A scientist measures a community at three stages of a succession…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A scientist measures a community at three stages of a succession. The gross primary productivity and the plant respiration are in for each square metre in a year. Pioneer stage: GPP , respiration . Middle stage: GPP , respiration . Climax: GPP , respiration .
- What is the net primary productivity at each stage?
- What is the ratio of the gross production to the respiration (P over R) at the climax? Give the answer to two decimals.
- Which stage has the largest NPP, and why does the climax have so little?
Need a reminder? The key ideaShow
Succession is a gradual and fairly predictable change in the species composition of an area. It begins with pioneer species and ends in a stable climax community. Primary succession starts without soil. Secondary succession starts where soil is left, so it is faster. The mean waiting time in a stage is divided by its chance of moving on.
The worked solution
Have you tried it?
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. GPP and respiration at three stages.
Plan. Subtract for the NPP. Divide for the ratio.
Step 1. (a) Pioneer: . Middle: . Climax: .
Step 2. (b) .
Step 3. (c) The middle stage has the largest NPP. The climax community is large, so it respires almost all that it produces. The P over R ratio is near , and little is left as net production.
Answer: , , ; ; the middle stage, because the large climax community uses nearly all its production in respiration.
Check. The ratio falls from to to along the sere.
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