Variation Patterns Of Plant And Soil Carbon Density In Alpine Peat Swamps And Their Environmental Response

Elevation,as an important driver of variability in the hydrothermal pattern of mountain ecosystems,creates local microclimates by regulating the spatial redistribution of temperature,precipitation and solar radiation intensity,which directly or indirectly affects the growth of plants and differences in soil physicochemical properties in the region,and plays an important role in the rate of carbon accumulation and turnover in alpine peat bog plants and soils.Therefore,the study of altitudinal variability patterns of plant and soil carbon density in alpine peat bogs can help to resolve the mechanism of peat bog carbon pool formation.As a concentrated development area of global alpine peat bog wetlands,the Gannan Plateau,with typical soil carbon accumulation and sequestration processes,is a key area for peat bog plant and soil organic carbon research,but the characteristics of plant carbon density and soil organic carbon distribution in this area and their response mechanisms to the environment are still unclear.In this paper,four peat bogs of 3450 m,3550 m,3650 m and 3750 m elevation gradient were selected as experimental sample sites in Gahai Wetland of International Importance according to the development and distribution characteristics of peat bogs in Gannan Plateau.The characteristics of peat bog environments and plant communities at different elevations were analyzed using ANOVA,redundancy analysis and throughput analysis,and the correlations between plant and soil carbon density and peat bog environments were investigated,and the environmental response mechanisms of soil carbon density in different soil layers under elevation gradients were explored.We also proposed countermeasures and suggestions for peat bog protection and management,which provide technical support for peat bog management in mountain ecosystems,in view of the biomass distribution preferences of peat plants and the distribution characteristics of plant soil carbon density on the altitude gradient and their main influencing factors,and in light of the current situation of peat bog utilization in Gannan.The main results are as follows.(1)The peat bog plant community was dominated by Kobresia tibetica,Blysmus sinocompressus and Care X kansuensis Nelmes,etc.The species composition and quantitative characteristics of the plant community changed as the sample site shifted from low to high altitude.Soil water content,soil total nitrogen and plant community height in peat bogs increased first and then decreased,while soil p H,soil temperature,average plant community density and coverage decreased gradually.The species composition of peat bog plant communities had high positive correlations with soil total nitrogen and soil organic carbon,and high negative correlations with soil p H,soil capacitance and soil temperature.(2)The above-ground biomass of peat bog plant communities,as well as stem,leaf and litter biomass and litter carbon content,tended to decrease gradually with increasing elevation.Belowground biomass,root biomass and root carbon content showed an increasing followed by decreasing.Aboveground biomass carbon density showed a decreasing trend in general,while belowground biomass carbon density and total biomass carbon density showed an increasing and then decreasing trend.Total biomass carbon density under the altitude gradient was significantly and positively correlated with total soil nitrogen,total soil phosphorus,soil water content,soil organic carbon and average plant community height,and significantly and negatively correlated with groundwater depth of burial and soil p H.Soil organic carbon in peat bogs had the greatest combined effect on total biomass carbon density.(3)Both soil organic carbon content and soil carbon density showed an increasing and then decreasing with increasing elevation,and the maximum content of soil organic carbon is 295.75 g/kg at 3650 m above sea level.On the altitude gradient,soil carbon density in the 0-30 cm and 30-60 cm soil layers of peat bogs was significantly correlated with total soil phosphorus,average plant community height,above-and belowground biomass,root biomass,and root and leaf carbon content.The carbon density content of the 60-90 cm soil layer was significantly correlated with total soil nitrogen,soil p H,soil capacitance,soil temperature and depth of groundwater burial.Soil carbon density in the 0-90 cm soil layer was significantly correlated with soil N and P,mean height,mean density of plant communities,belowground biomass,rhizome biomass and plant carbon content.The environmental factors with the highest combined effects on soil carbon density in the 0-30 cm,30-60 cm,60-90 cm and 0-90 cm soil layers were plant root biomass,soil temperature,soil temperature and root carbon content,respectively.