Monsoon Rainfall Manipulation Experiment (MRME): Net Primary Production Quadrat Data at the Sevilleta National Wildlife Refuge, New Mexico (2006- )

The Monsoon Rainfall Manipulation Experiment (MRME) is to understand changes in ecosystem structure and function of a semiarid grassland caused by increased precipitation variability, which alters the pulses of soil moisture that drive primary productivity, community composition, and ecosystem functioning. The overarching hypothesis being tested is 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 net primary production (ANPP) and soil respiration by providing sufficient deep soil moisture to sustain plant growth for longer periods of time during the summer monsoon.To measure ANPP (i.e., the change in plant biomass, represented by stems, flowers, fruit and foliage, over time), the vegetation variables in this dataset, including species composition and the cover and height of individuals, are sampled twice yearly (spring and fall) at permanent 1m x 1m plots. The data from these plots is used to build regressions correlating biomass and volume via weights of select harvested species obtained in SEV157, "Net Primary Productivity (NPP) Weight Data." This biomass data is included in SEV206, "Seasonal Biomass and Seasonal and Annual NPP for the Monsoon (MRME) Study."

季风降雨调控实验（Monsoon Rainfall Manipulation Experiment, MRME）旨在解析降水变异增强对半干旱草原生态系统结构与功能的影响：降水变异会改变驱动初级生产力、群落组成及生态系统功能的土壤水分脉冲事件。本实验所验证的核心假说为：降雨事件规模与变异的改变，会调控草原生产力、生态系统过程及植物群落动态。具体而言，本研究预测：大量小型降雨事件会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内维持更长时间的生长，进而提升地上净初级生产力（aboveground net primary production, ANPP）与土壤呼吸速率。为测定地上净初级生产力（即植物生物量随时间的变化，以茎秆、花、果实及叶片生物量表征），本数据集通过永久1m×1m样方每年开展两次植被调查（春季与秋季），采集的植被变量包括物种组成、单株盖度与高度。上述样方采集的数据，将通过SEV157数据集《净初级生产力（Net Primary Productivity, NPP）权重数据》中获取的选定收获物种的生物量权重，构建生物量与体积的回归模型。该生物量数据收录于SEV206数据集《季风降雨调控实验（MRME）研究的季节生物量及季节、年度净初级生产力》。