Question

20) Describe what alternative stable states are in the context of community succession. 

21) Why is it important to know how much primary production occurs in an ecosystem?

Answer 1

20) The theory of alternate stable state predicts that the ecosystem can exists under multiple states. where alternate stable state occurs, the selected set of variables will persist in one of a number of different possible configuration or at different equilibrium points that are locally stable. the community return to the same configuration after a small perturbation, but may shift to a different configuration or equilibrium after a large perturbation. because these shifts can represent catastrophic changes to the community, failure to predict the existence of these alternate states.

the current condition of an ecology system is its state. it is possible for them to occupy more than one state for a given set of environmental condition. alternate stable state are stable when they are maintained following further small perturbations.

examples of alternate stable state includes 1.the collapse of fisheries owing to food web interaction and harvesting and the shift from healthy coral reefs community to macro algae in marine environment,2. In the serengeti, there are shift between woodlands and herbaceous plants regulated by elephant activity and their pests, 3.shift between clear and turbid water states in ponds and lakes

21) The Primary Production is the rate at which biomass produced per unit area by the primary producer (both photoautotrophs and chemoautotrophs). the term 'primary' indicates that we are concerned with the first trophic level in the ecosystem. it can be expressed as grams of carbon assimilated or dry weight of organic matter or their energy equivalents. not all the primary productivity results from photoautotrophs,some primary productivity also occurs through chemoautotrophs.

the total rate of photosynthesis, including the biomass used up in respiration during the period of measurement is reffered as gross primary productivity(GPP).

the rate of storage of biomass in plant that exceeds the respiratory use by the plants during the period of measurement is net primary productivity(NPP). this is also termed net assimilation.

NPP = GPP - Respiration(R)

Primary productivity is usually measured as a rate of formation of biomass per unit area.methods to measure primary productivity vary as a function of the types of autotrophs in an ecosystem are:- Harvest method, Oxygen measurement method, Radioactive tracer method.

primary productivity measurement is important because it is the process that forms the foundation of food webs in most ecosystem. on land it is driven by temperature and availability of water and nutrients modified by land use. in aquatic ecosystem, it is driven by the availability of nutrients and light and to a lesser extent by temperature and other factors.