Response Of Soil Organic Carbon To Simulated Warming And Nitrogen Deposition In Typical Alpine Swamp Meadow In The Headwater Region Of The Yangtze River

As the two most prominent environmental problems,global warming and increased atmospheric nitrogen deposition have become the focus of scientists' research in recent years.Since the industrial revolution,the average temperature of the Earth's surface has increased by 0.60? in 20th century.According to the IPCC,the global average temperature will rise by 1.5R? in 21th century.in the past century,because of the increasing burning of fossil fuels and the abuse of nitrogenous compounds,humans have released a large number of nitrogenous compounds into the atmosphere and water.Atmospheric dry and wet nitrogen deposition in the atmosphere entering the terrestrial ecosystem is increasing year by year.With the development of the global economy,these two major problems of global warming and the increase of atmospheric nitrogen deposition will continue to exist,and these two environmental problems have a significant impact on the terrestrial soil organic carbon pool.The alpine swamp meadow ecosystem is the material basis for maintaining alpine animal husbandry.Plants living conditions in swamp meadows is harsh,and each ecological factor is often at the threshold boundary of survival.The alpine swamp meadow ecosystem is more sensitive and more rapid than other terrestrial ecosystems in response to global changes,so study the effects of soil carbon pools in alpine swamp meadow ecosystems on global warming and increased atmospheric nitrogen deposition.It is of great significance to study the response of the soil carbon pool of the Tibet Plateau and even the global ecosystem to global changes.This study selected alpine swamp meadow,which is typical and representative in alpine grassland ecosystem as research object.Open-top chambers(OTCs)were utilized to generate an artificially warmed environment and nitrogen fertilizer was applied to simulate nitrogen deposition,and aim of this study was to study the influences of elevated temperatures,nitrogen deposition,and their interaction on soil carbon pool organic carbon components(including MBC,DOC,SOC)and plant biomass(above and underground biomass)in alpine swamp meadow.The results are as follows:(1)Simulated warming has changed organic carbon composition in alpine swamp meadow.The soil microbial biomass carbon(MBC)in low amplitude warming plots increased significantly,in high amplitude warming plots the soil MBC was not affected obviously.Warming decreased dissolved organic carbon(DOC)at 0-20cm soil depth but the DOC at 20-30cm soil depth was not significantly influenced?Soil organic carbon(SOC)at 0-20cm soil depth in the warming plots were significantly lower than control plots.The SOC at 20-30cm soil depth increased obviously in low amplitude warming plots,but this positive effect was not significant in high amplitude warming plots.Warming showed obvious positive effects on aboveground biomass(AGB),and the greater increase in temperature,the more increase in above-ground biomass.Underground biomass(BGB)increased in T1 plots,in contrast,the BGB tended to be inhibited in high amplitude warming plots plots.The upper and lower layers of MBC and SOC are inconsistent with seasonal changes.The peak of the DOC appears in the boom season(August)(2)Simulated nitrogen deposition has changed organic carbon composition in alpine swamp meadow.The MBC in low amplitude nitrogen deposition plots increased significantly,and the soil MBC decreased obviously in high amplitude nitrogen deposition plots.Soil DOC at 0-20cm soil depth in the nitrogen deposition plots were lower than that in CK plots,but it did not reach a significant level.And there are no regular changes at 20-30cm soil depth.SOC at 0-20 cm soil depth increased obviously in low amplitude nitrogen deposition plots.And SOC at 0-20cm soil in plots were lower than CK in June and September,but higher than CK in August.Low amplitude nitrogen deposition increased DOC at 0—20cm soil depth.Nitrogen deposition showed obvious positive effects on plant biomass,and the greater increase in nitrogen concentration,the more increase in plant biomass.MBC and DOC showed the same seasonal variation after nitrogen application:the flourishing period(August)was greater than the plant litter period(September)was greater than the initial growth period(June),and the seasonal variation of SOC in the upper and lower layers of nitrogen application was different.(3)In the experiment of combined action of warming and nitrogen application,according to multivariate analysis of variance,it was found that there was an interaction between temperature increase and nitrogen application on MBC and SOC.According to the experimental data,it can be inferred that in the past few months of vegetation growth,the combination of warming and nitrogen application will increase the soil organic carbon storage in alpine swamp meadows in the source area of the Yangtze River.