Effect of soil nitrogen, carbon and moisture on methane uptake by dry tropical forest soils

Methane uptake was measured for two consecutive years for four forest and one savanna sites in a seasonally dry tropical region of India. The soils were nutrient-poor and well drained. These sites differed in vegetational cover and physico-chemical features of the soil. There were significant differences in CH4 consumption rates during the two years (mean 0.43 and 0.49 mg m-2 h-1), and at different sites (mean 0.36 to 0.57 mg m-2 h-1). The mean uptake rate was higher (P < 0.05) in dry seasons than in the rainy season at all the sites. There was a significant season and site interaction, indicating that the effect of different seasons differed across the sites. There was a positive relation between soil moisture and CH4 uptake rates during summer (the driest period) and a negative relation during the rest of the year. The results suggested that seasonally dry tropical forests are a strong sink for CH4, and C and N status of soils regulates the strength of the sink in the long term.