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Question

Difficulty: MediumEcological Succession

Arrange the following plant community stages in the correct chronological sequence of primary ecological succession occurring in a freshwater pond (hydrosere), from the initial pioneer stage to the mature climax community.

  1. 1Rooted submerged vegetation stage (e.g., Hydrilla and Vallisneria)
  2. 2Rooted floating-leaved plant stage (e.g., Nymphaea and Lotus)
  3. 3Reed-swamp / emergent plant stage (e.g., Typha and Phragmites)
  4. 4Sedge-meadow and marsh-shrub stage (e.g., Carex and Juncus)
  5. 5Climax woodland community (e.g., mesophytic trees)

Answer

The correct chronological sequence of hydrosere primary succession is: Rooted submerged vegetation stage → Rooted floating-leaved plant stage → Reed-swamp / emergent plant stage → Sedge-meadow and marsh-shrub stage → Climax woodland community.
Primary ecological succession in a freshwater pond (hydrosere) begins with submerged pioneer plants that deposit organic sediment on the pond bed. As water depth decreases, floating-leaved plants establish and shade out submerged species. Further siltation enables tall emergent reed-swamp plants to colonize, which trap more silt until the water gives way to saturated soil dominated by sedges and shrubs. Eventually, dry nutrient-rich soil forms, allowing a stable climax woodland community of trees to take over.

Step-by-Step Solution

1
Identify the pioneer submerged aquatic stage
Rooted submerged plants colonize bare muddy sediment in deep water.
Submerged pioneers require deep water cover and light penetrating to the pond bed to start organic matter deposition.
2
Determine the shift to floating-leaved vegetation
Accumulated mud reduces water depth, allowing rooted floating-leaved species to dominate.
Broad floating leaves cut off light to submerged plants, causing them to decay and rapidly build up the substrate.
3
Trace the emergence of amphibious reed-swamp plants
Water becomes shallow enough (1–2 metres) for tall emergent species with aerial stems to anchor.
Dense emergent roots trap airborne dust and silt, accelerating the drying out of the water body.
4
Follow the transition to marshy terrestrial land
Saturated soil replaces open water, supporting sedges, grasses, and tolerant shrubs.
Evapotranspiration and organic deposition eliminate standing water, transforming the habitat into wet land.
5
Identify the final climax community stage
Thick, fertile terrestrial soil forms, enabling tall climax trees to establish.
Woodland trees represent the stable, self-sustaining climax community in equilibrium with the regional climate.

Key Concept

Hydrosere Primary Succession
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Topics

Ecological Succession

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