Monsoon Rainfall Manipulation Experiment (MRME) Soil Temperature, Moisture and Carbon Dioxide Data from the Sevilleta National Wildlife Refuge, New Mexico

The Monsoon Rainfall Manipulation Experiment (MRME) is designed to understand changes in ecosystem structure and function of a semiarid grassland caused by increased precipitation variability, by altering rainfall pulses, and thus soil moisture, that drive primary productivity, community composition, and ecosystem functioning. The overarching hypothesis being tested is that changes in event size and frequency will alter grassland productivity, ecosystem processes, and plant community dynamics. Treatments include (1) a monthly addition of 20 mm of rain in addition to ambient, and a weekly addition of 5 mm of rain in addition to ambient during the months of July, August and September. It is predicted that changes in event size and variability will alter grassland productivity, ecosystem processes, and plant community dynamics. In particular, we predict that many small events will increase soil CO2 effluxes by stimulating microbial processes but not plant growth, whereas a small number of large events will increase aboveground NPP and soil respiration by providing sufficient deep soil moisture to sustain plant growth for longer periods of time during the summer monsoon.季风降雨调控实验（Monsoon Rainfall Manipulation Experiment, MRME）旨在通过改变降雨脉冲及其驱动初级生产力、群落组成与生态系统功能的土壤水分条件，阐明降水变异增强对半干旱草地生态系统结构与功能的影响。 本实验所验证的核心假说为：降雨事件的规模与频率变化将改变草地生产力、生态系统过程及植物群落动态。 实验设置如下两类处理：(1) 除自然降雨外，每月额外施加20 mm降水；以及在7、8、9月期间，除自然降雨外，每周额外施加5 mm降水。 研究预测，降雨事件规模与变异程度的变化将改变草地生产力、生态系统过程及植物群落动态。 具体而言，我们提出以下预测：多数小型降雨事件将通过刺激微生物过程提升土壤CO₂排放通量，但不会促进植物生长；而少量大型降雨事件则可通过提供充足的深层土壤水分，使植物在夏季季风期维持更长时间的生长，进而提升地上净初级生产力（aboveground NPP）与土壤呼吸速率。