Quantitative

Estimation of

Vegetation

Armin S. Coronado, MSc.

Department of Biology

College of Science

Polytechnic University of the Philippines

10 m

10 m 4 m

4 m 1 m

1 m

Trees

< 3m in height

Herbs and Grasses

• May assume different shapes (Circle or Rectangle) • Size and Quantity depends on vegetation type and objectives

• Lower Size = Higher Errors

• More Quadrats = Higher Precision

Quadrat Method

Line Intercept

can be used in crown cover assessment of a large area

Belt Transect

Center Line 1 m

1 m

N m

• Useful in Zonation of Vegetation

• Continuous sampling (N meters) within a specified

strip width

(Santos R. N. et al, 2000)

Direct Estimation of Top Cover

Visually estimate the top cover of the

whole quadrat

Record each species to the nearest

percent

The total for all species and bare ground

will equal 100%

Line intercept +

quadrat method

100 meters transect line

1m X 1m quadrat

10 meters distance between

sampling points

Transect/Quadrant Method

Braun-Blanquet 5 Point Scale

+ very rare less than 1%

1 rare 1% - 5%

2 occasional 6% - 25%

3 frequent 26% - 50%

4 common 51% - 75%

5 abundant 76% - 100%

Domin Scale + a single individual

1 scarce; 1-2 individuals

2 very scattered; cover small and < 1%

3 scattered, cover small, 1-4%

4 abundant, cover 5-10%

5 abundant, cover 11-25%

6 abundant, cover 26-33% 7 abundant, cover 34-50%

8 abundant, cover 51-75%

9 abundant, cover >75% but not complete 10 Cover practically complete

Abundance – Number of individuals per species

Density – individuals per unit area

Dominance – which species are dominant in

terms of height or area;

(Density x Height or Basal Area)

Frequency – Number of species appearing per

Plot

Importance Value – which species has more

influence on ecosystem;

(Rel Den + Rel Dom + Rel freq)

Parameters

Density Estimation

Density of a species

Relative density of a species

Dominance of a species

Relative dominance of a species

Frequency of a species

Relative frequency of a species

Importance value

Importance percentage

Diversity Measurements

Shannon-Weiner Index (H‟)

Pielou‟s Eveness Index (J‟)

Diversity and Distribution Indices

Shannon-Weiner Index (H’). It is a measure of the average degree of “uncertainty” in predicting to what species an individual chosen at random from a collection of S species and N individuals will belong (Magurran 1988).

s

H‟ = - [(ni / N) ln (ni / N)]

i = 1

Pielou’s Evenness Index (J’) - expresses H‟ relative to the maximum value that H‟ can obtain when all of the species in the sample are perfectly even with one individual per species (Magurran 1988).

J‟ = _ H„_

ln (S)

Fernando Biodiversity Scale

Parameters

Relative Values Shannon (H’) Index Pielou (J’) Evenness Index

Very High 3.5 and above 0.75-1.00

High 3.0-3.49 0.50-0.74

Moderate 2.5-2.99 0.25-0.49

Low 2.0-2.49 0.15-0.24

Very Low 1.9 & below 0.05-0.14

Point-Center Quarter Method

plotless method

sampling without a 2-dimensional area

based on distance measurement between the marked station to the trees or between trees

used to determine the parameters of a community

involves equally spaced points along a transect line

Point-Center Quarter Method

Choose an arbitrary straight line

Make sampling points every 10 meters

At each sampling point, make an imaginary division of the four quarters

Measure the distance of the nearest tree or shrub to the sampling point in each of the 4 quarters

Identify each tree or shrub to its species name or make a code for identification later

Measure the diameter breast height (DBH) of each of the tree sampled in each quarter

First Line (Compass Line)

2nd Line

Measured

Distance

10 meters

Point 1 Point 2

transect line

PCQM

Total Height

Merchantable Height – Part

of tree which is Usable

Diameter at Breast Height –

Outside Bark Diameter; 4.5

ft/ 1.3m from Ground

Basal Area = area outline of

a plant (Stem or Crown);

Total

Height

Merchantable

Height

DBH

Parameters (PCQM)

Mean distance

= total distance (d) / no. of distances (n)

Mean area per tree

= (d/n)2

Sampled area (in hectares)

= (100 m X mean distance) / 10,000

Absolute density of all species

= number of trees (n) samples / hectare

Parameters (PCQM)

Relative density of each species

= (density of each species / density of all species)

X 100

Absolute dominance of all species

= basal area of all trees sampled / hectare

Basal area

= r2

Parameters (PCQM)

Absolute dominance of each species

= basal area of each species / hectare

Relative dominance of each species

= (basal area of each species / basal area of all

species) X 100

Relative frequency of each species

= number of trees per species / total number of

trees (n)

Parameters (PCQM)

Importance value of each species

= relative density + relative dominance + relative

frequency

Importance percentage

= importance value / 3

Based from the analysis of the

collated data, which species is

most numerous In the community

most frequent in the community

most dominant in the community

most important in the community