology 460

21 Landscape Ecology 460

22 Geographic Ecology 484

23 Global Ecology 506 Appendix Statistical Tables 529

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Investigating the Evidence 3: Determining the Sample Median 52

Marine Shores: Life Between High and Low Tides 55 Transitional Environments: Estuaries, Salt Marshes, Mangrove Forests, and Freshwater Wetlands 58 Rivers and Streams: Life Blood and Pulse

of the Land 63 Lakes: Small Seas 67

4.1 Variation Within Populations 79

Variation in a Widely Distributed Plant 80 Variation in Alpine Fish Populations 80

Concept 4.3 Review 87

4.4 Evolution by Natural Selection 87

Heritability: Essential for Evolution 87 Investigating the Evidence 4: Variation in Data 88 Directional Selection: Adaptation by Soapberry Bugs

to New Host Plants 89

Preface xiii

Chapter 1 Introduction to Ecology: Historical

Foundations and Developing Frontiers 1

Concepts 1

1.1 Overview of Ecology 2

1.2 Sampling Ecological Research 3

The Ecology of Forest Birds: Old Tools and New 4 Forest Canopy Research: A Physical and Scientific Frontier 6 Climatic and Ecological Change: Past and Future 7

Investigating the Evidence 1: The Scientific Method—

Questions and Hypotheses 9

NATURAL HISTORY AND EVOLUTION

Chapter 2 Life on Land 11

Concepts 11

Terrestrial Biomes 12

2.1 Large-Scale Patterns of Climatic Variation 13

Temperature, Atmospheric Circulation, and Precipitation 13 Climate Diagrams 15

2.2 Soil: The Foundation of Terrestrial Biomes 16

Investigating the Evidence 2: Determining the Sample Mean 18

2.3 Natural History and Geography of Biomes 19

Tropical Rain Forest 20 Tropical Dry Forest 21 Tropical Savanna 23 Desert 25

Mediterranean Woodland and Shrubland 27 Temperate Grassland 30

Temperate Forest 31 Boreal Forest 34 Tundra 35 Mountains: Islands in the Sky 38

Applications: Climatic Variation and the Palmer Drought

Severity Index 41

Contents

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4.5 Change Due to Chance 92

Evidence of Genetic Drift in Chihuahua Spruce 92

Genetic Variation in Island Populations 93

Genetic Diversity and Butterfly Extinctions 94

Applications: Evolution and Agriculture 95

Evolution of Herbicide Resistance in Weeds 96

ADAPTATIONS TO THE ENVIRONMENT

Chapter5 Temperature Relations 99

Color of the Ground 101

Presence of Boulders and Burrows 102

5.3 Temperature and Performance of Organisms 105

Investigating the Evidence 5: Laboratory Experiments 106

Extreme Temperatures and Photosynthesis 107

Temperature and Microbial Activity 108

5.4 Regulating Body Temperature 109

Balancing Heat Gain against Heat Loss 109

Temperature Regulation by Plants 110

Temperature Regulation by Ectothermic Animals 112

Temperature Regulation by Endothermic Animals 114

Temperature Regulation by Thermogenic Plants 118

5.5 Surviving Extreme Temperatures 119

Inactivity 119

Reducing Metabolic Rate 120

Hibernation by a Tropical Species 120

Water Content of Air 127

Water Movement in Aquatic Environments 128

Water Movement between Soils and Plants 129

6.2 Water Regulation on Land 131

Water Acquisition by Animals 131 Water Acquisition by Plants 133 Water Conservation by Plants and Animals 134 Investigating the Evidence 6: Sample Size 136 Dissimilar Organisms with Similar Approaches

to Desert Life 138 Two Arthropods with Opposite Approaches

Chapter 7 Energy and Nutrient Relations 149 Concepts 149

7.5 Optimal Foraging Theory 165

Testing Optimal Foraging Theory 166 Optimal Foraging by Plants 167 Investigating the Evidence 7: Scatter Plots and the Relationship between Variables 168

Applications: Bioremediation—Using the Trophic

Diversity of Bacteria to Solve Environmental Problems 169

Leaking Underground Storage Tanks 169 Cyanide and Nitrates in Mine Spoils 170

Chapter 8 Social Relations 173 Concepts 173

8.1 Mate Choice versus Predation 175

Mate Choice and Sexual Selection in Guppies 176

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Contents vii

Chapter 10 Population Dynamics 218

Concepts 218 10.1 Dispersal 220

Dispersal of Expanding Populations 220 Range Changes in Response to Climate Change 221 Dispersal in Response to Changing Food Supply 222 Dispersal in Rivers and Streams 223

10.4 Age Distribution 231

Contrasting Tree Populations 231

A Dynamic Population in a Variable Climate 232

10.5 Rates of Population Change 233

Estimating Rates for an Annual Plant 233 Estimating Rates When Generations Overlap 234 Investigating the Evidence 10: Hypotheses and Statistical Significance 236

11.2 Logistic Population Growth 246

11.3 Limits to Population Growth 248

Environment and Birth and Death Among Darwin’s Finches 249

Investigating the Evidence 11: Frequency of Alternative Phenotypes in a Population 250

Applications: The Human Population 253

Distribution and Abundance 253 Population Dynamics 254 Population Growth 254

8.2 Mate Choice and Resource Provisioning 179

8.5 Eusociality 191

Eusocial Species 191 Evolution of Eusociality 193

Applications: Behavioral Ecology and Conservation 195

Tinbergen’s Framework 195 Environmental Enrichment and Development

9.1 Distribution Limits 200

Kangaroo Distributions and Climate 200

A Tiger Beetle of Cold Climates 201 Distributions of Plants Along a Moisture-Temperature Gradient 202

Distributions of Barnacles Along an Intertidal Exposure Gradient 203

9.2 Patterns on Small Scales 204

Scale, Distributions, and Mechanisms 205 Distributions of Tropical Bee Colonies 205 Distributions of Desert Shrubs 206

9.3 Patterns on Large Scales 208

Bird Populations Across North America 208 Investigating the Evidence 9: Clumped, Random, and Regular Distributions 209

Plant Distributions Along Moisture Gradients 210

9.4 Organism Size and Population Density 212

Animal Size and Population Density 212 Plant Size and Population Density 212

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Chapter 12 Life Histories 258

Concepts 258

12.1 Offspring Number Versus Size 259

Egg Size and Number in Fish 260

Seed Size and Number in Plants 262

Seed Size and Seedling Performance 263

12.2 Adult Survival and Reproductive Allocation 266

Life History Variation Among Species 266

Life History Variation Within Species 267

12.3 Life History Classification 270

r and K Selection 270

Plant Life Histories 271

Investigating the Evidence 12: A Statistical Test

for Distribution Pattern 272 Opportunistic, Equilibrium, and Periodic Life

Histories 274 Lifetime Reproductive Effort and Relative Offspring Size:

Two Central Variables? 275

Intraspecific Competition Among Plants 284

Intraspecific Competition Among Planthoppers 285

Interference Competition Among Terrestrial Isopods 285

13.2 Competitive Exclusion and Niches 286

The Feeding Niches of Darwin’s Finches 286

The Habitat Niche of a Salt Marsh Grass 288

13.3 Mathematical and Laboratory Models 289

Modeling Interspecific Competition 289

Laboratory Models of Competition 291

13.4 Competition and Niches 292

Niches and Competition Among Plants 293

Niche Overlap and Competition between Barnacles 293

Competition and the Habitat of a Salt Marsh Grass 295

Competition and the Niches of Small Rodents 295

Character Displacement 296

Evidence for Competition in Nature 298

Investigating the Evidence 13: Field Experiments 299

Applications: Competition between Native

and Invasive Species 300

Chapter 14 Exploitative Interactions: Predation,

Herbivory, Parasitism, and

Disease 303

Concepts 303 14.1 Complex Interactions 304

Parasites and Pathogens that Manipulate Host Behavior 304

The Entangling of Exploitation with Competition 307

14.2 Exploitation and Abundance 308

A Herbivorous Stream Insect and Its Algal Food 308 Bats, Birds, and Herbivory in a Tropical Forest 309

A Pathogenic Parasite, a Predator, and Its Prey 311

14.4 Refuges 320

Refuges and Host Persistence in Laboratory and Mathematical Models 320 Exploited Organisms and Their Wide Variety

of “Refuges” 321

14.5 Ratio-Dependent Models of Functional Response 323

Alternative Model for Trophic Ecology 324 Evidence for Ratio-Dependent Predation 324

Applications: The Value of Pest Control by Bats:

A Case Study 327

Chapter 15 Mutualism 331 Concepts 331

Zooxanthellae and Corals 342

A Coral Protection Mutualism 342

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Contents ix

17.2 Indirect Interactions 376

Indirect Commensalism 376 Apparent Competition 376

17.3 Keystone Species 378

Food Web Structure and Species Diversity 379 Experimental Removal of Sea Stars 380 Snail Effects on Algal Diversity 381 Fish as Keystone Species in River Food Webs 383 Investigating the Evidence 17: Using Confidence Intervals

Applications: Human Modification of Food Webs 388

The Empty Forest: Hunters and Tropical Rain Forest Animal Communities 388

Ants and Agriculture: Keystone Predators for Pest Control 389

Chapter 18 Primary and Secondary

Production 392 Concepts 392

18.1 Patterns of Terrestrial Primary Production 394

Actual Evapotranspiration and Terrestrial Primary Production 394

Soil Fertility and Terrestrial Primary Production 395

18.2 Patterns of Aquatic Primary Production 396

Patterns and Models 396 Whole Lake Experiments on Primary Production 397

Global Patterns of Marine Primary Production 397

18.3 Primary Producer Diversity 399

Terrestrial Plant Diversity and Primary Production 399 Algal Diversity and Aquatic Primary Production 400

Investigating the Evidence 18: Comparing Two Populations

with the t-Test 406

A Trophic Dynamic View of Ecosystems 406 Linking Primary Production

COMMUNITIES AND ECOSYSTEMS

Chapter 16 Species Abundance

and Diversity 352 Concepts 352

The Niches of Algae and Terrestrial Plants 360 Complexity in Plant Environments 361 Soil and Topographic Heterogeneity and the Diversity

of Tropical Forest Trees 361 Algal and Plant Species Diversity and Increased Nutrient Availability 363

Nitrogen Enrichment and Ectomycorrhizal Fungus Diversity 363

16.4 Disturbance and Diversity 364

The Nature and Sources of Disturbance 364 The Intermediate Disturbance Hypothesis 364 Disturbance and Diversity in the Intertidal Zone 365 Disturbance and Diversity in Temperate Grasslands 365

Applications: Disturbance by Humans 367

Urban Diversity 368

Chapter 17 Species Interactions

and Community Structure 372 Concepts 372

17.1 Community Webs 374

Detailed Food Webs Reveal Great Complexity 374 Strong Interactions and Food Web Structure 374

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Successional Mechanisms in the Rocky Intertidal Zone 447

Successional Mechanisms in Forests 449

20.4 Community and Ecosystem Stability 450

Lessons from the Park Grass Experiment 451 Replicate Disturbances and Desert Stream Stability 451

21.3 Origins of Landscape Structure and Change 471

Geological Processes, Climate, and Landscape Structure 472

Organisms and Landscape Structure 474 Fire and the Structure of a Mediterranean Landscape 478

Applications: Restoring a Riverine Landscape 479

Riverine Restoration: The Kissimmee River 479

Chapter 22 Geographic Ecology 484 Concepts 484

22.1 Area, Isolation, and Species Richness 486

Island Area and Species Richness 486 Island Isolation and Species Richness 488

22.2 The Equilibrium Model of Island Biogeography 489

Species Turnover on Islands 490 Experimental Island Biogeography 491 Colonization of New Islands by Plants 492

Applications: Using Stable Isotope Analysis to Study Feeding

19.1 Nutrient Cycles 415

The Phosphorus Cycle 416

The Nitrogen Cycle 417

The Carbon Cycle 418

19.2 Rates of Decomposition 419

Decomposition in Two Mediterranean Woodland

Ecosystems 419 Decomposition in Two Temperate Forest Ecosystems 420

Decomposition in Aquatic Ecosystems 422

Investigating the Evidence 19: Assumptions for Statistical

Tests 423

19.3 Organisms and Nutrients 425

Nutrient Cycling in Streams and Lakes 425

Animals and Nutrient Cycling in Terrestrial

Ecosystems 427 Plants and the Nutrient Dynamics of Ecosystems 428

19.4 Disturbance and Nutrients 429

Disturbance and Nutrient Loss from Forests 429

Flooding and Nutrient Export by Streams 430

20.1 Community Changes During Succession 437

Primary Succession at Glacier Bay 437

Secondary Succession in Temperate Forests 438

Succession in Rocky Intertidal Communities 439

Succession in Stream Communities 439

20.2 Ecosystem Changes During Succession 440

Ecosystem Changes at Glacier Bay 441

Four Million Years of Ecosystem Change 441

Recovery of Nutrient Retention

Following Disturbance 443 Succession and Stream Ecosystem Properties 445

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Contents xi

El Niño and Marine Populations 511

El Niño and the Great Salt Lake 513

El Niño and Terrestrial Populations in Australia 513

Applications: Impacts of Global Climate Change 525

Shifts in Biodiversity and Widespread Extinction

of Species 525 Human Impacts of Climate Change 526

Appendix Statistical Tables 529 Glossary 533

References 543 Photo Credits 554 Index 555

Manipulating Island Area 493 Island Biogeography Update 494

22.3 Latitudinal Gradients in Species Richness 494

Latitudinal Gradient Hypotheses 494 Area and Latitudinal Gradients in Species Richness 496 Continental Area and Species Richness 497

22.4 Historical and Regional Influences 498

Exceptional Patterns of Diversity 498 Investigating the Evidence 22: Sample Size Revisited 499

Historical and Regional Explanations 500

Applications: Global Positioning Systems, Remote Sensing,

and Geographic Information Systems 501

Global Positioning Systems 502 Remote Sensing 502

Geographic Information Systems 503

Chapter 23 Global Ecology 506

Concepts 506

The Atmospheric Envelope and the Greenhouse Earth 507

23.1 A Global System 508

The Historical Thread 509

El Niño and La Niña 510

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Contents xiii

Cononnntetetetetetetteeeeeeentntnntnntnnttss ss s xxixxixixixixixixixixixixixixxxxiiiiiiiiiiiiiiiiiiiiiiiiiiii

Preface

This book was written for students taking their first

under-graduate course in ecology I have assumed that students

in this one-semester course have some knowledge of basic

chemistry and mathematics and have had a course in general

biology, which included introductions to physiology,

biologi-cal diversity, and evolution

Organization of the Book

An evolutionary perspective forms the foundation of the

entire textbook, as it is needed to support understanding

of major concepts The textbook begins with a brief

intro-duction to the nature and history of the discipline of

ecol-ogy, followed by section I, which includes two chapters on

natural history—life on land and life in water and a chapter

on population genetics and natural selection Sections II

through VI build a hierarchical perspective through the

traditional subdisciplines of ecology: section II concerns

adaptations to the environment; section III focuses on

population ecology; section IV presents the ecology of

interactions; section V summarizes community and

ecosys-tem ecology; and finally, section VI discusses large-scale

ecology and includes chapters on landscape, geographic,

and global ecology These topics were first introduced in

section I within a natural history context In summary, the

book begins with the natural history of the planet,

consid-ers portions of the whole in the middle chaptconsid-ers, and ends

with another perspective of the entire planet in the

con-cluding chapter The features of this textbook were

care-fully planned to enhance the students’ comprehension of

the broad discipline of ecology

Features Designed with the

Student in Mind

All chapters are based on a distinctive learning system,

fea-turing the following key components:

Student Learning Outcomes: Educators are being asked

increasingly to develop concrete student learning outcomes

for courses across the curriculum In response to this need

and to help focus student progress through the content, all

sections of each chapter in the seventh edition begin with a

list of detailed student learning outcomes

Introduction: The introduction to each chapter presents

the student with the flavor of the subject and important

background information Some introductions include

historical events related to the subject; others

pre-sent an example of an ecological process All attempt

to engage students and draw them into the discussion that follows

Concepts: The goal of this book is to build a foundation of

ecological knowledge around key concepts I have found that while beginning ecology students can absorb a few central concepts well, they can easily get lost in a sea of details The key concepts are listed at the beginning of each chapter to alert the student to the major topics to follow and to provide a place where the student can find a list of the important points covered in each chapter The sections in which concepts are discussed focus on published studies and, wherever possible, the scientists who did the research are introduced This case-study approach supports the concepts with evidence, and introduces students to the methods and people that have cre-ated the discipline of ecology Each concept discussion ends with a series of concept review questions to help students test their knowledge and to reinforce key points made in the discussion

A group of Japanese macaques,

Macaca fuscata, huddles together

, conserving their body heat in the midst of dri

ving snow The ity to regulate body temperature, using beha

capac-vioral, anatomical, and physiological adaptations, enables these monk

eys to live through the cold winters in Nag

ano, Japan, site of the 1998

Winter Olympics

Adaptations

to the Environment

CHAPTER CONCEPTS 5.1 Macroclimate interacts with the local

landscape to produce microclimatic variation in temperature

100

5.2 Adapting to one set of environmental

conditions generally reduces

a population’s fitness in other environments 103

5.3 Most species perform best in a fairly

narrow range of temperatures

105

Investigating the Evidence 5:

Laboratory Experiments

106

5.4 Many organisms have evolved

ways to compensate for variations

in environmental temperature by regulating body temperature

109

5.5 Many organisms survive extreme

temperatures by entering a resting stage 119

Applications: Local Extinction of a Land Snail in

an Urban Heat Island

122 Summary 123 Key Terms 124 Review Questions 124

LEARNING OUTCOMES

After studying this section you should be able to do the following:

5.1 Distinguish between temperature and heat.

5.2 Explain the ecological signif

icance of tal temperatures.

environmen-T he thermometer w

as one of the f irst instruments to appear in the scientif

ic tool kit and we ha

ve been suring and reporting temperatures e

mea-ver since Howemea-ver, what do thermometers actually quantify?

Temperature is a

moL37282_ch05_099-124 indd 99 moL37282_ch05_099-124.indd 99

29/09/14 9:13 pm

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Illustrations: A great deal of effort has been put into the

devel-opment of illustrations, both photographs and line art The goal has been to create more effective pedagogical tools through skillful design and use of color, and to rearrange the traditional presentation of information in figures and

captions Much explanatory material is located within the illustrations, providing students with key information where they need it most The approach also provides

an ongoing tutorial on graph tion, a skill with which many introductory students need practice

interpreta-Detailed Explanations of Mathematics:

The mathematical aspects of ecology commonly challenge many students taking their first ecology course This text carefully explains all mathematical

expressions that arise to help students overcome these lenges In some cases, mathematical expressions are dissected

chal-in illustrations designed to complement their presentation chal-in the associated narrative

Visualizing a process involving a predator and its prey.

of these, a moth and a fly

Heinrich’s observations indicate bald-faced hornets ha

ve a prey capture rate of less

Birds eat a disproportionate number

of the conspicuous members of a peppered moth population.

Birds leave the population dominated

by better camouflaged individuals.

Figure 7.16 Birds and other predators act as agents of natural selection for impro

ved prey defense

Number of survi

1,000

10 100

1,000 801 789 776

734 764

688 640 571 439 252 96 6 3 0

199 12 13 12

46 30

48 69 132 187 156 90 3 3

Number of survivors

at beginning

of year

Number of deaths during year

1,000–199 801–12 789–13

Dall sheep surviving their first year

of life have a high probability of surviving to about age 9.

Sheep 10 years old and older are easier prey for wolves and die

To allow comparisons to other studies, number of Dall sheep surviving and dying within each year of life is converted to numbers per 1,000 births.

Survivorship curves are plotted using a log10 scale on the y-axis.

Figure 10.14 Dall sheep: from life table to survi

vorship curve (data from Murie 1944)

Small phytoplankton

Planktivorous invertebrates

Lake food web

By reducing planktivorous fish

populations, piscivores indirectly

increase populations of large

zooplankton and indirectly reduce

biomass of phytoplankton.

Piscivores

Large herbivorous zooplankton

Top-down influences on primary production

Figure 18.12 The trophic cascade hypothesis, a result of “cascading” indirect interactions

t a

t ( le p b sm pl sp pl tio

log led the

in De So, fed with cal man large large

of p

at th ton zoop mary

moL37282_ch18_392-413.indd 402

Provides a visual representation of a hypothesis involving a set of complex ecological interactions.

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Preface xv

chapter is organized are boldfaced and redefined in the summary to reemphasize the main points of the chapter

• Key Terms The listing of key terms provides page

num-bers for easy reference in each chapter

• Review Questions The review questions are designed

to help students think more deeply about each concept and to reflect on alternative views They also provide

a place to fill in any remaining gaps in the information presented and take students beyond the foundation estab-lished in the main body of the chapter

End-of-Book Material:

• Appendixes One appendix, “Statistical Tables,” is

available to the student for reference Answers to cept Review questions and answers to Critiquing the Evidence are now available with the book’s instructor resources

• Glossary List of all key terms and their definitions.

• References References are an important part of any

scientific work However, many undergraduates are tracted by a large number of references within the text One of the goals of a general ecology course should be to introduce these students to the primary literature without burying them in citations The number of citations has been reduced to those necessary to support detailed dis-cussions of particular research projects

• Index

“Investigating the Evidence” Boxes: These readings offer

“mini-lessons” on the scientific method, emphasizing

statis-tics and study design They are intended to present a broad

outline of the process of science, while also providing

step-by-step explanations The series of boxes begins in chapter 1

with an overview of the scientific method, which establishes

a conceptual context for more specific material in the next

21 chapters The last reading wraps up the series with a

dis-cussion of electronic literature searches Each Evidence box

ends with one or more questions, under the heading

“Critiqu-ing the Evidence.” This feature is intended to stimulate

criti-cal thinking about the box content

Applications: Many undergraduate students want to know

how abstract ideas and general relationships can be applied to

the ecological problems we face in the contemporary world

They are concerned with the practical side of ecology and

want to know more about how the tools of science can be

applied Including a discussion of applications in each chapter

motivates students to learn more of the underlying principles

of ecology In addition, it seems that environmental problems

are now so numerous and so pressing that they have erased a

once easy distinction between general and applied ecology

End-of-Chapter Material:

• Summary The chapter summary reviews the main

points of the content The concepts around which each

Confirming Pages

106 Section II Adaptations to the Environment

5.12 Describe the basic design of a laboratory e

xperiment.

5.13 Discuss the relati

ve strengths and weaknesses of laboratory experiments and f

ield observations in ecological studies.

One of the most po werful ways to test a hypothesis is through

an experiment Experiments used by ecologists generally f

all into one of tw

o categories—field experiments and tory experiments Field and laboratory e

labora-xperiments generally provide complementary information or e

vidence, and differ somewhat in their design Here we discuss the design of laboratory experiments

In a laboratory experiment, the researcher attempts to k

eep all factors relatively constant e

xcept one The one factor that is not kept constant is the one of interest to the e

xperimenter and

it is the one that the e

xperimenter varies across e

xperimental conditions Let’

s draw an example of a laboratory e

xperiment discussed in this chapter (see p 000) Based upon published

studies, Michael

Angilletta (2001) concluded that cally separated populations of the eastern fence lizard,

geographi- porus undulatus,

may differ physiologically or beha

viorally

Angilletta designed a laboratory e

xperiment to test the hypothesis that populations of

S undulatus from re

gions with significantly different climates dif

fer in how temperature affects their rates of metabolizable ener

gy intake The results

of that experiment are summarized by

figure 5.10 What we want to consider here is the design of the e

xperiment that duced those results

pro-What factors do you think Angilletta mayhave attempted to control in this e

xperiment? First, he used similar numbers of lizards from the tw

as lizard size Lizards

Laboratory Experiments

from both populations used in the e

xperiments had an a verage body mass of approximately 5.4 g Since males and females may differ physiologically

, Angilletta included approximately equal numbers of males and females in his e

xperiments He also was careful to expose all the lizards to the same quality

of light and to the same numbers of hours of light and ness and he maintained them in the same kinds of e

dark-xperimental enclosures Angilletta also fed all the lizards in his e

xperiment the same type of food: li

ve crickets The list could go on b

ut these are the major f

actors controlled in this e

xperiment

Now, what factors did Angilletta vary in that e

xperiment?

For each study population, Ne

w Jersey or South Carolina, he varied a single factor: temperature In the e

xperiment, letta maintained lizards from Ne

Angil-w Jersey and South Carolina at three temperatures: 30

8 , 33 8 , and 36 8 C and estimated their rates

of metabolizable ener

gy intake at these three temperatures.

Angilletta’s experiment revealed that lizards from both tions have a maximum metabolizable ener

popula-gy intake at 33 8 C

This result suggests, contrary to the study’

s hypothesis, that the optimum temperature for feeding does not dif

fer for the tw

o populations Ho

wever, the experiment also sho

wed that at 33 8 C

S undulatus from South Carolina ha

ve a higher metabolizable energy intake compared to lizards from Ne

w Jersey This result provides evidence of the geographic dif

ferences that Angilletta thought might exist across the range of

liz-icant factors but the one of interest In this case the main factor of interest was temperature.

C RITIQUING THE E VIDENCE 5

1 What is the greatest strength of laboratory e

xperiments in ecological research?

2 Why do ecologists generally supplement information resulting from laboratory e

xperiments with f ield observations or experiments?

Investigating the Evidence

5

the United States, living in a broad di

versity of climatic zones ( fig. 5.9 ) Taking advantage of this wide range of en

vironmental conditions, Michael

Angilletta (2001) studied the temperature

relations of S undulatus over a portion of its range In one of

his studies, Angilletta determined ho

w temperature influences metabolizable ener

gy intake, or MEI He measured MEI as the amount of energy consumed (C) minus ener

gy lost in feces (F) and uric acid (U), which is the nitrogen w

aste product produced

by lizards We can summarize MEI in equation form as:

MEI 5 C 2 F 2 U Angilletta studied tw

o populations from Ne

w Jersey and South Carolina, re

gions with substantially dif

ferent climates

He collected a sample of lizards from both populations and

30 8 , 33 8 , and 36 8 C Angilletta kept his study lizards in rate enclosures and pro

sepa-vided them with crick

ets that he had weighed to the nearest 0.1 mg as food Since he had deter

mined the energy content of an a

-verage cricket, Angilletta was able to determine the ener

gy intake by each lizard by ing the number of crick

count-ets they ate and calculating the ener

gy content of that number

He determined the ener

gy lost as feces (F) and uric acid (U) by collecting all the feces and uric acid material He estimated the a

verage energy content of feces and uric acid using a bomb calorimeter

Local Extinction of a Land Snail

in an Urban Heat Island

5.21 Outline changes in the distrib

ution of the snail

Arianta arbustorum around Basel, Switzerland, between 1900 and 1990.

5.22 Explain how urbanization generally creates a “heat

island.”

5.23 Review the evidence that temperature changes around the city of Basel are responsible for local extinctions of the snail

Arianta arbustorum Between 1906 and 1908, a Ph.D candidate named G Bollinger (1909) studied land snails in the vicinity of Basel, Switzerland.

Eighty-five years later

, Bruno and Anette Baur (1993) carefully resurveyed Bollinger’s study sites near Basel for the presence ofland snails In the process, the

y found that at least one snail

spe-cies, Arianta arb ustorum, had disappeared from se

veral of the sites This discovery led the Baurs to e

xplore the mechanisms that may have produced extinction of these local populations.

A arbustorum is a common land snail in meado

ws, ests, and other moist, v

for-egetated habitats in northwestern and central Europe

The species li ves at altitudes up to 2,700 m

in the Alps The Baurs report that the snail is se

xually mature

at 2 to 4 years and may li

ve up to 14 years Adult snails ha

ve shell diameters of 16 to 20 mm

The species is ditic Though individuals generally mate with other

hermaphro-A torum, they can fertilize their o

arbus-wn eggs Adults produce one

to three batches of 20 to 80 e

ggs each year They deposit their eggs in moss, under plant litter

, or in the soil Eggs generally hatch in 2 to 4 weeks, depending upon temperature

snail with a broader geographic distrib

ution that extends from southern Scandina

via to the Iberian peninsula

How did the Baurs document local e

xtinctions of

A. arbustorum? If you think about it a bit, you will probably

realize that it is usually easier to determine the presence of a species than its absence If you do not encounter a species dur

ing a survey, it may be that you just didn’

-t look hard enough

Fortunately, the Baurs had o

ver 13 years of experience doing

fieldwork on A arbustorum and knew its natural history well

For instance, the y knew that it is best to search for the snails after rainstorms, when up to 70% of the adult population is active Consequently, the Baurs searched Bollinger’

s study sites after hea

vy rains They concluded that the snail w

as absent at a site only after tw

o 2-hour surv eys failed to turn up either a living individual or an empty shell of the species

The Baurs found

A arbustorum still living at 13 of the

29 sites surv eyed by Bollinger near Basel Ele

ven of these remaining populations li

ved in deciduous forests and the other two lived on grassy ri

verbanks However, the Baurs could not

find the snail at 16 sites Eight of these sites had been ized, which made the habitat unsuitable for an

urban-y land snails because natural v

egetation had been remo

ved Between 1900 and 1990 the urbanized area of Basel had increased by 500%

However, the eight other sites where

A arbustorum had

dis-appeared were still co

vered by vegetation that appeared able Four of these sites were co

suit-vered by deciduous forest, three were on ri

verbanks, and one w

as on a railway ment These vegetated sites also supported populations of f

embank-ive other land snail species, including

C nemoralis

What caused the e

xtinction of A arbustorum at sites that

still supported other snails?

The Baurs compared the teristics of these sites with those of the sites where

charac-A torum had persisted They found no dif

arbus-ference between these two groups of sites in re

gard to slope, percent plant co

ver, height of vegetation, distance from w

ater, or number of other land snail species present

The first major difference the Baurs uncovered was in altitude The sites where

A arbustorum was

extinct had an average altitude of 274 m

The places where it survived had an average altitude of 420 m

The places where the snail had survi

ved were also cooler

A thermal image of the landscape tak

en from a satellite showed that surface temperatures in summer around Basel ranged from about 17

8 to 32.5 8 C Surface temperatures where

A arbustorum had survived averaged approximately 22

8 C, while the sites where the species had gone e

xtinct had surface temperatures that a

veraged approximately 25

8 C The sites where the snail w

as extinct were also much closer to v

ery hot areas with temperatures greater than 29

8 C Figure 5.34 is based on the Baurs’ thermal image of the area around Basel and shows where the snail w

as extinct and where it persisted

The Baurs attributed the higher temperatures at the eight sites where the snail is e

xtinct to heating by thermal radiation from the urbanized areas of the city

Buildings and pa vement store more heat than v

egetation In addition, the cooling ef

fect

of evaporation from v

egetation is lost when an area is b

uilt over Increased heat storage and reduced cooling mak

e ized landscapes thermal islands Heat ener

urban-gy stored in urban centers is transferred to the surrounding landscape through thermal radiation, H

r The Baurs documented higher temperatures at the sites near Basel where

A arbustorum is extinct and identified a

well-studied mechanism that could produce the higher peratures of these sites Ho

tem-wever, are the temperature dif

ences they observed sufficient to e

fer-xclude A arbustorum from

the warmer sites? The researchers compared the temperature

relations of A arbustorum

and C nemoralis to find some

clues They concentrated their studies on the influence of perature on reproduction by these tw

tem-o snail species

The eggs of each species were incubated at four temperatures—19 8 , 22 8 , 25 8 , and 29 8 C Notice that these temperatures fall within the range measured by the satellite image (see fig. 5.34 ) The eggs of both species hatched at a high rate at

19 8 C However, at higher temperatures, their e

ggs hatched at nificantly lower rates At 22 8 C, less than 50% of

sig-A arbustorum

eggs hatched, while the e

ggs of C. nemoralis continued to hatch

_099-124.indd 122 moL37282_ch05_099-124.indd 122

7/23/14 5:55 PM

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New to the Seventh Edition

The seventh edition expands the pedagogy by beginning

all sections of every chapter with a list of student

learn-ing outcomes—over 450 student learnlearn-ing outcomes in all

These outcomes are largely based on fundamental learning

outcomes for material covered in the text:

1 Define key terms

2 Explain the main concepts

3 Evaluate the strength of research presented in support of

main concepts, including a critique of study design

4 Interpret statistical evidence bearing on concepts,

expressed in graphical and numerical form

5 Apply the main concepts to interpretation of new

situations

A content thread focused on global change has been

developed and distributed across chapters, emphasizing

global climate change Students and instructors increasingly

look for ways to connect the concepts and practice of

ecologi-cal science to environmental issues arising from global climate

change The present edition explores how species are adjusting

their distributions and their critical life history events as

cli-mate changes The final chapter ends with a review of projected

impacts of climate change on ecosystems and human

popula-tions, infrastructure, and economic systems

This edition also builds on previous discussions of

human disturbance of ecosystems to consider how damaged

ecosystems can be restored The extent and intensity of human

impact on the biosphere grows with our population and

expand-ing global economy While climate change is the most

promi-nent aspect of contemporary global change, other facets, such as

damage or destruction of ecosystems, also call for solutions As

a result, there is greater need to restore damaged communities

and ecosystems In this context, the new edition adds an

intro-duction to the practice of ecological restoration, focusing on how

the process of restoring ecosystems can benefit from concepts

developed in academic studies of community and ecosystem

succession

The relationship between biodiversity and ecosystem

function is introduced through the positive influence of

pri-mary producer diversity on rates of pripri-mary production

Studies of biodiversity and ecosystem function are key elements

in ecology’s foundation Connecting these elements helps create

conceptual coherence across the discipline A growing body of

recent research does just that Therefore, this edition includes a

new section on the connection between biodiversity and

ecosys-tem function

The seventh edition introduces developments in trophic

ecology that build on classical models of predator-prey

inter-actions The early to middle twentieth century was a golden

age for theoretical ecology However, those developments have

not stopped Contemporary ecologists continue to build on that

legacy, improving our representation and understanding of

eco-logical systems as they do so The seventh edition updates the

discussion of consumer functional response by introducing

alter-native models based on the ratio of prey to predator numbers

rather than prey density per se This discussion is coupled with reviews of experimental and field studies that support the ratio-dependent models

The present edition connects ratio-dependent models

of functional response to patterns of consumer abundance and secondary production in ecosystems Previous editions

have provided thorough coverage of the ecology of primary production in terrestrial and aquatic ecosystems, but second-ary production has received much less attention This seventh edition addresses this deficiency by including a section that covers the fundamentals of secondary production The intro-duction to secondary production in this edition is presented

in the context of consumer responses to variations in primary production

New supplementary materials are placed online

Materi-als cut from the sixth edition and those previously cut from the fifth and fourth editions are available online Suggested read-ings have been updated and placed online, along with answers to Concept Review and Critiquing the Evidence questions

Significant Chapter-by-Chapter Changes

In chapters 1 to 23, numbered learning outcomes were

added to all concept discussions and Evaluating the Evidence and Applications features The average number of learning outcomes added to each chapter is 20

In chapter 10, a new Applications feature explores

evi-dence that plant and animal ranges have shifted northward and

to higher latitudes in the Northern Hemisphere during the recent period of rapid global warming This is the beginning of the global climate change thread in the seventh edition However, the presentation builds on earlier content in chapter 1 on population responses to climate change, including evolutionary responses, and in chapter 4 on temperature relations of organisms

In chapter 12, a new Applications feature reviews studies

that have shown shifts in the timing of flowering in plants and

of migration in birds in response to climate warming The cussion complements the earlier discussion of shifts in species ranges in chapter 10 by demonstrating that climate warming is not just inducing organisms to move in response to global warm-ing but also adjusting their life histories

dis-In chapter 13, the Lotka-Volterra equations have been

modified from previous editions to make them more standard, less cluttered, and easier for students to follow, which is essen-tial, since these equations are the foundation of the mathematical ecology covered in the text

In chapter 14, we revisit predator functional responses

first introduced in chapter 7 by evaluating alternatives to those models The Lotka-Volterra models of predator-prey interactions published in the early twentieth century stimulated a long line

of research More recently, researchers have offered alternatives that help identify where those classical mathematical models, with their simplifying assumptions, apply and where alternative formulations better account for aspects of predator-prey inter-actions, particularly at larger spatial and longer temporal scales The discussion in this chapter reviews how recent ratio-dependent functional response models better predict predator

Trang 18

Preface xvii

structure and function to these systems emerges as one of the great contemporary ecological challenges Increasingly ecolo-gists addressing this challenge are turning to the conceptual framework of ecological succession to guide their work Exam-ples of such work are included in this chapter to help bridge the historical divide between ecological theory and restoration practice

In chapter 23, the discussion of the Antarctic ozone hole

has been updated to 2013, including 35 years of data from NASA

on the size of the ozone hole The pattern shows that the mum size of the Antarctic ozone hole has stabilized, signaling

maxi-a bmaxi-asis for ozone recovery predicted by maxi-atmospheric scientists over the next 50 years, providing a bit of good planetary news The growing body of climate change research, published since

the earlier editions of Ecology Concepts and Applications, has

greatly improved understanding of how earth’s changing climate will impact ecosystems and human populations, if not stabilized

A discussion of these impacts concludes this edition, ing the relevance of ecological knowledge to sustaining natural

underscor-as well underscor-as human-centered systems

functional responses in experimental and natural settings The

discussion helps to dispel the idea that mathematical ecology

ceased to develop in the mid-twentieth century and reinforces the

complementary roles of theoretical, experimental, and

observa-tional studies

In chapter 18, a new concept connects primary producer

diversity to higher levels of primary production The chapter also

includes a new concept featuring the relationship between levels

of primary production and secondary production This discussion

provides a basis for introducing the fundamentals of secondary

production This addition also revisits the ratio-dependent

func-tional responses introduced in chapter 14 by extending the

impli-cations of those models beyond predator functional response to

the trophic structure of ecosystems The treatment also formally

introduces secondary production, filling a conceptual gap in

pre-vious editions

In chapter 20, the fields of ecological restoration and

restoration ecology are introduced for the first time Human

impact on the environment has altered ecological communities

and ecosystems in nearly every corner of the planet Restoring

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use Connect’s robust reporting features to generate powerful data that reflects student performance on specific topics, learn-ing outcomes, Bloom’s level, and more.

McGraw-Hill Connect ® Ecology is a digital teaching and

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Save Time with Auto-Graded

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Connecting Instructors

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Trang 20

McGraw-Hill LearnSmart ® is the only adaptive learning program proven to effectively assess a student’s knowledge of basic course content and help them master it By considering both confidence level and responses to actual content ques-tions, LearnSmart identifies what an individual student knows and doesn’t know and builds an optimal learning path, so that they spend less time on concepts they already know and more time on those they don’t LearnSmart also pre dicts when a student will forget concepts and introduces remedial content

to prevent this The result is that LearnSmart’s adaptive ing path helps stu dents learn faster, study more efficiently, and retain more knowledge, allow ing instructors to focus valuable class time on higher-level concepts

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Integrated and Adaptive

Learning Systems

xix

What You’ve Only Imagined

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A complete list of the people who have helped me with this project would be impossibly long However, during the devel-opment of this seventh edition, several colleagues freely shared their ideas and expertise, reviewed new sections, or offered the encouragement a project like this needs to keep

it going: Scott Collins, Cliff Dahm, Arturo Elosegi, Manuel Graça, Tom Kennedy, Tim Lowrey, Sam Loker, Rob Miller, Will Pockman, Steve Poe, Bob Sinsabaugh, Alain Thomas, Tom Turner, Lawrence Walker, Chris Witt, Blair Wolf I wish

to offer special thanks to Roger Arditi and Lev Ginzburg for their time and patience in helping me develop sections

on ratio-dependent models of functional response and their potential contributions to better understanding of predator-prey interactions and the trophic structure of ecosystems I am also grateful to Art Benke for helping me develop an over-view of secondary production for this edition and for helping integrate it with discussion of the effects of enrichment on ecosystem trophic structure John and Leah Vucetich helped bring their long-term research on wolf-moose interactions on Isle Royale to life by graciously allowing use of one of their many photos of interactions in this model predator and prey system In addition, I am indebted to the many students and instructors who have helped by contacting me with questions and suggestions for improvements

I also wish to acknowledge the skillful guidance and work throughout the publishing process given by many profession-als associated with McGraw-Hill during this project, including Becky Olson, Patrick Reidy, Carrie Burger, Fran Simon, April Southwood, Lynn Breithaupt, Mary Reeg, Angie Sigwarth, Tara McDermott, and Sheila Frank

Finally, I wish to thank all my family for support given throughout the project, especially Paulette Dompeling, Mary Ann Esparza, Dan Esparza, Hani Molles, Anders Molles, Mary Anne Nelson, and Keena

I gratefully acknowledge the many reviewers who, over the course of the last several revisions, have given of their time and expertise to help this textbook evolve to its present seventh edi-tion Their depth and breadth of knowledge and experience, both

as researchers and teachers, are humbling They continue my education, for which I am grateful, and I honestly could not have continued the improvement of this textbook without them

I gratefully acknowledge the many reviewers who, over the course of the last several revisions, have given of their time and expertise to help this textbook evolve to its pres ent edition Their depth and breadth of knowledge and experi-ence, both as researchers and teachers, are humbling They continue my education, for which I am grateful, and I hon-estly could not have continued the improvement of this text-book without them

Reviewers for the Seventh Edition

John Bacheller Hillsborough Community College Isaac Barjis City University of New York Dena Berg Tarrant County College NW Earl R Beyer Harrisburg Area Community College

Annual Editions: Environment 2015

by Eathorne

ISBN 978-1-25-916115-5

Annual Editions is a compilation of current articles from the

best of the public press The selections explore the global

environment, the world’s energy, the biosphere, natural

resources, and pollution Available through Create

Taking Sides: Clashing Views on Environmental Issues,

Sixteenth Edition by Easton ISBN: 978-1-25-916113-1

Taking Sides presents current versial issues in a debate-style format designed to stimulate student interest and develop critical thinking skills

contro-Each issue is thoughtfully framed with

an issue summary, an issue introduction, and a postscript or

challenge questions An online Instructor’s Resource Guide

with testing material is available Available through Create

Classic Edition Sources: Environmental Studies

Fourth Edition by Thomas Easton

ISBN 978-0-07-352764-2

Sources brings together selections of enduring intellec tual

value—classic articles, book excerpts, and research studies—

that have shaped ecology and environmental sci ence Edited

for length and level, the selections are orga nized topically

An annotated table of contents provides a quick and easy

review of the selections Supported by an online instructor’s

Resource Guide that provides a complete synopsis of each

selec-tion, guidelines for discussing the selection in class, and testing

materials Available through Create

Ecology Laboratory Manual, by Vodopich

(ISBN: 978-0-07-338318-7;

MHID: 0-07-338318-X)

Darrell Vodopich, co-author of Biology Laboratory Man ual,

has written a new lab manual for ecology This lab manual

offers straightforward procedures that are doable in a broad

range of classroom, lab, and field situations The procedures

have specific instructions that can be taught by a teaching

assistant with minimal experience as well as by a professor

Student Atlas of Environmental Issues, by Allen

(ISBN: 978-0-69-736520-0;

MHID: 0-69-736520-4)

This atlas is an invaluable pedagogical tool for exploring the human impact on the air, waters, biosphere, and land in every major world region This infor-mative resource provides a unique combination of maps and data that help students understand

the dimensions of the world’s environmental problems and

the geographic basis of these problems

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Preface xxi

Jerry Baskin University of Kentucky Thomas O Crist Miami University Peter Alpert University of Massachusetts—Amherst Mark Pyron Ball State University

Mary Bremigan Michigan State University

Reviewers for the Fifth Edition

Joel S Brown University of Illinois—Chicago Peter E Busher Boston University

Lloyd Fitzpatrick University of North Texas James A Fordyce University of Tennessee David L Gorchov Miami University Jamie Kneitel California State University—Sacramento John C Krenetsky Metropolitan State College of Denver Amy E Lesen Pratt Institute

D Nicholas McLetchie University of Kentucky Thomas Pliske Florida International University Nathan J Sanders University of Tennessee Robert M Schoch Boston University John F Weishampel University of Central Florida

Reviewers for the Fourth Edition

John M Anderies Arizona State University Eric M Anderson University of Wisconsin—Stevens Point David M Armstrong University of Colorado—Boulder Tom Arsuffi Texas State University

Michelle A Baker Utah State University Lawrence S Barden University of North Carolina—Charlotte Mark C Belk Brigham Young University

Brian D Bovard Florida International University Leslie S Bowker California Polytechnic State University—

San Luis Obispo Steven W Brewer University of North Carolina—Wilmington Arthur L Buikema, Jr Virginia Tech

David Byres Florida Community College—Jacksonville Erica A Corbett Southeastern Oklahoma State University Christopher Cronan University of Maine

Richard J Deslippe Texas Tech University Stephanie A Elliott University of Texas—San Antonio Lloyd Fitzpatrick University of North Texas

Irwin Forseth University of Maryland Douglas C Gayou University of Missouri—Columbia Frank S Gilliam Marshall University

Colleen Hatfield Rutgers University Thomas W Jurik Iowa State University Kimberley J Kolb California State University—Bakersfield Angelo Lattuca Mohawk Valley Community College David A Lipson San Diego State University Jay Mager Ohio Northern University Chris Migliaccio Miami Dade College

L Maynard Moe California State University—Bakersfield Don Moll Southwest Missouri State University

Timothy A Mousseau University of South Carolina Jean Pan University of Akron

Craig Plante College of Charleston Thomas Pliske Florida International University Kenneth A Schmidt Texas Tech University John Skillman California State University—San Bernardino John F Weishampel University of Central Florida

Jake F Weltzin University of Tennessee Rodney Will University of Georgia

Jamal Bittar The University of Toledo

Linda Bruslind Oregon State University

Sherri L Buerdsell West Virginia Northern Community College

Carrie E Burdzinski Delta College (University Center, Michigan)

William Dew Nipissing University

Harry G Deneer University of Saskatchewan

Phil Denette Delgado Community College

Jessica A DiGirolamo Broward College, Davie, Florida

Angela M Edwards Trident Technical College

Elyce Ervin University of Toledo

Teresa G Fischer Indian River State College

Christina Gan Highline Community College

Kathryn Germain Southwest Tennessee Community College

Linda Girouard Brescia University

Judy Gnarpe University of Alberta

Amy D Goode Illinois Central College

Robert C Hairston Harrisburg Area Community College

Nasreen S Haque City University of New York, New York

Daniel P Herman University of Wisconsin—Eau Claire

Ingrid Herrmann Santa Fe College

Sheela S Huddle Harrisburg Area Community College

Chike Igboechi Medgar Evers College of the City University

of New York Ilko G Iliev Southern University at Shreveport

Debra W Jackson University of Louisiana at Monroe

John C Jones Calhoun Community College

Judy Kaufman Monroe Community College

Peter S Kourtev Central Michigan University

Jonathan N Lawson Collin College, Plano Texas

Suzanne Long Monroe Community College

Mary Ann Merz West Virginia Northern Community College

Matthew Morgan Greenville Technical College

Christian Nwamba Wayne County Community

College District Amanda Thigpen Parker Pearl River Community College

Marceau Ratard Delgado Community College

Geraldine H Rimstidt Daytona State College

Seth Ririe Brigham Young University—ldaho

David M Rollins University of Maryland, College Park &

Prince Georges Community College Ben Rowley University of Central Arkansas

Eleftherios “Terry” Saropoulos Vanier College

Arif Sheena MacEwan College, Alberta, Canada

Richard H Shippee Vincennes University

Sasha A Showsh University of Wisconsin—Eau Claire

Susan J Stamler College of DuPage

Ronald J Stewart Humber ITAL, Toronto, Ontario

Victoria Auerbuch Stone UC Santa Cruz

David J Wartell Harrisburg Area Community College

TitYee Wong University of Memphis

Reviewers for the Sixth Edition

Michael Henshaw Grand Valley State University

Thomas Nash Arizona State University

Thomas Schoener University of California—Davis

Kevin Woo University of Central Florida

Deborah Waller Old Dominion University

William Kroll Loyola University of Chicago

James Manhart Texas A&M University

Jonathan Benstead University of Alabama

Robert Sanders Temple University

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Thomas W Jurik Iowa State University Karen L Kandl University of New Orleans Robert Keys Cornerstone University Mark E Knauss Shorter College Jean Knops University of Nebraska Anthony J Krzysik Embry-Riddle Aeronautical University Eddie N Laboy-Nieves InterAmerican University

of Puerto Rico Vic Landrum Washburn University Michael T Lanes University of Mary Tom Langen Clarkson University Kenneth A LaSota Robert Morris College Hugh Lefcort Gonzaga University Peter V Lindeman Edinboro University of Pennsylvania John F Logue University of South Carolina—Sumter John S Mackiewicz State University of New York—Albany Tim Maret Shippensburg University

Ken R Marion University of Alabama—Birmingham Vicky Meretsky Indiana University

John C Mertz Delaware Valley College Carolyn Meyer University of Wyoming Sheila G Miracle Southeast Community College—Bell City Timothy Mousseau University of South Carolina

Virginia Naples Northern Illinois University Peter Nonacs University of California—Los Angeles Mark H Olson Franklin and Marshall College David W Onstad University of Illinois—Champaign Fatimata A Palé Thiel College

Mary Lou Peltier Saint Martin’s College Carolyn Peters Spoon River College Kenneth L Petersen Dordt College Eric R Pianka University of Texas Raymond Pierotti University of Kansas—Lawrence David Pindel Corning Community College Jon K Piper Bethel College

Thomas E Pliske Florida International University Michael V Plummer Harding University

Ellen Porter Holtman Virginia Western Community College Diane Post University of Texas—Permian Basin

Kathleen Rath Marr Lakeland College Brian C Reeder Morehead State University Seth R Reice University of North Carolina—Chapel Hill Robin Richardson Winona State University

Carol D Riley Gainesville College Marianne W Robertson Millikin University Tom Robertson Portland Community College Bernadette M Roche Loyola College in Maryland Tatiana Roth Coppin State College

Neil Sabine Indiana University East Seema Sanjay Jejurikar Bellevue Community College Timothy Savisky University of Pittsburgh

Josh Schimel University of California—Santa Barbara Michael G Scott Lincoln University

Erik R Scully Towson University Michael J Sebetich William Paterson University Walter M Shriner Mount Hood Community College John Skillman California State University—San Bernardino Jerry M Skinner Keystone College

Garriet W Smith University of South Carolina—Aiken Stacy Smith Lexington Community College

Joseph Stabile Iona College Alan Stam Capital University Alan Stiven University of North Carolina—Chapel Hill

Craig E Williamson Miami University of Ohio

Jianguo (Jingle) Wu Arizona State University

Douglas Zook Boston University

Reviewers for the Third Edition

Sina Adl Dalhousie University, Canada

Harvey J Alexander College of Saint Rose

Peter Alpert University of Massachusetts—Amherst

Julie W Ambler Millersville University

Robert K Antibus Bluffton College

Tom L Arsuffi Southwest Texas State University

Claude D Baker Indiana University

Ellen H Baker Santa Monica College

Charles L Baube Oglethorpe University

Edmund Bedecarrax City College of San Francisco

Jerry Beilby Northwestern College

R P Benard American International College

Erica Bergquist Holyoke Community College

Richard A Boutwell Missouri Western State College

Ward Brady Arizona State University East—Mesa

Fred J Brenner Grove City College

Robert Brodman Saint Joseph’s College

Elaine R Brooks San Diego City College

Evert Brown Casper College

Stephanie Brown Fabritius Southwestern University

Rebecca S Burton Alverno College

James E Byers University of New Hampshire

Guy Cameron University of Cincinnati

Geralyn M Caplan Owensboro Community

and Technical College

Walter P Carson University of Pittsburgh

Ben Cash III Maryville College

Young D Choi Purdue University—Calumet

Ethan Clotfelter Providence College

Liane Cochran-Stafira Saint Xavier University

Joe Coelho Culver-Stockton College

Jerry L Cook Sam Houston State University

Tamara J Cook Sam Houston State University

Erica Corbett Southeastern Oklahoma State University

Tim Craig University of Minnesota

Jack A Cranford Virginia Tech

Greg Cronin University of Colorado—Denver

Todd Crowl Utah State University

Richard J Deslippe Texas Tech University

Kenneth M Duke Brevard College

Andy Dyer University of South Carolina

Ginny L Eckert University of Alaska

J Nicholas Ehringer Hillsborough Community College

George F Estabrook University of Michigan

Richard S Feldman Marist College

Charles A Francis University of Nebraska—Lincoln

Carl Freeman Wayne State University

J Phil Gibson Agnes Scott College

Robert R Glesener Brevard College

Michael L Golden Grossmont College

Paul Grecay Salisbury University

Lana Hamilton Northeast State Tech Community College

Brian Helmuth University of South Carolina

James R Hodgson Saint Norbert College

Jeremiah N Jarrett Central Connecticut State University

Krish Jayachandran Florida International University

Mark Jonasson Crafton Hills College

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Fred E Wasserman Boston University Phillip L Watson Ferris State University Donna Wear Augusta State University John F Wegner Emory State University Matt R Whiles Southern Illinois University Howard Whiteman Murray State University Craig E Williamson Lehigh University Gordon Wolfe California State University—Chico Derek Zelmer Emporia State University

Douglas Zook Boston University

Manuel C Molles Jr.

Eric D Storie Roanoke-Chowan Community College

William A Szelistowski Eckerd College

Robert Tatina Dakota Wesleyan University

Nina N Thumser California University of Pennsylvania

John A Tiedemann Monmouth University

Anne H Todd Bockarie Philadelphia University

Conrad Toepfer Millikin University

Donald E Trisel Fairmont State College

Dessie L A Underwood California State University—

Long Beach Carl Von Ende Northern Illinois University

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CHAPTER CONCEPTS

1.1 Ecologists study environmental

relationships ranging from those

of individual organisms to factors influencing global-scale processes 2 Concept 1.1 Review 3

1.2 Ecologists design their studies based on

their research questions, the temporal and spatial scale of their studies, and available research tools 3

Investigating the Evidence 1:

The Scientific Method—Questions and Hypotheses 9

Summary 10 Key Terms 10 Review Questions 10

1 Introduction

to Ecology Historical Foundations and Developing Frontiers

A yellow-rumped warbler, Dendroica coronata, feeding young

Ecological studies of warblers have made fundamental contributions

to the growth of ecological understanding

W hat is ecology? Ecology , the study of

relation-ships between organisms and the environment, has been a focus for human study for as long as

we have existed as a species Our survival has depended upon how well we could observe variations in the environment and predict the responses of organisms to those variations The earliest hunters and gatherers had to know the habits of their animal prey and where to find food plants Later, agricultur-ists had to be aware of variations in weather and soils and of how such variation might affect crops and livestock

Today, most of earth’s human population live in cities and most of us have little direct contact with nature More than ever before, though, the future of our species depends on how well we understand the relationships between organisms and the environ-ment Our species is rapidly changing earth’s environment, yet

we do not fully understand the consequences of these changes For instance, human activity has increased the quantity of nitro-gen cycling through the biosphere, changed land cover across the globe, and increased the atmospheric concentration of CO 2 Changes such as these threaten the diversity of life on earth and may endanger our life support system Because of the rapid pace

of environmental change at the dawn of the twenty-first century,

it is imperative that we continue as ardent students of ecology

LEARNING OUTCOME

1.1 Discuss the concept of environment as it pertains to the science of ecology

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Behind the simple definition of ecology lies a broad

sci-entific discipline Ecologists may study individual organisms,

entire forests or lakes, or even the whole earth The

mea-surements made by ecologists include counts of individual

organisms, rates of reproduction, or rates of processes such

as photosynthesis and decomposition Ecologists often spend

as much time studying nonbiological components of the

environment, such as temperature or soil chemistry, as they

spend studying organisms Meanwhile, the “environment” of

organisms in some ecological studies are other species While

you may think of ecologists as typically studying in the field,

some of the most important conceptual advances in ecology

have come from ecologists who build theoretical models or

do ecological research in the laboratory Clearly, our simple

definition of ecology does not communicate the great breadth

of the discipline or the diversity of its practitioners To get a

better idea of what ecology is, let’s briefly review the scope

of the discipline

1.1 Overview of Ecology

1.2 Describe the levels of ecological organization, for

example, population, studied by ecologists

1.3 Distinguish between the types of questions

addressed by ecologists working at different levels of

organization

1.4 Explain how knowledge of one level of ecological

organization can help guide research at another

level of organization

Ecologists study environmental relationships ranging

from those of individual organisms to factors influencing

global-scale processes This broad range of subjects can

be organized by arranging them as levels in a hierarchy of

ecological organization, such as that imbedded in the brief

table of contents and the sections of this book Figure 1.1

attempts to display such a hierarchy graphically

Historically, the ecology of individuals, which is presented

at the base of figure 1.1 , has been the domain of physiological

ecology and behavioral ecology Physiological ecologists have

emphasized the evolution (a process by which populations

change over time) of physiological and anatomical mechanisms

by which organisms solve problems posed by physical and

chemical variation in the environment Meanwhile, behavioral

ecologists have focused principally on evolution of behaviors

that allow animals to survive and reproduce in the face of

envi-ronmental variation Physiological and behavioral ecology are

informed by evolutionary theory, as are all other areas of ecology

There is a strong conceptual linkage between ecological

studies of individuals and of populations particularly where

they concern evolutionary processes Population ecology is

centered on the factors influencing population structure and

process, where a population is a group of individuals of a

sin-gle species inhabiting a defined area The processes studied

by population ecologists include adaptation, extinction, the

What factors influence the number of large mammal species living together in African grasslands?

What role does concentration of atmospheric CO2 play in the regulation of global temperature?

How has geologic history influenced regional diversity within certain groups of organisms?

How do vegetated corridors affect the rate of movement by mammals among isolated forest fragments?

How does fire affect nutrient availability in grassland ecosystems?

Do predators influence where zebras feed in the landscape?

How do zebras regulate their internal water balance?

What factors control zebra populations?

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Chapter 1 Introduction to Ecology 3

distribution and abundance of species, population growth and

regulation, and variation in the reproductive ecology of

spe-cies Population ecologists are particularly interested in how

these processes are influenced by nonbiological and

biologi-cal components of the environment

Bringing biological components of the environment into the picture takes us to the next level of organization, the ecol-

ogy of interactions such as predation, parasitism, and

com-petition Ecologists who study interactions between species

have often emphasized the evolutionary effects of the

inter-action on the species involved Other approaches explore the

effect of interactions on population structure or on properties

of ecological communities

The definition of an ecological community as an tion of interacting species links community ecology with the

associa-ecology of interactions Community and ecosystem associa-ecology

have a great deal in common, since both are concerned with the

factors controlling multispecies systems However, the objects

of their study differ While community ecologists concentrate on

the organisms inhabiting an area, ecosystem ecologists include

the physical and chemical factors influencing the community

and focus on processes such as energy flow and decomposition

To simplify their studies, ecologists have long attempted

to identify and study isolated communities and ecosystems

However, all communities and ecosystems on earth are open

systems subject to exchanges of materials, energy, and

organ-isms with other communities and ecosystems The study of

these exchanges, especially among ecosystems, is the

intel-lectual territory of landscape ecology However, landscapes

are not isolated either but part of geographical regions

sub-ject to large-scale and long-term regional processes These

regional processes are the subjects of geographic ecology

Geographic ecology in turn leads us to the largest spatial scale

and highest level of ecological organization—the biosphere ,

the portions of the earth that support life, including the land,

waters, and atmosphere

While this description of ecology provides a brief preview

of the material covered in this book, it is a rough sketch and

highly abstract To move beyond the abstraction represented

by figure 1.1 , we need to connect it to the work of the

scien-tists who have created the discipline of ecology To do so, let’s

briefly review the research of ecologists working at a broad

range of ecological levels emphasizing links between

histori-cal foundations and some developing frontiers ( fig. 1.2 )

Concept 1.1 Review

1 How does the level of ecological organization an

ecolo-gist studies influence the questions he or she poses?

2 While an ecologist may focus on a particular level of

ecological organization shown in figure 1.1 , might other levels of organization be relevant, for example, does an ecologist studying factors limiting numbers in a popula-tion of zebras need to consider the influences of interac-tions with other species or the influences of food on the survival of individuals?

1.2 Sampling Ecological Research

1.5 Describe some emerging frontiers in ecology

1.6 Explain how the use of stable isotopes has extended what it is possible to know about the ecology of warblers

1.7 Compare the spatial and temporal scales addressed

by the research of Robert MacArthur, Nalini Nadkarni, and Margaret Davis

Figure 1.2 Two rapidly developing frontiers in ecology

(a) Aeroecology: the interdisciplinary study of the ecology of the

earth-atmosphere boundary (Kunz et al 2008) New tools, such as the Indigo/

FLIR Merlin mid thermal camera that took this thermal infrared image

of flying Brazilian free-tailed bats, Tadarida braziliensis, have opened

this developing frontier in ecology This image depicts variation in the surface temperature of these bats Thermal infrared technology makes

it possible not only to detect and record the presence of free-ranging nocturnal organisms, but also to investigate their physiology and ecology

in a noninvasive manner (see chapter 5, p 114) (b) Urban ecology: the

study of urban areas as complex, dynamic ecological systems, influenced

by interconnected, biological, physical, and social components As gists focus their research on the environment where most members of our species live, they have made unexpected discoveries about the ecology of urban centers such as the city of Baltimore (see chapter 19, p 432)

ecolo-(a)

(b)

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Ecologists design their studies based on their research

questions, the temporal and spatial scale of their studies, and

available research tools Because the discipline is so broad,

ecological research can draw from all the physical and

biologi-cal sciences The following section of this chapter provides a

sample of ecological questions and approaches to research

The Ecology of Forest Birds:

Old Tools and New

Robert MacArthur gazed intently through his binoculars He

was watching a small bird, called a warbler, searching for

insects in the top of a spruce tree To the casual observer it might

have seemed that MacArthur was a weekend bird-watcher Yes,

he was intensely interested in the birds he was watching, but he

was just as interested in testing ecological theory

The year was 1955, and MacArthur was studying the

ecology of five species of warblers that live together in the

spruce forests of northeastern North America All five warbler

species, Cape May ( Dendroica tigrina ), yellow-rumped

( D. coronata ), black-throated green ( D virens ),

blackbur-nian ( D. fusca ), and bay-breasted ( D castanea ), are about

the same size and shape and all feed on insects Theory

pre-dicted that two species with identical ecological requirements

would compete with each other and that, as a consequence,

they could not live in the same environment indefinitely

Mac-Arthur wanted to understand how several warbler species with

apparently similar ecological requirements could live together

in the same forest

The warblers fed mainly by gleaning insects from the

bark and foliage of trees MacArthur predicted that these

warblers might be able to coexist and not compete with each other if they fed on the insects living in different zones within trees To map where the warblers fed, he subdivided trees into vertical and horizontal zones He then carefully recorded the amount of time warblers spent feeding in each

MacArthur’s prediction proved to be correct His titative observations demonstrated that the five warbler spe-cies in his study area fed in different zones in spruce trees As figure 1.3 shows, the Cape May warbler fed mainly among new needles and buds at the tops of trees The feeding zone

quan-of the blackburnian warbler overlapped broadly with that quan-of the Cape May warbler but extended farther down the tree The black-throated green warbler fed toward the trees’ interiors

The bay-breasted warbler concentrated its feeding in the rior of trees Finally, the yellow-rumped warbler fed mostly

inte-on the ground and low in the trees MacArthur’s observatiinte-ons showed that though these warblers live in the same forest, they extract food from different parts of that forest He con-cluded that feeding in different zones may reduce competition among the warblers of spruce forests

MacArthur’s study (1958) of foraging by warblers is

a true classic in the history of ecology However, like most studies it raised as many questions as it answered Scientific research is important both for what it teaches us directly about nature and for how it stimulates other studies that improve our understanding MacArthur’s work stimulated numerous studies of competition among many groups of organisms, including warblers Some of these studies produced results that supported his work and others produced different results

All added to our knowledge of competition between species and of warbler ecology

Cape May warbler

New needles and

buds at top of tree

Bare or lichen-covered lower trunk and middle branches

Black-throated green warbler

New needles and buds and some older needles

Yellow-rumped warbler

Bay-breasted warbler

Figure 1.3 Warbler feeding zones shown in beige The several warbler species that coexist in the forests of northeastern North America feed in

distinctive zones within forest trees

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Nearly half a century after Robert MacArthur studied the feeding ecology of warblers through the lenses of his binocu-

lars, a team of Canadian and U.S scientists led by Ryan Norris

(Norris et al 2005) worked to develop tools capable of

pen-etrating the feeding habitats of wide-ranging migratory birds

The object of their study was the American redstart ( Setophaga

ruticilla ), another colorful member of the warbler family

Paru-lidae ( fig. 1.4 ) American redstarts, like the warblers studied by

MacArthur, are long-distance migrants, nesting in temperate

North America but spending their winters mainly in tropical

Cen-tral America, northern South America, and the Caribbean islands

Historically, studies of wide-ranging bird species, such

as the American redstart, have focused mainly on their

tem-perate breeding grounds However, observations by

ecolo-gists had long suggested that the success of an individual

migratory bird during the breeding season may depend

criti-cally on the environmental conditions it experienced on its

tropical wintering grounds For example, it has been well

established that male migratory birds, arriving early on the

breeding grounds, are generally in better physical condition

compared to those arriving later Early arrivals also

gen-erally obtain the best breeding territories and have higher

reproductive success

Variation in arrival times and physical condition led ogists to ponder the connection between events on the win-

ecol-tering grounds and subsequent reproductive success among

birds in their breeding habitats To answer such a question,

we need a great deal of information, including where

indi-vidual birds live on the wintering grounds, how the winter

habitat correlates with physical condition during migration,

how winter habitat influences time of arrival on the breeding

grounds, and whether winter habitat correlates with

reproduc-tive success on the breeding grounds Clearly, the amount of

information required to answer such questions, concerning

environments separated by thousands of kilometers ( fig. 1.5 ),

exceeds what one person, or even a large team, can learn

through the lenses of binoculars

Often, ecologists have pioneered the use of more ful research tools, as the complexity of their questions have increased A tool to which ecologists turn increasingly to

power-understand the ecology of migratory birds is stable isotope analysis (see chapter 6, p 145) Isotopes of a chemical ele-

ment, for example, isotopes of carbon, have different atomic masses as a result of having different numbers of neutrons Carbon, for instance, has three isotopes (listed in order of increasing mass): 12 C, 13 C, and 14 C Of these three, 12 C and

13 C are stable isotopes because they do not undergo tive decay, whereas 14 C decays radioactively and is therefore unstable Stable isotopes have proven useful in the study of ecological processes—for example, identifying food sources, because the proportions of various isotopes differ across the environment

Stable isotope analysis provides ecologists with a new type of “lens” capable of revealing ecological relationships that would otherwise remain invisible For example, ecolo-gists using stable isotope analysis can track habitat use by American redstarts on their wintering grounds In Jamaica, older male American redstarts, along with some females, spend the winter in higher-productivity mangrove forest hab-itats, pushing most females and younger males into poorer-quality, dry scrub habitat The dominant plants in these two habitats and the insects that feed on them contain different proportions of the carbon isotopes 12 C and 13 C Therefore, the tissues of the birds spending their winters in the produc-tive mangrove habitat (lower 13 C) and those spending the winters in the poor scrub habitat (higher 13 C) are in effect chemically tagged As a consequence, today’s ecologist can analyze a very small sample of blood from an American red-start when it arrives on its temperate breeding ground and

Figure 1.4 A male American redstart, Setophaga ruticilla

Mature male American redstarts are highly territorial, dominating

high-quality feeding territories in their tropical wintering grounds,

pushing most female redstarts and young males into poorer-quality

feeding habitats

Breeding grounds Wintering grounds

American redstarts breed across much of North America, preferring forests with abundant shrubs.

American redstarts winter mainly on the Caribbean islands and the surrounding mainland.

Figure 1.5 Map of the breeding and wintering grounds of the

American redstart, Setophaga ruticilla

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know the habitat where it spent the winter When Ryan

Nor-ris and his research team made such measurements, they

found that male redstarts that had spent the winter in the

more productive mangrove habitat arrived on the breeding

grounds earlier and produced significantly more young birds

that survived to fledging

Stable isotope analysis and the role that it has played in

elucidating the ecology of a diversity of organisms will thread

its way through the text As is often the case in science, new

tools create new research frontiers Another of those frontiers

is to be found in the canopies of forests

Forest Canopy Research:

A Physical and Scientific Frontier

Studies of warblers showcase how ecologists approach

studies of one or a few species Other ecologists have been

concerned with the ecology of entire forests, lakes, or

grasslands, which they treat as ecosystems An ecosystem

includes all the organisms that live in an area and the

physi-cal environment with which those organisms interact Many

ecosystem studies have focused on nutrients , the raw

mate-rials that an organism must acquire from the environment

to live

For ecologists who study the budgets of nutrients such as

nitrogen, phosphorus, or calcium, one of the first steps is to

inventory their distribution within an ecosystem Inventories

by Nalini Nadkarni (1981, 1984a, 1984b) changed our ideas

of how tropical and temperate rain forests are structured

and how they function With the aid of mountain-climbing

equipment, Nadkarni slowly made her first ascent into the

canopy of the Costa Rican rain forest, a world explored by

few others and where she was to become a pioneer ( fig. 1.6 )

She stood on the rain forest floor and wondered about the

diversity of organisms and ecological relationships that

might be hidden in the canopy high above Her wonder soon

gave way to determination, and Nadkarni not only visited

the canopy but was among the first to explore the ecology of

this unseen world

Because of leaching by heavy rains, many rain forest

soils are poor in nutrients such as nitrogen and phosphorus

The low availability of nutrients in many rain forest soils has

produced one of ecology’s puzzles How can the prodigious

life of rain forests be maintained on such nutrient-poor soils?

Many factors contribute to the maintenance of this intense

biological activity Nadkarni’s research in the treetops

uncov-ered one of those factors, a significant store of nutrients in the

rain forest canopy

The nutrient stores in the rain forest canopy are

associ-ated with epiphytes Epiphytes are plants, such as many

orchids and ferns, that live on the branches and trunks of other

plants Epiphytes are not parasitic: they do not derive their

nutrition from the plant they grow on As they grow on the

branches of a tree they begin to trap organic matter, which

eventually forms a mat Epiphyte mats increase in thickness

up to 30 cm, providing a complex structure that supports a

diverse community of plants and animals

Epiphyte mats contain significant quantities of nutrients

Nadkarni estimated that these quantities in some tropical rain forests are equal to about half the nutrient content of the foli-age of the canopy trees In the temperate rain forests of the Olympic Peninsula in Washington, the mass of epiphytes is four times the mass of leaves on their host trees

Nadkarni’s research showed that in both temperate and tropical rain forests, trees access these nutrient stores by send-ing out roots from their trunks and branches high above the ground These roots grow into the epiphyte mats and extract nutrients from them As a consequence of this research, we now know that to understand the nutrient economy of rain for-ests the ecologist must venture into the treetops

Easier means of working in the rain forest canopy have been developed, and this research is no longer limited to the adventurous and agile New ways to access the forest canopy range from hot air balloons and aerial trams to large cranes

The Wind River Canopy Crane offers scientists access to any level within a 70 m tall coniferous forest in a 2.3 ha area near the Columbia River Gorge in Washington ( fig. 1.7 ) Research projects supported—and made far easier—by this crane and others have included the ecology of migratory birds in the forest canopy, photosynthesis by epiphytes living at differ-ent canopy heights, and vertical stratification of habitat use

by bats and beetles (Ozanne et al 2003) By 2006, there were

12 canopy cranes facilitating canopy research in temperate and tropical forests worldwide (Stork 2007) Nadkarni points Figure 1.6 Exploring the rain forest canopy What Nalini Nadkarni discovered helped solve an ecological puzzle

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out, in response to these developments, that the canopy as a

physical frontier may be closing, but its exploration as a

sci-entific frontier is just beginning, particularly as we attempt to

predict the ecological consequences of climate change

Climatic and Ecological Change:

Past and Future

The earth and its life are always changing However, many

of the most important changes occur over such long periods

of time or at such large spatial scales that they are difficult

to study Two approaches that provide insights into long-term

and large-scale processes are studies of pollen preserved in

lake sediments and evolutionary studies

Margaret Davis (1983, 1989) carefully searched through

a sample of lake sediments for pollen The sediments had

come from a lake in the Appalachian Mountains, and the

pollen they contained would help her document changes in

the community of plants living near the lake during the past

several thousand years Davis is a paleoecologist trained to

think at very large spatial scales and over very long periods of

time She has spent much of her professional career studying

changes in the distributions of plants during the Quaternary

period, particularly during the most recent 20,000 years

Some of the pollen produced by plants that live near a lake falls on the lake surface, sinks, and becomes trapped in

lake sediments As lake sediments build up over the ries, this pollen is preserved and forms a historical record

centu-of the kinds centu-of plants that lived nearby As the lakeside etation changes, the mix of pollen preserved in the lake’s sediments also changes In the example shown in figure 1.8 ,

veg-pollen from spruce trees, Picea spp., first appears in lake

sediments about 12,000 years ago then pollen from beech,

Fagus grandifolia, occurs in the sediments beginning about 8,000 years ago Chestnut pollen does not appear

in the sediments until about 2,000 years ago The pollen from all three tree species continues in the sediment record until about 1920, when chestnut blight killed most of the chestnut trees in the vicinity of the lake Thus, the pollen preserved in the sediments of lakes can be used to recon-struct the history of vegetation in the area Margaret B Davis, Ruth G Shaw, and Julie R Etterson review extensive evidence that during climate change, plants evolve, as well

as disperse (Davis and Shaw 2001; Davis, Shaw, and son 2005) As climate changes, plant populations simultane-ously change their geographic distributions and undergo the

Etter-evolutionary process of adaptation , which increases their

ability to live in the new climatic regime Meanwhile, dence of evolutionary responses to climate change is being discovered among many animal groups William Bradshaw and Christina Holzapfel (2006) summarized several stud-ies documenting evolutionary change in northern animals,

evi-Western red cedar

Pacific dogwood

Grand fir

Pacific yew

Western hemlock

Pacific silver fir

Douglas fir

Tree species

Canopy zonation

Physical conditions: greatest

exposure to sunlight and winds, highest variability in temperature

Over 40 m:

Characteristic animals: red crossbill,

warblers, flying squirrel

Physical conditions: partial shading,

lower exposure to winds, more equable temperatures

15 to 40 m

Characteristic animals: chickadees,

nuthatches, varied thrush

Physical conditions: lowest light

intensity and reduced temperature variation, diminished wind

Ground to 15 m

Characteristic animals: towhees,

American robin, winter wren, tailed deer, coyote

at any distance along crane arm.

Gondola housing scientists can

be lowered to study any level in the canopy.

Figure 1.7 The Wind River Canopy Crane provides access to the forest canopy for a broad range of ecology and ecological studies

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warming (see chapter 23, p 519) Research such as that

by Davis and her colleagues will be essential to predicting and understanding ecological responses to global climate change

In the remainder of this book we will fill in the details

of the sketch of ecology presented in this chapter This brief survey has only hinted at the conceptual basis for the research described Throughout this book we emphasize the concep-tual foundations of ecology Each chapter focuses on a few ecological concepts We also explore some of the applications associated with the concepts introduced Of course, the most important conceptual tool used by ecologists is the scientific method, which is introduced on page 9

We continue our exploration of ecology in section I with natural history and evolution Natural history is the founda-tion on which ecologists build modern ecology for which evo-lution provides a conceptual framework A major premise of this book is that knowledge of natural history and evolution improves our understanding of ecological relationships

Concept 1.2 Review

1 How were the warbler studies of Robert MacArthur and

those that focused on the American redstart similar?

How did they differ?

2 What aspects of Nalini Nadkarni’s research identify it

as “ecosystem ecology”? Give examples of research

in forest canopies that would address other levels of ecological organization (for examples, see fig. 1.1 )

3 The discussion of the research by Margaret Davis and

her colleagues did not identify the questions that they addressed What research questions can we infer from the above description of their work?

8,000

2,000 Present

12,000

100 Lake profile

Figure 1.8 The vegetation history of landscapes can be reconstructed using the pollen contained within the sediments of nearby lakes

Figure 1.9 Studies indicate that north American red squirrels,

Tamiasciurus hudsonicus, have been undergoing rapid evolution for

earlier breeding, during a recent period of increased average spring

temperatures in Canada’s Yukon Territory (Réale et al 2003)

ranging from small mammals and birds to insects ( fig. 1.9 ),

in response to increasing growing season length as a

conse-quence of the now-well-documented phenomenon of global

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A hypothesis is a possible answer to a question MacArthur’s main hypothesis (possible answer to his question) was: “Sev-eral warbler species are able to coexist because each species feeds on insects living in different zones within trees.”

Once a scientist or team of scientists proposes a esis (or multiple alternative hypotheses), the next step in the scientific method is to determine its validity by testing predic-tions that follow from the hypothesis Three fundamental ways

hypoth-to test hypotheses are through observation, experiments, and modeling These approaches, which are all represented in fig-ure 1 , will be discussed in detail in the “Investigating the Evi-dence” boxes and in the research discussed in later chapters

C RITIQUING THE E VIDENCE 1

1 How does the development of new research tools, such as canopy cranes and stable isotope analysis, affect the pro-cess of science as outlined by figure 1 of this “Investigat-ing the Evidence” box?

Investigating the Evidence 1

Data:

Gathering Management Display Summary Statistics Statistical Analysis Accept/Reject Hypothesis

Hypothesis not supported:

Change hypothesis

in light of new information.

Information:

Observation Experiment Modeling Published Studies

Test of hypothesis:

Observation Experiment Modeling

Question

Hypothesis

Prediction

Testing a hypothesis, whatever the outcome, increases the pool of information.

Hypothesis supported:

Conduct additional tests of the hypothesis.

Figure 1 Graphic summary of the scientific method The tific method centers on the use of information to propose and test hypotheses through observation, experiment, and modeling

The Scientific Method—Questions and Hypotheses

1.8 Distinguish between questions and hypotheses in the

scientific process

1.9 Discuss the scientific method, emphasizing

hypoth-esis testing

Ecologists explore the relationships between organisms and

environment using the methods of science The series of boxes

called “Investigating the Evidence” that are found throughout

the chapters of this book discuss various aspects of the

sci-entific method and its application to ecology While each box

describes only a small part of science, taken together, they

rep-resent a substantial introduction to the philosophy, techniques,

and practice of ecological science

Let us begin this distributed discussion with the most

basic point What is science? The word science comes from a

Latin word meaning “to know.” Broadly speaking, science is

a way of obtaining knowledge about the natural world using

certain formal procedures Those procedures, which make up

what we call “the scientific method,” are outlined in figure 1

Despite a great diversity of approaches to doing science,

sound scientific studies have many methodological

charac-teristics in common The most universal and critical aspects

of the scientific method are: asking interesting questions and

forming testable hypotheses

Questions and Hypotheses

What do scientists do? Simply put, scientists ask and attempt

to find answers to questions about the natural world

Ques-tions are the guiding lights of the scientific process

With-out them, exploration of nature lacks focus and yields little

understanding of the world Let’s consider a question asked

by an ecologist discussed in this chapter The main

ques-tion asked by Robert MacArthur in his studies of warblers

(p 4) was something like the following: “How can several

species of insect-eating warblers live in the same forest

with-out one species eventually excluding the others through

com-petition?” While this focus on questions may seem obvious,

one of the most common questions asked of scientists at

semi-nars and professional meetings is, “What is your question?”

If scientists are in the business of asking questions about nature, where does a hypothesis enter the process?

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Ecologists study environmental relationships ranging from

those of individual organisms to factors influencing

global-scale processes The research focus and questions posed by

ecologists differ across the levels of ecological organization

studied

Ecologists design their studies based on their research

questions, the temporal and spatial scale of their

stud-ies, and available research tools With this brief review

of research approaches and topics, we return to the question

asked at the beginning of the chapter: What is ecology?

Ecol-ogy is indeed the study of relationships between organisms

and the environment However, as you can see from the studies

reviewed, ecologists study those relationships over a large range of temporal and spatial scales using a wide variety of approaches Ecology includes Davis’s studies of vegetation moving across the North American continent over a span of thousands of years Ecology also includes the observational studies of birds in contemporary forests by MacArthur Ecolo-gists may study processes on plots measured in square centime-ters or, like those studying the ecology of migratory birds, study areas may span thousands of kilometers Important ecological discoveries have come from Nadkarni’s probing of the rain for-est canopy and from traces of stable isotopes in a droplet of blood Ecology includes all these approaches and many more

evolution 2 nutrient 6

stable isotope analysis 5 urban ecology 3 Key Terms

of nutrient storage in rain forest canopy resulted from the ogy of individual organisms, populations of organisms, and communities of species Explain

5 What do the studies of Margaret Davis tell us about the sition of forests in the Appalachian Mountains during the past 12,000 years (see fig. 1.8 )? Based on this research, what pre- dictions might you make about the future composition of these forests?

6 During the course of the studies reviewed in this chapter, each scientist or team of scientists measured certain variables What major variable studied by Margaret Davis and her research team distinguishes their work from that of the other research reviewed in the chapter?

1 Faced with the complexity of nature, ecologists have divided the

field of ecology into subdisciplines, each of which focuses on

one of the levels of organization pictured in figure 1.1 What is

the advantage of developing such subdisciplines within ecology?

2 What are the pitfalls of subdividing nature in the way it is

repre-sented in figure 1.1 ? In what ways does figure 1.1 misrepresent

nature?

3 What could you do to verify that the distinct feeding zones

used by the warblers studied by MacArthur (see fig. 1.3 ) are

the result of ongoing competition between the different species

of warblers? How might you examine the role of competition

in keeping some American redstarts out of the most productive

feeding areas on their wintering grounds?

4 Although Nalini Nadkarni’s studies of the rain forest canopy

addressed a question related to ecosystem structure, the patterns

Review Questions

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CHAPTER CONCEPTS

2.1 Uneven heating of the earth’s spherical surface by the sun and the tilt of the earth on its axis combine to produce predictable latitudinal and seasonal variation

in climate 13

2.2 Soil structure results from the term interaction of climate, organisms, topography, and parent mineral material 16

long-Investigating the Evidence 2:

Determining the Sample Mean 18

2.3 The geographic distribution of terrestrial

biomes corresponds closely to variation

in climate, especially prevailing temperature and precipitation 19

Applications: Climatic Variation and the Palmer

Drought Severity Index 41 Summary 42

Key Terms 43 Review Questions 44

Tigers, Panthera tigris, live in several biomes Despite a huge historic

range extending from Turkey through the rain forests of southern Asia

and to the temperate forests of Siberia, shrinking habitat and hunting

have reduced the number of tigers from an estimated 100,000 to

3,000–5,000 in just 100 years (data from IUCN Redlist)

2 Life on Land

Natural History and Evolution

2.1 Describe how natural history has helped with restoration of tropical dry forest in Costa Rica

2.2 List the main features used to differentiate the various terrestrial biomes

Detailed knowledge of natural history is proving

invaluable to restoration of natural ecosystems across the globe One of the most dramatic resto-ration successes that incorporated natural history into its approach comes from Costa Rica Daniel Janzen’s goal was

to restore tropical dry forest, a forest nearly as rich in species

as tropical rain forest, to Guanacaste National Park, Costa

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Rica As he studied the guanacaste tree, Enterolobium

cyclo-carpum ( fig. 2.1 ), however, he realized that something was

missing from the present-day forest The guanacaste tree, a

member of the pea family, produces disk-shaped fruit about

10 cm in diameter and 4 to 10 mm thick Each year, a large

tree produces up to 5,000 of these fruits, which fall to the

ground when ripe Janzen asked, Why does the guanacaste

tree produce so much fruit? His answer to this question was

that the fruit of the tree should promote seed dispersal by

animals

Janzen, however, knew of no living native animals of

the size and behavior that would make them dependable

dis-persers of guanacaste seeds Dependable disdis-persers would be

necessary to speed restoration of tropical dry forest across

Guanacaste National Park True, some large herbivores fed

on guanacaste fruits and dispersed the seeds with their feces

But most of these dispersers were cattle and horses, which

were introduced during the Spanish colonial period Had the

guanacaste tree evolved an elaborate fruit and produced

thou-sands of them each year in the absence of native dispersers?

On the surface, it appeared so

Janzen’s restoration of tropical dry forest was guided

by his knowledge of natural history , the study of how

organisms in a particular area are influenced by factors

such as climate, soils, predators, competitors, and

evolu-tionary history Natural history eventually led Janzen to an

understanding of the fruiting biology of the guanacaste tree

As he considered the long-term natural history of Central

American dry forest, he found what he was looking for: a

whole host of large herbivorous animals, including ground

sloths, camels, and horses The dry forest had once

sup-ported plenty of potential dispersers of guanacaste seeds

However, all these large animals became extinct about

10,000 years ago; overhunting by humans may have been a

contributory factor For thousands of years following these

extinctions the guanacaste tree prepared its annual feast of

fruits, but there were few large animals to consume them

Then about 500 years ago, Europeans introduced horses

and cattle, which ate the fruits of the guanacaste tree and

dispersed its seeds around the landscape ( fig. 2.2 ) Janzen recognized the practical value of livestock as seed dispers-ers and included them in his plan for tropical dry forest restoration

Janzen first tested the hypothesis that contemporary horses can act as effective seed dispersers for the guanacaste tree After this test, he applied his knowledge by incorporat-ing horses into the management plan for Guanacaste National Park The guanacaste tree and other trees in a similar predica-ment would have their dispersers, and restoration of tropical dry forest would be accelerated

Janzen’s natural history of tropical dry forest also includes people, unlike most natural histories He worked closely with people from all parts of Costa Rican society, from the president of the country to local schoolchildren

He realized that long-term support for Guanacaste National Park depended upon its contribution to the economic and cultural well-being of local people It’s the people in Janzen’s natural history that stand guard over the Guana-caste project Janzen calls his approach “biocultural res-toration,” an approach that seeks to preserve tropical dry forest for its own sake and as a place that provides a host of human benefits, ranging from drinking water to intellectual stimulation Using natural history as their guide, Janzen and the people of Costa Rica are restoring tropical dry forest in Guanacaste National Park

Janzen’s work (1981a, 1981b) shows how natural history can be used to address a practical problem Natural history also formed the foundation upon which modern ecology devel-oped Because ecological studies continue to be built upon a solid foundation of natural history, we devote chapters 2 and 3

to the natural history of the biosphere In chapter 2, we ine the natural history of life on land Before we begin that discussion, we need to introduce terrestrial biomes, the con-cept around which this chapter is built We also discuss the development and structure of soils, the foundation supporting terrestrial biomes

Terrestrial Biomes Chapter 2 focuses on major divisions of the terrestrial envi-

ronment called biomes Biomes are distinguished primarily

by their predominant plants and are associated with particular climates They consist of distinctive plant formations such as the tropical rain forest biome and the desert biome Because tropical rain forest and desert are characterized by very differ-ent types of plants and animals and occur in regions with very different climates, the natural histories of these biomes differ

a great deal The student of ecology should be aware of the major features of those differences

The main goal of chapter 2 is to take a large-scale perspective of nature before delving, in later chapters, into finer details of structure and process We pay particu-lar attention to the geographic distributions of the major biomes, the climate associated with each, their soils, their salient biological relationships, and the extent of human influences

Figure 2.1 A guanacaste tree, Enterolobium cyclocarpum, growing

in Costa Rica Guanacaste trees, which produce large amounts of edible

fruit, require large herbivores to disperse their seeds

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of Climatic Variation

2.3 Diagram the position of the sun relative to the

equator and tropics of Capricorn and Cancer, during the equinoxes and solstices

2.4 Describe how solar driven air circulation produces

regional differences in precipitation

2.5 Interpret a climate diagram

2.6 Explain the influence of the Coriolis effect on wind

direction

Uneven heating of the earth’s spherical surface by the sun

and the tilt of the earth on its axis combine to produce

pre-dictable latitudinal and seasonal variation in climate In

chapter 1, ecology was defined as the study of the relationships

between organisms and the environment Consequently,

geo-graphic and seasonal variations in temperature and precipitation

are fundamental aspects of terrestrial ecology and natural

his-tory Several attributes of climate vary predictably over the earth

For instance, average temperatures are lower and more seasonal

at middle and high latitudes Temperature generally shows little

seasonality near the equator, while rainfall may be markedly seasonal Deserts, which are concentrated in a narrow band of latitudes around the globe, receive little precipitation, which generally falls unpredictably in time and space What mecha-nisms produce these and other patterns of climatic variation?

Temperature, Atmospheric Circulation, and Precipitation

Much of earth’s climatic variation is caused by uneven ing of its surface by the sun This uneven heating results from the spherical shape of the earth and the angle at which the earth rotates on its axis as it orbits the sun Because the earth

heat-is a sphere, the sun’s rays are most concentrated where the sun is directly overhead However, the latitude at which the sun is directly overhead changes with the seasons This sea-sonal change occurs because the earth’s axis of rotation is not perpendicular to its plane of orbit about the sun but is tilted approximately 23.5 8 away from the perpendicular ( fig. 2.3 ) Because this tilted angle of rotation is maintained throughout earth’s orbit about the sun, the amount of solar energy received by the Northern and Southern Hemispheres changes seasonally During the northern summer the Northern Hemisphere is tilted toward the sun and receives more solar energy than the Southern Hemisphere During the northern

Guanacaste tree in fruit

Fallen fruit Extinct

feeding relation

Existing feeding relation

Guanacaste seedling

Extinct disperser (e.g., camel)

Present-day disperser (e.g., horses, and cattle)

Dung with intact seeds

Figure 2.2 Dispersers of guanacaste seeds—past and present Most of the original dispersers of guanacaste seeds went extinct over 10,000 years

ago Now the tree depends on introduced domestic livestock for its dispersal

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summer solstice on approximately June 21, the sun is directly

overhead at the tropic of Cancer, at 23.5 8 N latitude During

the northern winter solstice, on approximately December 21,

the sun is directly overhead at the tropic of Capricorn, at

23.5 8 S latitude During the northern winter, the Northern

Hemisphere is tilted away from the sun and the Southern

Hemisphere receives more solar energy The sun is directly

overhead at the equator during the spring and autumnal

equi-noxes, on approximately March 21 and September 22 or 23

On those dates, the Northern and Southern Hemispheres

receive approximately equal amounts of solar radiation

This seasonal shift in the latitude at which the sun is directly

overhead drives the march of the seasons At high latitudes, in

both the Northern and Southern Hemispheres, seasonal shifts in

input of solar energy produce winters with low average

temper-atures and shorter day lengths and summers with high average

temperatures and longer day lengths In many areas at middle

to high latitudes there are also significant seasonal changes in

precipitation Meanwhile, between the tropics of Cancer and

Capricorn, seasonal variations in temperature and day length

are slight, while precipitation may vary a great deal What

pro-duces spatial and temporal variation in precipitation?

Heating of the earth’s surface and atmosphere drives

circulation of the atmosphere and influences patterns of

pre-cipitation As shown in figure 2.4 a, the sun heats air at the

equator, causing it to expand and rise This warm, moist air

cools as it rises Since cool air holds less water vapor than

warm air, the water vapor carried by this rising air mass

con-denses and forms clouds, which produce the heavy rainfall

associated with tropical environments

Eventually, this equatorial air mass ceases to rise and

spreads north and south This high-altitude air is dry, since the

moisture it once held fell as tropical rains As this air mass flows

north and south, it cools, which increases its density

Eventu-ally, it sinks back to the earth’s surface at about 30 8 latitude and

spreads north and south This dry air draws moisture from the lands over which it flows and creates deserts in the process

Air moving from 30 8 latitude toward the equator pletes an atmospheric circulation cell at low latitudes As

figure 2.4 b shows, there are three such cells on either side of

the equator Air moving from 30 8 latitude toward the poles is part of the atmospheric circulation cell at middle latitudes

This warm air flowing from the south rises as it meets cold polar air flowing from the north As this air mass rises, mois-ture picked up at lower latitudes condenses to form the clouds that produce the abundant precipitation of temperate regions

The air rising over temperate regions spreads northward and southward at a high altitude, completing the middle- and high-latitude cells of general atmospheric circulation

The patterns of atmospheric circulation shown in

figure 2.4 b suggest that air movement is directly north and

south However, this does not reflect what we observe from the earth’s surface as the earth rotates from west to east An observer at tropical latitudes observes winds that blow from the northeast in the Northern Hemisphere and from the south-east in the Southern Hemisphere ( fig. 2.5 ) These are the

northeast and southeast trades Someone studying winds within the temperate belt between 30 8 and 60 8 latitude would observe that winds blow mainly from the west These are

the westerlies of temperate latitudes At high latitudes, our

observer would find that the predominant wind direction is

from the east These are the polar easterlies

Why don’t winds move directly north to south? The vailing winds do not move in a straight north–south direction

pre-because of the Coriolis effect In the Northern Hemisphere, the

Coriolis effect causes an apparent deflection of winds to the right

of their direction of travel and to the left in the Southern sphere We say “apparent” deflection because we see this deflec-tion only if we make our observations from the surface of the earth To an observer in space, it would appear that winds move

Figure 2.3 The seasons in the Northern and Southern Hemispheres

Constant tilt of 23.5°

from plane of orbit

Northern Hemisphere has spring

equinox as equator faces the

sun Southern Hemisphere has

autumnal equinox.

Northern Hemisphere has winter as it tilts away from the sun Southern

Hemisphere has summer as

it tilts toward the sun.

Northern Hemisphere has

summer as it tilts toward the sun

Southern Hemisphere has winter

as it tilts away from the sun.

Northern Hemisphere has autumnal equinox as equator faces the sun

Southern Hemisphere has spring equinox.

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in approximately a straight line, while the earth rotates beneath

them However, we need to keep in mind that the perspective

from the earth’s surface is the ecologically relevant perspective

The biomes that we discuss in chapter 2 are as earthbound as

our hypothetical observer Their distributions across the globe

are substantially influenced by global climate, particularly

geo-graphic variations in temperature and precipitation

Geographic variation in temperature and precipitation is very complex How can we study and represent geographic

variation in these climatic variables without being overwhelmed

by a mass of numbers? This practical problem is addressed by

a visual device called a climate diagram

Climate Diagrams

Climate diagrams were developed by Heinrich Walter (1985)

as a tool to explore the relationship between the distribution of terrestrial vegetation and climate Climate diagrams summarize

a great deal of useful climatic information, including seasonal variation in temperature and precipitation, the length and inten-sity of wet and dry seasons, and the portion of the year during which average minimum temperature is above and below 0 8 C

As shown in figure 2.6 , climate diagrams summarize matic information using a standardized structure The months

cli-of the year are plotted on the horizontal axis, beginning with

(a)

Sun heats air at equator.

Deserts (30°)

Equator (0° latitude)

Heavy rains fall

Warm air rises.

Some ascending air flows to the south.

Some ascending air

flows to the north.

Dry air flowing over land absorbs moisture.

a moist temperate climate.

Dry descending air absorbs moisture, forming deserts.

60 ⬚ N

60 ⬚ S (b)

There are three air circulation cells on each side of the equator.

Figure 2.4 ( a ) Solar-driven air circulation ( b ) Latitude and atmospheric circulation

Figure 2.5 The Coriolis effect and wind direction

Polar easterlies

Westerlies

Northeast trade winds

Southeast trade winds

Westerlies

Polar easterlies

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