Plant-mediated CH4 emission from a Phragmites-dominated wetland in an arid region, China

We investigated the effects of vascular plants on methane emissions from Wuliangsu Lake, a wetland in an and region of northwestern China. Under natural conditions in early June and late July, average CH4 fluxes were respectively 16.3 +/- 4.3 and 19.3 +/- 6.0 mg m(-2) h(-1). Whereas, shading treatments, which eliminated direct sunlight to plants, resulted in lower CH4 emission (8.2 +/- 1.9 and 10.2 +/- 2.6 mg m(-2) h(-1) for the two periods). When the culms were cut below the water surface, the fraction of CH4 emissions was about 18% and 15% of that of natural control systems in early June and late July, respectively. Our findings indicated that the photosynthesis of reed had a positive influence on the process of methane emission; however, effects on production and transport outweighed oxidation. Of the carbon fixed by photosynthesis, only 4.7% was returned to the atmosphere as CH4.