Lecture energy flow in ecosystems

Transformations of energyThe transformations of energy from solar radiation to chemical energy and mechanical energy and finally back to heat of Ecosystem Ecology... • PG: Gross primary

ENERGY FLOW IN ECOSYSTEMS

• All organisms require energy:

for growth, maintenance, reproduction, locomotion, etc.

• Hence, for all organisms there must be:

 A source of energy

 A loss of usable energy

The distribution of sola radiation energy in the biosphere

This pattern of energy flow among different organisms is

the TROPHIC STRUCTURE of an ecosystem

Transformations of energy

The transformations of energy from solar radiation

to chemical energy and mechanical energy and finally back to heat of Ecosystem Ecology.

Energy and biomass pyramids

• PG: Gross primary productivity

– = the total rate of photosynthesis

– = the rate of energy capture by producers (kcal/m2/yr)

– = the amount of new biomass of producers (g/m2/yr)

• PN = PG – R; Net primary production is thus the amount of

energy stored by the producers and potentially available to consumers and decomposers

• B: Standing crop Biomass – the amount of accumulated

organic matter found in an area at a given time

The concepts

• NU: Not consumed

• NA: Undigested / Fecal wastes

• R: Respiration

• P: Secondary productivity

– the rate of production of new biomass by consumers,

– the rate at which consumers convert organic material into new biomass of consumers

The concepts

 D: loss of biomass due to the dead of plants from t1 to t2

 C: loss of biomass due to consumption by consumer

 Aquatic ecosystems

 To estimate the change in O2 concentration in light/dark bottle

 Water sample containing phytoplankton

O2 produced by photosynthesis

O2 consumed in respiration

Limiting Factors control PN in Terrestrial ecosystems

Limiting Factors control PN in Aquatic ecosystems

100

10 50

0 20 40 60 80 100 120 140 160

P N

Nitrogen concentration (mg/l)

Primary production varies with time

Net primary production (NPP) and standing biomass allocation for

a 90-year-old Michigan forest estimated from inventory-based methods in which biomass growth is quantified over time

(Gough et al 2008)

Primary productivity limits secondary production

Primary productivity limits secondary production

Undigested 100J

200J (A)

Growth 33J (P)

Respiration

67J

Growth efficency (P/A) = 33/200 = 16,5%

a given trophic level (P n ) to trophic level it feeds

on (P n-1 )

TE = Pn / Pn-1

total energy

Production efficiency (x100) of various animal group

General patterns of energy flow through ecosystems

(Begon et al, 1986)

GRAZER SYSTEM

DECOMPOSER

SYSTEM

NET PRIMARY PRODUCTIVITY

DEAD ORGANIC

MATTER

FOREST

General patterns of energy flow through ecosystems

(Begon et al, 1986)

GRAZER SYSTEM

DECOMPOSER

SYSTEM

NET PRIMARY PRODUCTIVITY

DEAD ORGANIC

MATTER

GRASSLAND

General patterns of energy flow through ecosystems

(Begon et al, 1986)

GRAZER SYSTEM

DECOMPOSER

SYSTEM

NET PRIMARY PRODUCTIVITY

DEAD ORGANIC

MATTER

PHYTOPLANKTON COMMUNITY

General patterns of energy flow through ecosystems

(Begon et al, 1986)

GRAZER SYSTEM

DECOMPOSER

SYSTEM

NET PRIMARY PRODUCTIVITY

The net primary productivity of biomes

Estuaries Swamps and marshes

Tropical rain forest Temperate forest Northern coniferous forest (taiga)

Savanna Agricultural land Woodland and shrubland

Temperate grassland

Lakes and streams Continental shelf Open ocean Tundra (arctic and alpine)

Desert scrub Extreme desert

800 1,600 2,400 3,200 4,000 4,800 5,600 6,400 7,200 8,000 8,800 9,600

Net primary productivity

(kgC/m2/năm)

www.sage.wisc.edu

P: 3,5 - 10 B: 70 - 250

P: 3,5 - 5 B: 5 - 35

P: 1 - 4 B: 1 - 18

P: 4 - 20 B: 25 - 70

P: 0 - 2,5 B: 0 - 1 P: 0,1 - 4 B: 5

Primary Productivity and Biomass (ton/ha)