Question

In plant succession, when the climax is reached the net productivity
(a) Continues to increase
(b) Becomes halved
(c) Becomes stable
(d) Becomes zero
(e) Becomes $10\%$

Answer 1

According to classical ecological theory, succession stops when the series has arrived at an equilibrium or steady-state with the physical and biotic environment. Barring major disturbances, it will persist indefinitely

Complete answer:
The climax community remains stable as long as the environment remains unchanged. So, on reaching climax, the net productivity becomes stable. Ecological succession is the appearance and disappearance of communities in regular succession in a particular area until a final stable community emerges. In other words, it is a natural phenomenon by which an area or locality gets successively colonized by different communities until a stable final community is established. So, ecological succession essentially involves an orderly and successive replacement of communities in an area over a period of time, until the final community appears. Every community first gets established in an area and then modifies the environment. The modified environment becomes less suitable for it. So, the community finally disappears, making way for the appearance of another community. The regular and orderly repetition of this process results in ecological succession.

Additional Information:
- Ecological succession involves an orderly process, with directional and predictable changes in the community.
- These changes usually result from the modification of the abiotic environment by the biotic community and they culminate in the establishment of an almost stable community.
- Some of the changes are a progressive increase in the biomass or the organic content of the community, Steady increase in the nutrient conservation and decrease in nutrient loss, Increased incorporation of the nutrient with organisms, Progressive dominance of the decomposer component of the community, changes in the species composition with a progressive increase in the number of species in the community, etc.
So, the correct answer is '(c) Becomes stable'.

Note: During the initial stage, if a succession, biomass, species diversity, and species richness are relatively low, the nutrient source is largely extra-biotic, productivity is greater than respiration, the ratio between gross production and biomass is high, energy is channeled only through a few pathways, and species appear and disappear in regular succession from time to time.
- Gradually, slow and steady changes take place in species composition. Some species having wider tolerance will persist over a long period of time, forming a continuum from one stage to the next.
- During the mature final phase of succession, biomass, species diversity and species abundance become high, nutrient sources are largely biotic or organic, gross production is almost equal to respiration, the ratio between gross production and biomass is low, energy is channeled through many different pathways, and the succession of species stops establishing a stable final community.