Effects Of Simulated Acid Rain On CO₂ Emission And Microbial Communities In Farmland Soil

In this study,original soil column culture experiments were conducted to simulate the effects of different acidity and frequency of acid rain on CO₂ emissions from farmland soils,and to explore changes in soil physicochemical properties and soil microbial community structure and function under acid rain,attempting to clarify the effect of acid rain on soil CO₂ from multiple perspectives.Our experimental treatments were employed as follows:acidity of simulated acid rain treatments was divided into severe acid rain?pH=3?,moderate acid rain?pH=4?,mild acid rain?pH=5?,CK?pH?7.80?;The frequency of simulated acid rain was divided into three treatments:CK,low-frequency acid rain?ARF1?,and high-frequency acid rain?ARF2?.CO₂ was collected twice a month.Soil nutrients?0-10 cm?,soil microbial biomass and microbial community function under different treatments were measured at the end of the experiment.The main results are as follows:1.Under different acidity acid rain stress,the soil pH value decreased significantly,the total exchangeable acid and exchangeable H⁺content in soil increased significantly,and the soil total nitrogen contents under pH3 and pH4 acid rain treatment were significantly higher than those of CK.The total PLFA amount,bacterial PLFA amount,fungal PLFA amount,and actinomycete PLFA content with each acidity treatment were higher than that of CK,and the amount of bacterial PLFA and the actinomycete PLFA content between pH5treatment and CK were significantly different.The PLFA ratio of bacteria/fungus treated with different acidity was lower than CK,and the ratio of pH3 treatment was the lowest,which was significantly different from that of CK.Treatments with different acidity did not significantly alter soil CO₂ emission rates and cumulative CO₂ emissions.2.Acid rain treatment at different frequencies significantly reduced the soil pH value,and the exchangeable H⁺content increased significantly.The soil total nitrogen content increased significantly with the increase of simulated acid rain frequency.Soil pH value has significant negative correlations with soil alkalized nitrogen and total nitrogen.The total PLFA,bacterial PLFA,fungal PLFA,and actinomycete PLFA content were higher in all treatments than in CK,and there was a significant difference between ARF1 treatment and CK.For the entire observation period,simulated acid rain treatment did not significantly alter CO₂ emissions from farmland soils.In summary,this study used acid spray to simulate the acid rain treatment of farmland soil.By analyzing soil physicochemical properties,microbial community structure and function,and response of farmland soil CO₂ to simulated acid rain,it was found that short-term acid rain leaching significantly reduced soil pH value,soil total nitrogen content increased significantly,and soil microbial community structure changed to a certain extent,but the soil CO₂ emissions did not change significantly.The response of soil CO₂ emission to acid deposition is a complex process.To reveal its specific response mechanism,it is still necessary to conduct long-term positioning research in order to provide scientific basis for the change trend of farmland soil CO₂ emission.