Coarse woody detritus (CWD) is a critical component of forested ecosystems where it provides a multitude of ecosystem services. However, decomposition of woody detritus in forest ecosystems is often ignored. 

Prof. TANG Jianwei and his students of Xihsuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences conducted a three-year (from 2006-2008) study to characterize the contribution of woody detritus to carbon fluxes and nutrient cycling in Xishuangbanna tropical seasonal rainforests of southwest China.

They studied decomposition of three types of woody detritus in their original decay position to capture the contribution of these factors (position they were originally input into the system). 

The researchers sampled woody material from fallen trees, fallen large branches and snags to test the effects of physical position and nutrient concentrations on decay rates.  

They measured heterotrophic respiration rate, mass loss, and nutrient dynamics for three years from 2006 to 2008 for woody material from logs and large branches on the ground, as well as standing snags. 

They found that decay position significantly influenced the rate of decomposition for woody detritus in dry tropical rainforests of Xishuangbanna, SW China. They also observed seasonal variation in CO₂ flux for all three woody detritus types. 

The decay rate of fallen trees was larger than the other two materials. Water availability had a strong influence on the respiration rate of ground materials in rainy season, but the respiration of standing dead trees was not suppressed, at least for the first two years. Decrease of carbon concentration was observed for all the three materials at the late stage. 

There were large differences of P concentration and the ration of C and P among the materials, but their value became similar after three years.

The researchers thus concluded that phosphorus, not nitrogen, was the limiting element for wood decomposition in Xishuangbanna tropical seasonal rainforests.