In this file the students study concept , structure and attributes of community Plant sampling and sampling methods

1. Community
• Community represents the population
of all species living and interacting in
an area at a particular time.
Community concepts and attributes,
Method of sampling of plant communities

2. Concepts of community
• A group of organisms comprise population. Each
population has characteristics like natality,
mortality, age structure, growth dynamics and
so on.
• Several populations share a common habitat
and its resources; they interact among
themselves and develop into a biotic
community.
• Microorganisms, plants and animals populations
sharing a common habitat and interacting
among themselves develop into biotic
communities.

3. • The composition of a biotic community in any
habitat is dependent upon the occurrence of
environmental conditions in that habitat and
the ecological amplitude of species
populations.
• The transitional zone or junction between two
or more diverse communities is called
“ecotone”.
• The ecotone is a community termed as
ecotonal community with organisms of
overlapping communities and some of unique
types.

4. Structure of Community:
• Communities may be small, consisting of few species
populations in a small space, or large, comprise several
species populations in a large area.
• Communities usually categories by the ecologists in
various ways primarily based of habitat features like
water availability, high exposure of light, or other habitat
features.
• For instance, depending on the amount of water
availability, plant communities may be hydrophytic
(aquatic habitats), mesophytic (moderately moist soil
habitat) and xerophytic (dry or arid habitat).

5. • Similarly communities growing on conditions of
abundant light are called heliophytic and those
growing in shade sciophytic.
• Series of changes results in the development
of a relatively stable community, Such a stable
and mature community is called a climax
community, while communities of successional
stages are called seral community
• The plant community structures, composition
and other characteristics can be described in
both qualitative and quantitative means.

6. Difference between
Seral community
• 1. It is transitional community which
develops in an area during
succession.
• 2.The species composition changes
from time by time.
• 3. Food chains and food webs are
simple.
• 4. Biomass is small
• 5. Diversity is of lower degree
• 6. Niches are fewer and generalized
Climax community
• 1. It is final community that
develops in an area at the end of
biotic succession.
• 2. The Species are stable and species
composition does not change.
• 3. Food chains and food webs are
complex.
• 4. Biomass is high.
• 5. Diversity is of higher degree.
• 6. Niches are many and specialized

8. Attributes of community
• The attributes of a community are
classified into three main groups
A.Analytic characteristics
B.Synthetic Characteristics
C.Physiogonomic Characteristics

9. A.Analytical Characteristics
• The characteristics which can analyzed by
Qualitative or Quantitive methods.
Qualitative Method
• The characteristics which cannot be
measured.
Quantitative Method
• The characteristics which can be measured.

10. Qualitative Characteristics
i. Kind of species
ii. Stratification
(a)Overstory tree
(b)Crown
(c)Herbaceous plants
(d)Mosses and lichens
iii.Peridicity
iv. Vitality
v.Sociability

11. Quantitative Characteristics
i.Density
ii.Abundance
iii.Cover
iv.Frequency

12. Synthetic Characteristics
i. Presence
ii. Constancy
iii. Fidelity
iv. Dominance

13. Physiological Characteristics
• (a)Phanerophytes:include woody tree and shrub
• (b)Chamaeophytes:Inculde woody and semi-
wood
• (c)Hemi-cryptophytes:perennating bud are half
hidden in the surface of earth
• Cryptophytes:Bud in soil or under water.e.g
Hydrilla
• Therophytes:Annual plants,bud in plant seed

14. Plant Sampling
■ What is a sample?
• " A portion, piece, or segment that is
representative of a whole“
Why do we sample?
• it is usually impossible to measure the whole.
One big assumption...
■ That the sample is representative of the
whole.It is necessary to take enough samples
so that an accurate representation is obtained
■ It is important to avoid bias when sampling.

15. Sampling Methods
• Transects and Quadrants
Plants and Non-motile animals
• Aerial observations
Large trees and animals.

16. Transect Method
• A transect is a long rectangular sample plot.Use
to study the variation in vegetation
• Vegetation varies with the changing
enviornments
• Variations are caused by
slope,exposure,adaphicand topographical
irregularities.
• It also shows how one plant community replaced
by other.

17. Quadrats
• A quadrat is a sampling unit used for
quantative study of plant community.
• It may be rectangular or circular in shape.
• Used to measure coverage and
abundance of plants or animals
• A grid of known size is laid out and all the
organisms within each square are
counted.

19. Procedure
• Nails,cords and measuring tapes are required for making
quadrat.
• Quadrat is fixed at four points with the help of nails.
• Cords is tightly tied to four nails.At least 15-20 quadratso are
taken.
• There interval of twelve steps between each quadrat.The
size,shape and number of quadrates have been determined.
• The quadrats are distributed in random,uniform or stratified
manner.All plant species inside the quadrats are recorded.
Then number of indiviuals are counted.

20. Measurements Sampling methods
• Density
• Coverage
• Frequency
• Biomass
• Diversity

21. Density (D)
• The number of individuals per unit area
• (D)=n/A
• A=area
• n=number of individuals for species
• Eg. 10 dandelions/m²
Coverage (C)
• The proportion of ground that is occupied or area
covered by the plant species
• C = a / A
• a = the area covered by species
• A=total area

22. Frequency (f)
• The number of times a given event occurs
• Eg. the number of quadrants that contain maple trees as a ration of all the
quadrant
• f= j/k
• j= number of quadrants with specie.
• k=total number of quadrants
Biomass (B)
• Can be calculated by measuring the mass of the individuals
per unit area
• B=S W/A
• More appropriate measure than density or frequency when
• Number of individuals in hard to determine
• Photosynthesis and carbon fixation, energy and nutrient
transfer are more dependent upon biomass than the total
number of individuals.

23. Biomass Measurement methods
Fresh or wet weight
• used when organisms are alive
Dry weight
• used when the water content varies greatly
• Oven dry at 105°C to remove water
Ash-Free Weight
• Used when inorganic content varies greatly
• Oxidize at 500°C until only inorganic ash
remains

24. Diversity
• The measure of variety of an ecosystem.
• Consists of 2 components;
• The number of different species or the
richness of species in a specific area.
• The relative abundance of the individuals
of each species in a specific area