Effects Of Warming And Straw Application On Soil Respiration And Microbial Community Structure In Cropland

The greenhouse effect of greenhouse gas CO₂ is the main cause of climate warming.As an important link of the carbon cycle,the dynamics of soil respiration will directly affect the carbon balance.As the balancer of soil carbon sources and sinks,microorganism have an important impact on soil carbon emissions.Crop straw is an important resource of organic matter.The effects of the combination of warming and straw application on soil respiration and microbes are still unclear.This work was carried out in a field experiment at the Agro-meteorological Experiment Station of Nanjing University of Information Engineering from November 2020 to October 2022.The planting method was winter wheat and soybean rotation.There were four treatments:control（CK）,warming（WA）,straw application（SA）and warming+straw application（WASA）.Soil warming measures is performed by using heating tubes with infrared radiation function.Soil respiration rate was measured weekly by using portable soil carbon flux analyzer（LI-8100A）,along with soil temperature,soil moisture,and soil physical and chemical properties and microbial indicators were sampled to investigate the effects of different warming and straw applications on soil respiration and microbiology.The paper also aims to clarify the response of soil respiration,characterise the soil microbial community structure under warming and straw application conditions,and further elucidate the relationship between soil physicochemical properties,microorganisms and soil respiration.The main conclusions of this paper are as follows:（1）During the experimental period from 2020 to 2022,The variation of soil respiration has seasonal rhythm,which was consistent with the variation of soil temperature and the variation of temperature in this region.Due to the priming effect,soil respiration rates were briefly high at the beginning of the growing season,and then increased and then decreased throughout the growing season.Within a rotation year,soil respiration rates were higher in the soybean growing season than in the winter wheat growing season.Both warming and straw application had an effect on soil respiration rates,with the highest rates under the WASA treatment.（2）Temperature increase and straw application changed soil physicochemical properties.The warming and straw application increased total soil porosity,capillary porosity,field water holding capacity,organic carbon（SOC）and total nitrogen（TN）content,and significantly reduced soil p H.warming and straw application did not significantly affect soil microbial biomass carbon in 2020 and 2021,but soil microbial biomass carbon was higher in the WA and WASA treatments than in the CK treatment.Soil microbial biomass nitrogen was significantly different between treatments in 2020 and 2021,with CK,SA and WASA having lower soil microbial biomass nitrogen in 2022 than in 2021.（3）Warming and straw application significantly affected the community composition of soil bacteria,fungi and archaea.No significant differences（p>0.05）in the relative abundance of the dominant bacterial and archaeal communities were found between the warming and straw treatments.The most dominant communities of soil bacteria,fungi and archaea in 2020,2021and 2022 were identical at the phylum level and differed slightly at the genus level.There were effects of temperature increase and straw application on soil microbialαdiversity andβdiversity.Experimental treatments and duration resulted in different bacterial,fungal and archaealαandβdiversity.Compared to CK,SA partially offset the WA-induced decrease in bacterialαdiversity in 2020;fungalαdiversity was significantly higher in SA than in the other treatments in 2020.bacterial and fungal Bray-Curtis distances between treatments were generally greater in 2021 and 2022 than in 2020.There were significant correlations between bacterial and fungal alpha and beta diversity and soil physicochemical properties.At the phylum level,soil SOC had a significant effect on the community composition of bacteria,fungi and archaea.（4）Soil temperature significantly influenced soil respiration rates,followed by soil moisture and p H.There was a significant correlation between soil microbial diversity and soil respiration,and there was a significant correlation between bacterial Bray-Curtis distance,PD index and Chao1 index and soil respiration.Fungi Shannon index and Simpson index,archaea PD index and Chao1 index were significantly correlated with soil respiration,but not with fungi and archaeaβdiversity.The present study showed that warming and straw application promoted soil respiration and significantly changed the structure of the soil microbial community structure.In the context of warming and straw application,soil respiration was correlated with soil physicochemical properties and soil microbial community structure.This study provides basic data for exploring the effective use of crop straw in the context of global climate change to promote carbon peaking and carbon neutrality.