Effects Of Warming On Carbon And Water Fluxes In Ruoergai Alpine Peatland

Alpine peatland is very sensitive to global warming because of the slow decomposition rate of organic carbon caused by low temperature,which accumulates a large amount of organic carbon.The accumulation and decomposition of carbon has a strong coupling with water cycle,so the research on the response of carbon/water flux of typical peatland to warming can provide a theoretical basis for the management and sustainable use of alpine peatland under the background of global warming.Based on this,in the growing season of 2021 and 2022（June October）,OTC warming tests were set up in the alpine peatland of Ruoergai,Aba,Sichuan Province.The soil temperature（Ts）,soil water content（SWC）,net ecosystem CO₂ exchange（NEE）,ecosystem respiration（RE）Gross Primary Productivity（GPP）,ecosystem evapotranspiration（ET）,soil evaporation（E）,and plant transpiration（T）were measured and analyzed to explore their dynamic changes and response mechanisms to temperature.The following conclusions were obtained:（1）The soil temperature and soil water content in Ruoergai alpine peatland have significant seasonal dynamics.The soil moisture content is significantly affected by temperature（P<0.05）,with a maximum decrease of 10.43%in soil moisture content at a depth of 20 cm under high warming treatment in 2022,and a minimum decrease of 2.27%in soil moisture content at a depth of 5 cm under low warming treatment in 2022;The soil temperature did not show significant changes at depths of 10 cm and 20 cm.In 2022,the soil temperature of the sample plots treated with high temperature increase at a depth of 5cm showed significant changes,increasing by 2.33℃.（2）In 2021,the dry weight of aboveground biomass was not significantly affected by low warming treatment,while the dry weight of aboveground biomass was significantly reduced by high warming treatment.（3）The effect of warming on net ecosystem CO₂ exchange in Ruoergai alpine peatland in 2021 was not significant,and the net ecosystem CO₂ exchange in the sample plots treated with warming in 2022 was significantly reduced by 24.07%compared with the control group;During the two years,the ecosystem respiration of the plots treated with high temperature increased significantly,with an increase of 55.61%in 2021 and 24.07%in 2022.The plots treated with low temperature only showed a significant increase of 14.20%in 2022;In 2021 and 2022,the gross primary productivity of the low temperature treatment plots decreased by 11.48%and 1.83%,respectively.The gross primary productivity of the high temperature treatment plots increased by 2.71%and 6.2%,respectively,with no significant changes.（4）Warming has no significant effect on Ruoergai alpine peatland evaporation in2021 and 2022;In 2021,the high temperature treatment significantly increased the sample plot transpiration by 48.74%,while in 2022,the low temperature and high temperature treatment significantly increased the sample plot transpiration by 54.55%and 52.27%,respectively;Similar to the changes in transpiration,in 2021,the evapotranspiration of the high temperature treatment sample increased significantly by 44.40%.In 2022,the evapotranspiration of the low temperature and high temperature treatment sample increased significantly,reaching 43.27%and 64.49%,respectively.This is mainly due to the high T/ET ratio under high water content,with the highest T/ET reaching 0.97,and the T/ET of the warming treatment sample increased significantly for two years;There was a slight difference in water use efficiency between the two types of warming treatments,but both significantly decreased.（5）The main factor affecting ecosystem respiration is that soil temperature has a significant positive correlation;The main driving factor of evapotranspiration change in the first year is a significant positive correlation between soil temperature and soil moisture content in the second year;The main driving factor for water use efficiency is a significant positive correlation between soil moisture content;Soil temperature is the main influencing factor of T/ET and has a significant positive correlation.There is a significant negative correlation between water use efficiency and evapotranspiration,as well as T/ET.To sum up,warming has a significant impact on carbon and water fluxes in Zoige alpine peatland,and ecosystem respiration is significantly increased by two degrees of temperature;The total primary productivity of vegetation slightly decreases under the influence of low temperature increase,and slightly increases under the influence of high temperature increase,with no significant changes;The correlation between carbon exchange and temperature in the net ecosystem shows an increasing trend year by year;The significant increase of ecosystem evapotranspiration was mainly due to plant transpiration,and soil evaporation was not significantly affected by warming.The high ratio of T/ET was an important reason,and T/ET showed a significant positive correlation with temperature;The two types of water use efficiency are significantly reduced by the influence of temperature.Soil temperature and soil moisture content are the main driving factors for these indicators.There is also a significant negative correlation between water use efficiency and evapotranspiration and T/ET.