種多様性
This hypothesis states that diversity increases with increasing rainfall, however the correlation between rainfall and plant diversity varies from region to region. The consistency of rainfall seems to correlate more with species richness than total annual rainfall. Species diversity appears to level off when annual rainfall reaches about 4,000mm, however this could be due to sampling limitations. Rainfall and soil richness affect productivity trends which are also believed to affect diversity. A mid elevation peak is usually seen in mean annual rainfall.