Effects Of Simulated Warming And Nitrogen Addition On Carbon Exchange In Alpine Wetland Ecosystem Of Qinghai Lake

Climate warming and nitrogen deposition may affect environmental factors and plant growth of alpine wetlands,which could have an impact on the carbon cycle of wetland ecosystem.In order to investigate such effects,we conducted a experimental at the field observation station of Qinghai Normal University,Yikewulan Wayan Mountain Wetland in Qinghai Lake Basin.The open-top temperature chamber was used to elevate the temperature and the artificial nitrogen fertilizer was used to simulate the nitrogen deposition,and the static box method was adopted to measure the ecosystem carbon exchange.Four treatments,i.e.,control,warming,nitrogen addition and both warming and nitrogen addition,were set to study the effects of warming and nitrogen deposition on the carbon exchange in alpine wetland ecosystem.Our research will provide a theoretical basis for carbon exchange in alpine wetland ecosystems.The research results are as follows:(1)Simulated warming increased soil temperature and reduced soil moisture,and had a more pronounced effect on soil temperature at 15 cm and soil moisture at 10 cm.For soil total carbon and total nitrogen,regardless of the influence of soil depth,temperature increase and nitrogen addition and interaction increase soil total carbon and total nitrogen content.(2)For aboveground biomass,warming and interaction enlarged aboveground biomass,while nitrogen addition reduced aboveground biomass.For belowground biomass at 0-10 cm,the warming and interaction had positive effects while nitrogen addition had negative ones;10-20 cm,the belowground biomass was highest in control,followed by warming nitrogen addition,nitrogen addition and warming.(3)Under different treatments,the carbon exchange rate of ecosystem showed obvious diurnal and seasonal variations.In the early and late growing season,the carbon absorption capacity of ecosystem was low,whereas in the middle of the growing season,the carbon absorption capacity was much stronger.The average diurnal and seasonal variations were basically the same under different treatments,net ecosystem exchange(NEE)generally showed a “U” trend;ecosystem respiration(ER)showed a unimodal trend;gross ecosystem productivity(GEP)showed an inverted “U” trend.(4)Warming promoted the carbon absorption by increasing NEE and GEP in the whole study period,but the effects were not statistically significant(P>0.05).The effect on ER was either not obvious.Under warming,there were significant differences in NEE,ER and GEP among different months of the same treatment(P<0.05).The effect of nitrogen addition on NEE,ER and GEP was not significant during the study period(P>0.05).The interaction of warming and nitrogen addition increased GEP in the peak of growing season and increased ER in the whole growing season,but there was little effect on NEE.The difference of NEE and GEP between different treatments were not significant level(P>0.05),but the difference of ER under the interaction was significant(P<0.05).