(1) Primary succession: The succession process which starts in those base areas where there was no vegetation and animals earlier, is called primary succession. Such sites may be fresh lava flows, volcanic ash plains, newly formed sand dunes of flood plains, etc. it takes a very long period for the development of proper soil and arrival of pioneer vegetation communities. Slowly a vegetation community begins to develop passing through the seral stages such as herb community, scrub community, forest community or preclimax and finally climax community (climatic climax) . The vegetation supporting it is called climax vegetation. In the intervening stages all those rules of evolution such as intra and inter-specific competition, survival of fittest, natural selection, invasion of new plant and animal species, changes brought in by external forces etc work in full force.
(2) Secondary succession: It refers to development of sequence of vegetation in those areas which had vegetation cover earlier but now have been rendered nude due to destruction of vegetation, either partly or completely, through either natural or manmade process e.g. Development of new forest on an abandoned land after shifting cultivation or jhum.
Ecosystem goods and Services / Ecological Services
Ecosystems provide many goods and services that are of vital importance for functioning of the biosphere, and provide basis for the delivery of tangible benefits to human society. These ecological services or benefits can be divided into following categories:
(1) Supporting services:
