A volcanic eruption deposits a thick layer of lava over a coastal woodland, destroying all existing vegetation and organic soil. Over several centuries, lichens colonize the cooled basalt rock, followed sequentially by mosses, ferns, shrubs, and ultimately a climax rainforest. Which of the following best explains why succession on this lava substrate takes significantly longer to reach a climax community than succession on abandoned agricultural land?
- The bare lava lacks pre-existing soil and seed banks, requiring prolonged weathering and humus buildup before vascular plants can establish.Cevap
- BAbandoned agricultural land undergoes primary succession, which requires pioneer lichens to first decompose residual crop waste before herbaceous plants appear.
- CPioneer mosses colonizing the lava substrate lack vascular tissues, preventing them from accumulating organic matter or contributing to soil formation.
- DSecondary succession on agricultural land skips pioneer and seral stages completely because climax forest seeds are already fully grown in the soil.
Cevap
Primary succession on bare lava requires the initial formation of soil through weathering and organic accumulation, whereas secondary succession on abandoned agricultural land starts with pre-existing soil.
Primary succession occurs on newly formed, soil-less surfaces such as lava flows or exposed rock. The process takes a long time because pioneer species like lichens must weather the rock substrate and produce organic humus to form topsoil before vascular herbs, shrubs, and climax trees can establish.
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Primary versus Secondary Ecological Succession