Which of the following statement is INCORRECT ?

Options

A. The pioneer community in hydrosere are phytoplanktons.
B. The climax community remains stable even if environment changes
C. Both hydrarch and xerarch successions lead to mesic conditions.
D. As succession proceeds, the number and type of animals and decomposers changes.

Answer

To determine which statement is incorrect, let's analyze each option step by step:

1. **Option 1: The pioneer community in hydrosere are phytoplankton.**
- This statement is **correct**. In a hydrosere (a type of ecological succession that occurs in aquatic environments), phytoplankton are indeed considered the pioneer community. They are the first organisms to colonize the water body and play a crucial role in the ecosystem.

2. **Option 2: The climax community remains stable even if the environment changes.**
- This statement is **incorrect**. The climax community represents the final stage of ecological succession and is typically stable, but it can become unstable if there are significant changes in the environment, such as natural disasters or human activities. Therefore, this option is the one that does not hold true.

3. **Option 3: Both hydrarch and xerarch conditions lead to the climax community.**
- This statement is **correct**. Both hydrarch (aquatic to terrestrial succession) and xerarch (succession in dry environments) can lead to the formation of a climax community, which is characterized by a stable ecosystem.

4. **Option 4: As succession proceeds, the number and type of animals and decomposers change.**
- This statement is **correct**. During ecological succession, as the vegetation changes, it affects the habitat and resources available, leading to changes in the number and types of animals and decomposers present in the ecosystem.

Based on the analysis, the **incorrect statement** is option 2.

### Summary of the Solution:
- The incorrect statement is: **"The climax community remains stable even if the environment changes."**