Thermal Adaptation Of Soil Microbial Respiration Of Farmland In Typical Climatic Zones In China

The response of terrestrial ecosystem carbon cycle to global warming is currently a hot issue studied by scholars at home and abroad.Some scholars have proposed that as the temperature continues to rise,soil microbial respiration will produce thermal adaptability to slow down the increase in its respiration.As the rate-limiting step of soil respiration,soil enzyme activity is one of the mechanisms of soil microbial respiration and thermal adaptation.Based on this,this paper selects five farmland ecosystem soils from different climatic zones in my country to study their response to environmental temperature;and conducts laboratory simulation warming experiments to study the effects of different culture temperatures(10?,30?)on soil microbial respiration Influence,observe its thermal adaptability;select five kinds of enzymes related to the carbon,nitrogen and phosphorus cycle,observe the response of their activities to warming,and explore the mechanism of their changes with the help of kinetics.The following results are obtained:(1)Soil microbial respiration in our country's farmland ecosystems did not produce thermal adaptation on the annual mean temperature(MAT)gradient,which may be due to the small sample size and differences in soil properties.On the MAT gradient,the soil?-glucosidase,xylanase,and cellobiohydrolase activities decrease with the increase of MAT,and are significantly negatively correlated with MAT.These key enzymes involved in cellulose and hemicellulose degradation contribute significantly to the thermal adaptation of soil microbial respiration.The Q₁₀of farmland soil enzymes in all climatic zones is greater than 1,and the Q₁₀of the lower temperature(10-20?)interval is greater than the higher temperature(20-30?)interval.The Q₁₀of cellobiohydrolase is the highest,indicating that it has the strongest response to temperature changes.?-glucosidase and cellobiohydrolase Q₁₀are significantly negatively correlated with climate factors MAT and MAP,showing thermal adaptability.(2)The content of microbial biomass carbon(MBC)varies with the nature of the soil,the cultivation temperature and the cultivation time.The MBC content is different among different soil samples.The order of magnitude is:Lou soil>Black soil>Red soil>Lateritic red soil>Brown soil.During the cultivation stage,the microbial biomass carbon of soil cultivated at high temperature is higher than that of soil cultivated at low temperature.Brown soil and loess soil had thermal adaptation on the 84th and 63rd day,respectively,which are the first types of adaptation.The Black soil,Red soil and Lateritic red soil did not find thermal adaptation during the 84-day cultivation period,indicating the thermal adaptation of soil microbial respiration It is related to soil properties and cultivation time.(3)The soil enzyme activity increased with the increase of measured temperature and decreased with the extension of culture time.At the same measuring temperature,the enzyme activity of soil cultured at low temperature was higher than that of soil cultured at high temperature.The difference increased with the increase of culture time,indicating that soil enzymes had an adaptive response to temperature increase.(4)Soil enzyme V_maxincreased with the measured temperature in different climatic zones,while K_mshowed different rules with the measured temperature.The response to temperature was complex.V_max/K_mincreased with the increase of temperature.The respiration of soil microorganisms produces heat-adapted brown soil xylanase,N-acetylglucosaminidase,and acid phosphatase.Vmax has an adaptive response.Only the V_maxof cellobiohydrolase in loess soil has an adaptive response,indicating that the microorganisms The thermal adaptation of respiration may be due to the adaptation of certain enzymes in the soil.The catalytic efficiency V_max/K_mof?-glucosidase,xylanase,and cellobiohydrolase is extremely significantly negatively correlated with MAT(p<0.01),showing thermal adaptability at the latitude level.(5)In summary,by studying the response of farmland soils in different temperature zones to environmental temperature and simulated warming,observing the changes in enzyme activity and kinetic parameters during the warming process,in order to deeply explore the thermal adaptability of farmland soil microbial respiration and its The mechanism provides a theoretical basis.