玉米秸秆对滨海中度盐土微生物活性的提升及机理

Improvement and mechanism of maize straw on microbial activity in coastal moderately saline soils

揭示秸秆添加对滨海中度盐土微生物活性的影响,并探讨其提升机理,可为改善滨海盐土微生物生态功能提供新思路.以山东东营中度盐渍土壤(1501μS/cm)、非盐渍土壤(116.9μS/cm)为供试土壤,分别添加玉米秸秆、不添加秸秆进行室内培养实验.恒温避光培养2个月后进行脱氢酶活性、参与养分循环的9种胞外酶活性以及微生物底物代谢热动力学的测定分析.结果显示,秸秆的添加极大缓解了盐对微生物活性的抑制作用,体现在土壤脱氢酶胞外酶活性显著提升,微生物底物诱导代谢热散逸动力学曲线向非盐渍土壤趋同.玉米秸秆的添加使盐渍土壤碳、氮、磷、硫获取胞外酶活性比例由0.46:1:0.73:1.62变为1.08:1:0.62:0.85,极大增加了碳获取胞外酶的生产比例;而非盐渍土壤胞外酶化学计量比没有发生明显变化.此外,添加秸秆使土壤微生物生物量均得到显著提高,且使盐渍土壤中单位微生物生物量脱氢酶活性从0.37提高到0.66,而对非盐渍土壤却没有显著的促进作用.整体而言,添加秸秆,极大地缓解中度盐渍土壤盐分对微生物活性的抑制作用,加大了盐土微生物对参与碳循环的胞外酶的生产获取以更多的碳源供微生物抵御盐胁迫,进而提升单个细胞活性及微生物生物量,最终使微生物活性得到恢复.

With the aim of improving microbial ecological functions in coastal saline soils,we investigated the effects of straw addition on microbial activity and discussed the mechanisms involved.Soils with moderate-salinity(1501μS/cm)and non-salinity(116.9μS/cm),collected from the coastal areas of Dongying,Shandong Province,China,were incubated with and without maize straw.The activities of dehydrogenase and nine ecoenzymes related to element(C,N,P,and S)cycling were determined after incubation for two months at 28℃.Microbial metabolic activity was evaluated using substrate-induced heat release curves and monitored using microcalorimetric technology.The results showed that microbial activity was significantly inhibited in saline soils.The addition of maize straw can greatly alleviate salt restrictions on microbial activity,which is reflected by the significantly increased activities of both dehydrogenase and the nine ecoenzymes.The substrate-induced heat release curves of the saline soils after straw addition were similar to those of the non-saline soils.Microbial ecoenzymatic stoichiometry showed that the ratio of C,N,P,and S acquiring ecoenzymes activity was shifted from 0.46:1:0.73:1.62 to 1.08:1:0.62:0.85 in saline soils by straw addition,indicating a greatly improved proportion of carbon acquiring ecoenzyme production.In contrast,in non-saline soils,the ecoenzymatic stoichiometry remained stable with and without straw addition.Straw addition not only significantly increased soil microbial biomass in saline soils,but also elevated dehydrogenase activity per unit microbial biomass,from 0.37 to 0.66.In conclusion,1)straw addition significantly alleviated the inhibition of salt on microbial activity in moderate-salinity soils,2)it remarkably promoted the microbial production of C-acquiring ecoenzymes to resist salt stress,improved both microbial biomass and the activity of microbial biomass,and consequently recovered soil microbial activity.