Nutrient dynamics of foliar litter in reciprocal decomposition in tropical and subtropical forests.

In order to explore the effects of global warming on the decomposition rate of forest litter and the release of nutrients, an experiment was designed to decompose reciprocally forest foliar litter in two sites across climatic zones:Mt. Jianfengling in Hainan Province in the tropics and Mt. Dinghushan in Guangdong Province in the subtropics. The two sites have similar altitudes, soil types, annual mean rainfall and seasonality of dry and wet. The main difference between these two sites is the annual mean temperature with the difference of 3.7℃. Foliar litters of 10 native dominant tree species have been collected from the two sites and divided into single-species litter and mixed litter. They are decomposed reciprocally in the two sites. The results indicate that litter decomposes in the tropical site 1.36—3.06 times as rapidly as in the subtropical site. Apparent Q10, calculated on the basis of temperature difference between two sites, ranges from 3.7 to 7.5. The return amount of N, P and C will increase by 32.42,1.033 and 741.1 kg/hm² in Mt. Dinghushan in the first year's litter decomposition under the prevailing temperature condition. Only in Mt. Dinghushan is the correlation between decomposition rate constant and initial litter quality high and significant in lignin∶N ratio, lignin, lignin∶P ratio, HLQ and C.This is not the case at Mt. Jianfengling.