Barrons AP Environmental Science

(Marvins-Underground-K-12) #1

  1. (B) In primary succession, which occurs in virtually a lifeless area (e.g., area
    below a retreating glacier), pioneer species like lichen, algae, and fungus, as
    well as other abiotic factors like wind and water, start to change or create
    conditions better suited for vascular plant growth. These changes include
    accumulation of organic matter in the litter or humic layer, alteration of soil
    nutrients, and change in pH or water content of soil. These pioneer plants
    are then dominated and often replaced by plants better adapted to less
    austere conditions, such as grasses and shrubs that are able to live in thin,
    mineral-based soils. The structure of the plants themselves can also alter the
    community. For example, when larger species like trees mature, they
    produce shade on the developing forest floor, which tends to exclude light-
    requiring species allowing shade-tolerant species to invade the area.

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