Question

Identify the correct sequence of seral stages in hydrarch succession.
I. Shrub stage
II. Reed swamp stage
III. Rooted submerged plant stage
IV. Phytoplankton stage
V. Free-floating plant stage
VI. Forest stage

• A. IV, III, V, II, I, VI
• B. III, V, I, VI, II, IV
• C. II, IV, III, I, V, VI
• D. IV, VI, V, III, II, I

Answer 1

The correct option is A IV, III, V, II, I, VI

Ecological succession refers to the process by which a sequence of increasingly complex communities develop over time in a given area, ultimately forming a stable climax community. This process is fairly prdictable and in accordance with the changing physical environment.
Based on the nature of the habitat, succession of plants are of two types :

• Hydrarch succession - It takes place in wetter areas and progresses towards mesic conditions (medium water conditions).
  
• Xerarch succession - It takes place in dry areas and progresses towards mesic conditions.

The sequence of communities in hydrarch succession are as follows:

1. Phytoplankton stage - Phytoplankton are the pioneeer species. The death of these organisms provide organic matter or humus to the bottom layer of soil.
   
2. Submerged stage - The water becomes shallower, and submerged rooted plants get established leading to accumulation of more organic matter.
   
3. Free-floating stage - The plants with roots and leaves floating on the surface occupy the area. The submerged plants die and decay to further contribute to humus formation. In this stage, the water becomes shallower in the periphery of the water body.
   
4. Reed swamp stage - The water continues to get shallower. It is now suitable for the emergence of amphibious plants like reed grasses. They also form humus and their tangles roots accumulate silt.
   
5. Shrub stage - Shrubs are able to tolerate sunlight and water logged condition. They transpire large amounts of water while continuing to add humus to the soil layer.
   
6. Forest stage - This is the climax stage where the soil becomes suitable for development of trees. The forest can be coniferous, deciduous or temperate.