Question

Difference between primary productivity and standing crop in ecology

Answer 1

Quantitative measurements of photosynthesis (by carbon—14) and chlorophyll were made for algal mats which had developed at a series of stations along the thermal gradient formed by the outflow channel of a hot spring at Yellowstone National Park. The temperature range studied was from 30°—70°. Comparisons were made of photosynthetic efficiency, which had been measured and calculated in different ways. There was no simple correlation between standing crop (as measured by chlorophyll, protein or RNA per unit area) and photosynthesis. Animal grazers on the algal mats occur only at temperatures below 50°; the low standing crop at the lower temperatures may be due to the comsumption of algae and bacteria by these animals. At a temperature of 58oC, very thick mats are found, composed mostly of filamentous bacteria with a surface layer of algae. It is suggested that the organic carbon originating from the algae is assimilated by these bacteria and is not released because of the absence of grazers. At temperatures close to the upper limit for algal growth, standing crop is low although photosynthetic efficiency is high, and the algae are optimally adapted to the temperatures at which they are living. Some physiological factor other than photosynthesis may limit the growth of algae at these highest temperatures. The value of hot springs as models to study aspects of ecosystem trophodynamics is shown by this work.





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Answer 2

How much of the sun's energy is available to and assimilated by plants, and how is that measured?

How are gross production, net production, and ecosystem production related? 

How are standing crop, turnover rate, and net primary production related? 

What types of ecosystems have the highest rates of production, and which make the biggest contributions to worldwide primary production? 

What factors limit the amount of primary production locally and worldwide? 

What is the efficiency with which energy is converted from trophic level to trophic level? 

What are the differences between assimilation efficiency, net production efficiency, and ecological efficiency? 

How do ecosystems differ in the amount of biomass or number of organisms present at any point in time, and generated over time, at each trophic level

How much energy is available to humans, how much do we use, and is that amount sustainable