Concepts of community and continuum analysis of communities

Concepts of community and continuum analysis of communities

The group of similar type of plant growing in similar climate and edaphic zone.  It is called as community and the study of community is known as synecology.  Basically, the name of the community is provided and classified on the basis of following feature:

            1)         Major structural features like: dominate species, life forms or indicates.

            2)         Physical habitat of the community.

            3)         Functional behavior of the community.

Actually, community maintains the continuity, because the edge effect and ecotone zone is the common area in between two communities.  This concept of continuity is called as continuum concept, which is determined by the gradient analysis based on so many coefficient, which are known as community coefficient.  When the communities and species are arranged according to their gradients, then this is known as ordination and the ordered arrangement of species and community is known as continuum.

Continuum and Ordination of Community

Community is the complex structure of vegetation, the main basis of its classification and name of classification and community is structure of community, because its, composed of organisms.  So according to some ecologist, the name of the community should be given on the basis of dominant, then known as pine community.  But it is suitable when only one or two species are changing, then these criteria cannot be used.  It is also proposed that the name of community should be given on the basis of eco system.  It should be meaningful and indicate the structure of community.  So, generally the stable characters of community are used.  Like for aquatic communities, stream rapids community, mud flat community and pelagic community or sand beach community.  It is well known that communities show successive changes.  So it is the interesting problem that where is the boundary of one community and from which place, second community gets started, and in the majority of cases, the communities and the species are delimited from one another and the continuity is maintained from one community to another community. 

According to Clements and Daubenmire, communities are discrete units with definite boundaries.  But according to Gleason, Curtis, Whittaker and Goodball, population indicates the response, which is independent of environmental gradient.  In this case, communities overlap with each other, and it is named as continuum.  Whittaker analysed the great smoky mountain national park and obtained the altitudinal gradient view from floor to top. Five zones are studied which are following :

            i)          Multihued cove forest

            ii)         Dark green Hemlock forest

            iii)        Dark red oak forest

            iv)        Reddish brown oak heath vegetation

            v)         Light green pine forest

We can consider the 5 zones as discrete communities, or 5 zones can be considered as single continuum.  In these communities, the response of individual species is changing according to environmental conditions.  Whittaker studied about 15 species, which are dominant trees and observed the overlapping along gradient.

To find out the continuum in the continuity, population species and community is arranged in ordered form, for which different techniques are used.

These techniques are called as ordination techniques and ordering the species, population and community is called as ordination.  So, the ecologists who are using the geographical approach observe the continuity in the communities, while ecologist working in the topographic or steep gradient uses the term zonal concept.  Continuum concept is based on the continuity of community.  Beals compared the vegetation change in a steep and gentle attitudinal gradient and clearly indicated that in the gentle gradient, the discontinuity is very less, while in the steep gradient, the discontinuity is much more.  It is studied with the help of dissimilarity indices.

Beals concluded that in steep gradient, vegetation could impose disjunctions.  Although the environment gradient is continues while in a gentle gradient indicates reverse condition.  So the three important processes are responsible for creating differentiation in community.

            a.         Competitive exclusion

            b.         Symbiosis between groups of species

          c.         Co-evolution of the groups of species.