SUNDAY, 15 AUGUST 2010
Two recent studies of tropical tree communities in Panama have addressed this issue. By measuring survival close to trees of the same and different species, Comita and coworkers confirm in Science  that seedlings were much more likely to die when they grow close to neighbouring trees of their own species. A second study, published by Mangan and colleagues in Nature  showed that soil-dwelling organisms were responsible for the differences in mortality. Both studies found that the strength of the negative feedback constraints varied for different species, but unexpectedly, it was the rare species in the community that were most susceptible. This means that the relative abundances observed today are the result and not the cause of the negative feedback, with susceptibility to soil biota emerging as a major force in determining relative species abundance. Furthermore, the reports demonstrated that the strength of the feedback is sufficient to have a community-wide effect. This has important implications for conservation efforts, where an understanding of the mechanisms that control species abundances are essential, particularly because the rarest species have the least ability to regenerate.
Written by Robert Jones
- L. S. Comita et al., “Asymmetric Density Dependence Shapes Species Abundances in a Tropical Tree Community,” Science 329, no. 5989 (2010): 330-332.
- Scott A. Mangan et al., “Negative plant–soil feedback predicts tree-species relative abundance in a tropical forest,” Nature 466, no. 7307 (2010): 752-755.