this presentation is about the characteristics of a community

1. A plant community (sometimes "phytocoenosis" or
"phytocenosis") is a collection or association of plant
species within a designated geographical unit, which
forms a relatively uniform patch, distinguishable from
neighboring patches of different vegetation types.
The components of each plant community are
influenced by soil type, topography, climate and
human disturbance. In many cases there are several
soil types within a given phytocoenosis.

2.  Generally, analysis of community characters is
being done for.
 (i) To record variation within and between
communities.
 (ii) For naming and classifying communities.

3.  Analytical characteristics are those features of
community which can be observed or measured
directly in each aspect. It involves measurements of
various characters in sample plots, commonly
known as quadrats.
 Measurements made in sample plots (quadrats) are
scientifically processed to reflect the characteristics
of the entire community.

4.  (i) Analytical, and
 (ii) Synthetic are studied in a community at the
same time.
 1. Analytic Characters:
 They are directly observed or measured in sample
plots.
 They include kinds and number of species,
distribution of individuals, number of individuals,
height of plants, etc.

5.  2. Synthetic Characters:
 They are derived from the measurements of analytic
characters and utilize data obtained in the analysis
of a number of stands

6.  Analytical characters are of two types:
 (i) Qualitative: They are based on no quantitative
observations, e.g., species composition and
stratification of vegetation. They are expressed only
in qualitative way.
 (ii) Quantitative: They are expressed in quantitative
terms. The major quantitative characters include
frequency, diversity, cover, biomass, leaf size,
abundance, dominance, etc.

7.  Stratification:
 Both the light and growth forms of the plants emphasize
height. A plant community conveys differences in the
heights, or stratification of the components.
 Trees are generally taller than shrubs which are usually
taller than herbs and the later taller than mosses and
lichens.
 Tropical forests are characterized by a marked vertical
stratification.
 Stratification results in an upper strata or canopy
receiving more solar energy and in instance of dense
foliage, little sunlight reaches ground, reducing
photosynthesis and plant growth at that level.

8.  Stratification is also seen in the underground plant parts,
that is the root and the rhizome system.
 Root system of the different plants tap moisture and
nutrient from different soil depths. This enables them to
avoid competition and too much exploitation of a
particular soil layer.
 Aquatic ecosystem also involved marked stratification.
In the lake ecosystem light penetration, temperature and
availability of oxygen vary with the depth of the water.
 In terms of availability of light water body is divided in
two zones.
 A) upper lighted zone dominated by phytoplanktons,
maximum photosynthetic zone
 B) lower zone where decomposition is most active.

9.  Vitality and vigour:
 Vitality is related to the conditions of a plant and its
capacity to complete its life cycle. While the vigour
refers more specifically to the health or development
within a certain age.
 The criteria used in determining the vigour may be rate
and total amount of growth especially in height.
 Rapidity of growth renewal in spring or following
mowing or grazing.
 Area of foliage, colour and turgidity of leaves and stem.
 Degree of damage caused by disease or insects.
 Time of appearance and no. and height of flower stalks.
 Rate of growth and extent of root system.
 Apperance and development of new stems and leaves.

10.  Periodicity:
 it refers to the study of the seasonal changes in the
community.
 It is strong fixed character in plants.
 Different plants have different periods of seed
germination, vegetative growth, flowering and fruiting,
leaf fall, seed and fruit dispersal.
 A study of date and time of these events is called
phenology.
 Phenology is the calendar of events in the life history of
a plant. which may differ from species to species in a
community.
 Phenological changes gives a definite look to a
community.
 The appearance of community as a whole at different
seasons is called aspection.

11.  It is the assessment of characters from their outer
appearances. The general appearance of vegetation
can be determined by growth form of dominant
species.
 On basis of appearance it may be defined as
grassland, forest etc.

12.  It refers to the nature of grouping of individual
plants, that whether they grow singly, in patches, in
colonies or evenly intermixed.
 It expresses the degree of association between
species.

13.  the form and structure of terrestrial communities
are determined by the nature of vegetation .
Vegetation may be classified according to the
growth form. The most widely used vascular plant
life form classification system was formulated by C.
Raunkiaer.
 This system identifies life- forms based on a single
criterion, that is the location of the perrenating buds
(shoot apical meristem) with respect to the ground
level.

14.  Five major life-forms are recognized.
 A) phanerophytes: have bud bearing shoots in air,
higher than 0.5 m from ground eg, tall trees and tall
shrubs.
 B) Chamaephyte: buds above the soil, less than 0.5
m high, eg, small shrubs and herbs.
 C) Hemicryptophyte: renewal buds locatd at ground
level, eg prostate shrubs and herbs that die back
each year.
 D) Cryptophyte: location of perennating tissue in
the soil, eg, rhizomatous grasses and bulb forming
herbs.
 E) Therophytes: have embryonic apical meristem
protected by seed coat. eg, Annuals.

15.  Frequency:
 This is based on percentage of sample plots in
which a species is present, indicating its
dispersion in space.
 Frequency percentage = number of sampling
units in which that species occurred / number
of sampling units studied Χ 100

16.  Diversity:
 This is denoted by number of individuals per
unit area, indicating the relative abundance of a
species.
 Cover and Basal Area:
 This is percentage land area occupied by a
species, indicating the influence zone of a
species. Although sometimes used in general
sense for the area occupied by a plant, (which
may be the herbage cover or the cover of basal
area), it is generally used for above ground
parts.

17.  Biomass:
 This expresses quantity of living materials per unit
area, indicating the growth of a species. Thus,
biomass is the standing crop expressed in terms of
weight (i.e., organism mass) of the living matter
present.
 The amount of living material, present in a
component population at any time, is known as the
standing crop, which may be expressed in terms of
weight per unit area.

18.  Leaf Area:
 The percentages of species having different leaf
sizes, indicating the adaptation of the vegetation to
the prevailing environment.
 As the leaves are essential part and are very much
affected by climate condition, their shapes and sizes
have been taken as important criteria in
determination of quantitative characters.

19.  Density:
 Density represents the numerical strength of a
species in the community. The number of
individuals of that species in any unit area is its
density. This gives an idea of degree of competition.
 Density = Number of individuals of the species in
all the sampling unit/Total number of sampling units
studied
 The value thus obtained is then expressed as number
of individuals per unit area.

20.  Abundance:
 This is the number of individuals of any species per
sampling unit of occurrence.
 It is calculated as follows: Abundance =Total
number of individuals of the species in all the
sampling units/Number of sampling units studied

21.  These are determined after computing the data on
the quantitative and quantitative characters of the
community.
 For comparing the vegetation of different areas,
community comparison needs the calculation of
their synthetic characters. These are determined in
terms of presence and Constance, fidelity, etc.

22.  Presence and Constance:
 It expresses the extent of occurrence of the
individuals of a particular species in the community.
 Fidelity:
 This is the degree with which a species is restricted
in distribution to one kind of community. Such
species are sometimes known as indicators.