| China is the world’s third-largest nitrogen deposition region, atmospheric N deposition has had a serious impact on China’s forest ecosystems.N deposition produce the change of the forest plants composition, which changes the litter amount and chemical composition, resulting in litter and soil nutrient content, number and structure of soil-microbial communities change. All these impact affect litter decomposition, nutrient release and biochemical processes such as carbon and nitrogen cycles and ultimately affect material cycle and energy circulation of forest ecosystem.Cryptomeria fortunei, which is of highly economic value, is the one of the main afforestation tree in subtropical region of China.This study discussed the response of Cryptomeria fortunei plantation litter decomposition in the Rainy Area of West China to simulated N and composition change from1th2012to1th2013. There were12treatments in this experiment:CK(Comparison)、 LN(Low N,5kg·hm-2·a-1)、MN(Middle N,10kg·hm-2·a-1)、HN(High N,15kg-hm-2·a-1)、 SL(Cunninghamia lanceolata litter mixed with Cryptomeria fortunei at a ratio of1:1)、NL(Phoebe bournei litter mixed with Cryptomeria fortunei at a ratio of1:1)、LSLN(Low N+Cunninghamia lanceolata litter mixed with Cryptomeria fortunei)、LSMN(Middle N+Cunninghamia lanceolata litter mixed with Cryptomeria fortunei)、LSHN(High-N+Cunninghamia lanceolata litter mixed with Cryptomeria fortunei)、LNLN(Low N+Phoebe bournei litter mixed with Cryptomeria fortunei)、 LNMN(Middle N+Phoebe bournei litter mixed with Cryptomeria fortunei) and LNHN(High N+Phoebe bournei litter mixed with Cryptomeria fortunei). The main results as follows:(1) During the trial period, LN and HN promoted litter decomposition while MN initially inhibited litter decomposition and then promoted. LN、MN and HN significantly decreased the mass remaining (p<0.05). Among the changes in litter composition, SL and NL promoted litter decomposition and showed a significantly effect after12months(p<0.05).NL presented a higher promotion effect than SL. As to N deposition well changes in litter composition, in addition to LSLN inhibited at first and then promoted litter decomposition, the other treatments accelerated litter decomposition.(2) During the trial period, the effect of LN and MN on litter organic carbon releasing showed as follows:promoted—inhibited—promoted. However, HN significantly decreased litter organic carbon content which presented a promotion effect on litter decomposition(p<0.05). Among the changes in litter composition, litter organic carbon content decreased firstly.increased then,decreased at the end.SL and NL significantly promoted litter organic carbon release. As to N deposition well changes in litter composition, each treatments decreased litter organic carbon content in the first6th months and fluctcated around initial vule in12th months.(3) During the trial period, each treatments increased N content and remaining significantly (p<0.05) and inhibited N release. Among the changes in litter composition, SL and NL expressed an insignificant promotion effect on N release. As to N deposition well changes in litter composition, each treatments increased N content and remaining significantly and promoted N release largely.(4) During the trial period, LN and HN decreased C/N ratio. MN decreased C/N ratio after9months and increased in other period. Among the changes in litter composition, SL decreased C/N ratio while NL decreased firstly, increased then,decreased in the end. As to N deposition well changes in litter composition, each treatments decreased C/N ratio and showed a significant effect after12months. The decreasing effect of each treatments on C/N ratio in each period was differential. The change law was not abvious.(5) During the trial period, LN decreased P content and promoted P release; MN and HN increased P content and inhibited P release significantly(p<0.05). Among the changes in litter composition, SL inhibited P release significantly and NL expressed a weak promotion effect to P release.. As to N deposition well changes in litter composition, each treatments inhibited P release.(6) During the trial period, each treatments decreased K content and remaining and promoted P release significantly (p<0.05). K content and remaining of MN was minimum, which entrusted MN the maximum promotion effect. Among the changes in litter composition, each treatments significantly decreased K content and promoted K release. SL showed a higher promotion effect than NL. As to N deposition well changes in litter composition, each treatments decreased K content and remaining and promoted K release. |
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