Litter Decomposition Of Elymus Nutans And Its Response To UV-B On The Eastern Alpine Meadow Of Qinghai-Tibet Plateau

As a result of stratospheric ozone depletion, more solar ultraviolet-B radiation (UV-B, 280-315 nm) is reaching the Earth's surface. Enhanced levels of UV-B may, in turn, alter ecosystem processes such as litter decomposition. Solar UV-B radiation could affect composition both indirectly, by changes in the chemical composition of leaves during growth, or directly by photochemical breakdown of litter and varying decomposer communities exposed to sunlight.In this experiment, in order to examine the effects of the present and decreased UV-B radiation on the growth and decomposition of Elymus nutans. We examined indirect and direct effects of solar UV-B radiation on litter decomposition of Elymus nutans. There are two factors growing environment (Reduced UV-B and ambient UV-B) and decomposing environment (Reduced UV-B and ambient UV-B) and four treatments. The variables total C content, total nitrogen content, total phosphorus content and cellulose, UV-B absorbing compounds, hemicelluloses, lignin during the period from 2008 to 2009.The UV-B reduction during plant growth resulted in significant changes in litter quality. We found significant effects of reduced UV-B radiation on any of the litter chemistry parameters. Near-ambient UV-B received during plant growth increased the concentrations of nitrogen, Lignin, cellulose, UV-B absorbing compounds, C/N ratio, lignin/N ratio and increased the concentrations of phosphorus. Total C content and hemicelluloses were unaffected by UV-B exposure. Reduced UV-B treatment received during plant growth increased the litter quality.UV-B radiation affects the released of C,N,P and direct effects are persistent for the whole decomposition period. P concentration varied turns out to be first quickly then slowly, C and N appears the opposite. Although these treads were not disrupted by the UV-B addition treatment, C,N,P concentration varied significantly for different UV-B radiation.We found that litter that decomposed under reduced UV-B had significantly more mass loss than litter that decomposed under near-ambient UV-B. UV-B treatment (reduced) applied during decomposition increased the decay rate. The UV-B conditions received by plants during growth, which did not affect mass loss in early stages of decomposition. On the other hand, there was a marginally significant indirect effect of ambient UV-B during the late stages of decomposition, suggesting increased mass loss.Thus, solar UV-B radiation affects the decomposition of Elymus nutans litter directly and indirectly, and direct effects are persistent for the whole decomposition period.