The question asks to identify the statement that is NOT correct regarding mangrove forests. Let's analyze each option:

Mangrove Habitat and Soil Conditions

Option 1: Mangrove trees grow in areas with oxygen-rich soil. This statement is incorrect. Mangrove ecosystems thrive in waterlogged, anaerobic (low-oxygen) soil conditions. Their specialized root systems (like pneumatophores) are adapted to extract oxygen from the air, not from oxygen-rich soil.

Mangrove Ecological Roles

Option 2: Mangrove forests stabilise the coastline, reducing erosion. This statement is correct. The dense root systems of mangrove trees help to bind soil together and dissipate wave energy, effectively protecting coastlines from erosion and storm surges.

Mangrove Climate Tolerance

Option 3: They cannot withstand freezing temperatures. This statement is correct. Most mangrove species are found in tropical and subtropical regions and are sensitive to frost and freezing temperatures. Prolonged exposure can be lethal.

Mangrove Plant Type and Salinity

Option 4: Mangroves are salt tolerant herbs. This statement is partially correct but potentially misleading. Mangroves are indeed highly salt-tolerant plants, a crucial adaptation for their intertidal habitat. However, they are typically trees or shrubs, not primarily herbs, although some smaller species might exist. Despite this nuance, their salt tolerance is a defining characteristic.

Conclusion on Incorrect Statement

Based on the analysis, the most definitively incorrect statement is that mangrove trees grow in oxygen-rich soil. Mangrove environments are characterized by low-oxygen (anaerobic) soils.

Therefore, the statement that is NOT correct about mangrove forests is:

• Mangrove trees grow in areas with oxygen-rich soil.