Effects Of Short-term Nitrogen Addition On Soil Microbial Carbon Source Utilization Characteristics And Soil Respiration In Wetland

As global temperatures continue to rise,issues such as global carbon imbalance caused by global warming have become increasingly prominent.Riparian wetlands,as a transitional zone between aquatic and terrestrial ecosystems,are important sources and sinks of soil carbon.However,due to factors such as agricultural drainage in riparian wetlands,nitrogen loading has been increasing,which has significant impacts on carbon cycling processes including soil microbial carbon metabolism and soil respiration.Therefore,a thorough investigation of the changes in soil microbial carbon source metabolism and soil respiration rate in riparian wetlands is of great significance for understanding the carbon cycling mechanism between soil and atmosphere under global carbon imbalance and for understanding global climate change.In this study,Daihai Lake riparian wetlands were selected as the research object,and three different vegetation types,namely wet meadow,bare land,and abandoned land,were chosen for nitrogen addition experiments.In situ measurement and Biolog-ECO microplate method were used to investigate the short-term(≤1 year)effects of nitrogen addition on soil respiration and soil microbial carbon utilization characteristics in the Daihai Lake riparian wetlands.The results are as follows:(1)Short-term nitrogen addition did not have a significant effect on soil respiration(P>0.05).However,there were significant differences in soil respiration among different vegetation types in the riparian wetlands(P<0.05).In addition,different riparian wetlands had different responses to nitrogen addition.Under nitrogen addition,the soil respiration of wet meadow and bare land decreased by4.20% and 15.70%,respectively,while the soil respiration of abandoned land increased by 12.00%.(2)Short-term nitrogen addition did not have a significant effect on the metabolic capacity of soil microbial carbon sources and the functional diversity of soil microbial communities(P>0.05).However,there were significant differences in the metabolic capacity of soil microbial carbon sources and the functional diversity of soil microbial communities among different vegetation types in the riparian wetlands(P<0.05).Among them,the diversity indices of soil carbon source microbial communities in wet meadow were higher than those in bare land and abandoned land.In addition,different riparian wetlands had different main types of microbial carbon source metabolism.Wet meadow and bare land mainly metabolized sugar substances,while abandoned land mainly metabolized intermediate products and secondary metabolites as well as sugar substances.(3)In this study,soil moisture,soil nitrogen content,soil temperature,soil cellulase activity,and soil pH were important factors affecting soil respiration in wetlands.Among them,soil temperature was significantly positively correlated with soil respiration,while soil moisture,soil nitrogen content,soil cellulase activity,and soil pH were significantly negatively correlated with soil respiration.In summary,the results of this study provide reference value for predicting the soil carbon cycling mechanism in riparian wetlands under increasing nitrogen loading.