Effects Of Simulated Climate Warming And Nitrogen Addition On Soil Priming Effect And Related Microbial Changes

With global warming and the intensification of atmospheric nitrogen deposition,the conversion of soil organic carbon has attracted wide attention.Soil priming effect played an important role in the transformation of soil organic matter.Its presence makes the decomposition rate of soil organic matter change sharply and strongly in a short period,and its response to future climate change will significantly affect the stability of the soil carbon pool.Therefore,under the background of climate warming and atmospheric nitrogen deposition,it is of ecological significance to study the effects of simulated temperature increase and nitrogen enrichment on soil priming effect.Based on 4 years of gradient warming and nitrogen addition of Zoige alpine peat wetland,this study analyzed the effects of temperature increase and nitrogen addition on soil priming effect through field simulation experiment combined with indoor culture,combined with high-throughput sequencing method and isotope technology.The results of field simulation showed that clipping treatment changed the mineralization rate of soil organic matter.After clipping treatment,the content of total nitrogen and organic carbon in soil decreased significantly from Day 7 to Day 14,and the decrease increased with the increase of temperature.The shading treatment had no significant effect on soil carbon and nitrogen content,and the total nitrogen content of the soil was higher than that of no treatment,indicating that the mineralization rate of soil organic carbon was inhibited.Therefore,it can be inferred that clipping treatment has a positive priming effect,while shading treatment has a negative priming effect.The influence of temperature on soil microbial biomass carbon and enzyme activity increased with the increase of temperature,but the difference between moderate and high temperatures was not obvious.The activity of microbial carbon and enzyme activity both peaked on Day 7.The analysis of soil microbial community structure on Day 7 and Day 28 showed that clipping treatment increased soil microbial abundance,and the rule of species diversity was as follows: clipping > untreated > shading.On Day 7,the relative abundance of Proteobacteria decreased,while the relative abundance of Acidobacteria and Actinomycetes increased,that is,the relative abundance of type K microorganisms increased compared with type r microorganisms.It can be speculated that a real priming effect was produced,and the intensity of the priming effect increased with the increase of temperature.The results of laboratory culture experiments showed that the soil priming effect had a significant lasting effect from Day 3 to 60.Increasing temperature significantly increases the intensity of the priming effect.The addition of nitrogen at different temperatures changed the intensity of soil priming effect from positive to negative,and the intensity of low nitrogen,medium nitrogen,and high nitrogen decreased by 71.1%,90.8% and 113.3% on average,respectively,compared with that of the control carbon.In the 15 ? treatment,the intensity of the soil carbon priming effect was weakened with the increase of nitrogen addition level.The activities of soil urease,protease,and ?-glucosidase decreased with the increase of carbon content.The experimental results showed that the higher the temperature,the more significant the reduction of the intensity of soil carbon priming effect was caused by nitrogen addition.Under the combined action of future climate warming and atmospheric nitrogen deposition,global warming may lead to the increase of microbial activity,and the positive soil carbon priming effect is prone to occur,accelerating the mineralization of soil organic matter.However,atmospheric nitrogen deposition may lead to the negative priming effect of soil,which makes soil microorganisms more inclined to take advantage of organic matter which is easy to be used to reduce the decomposition of organic matter which is difficult to decompose,to buffer the increase of instability of soil carbon pool caused by climate warming.Further quantification of the effects of both on soil priming effect is needed,which may be critical for the development of models to accurately predict the stability of soil carbon dynamics and future responses to climate change.