The Impacts Of Increased Air Temperature And Nitrogen Deposition On Ecosystem Carbon Exchange In A Desert Steppe

In the context of carbon peaking and carbon neutral strategies,it is an important task to assess the carbon sink potential of existing ecosystems and enhance the carbon sink capacity of ecosystems.Climate warming and increased nitrogen deposition have profoundly influenced ecosystem structure and functioning,especially in ecologically fragile desert grassland ecosystems.However,how climate warming and nitrogen deposition affect the key components of the carbon cycle in a desert steppe are poorly understood.In the present study,net ecosystem carbon exchange(NEE),ecosystem respiration(ER)and gross ecosystem productivity(GEP)were measured using a static box method,based on a long-term global change manipulation experiment at Siziwang Banner in Inner Mongolia,in order to investigate the effects of warming and nitrogen deposition on key components of the carbon cycle in the desert steppe.The results are as follows.(1)Warming and N addition had no significant effect on NEE,ER,and GEP.Combined warming and N addition had different degrees of effect on the carbon exchange fraction.Combined warming and N addition significantly enhanced ER in May and July 2021.Combined warming and N addition significantly enhanced ER and GEP in August 2021.N addition significantly increased NEE and GEP in September2022.Enhanced net carbon sequestration capacity of ecosystem.(2)There is intra-and inter-annual variability in the key components of carbon exchange.Both NEE and GEP are higher in 2022 than in 2021,and there is no significant inter-annual variability in ER.NEE,ER and GEP all show an increase,then decrease,then increase and then decrease in 2021.Both NEE and GEP show an increase and then decrease in 2022,and ER shows an increase and then decrease in 2022.(3)There are correlations between key components of carbon exchange and environmental factors.Soil moisture was positively correlated with NEE,ER,and GEP.Soil temperature was negatively correlated with NEE and GEP,and positively correlated with ER in 2021.Soil temperature was negatively correlated with NEE,ER,and GEP.(4)In this desert steppe,the negative value of NEE indicated that this ecosystem acted as a weak carbon sink with carbon sequestration potential,which contributes to mitigating the consequences of global change.This study provides data support for carbon sequestration and potential of fragile ecosystems under climate change,provides reference for carbon peaking and carbon neutral,grassland policy actions and grassland technology actions,and provides scientific basis for scientific conservation and utilization of grasslands.