Differences Between Secondary and Primary Succession
Primary Succession begins with bare rock with no layer of soil for plants to grow. The disturbances are volcanic eruptions with lava flows, receding glaciers, and uncovered land caused by tectonic uplift or dropping sea levels. The pioneers species are the lichens and moss that break down the rock and begin the cycle. The process is very slow, and it can take thousands of years to reach the last point of a climax community.
Secondary Succession begins with a existing layer of soil already and is mainly caused from wild fires, human destruction such as clear-cutting of a forest, extended droughts or floods, or tornados. Because of the soil already being there, it would be a faster process. The pioneers species would be the seeds sprouting in the soil that survived the disturbance or may be dropped by birds in the wind. If the climax community is a grassland or meadow, it only takes a few years or a decade. If it was a hardwood forest, it may take 100-200 years until it reach equilibrium.
A very thick layer of soil that can now support complex plants like trees. The size of plants increases, and the soil built up from all the plant life to change its depth and fertility makes life possible for the next plant community.
A biodiversity community that is stable with many varieties of animals and plants combine and equalize each other. Once achieved, it tends to continue with little changes.