There are four major structural and functional attributes of ecological succession, which are as follows:
1. There is an increase in structural complexity or the kinds of animals and plants change continuously with succession, no matter what is their taxonomic group.
2. The diversity of species tends to increase with succession. Increase in diversity of heterotrophs is especially striking. The variety of microbes and heterotrophic plants and animals is likely to be much greater in the later stages of succession than in the early stages. Maximum diversity of autotrophs in many ecosystems seems to be reached earlier in succession.
3. Biomass and standing crop of organic matter increase with succession. According to Odum, the increase in amount of, and the change in, organic structure are two of the main factors bringing about the succession of species. The enlargement of organic structure is, of course, related in a cause-and -effect manner to the increase in species diversity. As biomass increases, stratification and zonation create many new habitat niches such as litter, humus, bark and dead wood in a forest.
4. Species, biomass, and the P/R ratio (the ratio of gross production of the community to total respiration of the community, i.e., the respiration of both animals and plants) continue to change long after the maximum gross primary production possible for the site has been achieved. Thus, a decrease in net community production and a corresponding increase in community respiration are two of the most striking and important trends in succession. As indicated in Table 4.2, gross production may be expected to increase in the early stages of primary succession, with little or no change in later stages or in secondary succession.