To Simulate The Effects Of Climate Change On The Structure Of Soil Nitrification And Denitrifying Bacterial Communities In The Wheat Rhizosphere

Climate change,mainly characterized by rising atmospheric CO2concentrations and rising temperatures,has had serious impacts on global food production and agricultural production,threatening the sustainability of agriculture.Soil microorganisms are the main drivers of soil nitrogen conversion,which determine the inorganic nitrogen concentration and N2O emissions,so they have an important role in improving soil quality and slowing down climate change trends.However,the impact of global climate change factors on farmland soil N2O emissions and its microbial regulation mechanism in China are still uncertain.Based on the open simulated climate change test platform,we monitored soil N2O emission in wheat season,analyzed the physical and chemical properties of wheat tiller,heading and mature period,and studied the influence of atmospheric CO₂ concentration on the abundance and community structure of ammonia-oxidizing bacteria(AOB),AOA)and denitrifying microorganisms(nir K,nir S and nos Z).The climate change platform has four treatments:atmospheric CO2 concentration increase treatment(500ppmv,CE),temperature increase treatment(+2?,WA),atmospheric CO2 concentration and temperature increase treatment(CW),and control treatment(CK).The main study results are as follows:(1)Effect of atmospheric CO₂ concentration increase and warming on soil properties:CE treatment significantly improves organic carbon(SOC)and total nitrogen(TN)in wheat soil,but reduces soil effective phosphorus(AP)and quick potassium(AK)content;WA treatment improves TN and AK content,but reduces soil p H and AP.In CW treatment,elevated CO2 concentration and warming interaction had no effect on soil inorganic nitrogen(NH4+/NO3-),but significantly increased SOC and TN.(2)Effect of atmospheric CO₂ concentration increase and warming on AOB and AOA community structure:The results indicate that CO₂ concentration increase and warming may change AOB abundance and community composition in wheat soil,but may have no effect on AOA abundance and community composition.CE treatment significantly increased AOB abundance(47.4%),and WA treatment reduced AOB abundance(18.1%),while CW treatment had no significant effect on AOB abundance.High-throughput sequencing analysis showed that Nitrosospira and Nitrosomonas were the two genus-like microorganisms with the highest relative abundance in the AOB community,with elevated CO₂ concentrations increasing the relative abundance of genus Nitrosospira and decreasing the relative abundance of genus Nitrosomonas.Redundancy analysis(RDA)analysis showed that increasing CO₂concentration significantly changed AOB community structure,while warming had no effect on AOB community structure,and soil SOC,p H and TN are possible key factors to change AOB community structure.(3)Effect of atmospheric CO₂ concentration increase and warming on denitrification microbial community structure:compared with control,the increase of nir K gene abundance in denitrification bacteria(29.1%),and warming treatment reduced the abundance of nir S and nos Z genes by 8.6%and 21.9%,respectively.WA treatment significantly improved the nir K-community concentration index and had no effect on the nir S-and nos Z-community diversity index;CE and CW treatment significantly reduced the nos Z-community diversity index(Shannon and Chao1).RDA analysis showed that elevated CO₂ concentrations significantly altered nir K-and nos Z-denitrifying microbial community structure,while heating had no effect on their family energy,and soil SOC,p H and TN were also key factors that might alter the structure of nirK and nosZ denitrifying microbial communities.