Say whether each case begins a primary or a secondary succession, and give one reason…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Say whether each case begins a primary or a secondary succession, and give one reason.
- A new island is made by a volcano and its lava cools.
- A farmer leaves a field alone for twenty years.
- A forest fire burns all the trees, and the soil is left.
- A glacier melts and leaves bare rock.
- A new reservoir fills behind a dam, in a dry valley.
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.
Step 1. (a) Primary. The lava is new, with no soil and no life.
Step 2. (b) Secondary. The soil is there, with seeds in it.
Step 3. (c) Secondary. The living things are gone, but the soil is left.
Step 4. (d) Primary. The bare rock has no soil.
Step 5. (e) Primary. A newly created pond or reservoir has no earlier community in it, so a hydrarch sere begins.
Answer: (a) primary; (b) secondary; (c) secondary; (d) primary; (e) primary.
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