Question

How does succession differ in terrestrial and aquatic system? Give salient features.

Answer 1

Succession in terrestrial (xerarch) and aquatic (hydrarch) systems both leads to a mesic climax community, but the starting conditions and pathways differ.

Basis of Difference	Terrestrial (Xerarch) Succession	Aquatic (Hydrarch) Succession
Habitat	Dry areas such as bare rocks, sand dunes, lava flows	Water bodies such as ponds, lakes and marshes
Progression	From xeric to mesic conditions	From hydric to mesic conditions
Pioneer organisms	Lichens and mosses	Phytoplankton and zooplankton
Main stages	Lichens → Mosses → Herbs → Shrubs → Forest	Phytoplankton → Submerged plants → Floating plants → Reed swamp → Marsh meadow → Scrub → Forest
Soil formation	Soil forms from rock weathering and organic remains	Humus from dead plants fills the water body and reduces its depth
Time taken	Usually hundreds to about 1000 years	Usually several hundred years or more, depending on silting

Salient features:

1. Both successions move towards a mesic climax community.
2. Pioneers modify the environment and make it suitable for the next stage.
3. Hydrarch succession turns a lake into land through gradual silting and humus accumulation.
4. Xerarch succession begins with rock weathering by lichens.

Terrestrial succession builds soil on rock, while aquatic succession fills water bodies with sediment and humus until land forms.