Effect Of Snow Removal On Litter Decomposition Of Picea Asperata And Abies Faxoniana In Western Sichuan

Affected by global climate change,the temporal and spatial pattern of winter snowfall in high latitudes has been deeply influenced in recent decades.The subalpine area of western Sichuan located on the eastern edge of the Qinghai-Tibet Plateau is also affected and seasonal snow cover is decreasing in winter.Litter decomposition is an important process of carbon and nutrient cycling in forest ecosystems,it is also the key link to connect vegetation,soil and microorganism.Seasonal snow cover is an important ecological factor in the biochemical cycle of the subalpine forest ecosystem in western Sichuan,the reduction of seasonal snow in winter due to climate change may have a profound impact on litter decomposition in western Sichuan subalpine forests.Therefore,our study takes the leaves of Picea asperata and Abies faxoniana as the research object,two common conifer species in the subalpine area of western Sichuan.Combined with field snow control experiment(sonw removal and natural snow)and litter decomposition bag method to explore the effects of snow cover change on mass loss and element release during litter decomposition.The results are as follows:(1)Snow removal significantly reduced soil temperature and water content of litter in winter.Conversely,snow removal significantly increased the frequency of soil freezethaw cycles.During the snow cover period,the frequency of freeze-thaw cycles in the surface soil of the snow removal plot is 2.36 times higher than control,but the water content of litter is only 38.41% of the control.The water content of litter of Picea asperata and Abies faxoniana decreased by 15.78% and 27.83% in winter because of snow removal,respectively.There is no significant difference between soil temperature and water content of litter in growing season.(2)In the period of experiment,the mass residual rate of litter in Picea asperata and Abies faxoniana after snow removal was significantly higher than control.In winter,the mass residual rate of litter in Picea asperata and Abies faxoniana after snow removal was3.29% and 4.85% higher than control,respectively.In the growing season,the mass residual rate of litter in Picea asperata and Abies faxoniana after snow removal was15.77% and 12.81% higher than control,respectively.Whether the plot is treated with snow removal or not,the mass loss rate of litter of two tree species is higher in growing season than in winter.In the same season and treatment,the mass loss rate of litter of Picea asperata was significantly higher than Abies faxoniana.(3)Regardless of species and treatment,in the first year of decomposition,C,N,P,K and Na elements were released;Ca and Mn elements were released during the growing season and enriched in winter;Fe and Mg were enriched.In addition,the release rate of C,N,P,K and Na in the growing season is significantly higher than winter,and the enrichment degree of Fe and Mg in winter is significantly higher than growing season.Snow removal significantly affected the release or enrichment rate of elements during the decomposition of Picea asperata and Abies faxoniana,snow removal significantly inhibited the release of C,P,and Na elements and the enrichment of Ca,Mg,and Fe elements in the winter litter of two tree species.(4)Statistical analysis showed that there was a significant correlation between the initial substrate quality and the release rate of elements(except Mn element).Soil temperature,C:N,C:P and water content of litter were positively correlated with mass loss of litter,there was a significant negative correlation between the frequency of freeze-thaw cycles and the mass loss of litter.Besides,soil temperature,water content and C:P of litter were positively correlated with the release rates of Mg,Fe and Mn elements,water content and N:P of litter were significantly negatively correlated with the release rate of K element,soil temperature and C:N of litter were significantly positively correlated with the release rate of C,N,Ca and Mn element.Soil temperature was significantly negatively correlated with the release rate of K element,N:P of litter was significantly negatively correlated with the release rate of C,N,Ca and Na element,the frequency of freeze-thaw cycles was significantly negatively correlated with the release rate of all elements(except K and P elements).Above all,Snow removal significantly affected the decomposition rate and element release of litters of Picea asperata and Abies faxoniana in subalpine areas of western Sichuan and the snow removal effect was related to species and seasons.Soil temperature and the frequency of freeze-thaw cycle are the main factors affecting the decomposition rate of litter.The results provide a scientific basis for further understanding the response of mineral cycling in forest of the subalpine area in western Sichuan to climate change.