黄土高原刺槐林根际和非根际土壤微生物元素利用效率的季节差异

To investigate the seasonal dynamics and influencing factors of microbial elements use efficiency in the rhizosphere and bulk soils,the rhizosphere and bulk soils of Robinia pseudoacacia plantations in three seasons(Spring,Summer,and Autumn)were selected as the study objects in Ansai area of the Loess Plateau.Soil physicochemical properties,microbial biomass were measured,and stoichiometric imbalance,vector characteristics,and element use efficiency were calculated.The results showed that:(1)In rhizosphere and bulk soil,the variation of C:N imbalance showed summer>spring>autumn and reached a maximum value in summer(0.91 and 3.22),while C:P and N:P imbalance showed a trend of first decreasing and then increasing,suggesting that microorganisms were seasonally affected by substrate imbalance.(2)Changes in vector angle and vector length indicated that both rhizosphere and bulk soil microorganisms were affected by stronger carbon and nitrogen limitation in summer,and stronger phosphorus limitation in spring and autumn(3)The soil microbial carbon use efficiency were the lowest in summer(0.18 and 0.10),and the nitrogen and phosphorus use efficiency were the highest in summer(0.83 and 0.93,0.93 and 0.96)in rhizosphere and bulk soil.(4)Partial least squares path modeling results showed that microorganisms in rhizosphere and bulk soil indirectly influenced elemental use efficiency through stoichiometric imbalance characteristics and extracellular enzyme activities,while stoichiometric imbalance in bulk soil had a direct effect on microbial elemental use efficiency.The results of the study contribute to an in-depth understanding of the nutrient utilization mechanisms of rhizosphere and bulk soil microorganisms in plantation forests,and provide a theoretical basis for the management of plantation forests in ecologically fragile areas.