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Difficulty: EasyEcological Succession

Arrange the following ecological stages in the correct chronological sequence during primary succession on a bare rock surface, starting from the pioneer stage to the climax community.

  1. 1Crustose lichens colonising the bare rock surface
  2. 2Mosses replacing lichens as a thin soil layer accumulates
  3. 3Grasses and small herbaceous plants establishing in the soil
  4. 4Trees forming a stable climax forest community

Answer

The correct sequence starts with crustose lichens colonising the bare rock surface, followed by mosses replacing lichens as thin soil accumulates, then grasses and small herbaceous plants establishing in the soil, and concluding with trees forming a stable climax forest community.
Primary succession on bare rock begins with crustose lichens (pioneer stage) because they do not require soil. As lichens weather the rock and organic matter accumulates, mosses follow. The deepening soil then allows grasses and herbaceous plants to establish, eventually leading to a mature climax forest of trees.

Step-by-Step Solution

1
Identify the pioneer stage on bare substrate
Crustose lichens are the pioneer organisms that can colonise bare rock.
Bare rock lacks soil, requiring pioneer species that can endure harsh conditions and initiate weathering.
2
Determine the early seral stage following lichen decomposition
Mosses colonise the newly formed thin soil layer.
Lichen decay creates a shallow soil layer suitable for bryophytes like mosses.
3
Identify the intermediate seral stage of herbaceous vegetation
Grasses and herbaceous plants take root.
Accumulated organic matter from mosses forms deeper soil capable of supporting vascular plants.
4
Identify the final climax community
Trees establish a mature climax forest.
Deep, nutrient-rich soil allows woody perennials and trees to dominate the habitat long-term.

Key Concept

Primary Succession (Xerosere)
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Topics

Ecological Succession

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