NR 326 Lecture 4 Measuring site quality

What is Site Quality?The productive capacity of a site, usually expressed as volume production of a given species SAF, 2008 Climate Topography Edaphic Site quality... Why do we care ab

What is site?

Shelford’s Law of Tolerance

Trees need certain climate condition in order to survive Furthermore, even when a tree species has the basic factors to

type and quality of

the vegetation the

area can carry

(SAF, 2008)

- Location

- Environment

What is Site Quality?

The productive capacity of a site, usually expressed as volume production of a given species (SAF, 2008)

Climate

Topography

Edaphic

Site quality

Why do we care about site quality?

 Site quality is measure

of relative productive

capacity of a site for a

particular species

 Different site gives

different growth response

to different species.

 Site quality can be used

to estimate potential yield

of particular species

Site Quality

• Liebig's law of the

Site Quality

The

minimum

Growth is controlled not

by the total amount of

resources available, but

by the scarcest resource

Site Quality

W ate r

Lig ht

Site Classification

A common way of expressing relative site quality is to set

up from three to five classes, or ordinal ranks, such as site

I, II and III The characteristics of each class must be defined to enable any area to be classified

Site Classification System

A common way of expressing

relative site quality is to set up

from three to five classes, or

ordinal ranks, such as site I, II and

III The characteristics of each

class must be defined to enable

any area to be classified

Ecological Site Classification (US)

Ecological Site Classification system (US)

Factors considered

Region Domain Broad climate

Division Province Climate and veg biomes Sub-region Section

Subsection Local climate, topography

& geology Landscape Land type

association (LTA) Landform, soil, geol., hydrology.

Land unit (local) Land type

Land phase Veg., soil and topo.

Site Classification System (VN)

Dạng đất đai (type) Dạng lập địa

Site Classification System (VN)

Vùng In the North: - number of cold months - T of coldest month

In the South: - number of dry months (P ≤ 2T)

- Dry index: X = S.A.D (Ps ≤ 2T; Pa ≤ T; Ps = 0) Tiểu vùng - Climate: T; P; number of dry months

Site Classification System (VN)

Whole country Zone Sub-zone Region Number of

Sub-region

The North of the 16 th

parallel north

Tonkin and Thanh Hoa

Coast

Binh Tri Thien 28

The South of the 16 th

parallel north

South Central Coast

Central Coast 26 South Central Coast 14 The South and

Central highlands

Central highlands 25

Mekong delta 10

Classify by Site Factors

It is effective climatic,

edaphic and biotic

factors which influence

development of forest

or other vegetation in

locality

important ecological factor

that controls the distribution

Climatic diagram of Tan Lac district

(Tran Viet Ha, 2010)

 Climate:

Site Factor

•Terrain: mountain; hill;

highland; delta; kaster

•Slope: level ; gentle;

moderate ; steep; very steep

Site Factor

•Bedrock

•Soil characteristics

 Soil:

Site Factor

 Vegetation:

Forest types in Vietnam

•Moist evergreen lowland

forest;

•Moist evergreen upland

forest;

•Moist deciduous forest;

•Dry deciduous forest;

•Bamboo forest/ Bamboo

mixed forest;

•Mangrove

forest/Freshwater swamp

Plant Indicators

The characteristics of the vegetation can be used as an indicator to evaluate site quality This approach is based on the theory that certain species of lower vegetation, i.e herbs and shrubs are clear indicators of the suitability of the site for a particular tree species or forest type As such they can be used to describe and differentiate site qualities

Plant Indicators

Lowbush blueberry

indicate acidic soils

Plant Indicators

Rhodomyrtus tomentosa

indicate dry, acidic soils

Rhodomyrtus tomentosa

Plant Indicators

Typha angustifolia

indicates asid

sulfate soil

Another way to measure site quality

Site Index

Defined = average height of dominant and dominant trees that have been free-to-grow (not suppressed) in a stand at some base index age for a particular species

co-Direct measure of site productivity

Indirect measures of site productivity: soils, landform, indicator species

Site index curves allow estimation of site index before and after the base age

Site Index

Height of dominant/ core dominant tree at a base age

Stand height: the mean height of the dominant trees in

a stand or crop, generally based on a predetermined number of the thickest or tallest stems

Top height: the average height of the 40 trees/ac (100

trees/ha) of the largest diameter

Site Index

Base age:

at this age the height of trees reaches stable stage (usually 50 years for hardwoods and 25 years for southern pine)

In Vietnam with fast growth species base age is 8 to 12

or ≥ 15 (Cunminghamia lanceolata; Pinus massoniana; tectona grandis; Cinnamomum cassia)

0.00 5.00 10.00 15.00 20.00 25.00

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Ho(m )

A(tuổi)

I II III IV

Ao

Site Index Curves of Manglietia glauca

(Vu Tien Hinh 2013)