光照与紫外辐射对亚热带树木叶片排放CH4的影响

植物排放甲烷（CH4）的来源尚存很大争议，而光照和紫外辐射胁迫可能是植物排放CH4的重要影响因素．本研究选择亚热带常见树种米槠、木荷、浙江桂、罗浮栲、杉木、马尾松和柑橘7种树木为研究对象，利用控制实验研究了光照和增强紫外辐射对树木叶片CH4排放的影响．结果表明：7种树木叶片的平均CH4排放速率在光照条件下（21.176ng·CH4·g^-1DW·h^-1）是在黑暗条件下（9．699ng·CH4·g^-1DW·h^-1）的2．2倍，光照对不同树木叶片CH4排放速率的影响具有显著差异；在高UV-B辐射强度处理下，除浙江桂和柑橘外，其他5种树木的CH4排放速率均显著高于低UV—B辐射强度处理的CH4排放速率；树种及其与光照或UV辐射的交互作用对树木叶片CH4排放速率的都具有显著影响，光照或增强UV辐射强度对排放速率较低的树木种类排放CH4的促进作用更强．

Effects of Sunlight and UV Radiation on CH4 Emissions from Subtropical Tree Leaves

While many aspects of methane （ CH4 ） emissions from plants are far from clear, sunlight and UV radiation are suggested to be major environmental factors. In this study, some common sub- tropical tree species, such as Castanopsis carlesii, Schima superb, Cinnamomum chekiangense, Cast- sanopsis fabri, Cunninghamia lanceolata, Pinus massoniana and Citrus reticulata, were chosen to in- vestigate effects of sunlight and UV radiation on CH4 emissions from their leaves under laboratory incu- bation. The results showed that the average emissions rate of all 7 leaf types was 2.2 times higher in sunlight （21.176 ng ·CH4 g-lDW · h-1） than in darkness （9. 699 ng · CH4 · g-1DW · h-l）, and effects of sunlight on CH4 emissions by different tree leaves had significant differences. Moreover, at high UV-B radiation, the CH4 emissions rates of other 5 leaf types, except C. chekiangense and C. reticulate, were significantly higher than those at low UV-B radiation. The results also indicated that tree species as well as its interaction with sunlight or UV-B radiation had significant effects on the plant emissions rate. Sunlight or the enhancement of UV-B radiation had a stronger effect on CH4 emissionsfrom those tree species with lower emissions rate.