Primary Study Of Soil Dissolved Organic Carbon Adjusting Soil Bacterial Diversity

Soil dissolved organic carbon(DOC)account for a small proportion of the soil organic carbon(SOC),but DOC is very sensitive to the fertility status of the farmland,and it is the most important and active part of the soil organic carbon.In this study,we analyzed the correlation between the content of SOC and DOC,and processed some physiological behaviors of soil ecological isolated bacteria and soil pathogenic bacteria with different concentrations of DOC,bacterial motility,bacterial biofilm and carbon sources utilization in the laboratory and soil test.We analyzed and discussed the relationship between several soil health indexes such as soil organic matter,DOC content,soil enzymes activities,the number of soil bacteria and the early growth and development status of tobacco.We aimed at providing a scientific basis for revealing the mechanism of soil bacterial diversity in soil DOC.The main results were as follows:(1)There was a significant positive linear correlation between the content of SOC and DOC.By measuring the acid soil of Jiangxi tobacco field and the basic soil samples in Henan tobacco field,it was found that regions where has higher organic matter,the DOC concentration is higher too.Correlation analysis showed that the soil organic carbon content was significantly positively correlated with DOC content,linear equation was y = 21.835 x + 77.222(R2 = 0.95397),and the significant correlation coefficient was 0.954(P < 0.05).(2)DOC can promote the growth of soil ecological bacteria,bacteria wilt and bacteria wildfire and show a positive dose effect.But the effect of DOC on bacteria was different in rich bacteria and in poor nutrition medium.In the lab experiment,we found the reproduction rate of bacteria in rich nutrition and in poor nutrition added DOC were higher than those of the control(no added DOC),but it was more obvious in poor nutrition medium after added DOC.Single strain soil bacteria or their mixture have shown the same results.But when all soil bacteria were cultured together,the proportion of bacteria wilt and the DOC concentration showed negative correlation trend,which indicated that with increasing DOC concentration,the competitive ability of bacteria wilt for nutrition was inhibited by the soil eco-bacteria community.(3)DOC can improve the motility of a variety of bacteria,and the sensitivity of different soil bacteria on DOC is different.According to the different sensitivity of DOC,the tested bacteria could be divided into three categories: 5 strains of soil isolated bacteria include 30?P3?38?A5?A21 were extremely sensitive to DOC,because the bacteria motor in low and high DOC concentrations had reached a significant difference related to the control;3 strains soil isolated bacteria P1?A7?P8 were sensitive to DOC,because the bacteria motor in high DOC concentration were significantly different with the control;Bacteria wilt and soil ecological bacteria A3 was not sensitive to DOC,because although DOC can promote their movement,but there was no significant difference with their own controls(P < 0.05).(4)Under both rich and poor nutrition condition,increasing DOC can enhance the ability of biofilm formation of soil bacteria,but the bacteria biofilm formation ability under rich condition was stronger than that under poor condition.According to the different sensitivities of the tested bacteria to DOC,we divided the tested bacteria into 3 types: 1)Extremely sensitive type.Including an soil ecological bacterium strain,very sensitive under both rich and poor nutrition conditions,3 strains(including bacteria wilt),very sensitive under rich nutrition condition,and one strain,only sensitive to the poor nutrition condition;2)Sensitive type.Including 3 strains of soil ecological bacteria,sensitive under rich nutrition condition,and one strain,sensitive to the poor nutrition condition;3)Insensitive type.Including 3 strains only insensitive to rich condition and 6 strains,insensitive to poor condition.Under poor nutrition condition,the sensitivity of most tested bacteria to DOC were decreased,only A10,one type of soil ecological bacteria,showed the opposite situation,but the biofilm formation ability of bacteria wilt was significantly inhibited under poor nutrition condition.(5)The results of bare soil and potted tobacco test of continuous cropping tobacco feild added with DOC showed that: increasing the DOC content of soil can promote the growth of tobacco and enhance the vitality of root system;it can also increase the content of soil organic carbon,soil enzymes(amylase,invertase and cellulase)activities,sole carbon source utilization ability,and Shannon,Simpson and Mc Intosh diversity indexs of soil bacteria were improved,while the relative proportions of soil pathogens reduce.All these showed that increasing DOC could improve soil micro-ecological and showed some positive dose effect on soil health remediation of continuous cropping tobacco field.Comprehensive analysis the results above,it is suggested that DOC can directly affect a series of physio-chemical metabolism of soil bacteria,and then adjust soil bacteria diversity and soil micro-ecological environment,but the effect of DOC on different soil bacteria species are different.This results of this study have not been reported at home and aborad.