A previous study by researchers from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences has confirmed that soil phosphorous is very deficient and substantially affects the community assembly.

To further investigate the effects of soil nutrient (nitrogen and phosphorus) heterogeneity on tree species diversity, they randomly established 39 forest vegetation plots each with 400 m² (20 × 20 meters) in the Xishuangbanna tropical seasonal rainforest in southwestern China.

The researchers measured soil nutrient (N and P) availability and heterogeneity, tree species diversity, and community phylogenetic structure in each plot. They sampled 500 grams of soil from each of the four corners from the one to ten centimeters depth below the litter layer in each plot.

In the study, they found that soil phosphorus heterogeneity significantly promoted tree species diversity. Soil phosphorus heterogeneity but not the availability significantly affects tree species diversity within community although the soil phosphorus heterogeneity and availability are also correlated.

An increase in soil nitrogen availability or heterogeneity may not affect tree species diversity because it is not a limiting nutrient.

They identified a significant positive correlation between soil phosphorus heterogeneity and tree species diversity in the Xishuangbanna tropical seasonal rainforest, and further community phylogenetic analysis indicated that the trees in plots with low soil phosphorus heterogeneity were phylogenetically overdispersed, whereas those in plots with high heterogeneity were clustered.

The results indicated that soil phosphorus heterogeneity significantly affects tree diversity in the Xishuangbanna tropical seasonal rainforest, suggesting that deterministic processes are dominant in this tropical forest assembly.

The study entitled “Soil phosphorus heterogeneity promotes tree species diversity and phylogenetic clustering in a tropical seasonal rainforest” has been published in Ecology and Evolution.