Leaf Litter Decomposition Characteristics In The Mixed-broadleaved Korean Pine Forest In Changbai Mountain

Litter decomposition plays an important role in chemical cycling and signifies a crucial pathway for nutrient return to the soil.The mixed-broadleaved Korean pine forest is a typical forest type in Northeast China,which plays an important role in maintaining the stability of regional ecosystem.Researches on litter decomposition process of broad-leaved Korean pine forest can enrich the basic data and provide reference for nutrient cycling in this area.In this study,the common tree species were selected as the research object.Using the litter fall traps,we studied the dynamics of annual litter production and nutrient return.Litter bag method in the field and laboratory analysis were used to study the relationship between litter decomposition rate and leaf litter functional traits,and to determine the dynamics of leaf weight,elements(C,N,P)and their ratios.And then,we studied the effect of functional identity,functional diversity and species richness to litter mixture decomposition.The main results are as follows:(1)The pattern of annual litter production and nutrient return in the broad-leaved Korean pine forest can be described by single-peaked curve.The annual total amount of litter production,C,N and P were3227.78 kg/hm~2,1494.57 kg/hm~2,31.04 kg/hm~2 and 3.13 kg/hm~2,respectively.The amount of litter and nutrient return mainly occurred in September to October,and 57%of litterfall occurred in October.(2)The litterfall dynamics of different tree species are different.The litterfall dynamics of Korean pine is double-peak curve,and the peak occurred in October.While the litterfall dynamics of broad-leaved tree species is single-peak curve and the peak occurred in September to October.The main sources of leaf litter were Pinus koraiensis,Tilia amurensis,Quercus mongolica,Acer mono and Fraxinus mandshurica accounting for 80%of the overall amount.(3)After 365 days of decomposition,the mass loss of 30 tree species ranged from 20.56%to 92.11%.According to Olson model,the decomposition coefficients of main tree species ranged from 0.24 to 1.64.And the time required for 50%decomposition takes 0.43-2.86 years for different species and the time required for 95%decomposition takes 1.83-12.37 years.(4)Correlation analysis showed that 18 of the 26 traits were significantly correlated with leaf litter decomposition.Among them,leaf thickness,leaf N content,leaf P content,lignin,lignin:N,lignin:P had a strong correlation with litter decomposition rate.Stepwise regression analysis showed that leaf N content and LSP could predict litter decomposition rate in broad-leaved Korean pine forest.(5)C,N and P of different tree species exhibited different loss patterns.Leaf carbon generally directly lost during the decomposition process.While the loss patterns of N and P for different tree species is more complex.As for the tree species with high k,the N and P directly lost during the decomposition process,while the loss patterns of N and P showed fluctuating change for the tree species with low k.(6)The stoichiometry of different tree species also showed different trends during the decomposition process.C:N value showed a fluctuating downward trend among all tree species,but C:P value and N:P value showed a fluctuating trend and lack a certain regularity.C:N and C:P values were greatly affected by the initial characters of litter during decomposition process.However,the correlation between N:P value and leaf litter characters was gradually smaller during decomposition.(7)Functional identity,species diversity and functional diversity have different effects on the mass loss and mixing effect for mixed litter decomposition.The results showed that there was a significant linear relationship between functional identity,functional diversity and mass loss for different combinations,and the ability of functional characteristics to explain mixed decomposition rate was stronger than that of functional diversity.The mixed effects of different combinations were not related to functional identity and functional diversity,but negatively related to species diversity.