Effects Of Snow-depth Manipulation On Foliar Litter Decomposition And Nutrient Release Of Fraxinus Mandshurica And Larix Gmelinii

Decomposition of litter is an important process of material circulation in ecosystems.Changes in Seasonal snow-depth caused by climate change may play an important role in foliar litter decomposition in temperate forest,further changing the material cycling and other key ecosystem processes.Although there are many studies on litter decomposition and nutrient release,the process of element dynamics in response to global change need to be further researched urgently.A field experiment was conducted with litterbag in a temperate Korean pine plantation in Maoershan,northeast China,to explore the effects of different treatments(control,snow-addition,snow-removal)on foliar litter decomposition of Manchurian ash(Fraxinus mands hurica)and Dahurian larch(Larixgmelinii)The litterbags were sampled at the early stage of freeze-thaw stage,late freezing stage,thawing stage,early snow-free stage,middle snow-free stage and late snow-free stage.Decomposition rate,C,N and P release rate,and cellulose and lignin loss rate together with the changes of litter quality were investigated.The aim was to reveal the mechanisms of the effects of snow cover on litter decomposition,and to provide efficient information for understanding the key ecological processes such as material circulation in alpine forest and their reaction on the process of climate change.C,N and P release rate,cellulose and lignin loss rate together with decomposition rate were investigated in expecting to provide basic data for the prediction on the material circulation of forest ecological systems under the global climate change.(1)Contrary to the snow-free stage,snow depth and environment variable changed significantly during the snow-cover stage(the onset of freezing stage,late freezing stage and thawing stage).(2)After the decomposition of the whole year,the mass loss varied from 51.29%to 57.39%for Manchurian ash,and 21.67%to 31.36%for Dahurian larch.The decomposition constants for the foliar litter of the two species were the highest with the treatment of snow-addition,and were the lowest under the treatment of snow-removal.The time of decomposition for 50%and 95%were shortened under the snow-addition treatment and extended under the snow-removal treatment,respectively.(3)The decomposition rates of the foliar litter were severely influenced by species,snow-depths,decomposition periods and environmental variables.Decomposition factors of foliar litter vary with different decomposition periods.During the snow-covered stage,environmental variables were the leading factors affecting the decomposition of foliar litter.During the snow-free stage,the decomposition was significantly influenced by the initial quality of litter.(4)The results of decomposing experiment indicated that snow cover had obvious effects on litter quality,but different species displayed different responses to the snow cover in different key periods.Snow depth significantly affected C concentration of foliar litter of Dahurian larch during decomposition,but its effect on Manchurian ash was not significant during late decomposition.Treatments of snow depth significantly affected the lignin and cellulose content of foliar litter for both species during decomposition.The ratio of N/P under different snow covers showed significant differences in the decomposition of whole year.The contents of C,cellulose,and the ratio of C/N showed a trend of decline,but C content and the ratio of C/P showed a trend of rising as the foliar litter decomposition proceeded.(5)As the snow depth increased seasonally,litter C remaining rate,P remaining rate,cellulose remaining rate,lignin remaining rate,C/N and C/P decreased regardless of species.The C release rates of the two species were the highest in the snow-addition treatment and lowest in the snow-removal treatment.The N release rate for Manchurian ash was the highest in the snow-addition treatment and the lowest in the snow-removal treatment,and the N accumulation rate for Dahurian larch was the highest in the snow-removal treatment and lowest in the control.The P release rates of two species were the highest in the snow-addition treatment and the lowest in the snow-removal treatment.The lignin and cellulose loss rates of the two species were the highest in the snow addition treatment and the lowest in the snow removal treatment.In conclusion,treatments of snow depth significantly affected the foliar litter decomposition in the temperate forest,but the responses were regulated by the litter quality and the depths of snow.In different periods,the decomposition rate increased with the snow depth.Snow-addition treatment significantly promoted the litter decomposition during snow-covered stage,while snow-removal significantly promoted the litter decomposition during snow-free stage.Results of decomposition experiments indicated that snow-addition treatment would speed up the rate of litter decomposition in the temperate forest.These results can provide basic data for the prediction of the effects of climate changes on the decomposition,nutrient release and material circulation of temperate forests.