| The invasion of Phyllostachys edulis into surrounding forest has many negative impacts on key ecological processes and functions in forest ecosystems,and has received widely attention in the field of ecology.There are many studies on the invasion of P.edulis into broad-leaved evergreen and coniferous forests,but few studies on the invasion into deciduous broad-leaved forests,deciduous broad-leaved forests have important ecological significance in improving the production capacity of forest ecosystems,maintaining nutrient and material cycling,etc.Therefore,it is necessary to explore the decomposition characteristics and influencing factors of litter caused by the invasion of P.edulis into deciduous broad-leaved forests.In this study,three forest stands were selected as the experimental plots,namely P.edulis forest,mixed forest（P.edulis-deciduous broad-leaved trees）and deciduous broad-leaved forest（Quercus acutissima forest）.We used the litter bag method to carry out litter decomposition experiments in the field,analyzed the mass residual rate and decomposition rate during the invasion of P.edulis,and we also measured the soil physicochemical properties,soil enzyme activities,microbial biomass and other indexes in the three forest stands to explore the main factors affecting litter decomposition in the process of P.edulis invasion.The main findings were as follows:（1）With the invasion of P.edulis,soil p H and soil water content（SM）increased significantly（P<0.05）,and the contents of NO3--N,SOC,TN and AP decreased in general.The changes of NH4+-N content were not consistent,and the contents of TP were the highest in the mixed forest.Except for TN content,SM,p H and nutrient content were significantly different in time（P<0.05）,but the change trend was not consistent.（2）Compared with the mixed forest and Q.acutissima forest,the soil of P.edulis forest showed lower activity of BG and CBH.The soil enzyme activity was higher in April and July,but lower in January and October.The correlation analysis showed that soil enzyme activity was mainly affected by p H,SOC,NH4+-N,NO3--N,TN and TP.The total PLFA content,fungi,bacteria,actinomycetes and F:B were higher in the mixed forest and Q.acutissima forest than those in the P.edulis forest.The microbes were significantly affected by SM and AP（P<0.05）.（3）The decomposition of three litters（P.edulis litter,Q.acutissima litter and mixed litters）in the same or different forest environments was studied,and found that the mass residual rate of leaves was higher in the P.edulis forest,lower in the Q.acutissima forest,and the residue rate of P.edulis litters was higher and that of Q.acutissima litter was lower in the same forest environment.It indicated that the litter decomposition was slower with the invasion of P.edulis.（4）At the end of the experiment,the residue rate of C and N in litter was lower than the initial content,and the residue rate of P in P.edulis litter and mixed litter was lower than the initial content except for the residue rate of P in Q.acutissima litter.Under the condition of mixed forest,the residue rate of litter C and P was the highest,while the lowest was in P.edulis forest（except for P.edulis litter C and Q.acutissima litter P）.Among the three kinds of litter,the residue rate of C and N in P.edulis litter was the highest,while the residue rate of P in Q.acutissima litter was the highest.（5）Through redundancy analysis,it was found that litter decomposition was mainly affected by Bacteria,actinomycetes,total PLFA biomass,fungi,AP,POX,SM and SOC.SM was positively correlated with litter residue rate（P<0.05）,SOC and AP were negatively correlated with litter residue rate（P<0.05）,POX enzyme activity was negatively correlated with litter C and N residue rate（P<0.05）.There was a significant positive correlation between total PLFA biomass,bacteria and C residue rate（P<0.05）;AP,soil total PLFA biomass,bacteria,fungi and actinomycetes were positively correlated with N residue rate（P<0.05）. |
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