Abstract:Using open-top Chambers(OTCs) and UV-lamps,we manipulated climate warming and enhanced UV-B radiation.The parameters of photosynthetic gas exchange and chlorophyll fluorescence of Picea asperata seedlings in the eastern fringe of the Tibetan Plateau,where climate warming and enhanced UV-B radiation(UV-B) were severe,were measured to investigate its photosynthetic responses to the two worsening environmental factors.The results showed that:(1)Enhanced UV-B restrained the net photosynthetic rate(Pn),the maximum photosynthetic rate(Pmax) and the apparent quantum yield(Φ).However,it increased the photosynthetic light compensation point(LCP).In addition,enhanced UV-B induced photo-inhibition of the photosynthetic system Ⅱ(PS Ⅱ) in P.asperata seedlings,and it reduced the effective quantum yield of PS Ⅱ(ΦPS Ⅱ).In the end,enhanced UV-B significantly inhibited shoot elongation,root growth and biomass accumulation.(2)OTCs warming significantly enhanced Pn and Pmax,but it had no effects on Gs,Tr and Φ.(3)UV-B effects on photosynthesis were amended by warming to some extent,which could be judging from the increased Pn,Pmax,intrinsic efficiency(Fv/Fm) and ΦPSⅡ of PSⅡ,and the improved growth.In the end,warming could alleviate the harmful effects of enhanced UV-B on photosynthesis of P.asperata.