Soil organic carbon and its easily decomposed components under precipitation change and nitrogen addition in a desert steppe in northwest China
Aims Soil organic carbon(C)pool plays an important role in regulating terrestrial C cycle and global climate,etc.The purpose of this study is to furnish data that will facilitate the scientific prediction of the C sink function of the grasslands in semi-arid regions under global change.Methods Based on a two-factor field experiment of precipitation change(-50％,-30％,natural,+30％,+50％)and nitrogen(N)addition(0 and 5 g·m-2·a-1)established in 2017 in a desert steppe in Ningxia,we explored the response patterns and driving factors of soil organic C characteristics(content,storage,and components)in 0-60 cm soils after 4 years of treatments.Important findings N addition had little effects on soil organic C characteristics.In contrast,precipitation exerted a significant influence on soil organic C characteristics,with the magnitude of the effect contingent up on the N level and soil depth.In the absence of N addition,both increasing and decreasing precipitation had a minimal impact on organic C characteristics across the whole 0-60 cm depth.In contrast,a 30％reduction in precipitation led to a significant increase in the content of easily oxidized organic C and dissolved organic C,while a 30％increase in precipitation resulted in a significant increase in the content of particulate organic C and light fraction organic C under 5 g·m-2·a-1 N addition.The content of soil organic C and its storage were positively correlated with soil water content,cellobiohydrolase activity and alkaline phosphatase activity.Conversely,they were negatively correlated with soil NO3-N.The content of easily oxidized organic C,particulate organic C and light fraction organic C was found to be positively correlated with soil leucine aminopeptidase activity and the Simpson dominance index,while negatively correlated with microbial biomass N content.Dissolved organic C and microbial biomass C content showed the opposite relationship with the three indices above.These findings indicate that alterations in precipitation levels exert minimal influence on soil organic C content and its storage in the context of N addition.However,moderate increases and decreases in precipitation will diminish soil organic C stability by influencing soil water content,N availability,enzyme activity and plant community dominance,which may,in turn,elevate the risk of soil C emission in desert steppes.
万方数据
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