冻融对温带土壤可溶性氮库、氮转化过程及细菌群落多样性的影响

Effects of freeze-thaw on dissolved nitrogen pool,nitrogen transformation processes and diversity of bacterial community in temperate soils

土壤冻融会影响土壤氮的有效性。氮的转化与土壤微生物密不可分,而土壤冻融对温带土壤细菌群落的影响并不十分清楚。假设:冻融影响细菌群落结构多样性及其组成,从而改变土壤可溶氮含量和氮转化过程。为了验证这一假设,本研究设计了不同冻融循环次数(分别为6次和15次循环)的培养试验,并以2℃恒温培养作为对照。结果表明:随着冻融循环次数的增加,可溶性全氮、可溶性无机氮、微生物生物量氮和净氮矿化率均显著降低。冻融循环次数对细菌α多样性(包括Chao1和Shannon指数)无显著影响,恒温培养的培养周期数与细菌的α多样性呈显著正相关。冻融处理显著影响细菌群落功能和组成,但冻融循环次数对细菌群落结构的影响较小。偏冗余分析表明,冻融处理下细菌群落结构和功能多样性与土壤可溶氮含量和氮转化过程密切相关。

Soil freeze-thaw could affect nitrogen(N)availability.The N transformation is closely related with soil microbes.The effect of soil freeze-thaw on the soil bacterial communities in the temperate zone is still not clear.We hypothesized that freeze-thaw events could affect the diversity and composition of bacterial communities,thereby changing the contents of soil dissolved nitrogen pools as well as the N transformation process.In this study,microcosms with different freeze-thaw cycles(six and fifteen cycles)were designed,with the constant temperature at 2℃as the control.The results showed that the contents of dissolved total nitrogen,dissolved inorganic nitrogen,microbial biomass nitrogen and net nitrogen mineralization rate were decreased significantly in response to increasing cycles of freeze-thaw.The number of freeze-thaw cycles did not affect bacterialαdiversity.In contrast,the duration of incubation was positively correlated with bacterialαdiversity including Chao1 and Shannon indices.Freeze-thaw treatment significantly affected the function and composition of bacterial communities,but the number of freeze-thaw cycles had little effect on the bacterial community structure.The partial redundant analysis showed that under freeze-thaw treatments,both the composition and function of bacterial community were significantly related to soil dissolved N pools and N transformation processes.