Most tropical forests grow on well-drained upland soils that are too dry to emit CH4 but act instead as an important sink for atmospheric CH4. It is not well understood if upland tropical rain forest soils are potential sinks or sources in the global atmospheric CH4 budget. The eddy covariance method (a LI-7700 open-path methane analyzer, LI-COR Bio-sciences, Lincoln, NE, USA) was used to measure the whole-ecosystem exchange of CH4 fluxes continuously from 2012 to 2015 in a tropical rain forests on Hainan Island, China. The total area of the Jianfengling National Natural Reserve is about 470 km2 , where the mountain rain forest covers about 150 km2. The forest region is dominated mainly by Gironnierasubaequalis, Cryptocaryachinensis, Livistonasaribus, and Mallotushookerianus, and has a tropical monsoon climate with obviously wet and dry season.
Results/Conclusions
The annual net uptake of CH4 by soil was larger than the measured CH4 budget from static chamber technique. The observed rate of CH4 uptake (sink) was dominant by wet season (growing season) and correlated well with ecosystem productive and soil moisture. Our results suggest that even under wet season conditions CH4 uptake may be significant. Methane fluxes in tropical rain forests can play a vital role in determing future concentration of atmospheric CH4.