Effects Of Carbon Addition On Carbon Pool Dynamics And CO₂-Assimilating Bacteria Diversity Of Two Typical Soils In Northeast China

Carbon source has high biochemical stability and strong adsorption performance,which plays an important role in improving soil quality,increasing the number of soil microorganisms and maintaining the stability of soil carbon pool.To clarify the mechanism of different carbon sources in soil carbon metabolism is of great significance to maintain and improve soil quality.Straw,biochar and nano-carbon were added in the black and saline fields in the northeast of China,in order to study the changes of soil carbon pool dynamics and CO₂-assimilating bacteria and comparing the difference of response mechanism between the two types of soils.The study would provide basis for maintaining productivity of black and saline soils.The results were as follows:1.The chemical properties,ecological metrological characteristics and soil carbon pool dynamic indexes in the rhizosphere were mostly higher than in the non-rhizosphere with three different carbon treatments in black soil and saline-alkali soil.However,compared with the no carbon addition treatment,the change of above indexes in the rhizosphere and in the non-rhizosphere with three carbon addition treatments were different.2.After the addition of three carbon sources,soil pH increased in the rhizosphere and non-rhizosphere of black soil,but decreased in the non-rhizosphere of saline soil.In black and saline-alkali soil,the nutrient content in rhizosphere and non-root after adding three carbon sources decreased mostly,but the content of available nitrogen with three carbon addition in the rhizosphere of black soil,the content of organic carbon and total phosphorus with biochar adding in the non-rhizosphere of black soil and with straw adding in the non-rhizosphere of saline-alkali soil increased.Soil ecological stoichiometry characteristics with three carbon addition were mostly unchanged or decreased by nutrient changes in black soil and saline-alkali soil,but C:N increased with three carbon addition and C:P increased after straw and biochar addition in non-rhizosphere soil.3.In black soils,after the addition of the three carbon sources,the dynamic index of soil carbon stocks mostly decreased,but soil rhizosphere active organic carbon after straw addition,soil non-rhizosphere inactive organic carbon after straw and biochar addition,and soil non-rhizosphere carbon bank index after biochar addition increased.In saline-alkali soils,soil active organic carbon,carbon stock activity,carbon stock activity index and carbon stock management index all increased in rhizosphere and decreased in non-rhizosphere after the addition of three carbon sources.The soil inactive organic carbon and carbon stock index decreased in rhizosphere,while the soil inactive organic carbon and soil carbon stock index increased in rhizosphere after the addition of straw and biochar.4.In terms of community composition and relative abundance,the predominant phylum in black soil and saline-alkali soil after no carbon and three kinds of carbon treatments is Proteobacteria,and the dominant bacterium is?-proteobacteria.After the addition of three carbon sources,the species abundance of CO2-assimilating bacteria in black soil was greater than that in saline-alkali soil,and the species abundance of CO2-assimilating bacteria in black soil was improved by the addition of biochar.The Observed species index,Chao1 index and Shannon index of CO2-assimilating bacteria have not changed or decreased in black soil and saline-alkali soil.There were significant differences among community groups in black soil after straw adding,mainly includes Thioalkalivibrio and Thiocystis.After the addition of biochar to saline-alkali soil,the main species were Thiobacillaceae and Nitrosomonadales.5.The results of principal component analysis showed that carbon metabolism of black and saline-alkali soil was still regulated by soil chemistry,ecological stoichiometry,carbon pool dynamic and CO2-assimilating bacteria after the addition of three carbon sources,but in the black soil,the proportion of phosphorus in soil decreased and the diversity of carbon metabolism microorganisms increased,and the CO2-assimilating bacteria in saline soil play a smaller role.