Two model lakes are compared. In each, the best net primary productivity, when nothing is short, is…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Two model lakes are compared. In each, the best net primary productivity, when nothing is short, is of dry matter for each square metre in a year. The scarcest factor sets the productivity.
Lake A: light at of its best supply, nutrients at , temperature factor at .
Lake B: light at , nutrients at , temperature factor at .
- What is the productivity of Lake A?
- What is the productivity of Lake B?
- A farmer's runoff raises the nutrients of both lakes to . What is the productivity of Lake A now?
- What happens to Lake B, and why?
Need a reminder? The key ideaShow
Secondary productivity is the rate of formation of new organic matter by consumers. Primary productivity depends on the species, the environmental factors, the nutrients and the photosynthetic capacity. The scarcest factor sets the rate. For an animal, and .
The worked solution
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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. Best productivity for each square metre in a year. Supplies as listed.
Plan. Find the smallest supply, then take that share of .
Step 1. (a) Lake A: the smallest is . .
Step 2. (b) Lake B: the smallest is (the light). .
Step 3. (c) Lake A after the runoff: the supplies are , and . The smallest is . .
Step 4. (d) Lake B: the nutrients rose from to , but they were not the scarcest factor. The light, at , is still the smallest, so the productivity stays at .
Answer: ; ; ; no change, because light limits Lake B.
Watch out. Adding more of a factor that is not the scarcest does not help.
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