Global change profoundly influences the primary productivity of forest ecosystem and consequently alters the above- and belowground litter inputs to soils. Thus, shifts in plant litter inputs can directly or indirectly affect the biotic and abiotic drivers of soil methane (CH₄) oxidation, and ultimately may have a long-lasting effect on the CH₄ sink strength of forests.  

In recent years, the effects of changes in above- and belowground plant litter on CH₄ uptake have been extensively studied. However, the underlying mechanism of the CH₄ sinks in a changing climate remains uncertain. 

Supervised by Prof. CHENG Xiaoli, WU Junjun, a research assistant of Wuhan Botanical Garden, conducted a detritus input and removal treatment in a coniferous forest ecosystem in subtropical China to investigate the response of soil net CH₄ uptake rates to litter input change. 

The net CH₄ uptake rate responded differently to the shifts in above- and belowground litter input. Treatments involved in aboveground litter removal significantly decreased the net CH₄ uptake rate. While, root exclusion had negligible effect on the net CH₄ uptake rate. The reason was probably that litter layer removal significantly reduced soil substrates availability and the abundance methanotrophs. However, root exclusion had little influence on these parameters.

It was noteworthy that the litter addition significantly reduced the net CH₄ uptake rate under wet conditions, but no significant effect was found under dry conditions. This was possibly because the litter addition had little effect on substrate availability, but significantly reduced the abundance of methanotrophic bacteria under wet conditions 

Results demonstrated that shifts in plant litter input, especially aboveground litter input would have stronger influence on soils acting as atmospheric CH₄ sink than roots. Under global change scenario, aboveground litter input change combined with the increased frequency of extreme wet and dry events could have important effects on the strength of atmospheric CH₄ uptake by soils of subtropical plantations. 

This research was financially supported by the National Natural Science Foundation of China and the "Strategic Priority Research Program B of the Chinese Academy of Sciences".

Results have been published in Agricultural and Forest Meteorology entitled "Soil net methane uptake rates in response to short-term litter input change in a coniferous forest ecosystem of central China". 

The response of soil net CH₄ uptake rates to plant litter input change and dry and wet seasons. (Image by CHENG's Group)