Explain how gross, net, primary and secondary productivity change across successional stages after respiratory and transfer losses.
Explain how the process of succession leads to changes in productivity.
General:
a. GPP continues to increase throughout the successional stages due to increasing nutrient cycling / improved soil fertility/nutrients leads to greater productivity;
b. NP as a proportion of GP decreases throughout the stages due to increasing respiration from consumers/decomposers;
In primary succession/pioneer community:
c. Abiotic conditions are poor/nutrient levels are low so GPP is low;
d. NP of the community is high/NP as a proportion of the GP is high due to low consumption/respiration;
In intermediate stages:
e. Secondary productivity increases as consumers join food chain;
f. NP/increase in biomass of entire community slows due to consumption of GPP/increased respiratory losses by consumers;
In climax community/final stages
g. Secondary productivity is at maximum as food chains are fully developed;
h. GPP is at maximum due to plant communities reaching carrying capacity;
i. No NP/biomass gains for community as a whole as all PP being consumed/lost to respiration;