Effects Of Moso Bamboo Expansion On Litter Decomposition,Soil N₂O And CO₂ Emissions Under Simulated N Deposition

Moso bamboo（Phyllostachys edulis（Carriere）J.Houzeau）is an important forest resource in the south of China,because of its cloning growth of the breeding mode,the expansion potential is huge.The area of moso bamboo forest has been a continuous growth trend in recent years,and has caused a variety of ecological problems.Studies have shown that the expansion of bamboo under nitrogen deposition has an important effect on soil N₂O and CO₂ emissions,but the mechanism of its internal effects is unclear.Based on the important position of litter in nutrient cycle and energy flow of forest ecosystem and the background of increasing nitrogen deposition in the world,this study takes the change of litter input caused by the expansion of bamboo as the starting point,and the bamboo formed by the expansion of moso bamboo-Japan cedar（Cryptomeria japonica（L.F.）D.Don）mixed forest as the object of study,set up two-factor multi-level complete randomized test,that is,three kinds of litter cover treatment（bamboo litter,Japanese cedar litter and the two 1:1mixed litter）,two simulated nitrogen deposition level(control vs.8 g N m^-2·yr^-1).In situ observation of soil N₂O and CO₂ emission flux by static box-gas chromatography,the effects of litter input on the decomposition of Japanese cedar litter and the release of nutrient were investigated by decomposition bag method,and the influence of the input of litter on soil microbial community was studied by phospholipid fatty acid method（PLFAs）.The purpose of this paper is to reveal the influence of litter input and decomposition on soil N₂O and CO₂emission and its influence mechanism in the process of bamboo expansion under the background of nitrogen deposition.The main findings are as follows:（1）The N₂O emission of the soil covered by the moso bamboo-Japan cedar mixed litter is less than the N₂O emission of the moso bamboo litter and Japanese cedar litter covered alone,but the CO₂ emission from the mixed litter is higher than that of the moso bamboo and Japan cedar litter covered alone.（2）Simulated nitrogen deposition significantly increased soil N₂O cumulative emissions and had no significant effect on soil CO₂ emissions.The interaction between simulated nitrogen deposition and litter types had a significant effect on soil N₂O emissions,but had no significant effect on soil CO₂ emissions.（3）The input of moso bamboo promoted the decomposition of Japanese cedar litter,and accelerated the loss of litter quality and nutrient release.Simulated nitrogen deposition has a significant effect on the mass loss of litter decomposition,but has no significant effect on nutrient release during litter decomposition.（4）The mixed decomposition of moso bamboo–Japanese cedar mixed litter significantly changed the microbial community structure,and increased amount of soil microbial fungi,bacteria,actinomycetes,Gram-negative bacteria,Gram-positive bacteria,and the total amount of microbial.（5）The litter input of moso bamboo litter and decomposed with the Japanese cedar litter promoted the decomposition of Japanese cedar litter,accelerated nutrient input and increased soil microbial biomass,which is one of the important reasons affecting the difference of soil N₂O and CO₂ emissions.In summary,the expansion of litter input from moso bamboo accelerates the decomposition and nutrient release of Japanese cedar litter,increases soil various groups and microbial aggregates,and increases soil CO₂ emissions,but does not promote soil N₂O emissions.Nitrogen deposition promoted the decomposition of litter and increased the N₂O emissions,but did not significantly affect the CO₂ emissions.The effects of mixed decomposition of moso bamboo on litter nutrient release and soil microbial are important causes of differences in soil N₂O and CO₂ emissions.In the context of the increasingly serious expansion of bamboo and the increasing global nitrogen deposition,this is unfavorable for mitigating global climate change.Therefore,in the future management of subtropical bamboo expansion under global climate change conditions,the composition,structure and various factors of ecosystems must be explicitly considered.The mutual influence.This study enriches and perfects the ecological impact research theory of bamboo expansion,and provides data support and theoretical basis for comprehensive evaluation of the ecological effects of bamboo expansion.oretical basis for comprehensive evaluation of ecological effect of moso bamboo expansion.