In 2009 and 2010, the joint Sino-German-Swiss Research Unit BEF-China has established a large-scale forest Biodiversity-Ecosystem Functioning experiment in subtropical forests at Xingangshan (Jiangxi Province, China). The overall aim of BEF-China is to relate functions and services of a forest ecosystem to the biodiversity of tree and shrub species, as well as to study the interactions with other trophic strata (herb layer, soil macrofauna, herbivores, decomposers, mycorrhiza, soil microorganisms) and with abiotic variables (soil properties, topography).
In total, 566 plots of 400 trees each, ranging in diversity form monocultures to 24-species mixtures were established. The experiment used 42 native tree species and 10 shrub species, combined into different pools. Overall, the area covered by the experimental sites is about 50 ha. The BEF-China project employs a novel design using nested species compositions representing replicated random and non-random extinction scenarios and a two-way factorial combination of tree x shrub species richness gradients. Experimental sites have been complemented by “comparative study plots” in a nearby forest nature reserve with natural assemblages of trees species that have been included in the experiment.
Results/Conclusions
The high establishment success of tree and shrub seedlings in the experimental plots of BEF-China demonstrates the feasibility of planting large-scale diverse forest stands in the subtropics, even with many species which have not been cultivated in plantations before. Seedling mortality did vary among species, with deciduous species having higher survival rates than evergreen species. Survival rates were also significantly affected by tree species richness at planting, indicating that, already at the very early stages of a biodiversity experiment, diversity effects cannot be ruled out.
The first results on tree growth patterns showed strongly species-specific responses. Moreover, we found that in general the top soil under faster-growing species held more microbial biomass than under slower-growing species. Aboveground herbivory also varied strongly among tree species, but was independent of tree species richness. Invasion resistance of understory vegetation at the early stages of plot establishment was more strongly correlated with abiotic variables than with tree diversity. We hypothesize that the ecosystem functions of our experimental plots which are now dominated by species-specific effects and abiotic variables will increasingly be influenced by diversity effects and biotic interactions. However, already at the earliest stages such effects are visible.