Dynamics Of Carbon,Nitrogen And Phosphorus During Leaf Litter Decomposition In A Stream Of The Changbai Mountains During Winter

Leaf litter from riparian vegetation is the main energy source of forest headwater streams.Leaf litter decomposition and the nutrient release during this process are the key links of nutrient cycling and energy flow between soil and water.In cold regions,leaf litter flows into streams in the brief autumn,and then the subsequent winter season is the main period of leaf litter decomposition.However,there is little research on the leaf litter decomposition and the nutrient release dynamics in headwater streams during the winter season?stream pre-freezing period,freezing period,and thawing period?,and the role of macroinvertebrates in this process is still unclear.Therefore,the decomposition of leaf litter,the release dynamic characteristics of C,N,and P during winter,and the role of macroinvertebrates in this process are investigated in this study.Specifically,a forest headwater stream in the Changbai Mountains area is taken as the research site,the leaf litter of Acer mono and Quecus mongolica is used as the research objects,and the litterbag method is employed.The main conclusions are drawn as follows:1)The fast decomposition rate of leaf litter was maintained during winter,and the mass loss of leaf litter was significantly promoted by macroinvertebrates.The decomposition rates of two kinds of leaf litter are significantly different;specifically,the decomposition rate of leaf litter of Acer mono(0.0152±0.0030d^-1)was significantly higher than the leaf litter of Quecus mongolica(0.0064±0.0017d^-1).Macroinvertebrates promoted the decomposition of leaf litter while their contributions to the decomposition of two kinds of leaf litter were significantly different.After 170 days of decomposition,macroinvertebrates increased the mass-loss rates of Quecus mongolica and Acer mono by 18.46%and 27.32%,respectively;the contribution of macroinvertebrates to the leaf litter decomposition of Acer mono was significantly higher than that of Quecus mongolica.Besides,the mass-loss rate of leaf litter decomposition in different periods during winter was analyzed.The results indicated that the effect of macroinvertebrates on leaf litter decomposition mainly occurred in the freezing period.2)During the winter decomposition of leaf litter of Acer mono and Quecus mongolica,the release dynamics of C,N,and P were different.C and P of the two kinds of leaf litter exhibited a direct release pattern;the release of C was concentrated in the pre-freezing period;the release of P was concentrated in the freezing period.N of the leaf litter of Quecus mongolica exhibited enrichment-release pattern while the N of the leaf litter of Acer mono exhibited a release phenomenon in each period;Meanwhile,the release of N of the two kinds of leaf litter was concentrated in the freezing period.The release of C,N,and P of the leaf litter in different periods was significantly promoted by macroinvertebrates.The main period of action of macroinvertebrates to C was the pre-freezing period while the main period of action of macroinvertebrates of N and P was the freezing period and the thawing period.3)The relationship between environmental factors and the nutrient release of leaf litter was analyzed.Pearson correlation analysis suggested that the nutrient release dynamics of leaf litter had no significant correlation with stream environmental factors such as water temperature,velocity,and pH value.It indicated that during the leaf litter decomposition in the headwater stream of the Changbai Mountains in winter,the effects of leaf litter quality and decomposer on the nutrient release dynamics were greater than the environmental factors.