氮沉降的遗留效应对内蒙古典型草原根系动态的影响

随着各国对含氮化合物排放的管控日趋严格，很多地区的氮沉降呈现下降趋势。因此，探索已发生的氮沉降对生态系统的后续影响，即其遗留效应，将是生态学领域中的重要课题之一。根系是养分和水分吸收的重要器官，可以通过调控其生长、死亡和存活时间，使植物养分吸收和利用效率最大化，然而，氮沉降将会对植物根系动态产生何种遗留效应尚属于知识空白。本研究拟以内蒙古锡林郭勒典型草原生态系统为研究对象，依托现有模拟氮沉降及停止氮添加的野外实验平台，通过野外控制实验以及对根系的原位追踪观测，研究草原根系动态，即根系出生和死亡、根系周转、根系寿命等指标，对不同程度氮素遗留效应的变化规律。结合研究根系动态与草原地上净生产力、群落物种组成及土壤理化性质的关系，探究生物因子与非生物环境中影响根系动态的驱动因素，本研究中根系动态的响应将为预测未来氮沉降变化对温带草地生态系统结构和功能的影响提供数据支持和理论依据。

As the emission of nitrogenous compounds has been controlled strictly by numerous countries, the nitrogen deposition in many regions shows a downward trend. Therefore, exploring the subsequent effects of historical nitrogen deposition, that is, the legacy effects, will be one of the vital topics in the field of ecology. Roots, known as the important organ for water and nutrients absorption, could regulate the growth, mortality, and survival duration to maximize the efficiency of nutrient absorption and utilization. However, there is still a huge knowledge gap about the legacy effects of historical nitrogen input which may influence root dynamics. This study would focus on a temperate steppe, relying on a field experiment that simulates the nitrogen deposition and cessation of nitrogen deposition in Xilinhot, Inner Mongolia. With the control experiment in the field and follow-up observations of root systems in situ, we will study the patterns of root dynamics, that is, the root birth, death, turnover, and lifespan, in response to the accumulative nitrogen addition at different levels. Additionally, this study will be concerned with root turnover which would be related to aboveground net primary productivity, community species composition, and soil properties of the grassland, with aims to explore the driving causes among possible biotic and abiotic factors affecting root dynamics. This study will have clear implications for the formulation of root responses to historical nitrogen deposition in global biogeochemical cycle models to more accurately predict the potential impact of nitrogen deposition on the structure and function of the temperate steppe ecosystem in the future.