Forests contain a large fraction of the Earth’s biodiversity. But to what extent does the species composition of forests change over time, and to what extent is it stable? To address this question, we analysed data from 12 long-term Center for Tropical Forest Science plots around the world. Together, these plots contain over 2 million individual trees and over 4000 tree species and have been monitored for periods of 6 to 28 years. We found that forest communities are far from stable over time: the data are consistent with the hypothesis that environmental variables, such as climate, are causing strong fluctuations in tree species abundances at all 12 of our sites over time. This poses challenges to existing theories of biodiversity, which are based largely on notions of stability and demographic variance, and points the way to new theories that will give a more adequate explanation of forest dynamics.

The paper can be accessed here.