How to Distinguish Between Primary and Secondary Succession
- 1). Find out the steps of the succession chain in the area where you are working. In the Green Mountains of Vermont, for example, lichen are the first species to colonize bare rock. They are eventually displaced by moss and herbs, which are then displaced by grasses. Sun-loving trees such as poplars then displace grass. Shade-loving maples eventually displace the poplars and are characteristic of the area's climax community.
- 2). Walk your site and dig your fingers into the ground. Is the ground primarily composed of bare rock, such as that left behind after a volcanic eruption or retreating glacier? If so, you are on a site where primary succession is taking place. Unless the rock was formed or exposed very recently, you will probably see lichen covering some of it. If the ground contains soil (even if that soil is very thin or sparse), you may be witnessing either primary or secondary succession.
- 3). Look for vegetation other than lichen, moss, and herbs. If you find such vegetation, you are witnessing secondary succession unless the site is very new and has never been disturbed by humans. Confirm your conclusion by researching the history of the site.
If you do not find such vegetation, further investigation is needed. - 4). Look for downed or rotting vegetation characteristic of communities farther along the succession chain, such as fallen trees or dried grass. In a heavily disturbed area be sure to look carefully, as these signs may be hard to find (such as the remnants of old tree roots sticking out of ground that has been heavily grazed).
If you find these signs, you are witnessing secondary succession. The fallen or rotting plants were formerly dominant here and will eventually reassert that dominance as succession proceeds. If you find no such signs, further investigation is needed. - 5). Find the edge of your disturbed patch of ground and evaluate the adjacent biological community. If it is two or more steps farther along the succession chain than your evaluation patch, your disturbed area is almost certainly undergoing secondary succession. In all likelihood, a recent event such as a wildfire or human activity produced the disturbed ground you are evaluating.
If the adjacent community is only one succession step farther along, or if your disturbed patch of ground is exceptionally large, you may not be able to evaluate the site in person. - 6). Research the history of your disturbed patch to determine whether the bedrock formed recently. If so, the site is undergoing primary succession. If not, it is undergoing secondary succession.
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