this presentation deals with the plant biodiversity. the different prospectives of occurence of plant species. how plant compete with each other to derive nutrition and for their survival. defines the growth pattern as well as qualitative and quantitative characters of a pant community.

1. PLANT
COMMUNITY
Saloni sharma (M.sc botany)
specializing in plant science and
microbial biotechnology

2. INTRODUCTION
– COMMUNITY is defined as an assemblage of a number of organisms usually of different
species which occupies the same habitat. eg.. Forest, etc.
– Community essentially is biotic as plants, animals & micro organisms all interact.
– Concept of community is given by FORBES in 1844 as “ regions distinguished from each
other by the association of species.
– MOBIUS in 1877 recognised the ‘biotic nature of communities’.
– R.H WHITTAKER (1970) has defined community as “ functional system of interacting, niche-
differentiated species and community structure.
– Niches differentiation of the species, species diversity and differentiation in space and time
enable a large no. of plants to exist in a community and utilize the resources for their
benefits.

3. – Community is a larger unit than the population and it acquires many
characteristics that are not found in its constituents.
– Minor communities are greatly influenced by the input from the adjacent
community while major community are relatively interdependent and self
sufficient on their habitat.
– Communities differ from place to place and at the same place at different
times.
– The biological potentiality of each species determines a tolerance range
towards environmental conditions in which the species can easily grow.
– The range of environment that a taxa can tolerate is called as “ECOLOGICAL
AMPLITUDE”.

4. Biotic community is an arrangement of
organisms and not a group of organisms. The
organisms have certain food or tropic
relationship among themselves.
Communities merge with each other in
adjacent areas sometimes sharply and
sometimes gradually. In most cases,
biological activites in plants are remarkably
interwoven with animal activities and vice
versa.

5. Plant and animal aggregations organizing into community are
strongly dependent upon habitat characters and other
conditons of the environment. eg. In pond abundance of
overlaying water determines the region where community of
NYMPHEA, SALVINIA,AZOLLA, etc.. are well developed.
In a broadly similar environment, different components of a
community occupy different zones, strata or layers to suit their
ecological requirements.
Each individuals has a different way of life and may have a
different role to play in the community.
The way of life and the role of each species is referred as its “
NICHES”.

6. – The vertical distribution of different species occupying different levels
is called as “STRATIFICATION”.
– These layers may often bring together vary different from life
forms.e.g ..a tree and a climber may both be represented in the top
layers.
– Several times communities may merge into each other, the boundry
between the two types of communities is quite sharp while in some
cases with gradual differences in community structure boundries are
less defining.
– The zone of vegetation which democrats the transition of one type of
community into another k/a “ECOTONE”.

7. Other ecological concept regarding community character Is
that it is dynamic and it changes in form and compositon in
the course of time .This is called as “ECOLOGICAL
SUCCESSION”. The study of plant community is done
through samples of small unit areas and through this the
entire community structure picture is developed.

8. Community unit concept :-
Each community is an integral unit with definite boundry. It consist of evolved
species with similar distribution along environmental gradient.
CLEMETS has compared community with organisms it arises, grows matures
and dies.
Continum concept :-
CURTIS and McINTOSH & WHITTAKER (1956) have shown that vegetation is in
continuum with a changing species composition along environmental gradient.
Eg..within broadly defined habitats as FORESTS,GRASSLAND SPECIES
POPULATION replaces one another continuously along gradient of physical
conditons.
SPECIES RATHER THAN COMMUNTY IS THE BASIC UNIT OF VEGETATION.

9. SYNTHETIC APPROACH
It is synthesis of two classical views.
SPECIES INTERDEPENDENCE occurs.
Positve interaction among species. Eg.. MUTUALISM
KEYSTONE SPECIES is a species that is of demonstrable importance for
ecosystem functioning.
Keystone species are not dominant, their no. is low but their control over
community is high.

10. THANKING
YOU