Two model lakes are compared. In each, the best net primary productivity, when nothing is short, is…
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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?
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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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