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Why does secondary succession usually begin faster than primary succession?

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Diagram showing energy flow in a food chain from a tree to a caterpillar, then to a bird, and finally to microbes, with red arrows illustrating energy transfer and heat loss at each stage. — community ecology Energy transfer and heat loss along a food chain.

Secondary succession typically proceeds faster than primary succession because it occurs in environments where a biological community previously existed and was not completely destroyed.123

Unlike primary succession, which begins in essentially lifeless areas—such as bare rock, lava flows, or glacial retreats—where soil must first be created, secondary succession takes place in areas where the soil remains intact. This soil often retains essential nutrients and a soil seed bank, which acts as a reservoir of dormant seeds and biological remnants.2341567

Because these biological "legacies" are already present, plants can begin to sprout and recolonize the habitat shortly after a disturbance passes. In contrast, primary succession requires a much longer initial phase where pioneer species, such as lichens, must first colonize barren surfaces and slowly contribute to the formation of soil before more complex life can establish itself.1654