The 20-ha tropical forest dynamics plot in Xishuangbanna of Xishuangbanna Tropical Botanical Garden (XTBG) is part of a global network coordinatedby the Center for Tropical Forest Science/Smithsonian Institution Global Earth Observatories (CTFS/SIGEO) (http://www.sigeo.si.edu/) and currently the only one in tropical China. This global network conducts analyses of forest structure, composition and diversity at fine spatial scales. The network has a new paper exploring the relationship between tree species richness and forest biodiversity and function published in Journal of Ecology.
By taking advantage of the globally distributed network of permanent forest plots (SIGEO),Ryan A. Chisholm and his coauthors (including CAO Min of XTBG)conducted an analysis of relationships between tree species richness, biomass and productivity in 25 forest plots of area 8–50 ha from across the world. They utilized a global data set of large-scale forest plots to investigate how the relationship of tree species richness to forest biomass and productivity varied across a range of spatial grains within sites and to test whether the observed patterns were general across sites.
They predicted that richness and function (the latter measured by productivity and biomass) would be positively related at most sites and that productivity would be strongly positively related to biomass at all sites. They also predicted that successional processes associated with treefall gaps might lead to negative relationships at small spatial grains at some sites, because areas that have recently been in gaps typically have many small stems, high species richness and low biomass, while areas with mature trees have fewer, larger stems, lower species richness and higher biomass.
The study found that at the smallest spatial grain (0.04 ha), productivity and biomass were both positively related to species richness within most forest plots. At the larger spatial grains (0.25 and 1 ha) were qualitatively different: relationships between richness and productivity were weak and often negative.
Their results highlighted the fundamental role of scale in determining the observed relationship between species richness and ecosystem function in forests. Their study showed that the relationship of tree species richness with biomass and productivity changed qualitatively when moving from scales typical of forest surveys (0.04 ha) to slightly larger scales (0.25 and 1 ha). The researchers proposed it be recognized in forest conservation policy and management.