Warming-El Nino-Nitrogen Deposition Experiment (WENNDEx): Net Primary Production Quadrat Data at the Sevilleta National Wildlife Refuge, New Mexico (2006 - )

Humans are creating significant global environmental change, including shifts in climate, increased nitrogen (N) deposition, and the facilitation of species invasions. A multi-factorial field experiment is being performed in an arid grassland within the Sevilleta National Wildlife Refuge (NWR) to simulate increased nighttime temperature, higher N deposition, and heightened El Niño frequency (which increases winter precipitation by an average of 50%). The purpose of the experiment is to better understand the potential effects of environmental change on grassland community composition and the growth of introduced creosote seeds and seedlings. The focus is on the response of three dominant species, all of which are near their range margins and thus may be particularly susceptible to environmental change.It is hypothesized that warmer summer temperatures and increased evaporation will favor growth of black grama (Bouteloua eriopoda), a desert grass, but that increased winter precipitation and/or available nitrogen will favor the growth of blue grama (Bouteloua gracilis), a shortgrass prairie species. Furthermore, it is thought that the growth and survival of introduced creosote (Larrea tridentata) seeds and seedlings will be promoted by heightened winter precipitation, N addition, and warmer nighttime temperatures. Treatment effects on limiting resources (soil moisture, nitrogen mineralization), species growth (photosynthetic rates, creosote shoot elongation), species abundance, and net primary production (NPP) are all being measured to determine the interactive effects of key global change drivers on arid grassland plant community dynamics.To measure above-ground NPP (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 SEV205, "Warming-El Nino-Nitrogen Deposition Experiment (WENNDEx): Seasonal Biomass and Seasonal and Annual NPP."

人类活动正引发显著的全球环境变化，包括气候格局改变、氮（N）沉降增加以及外来物种入侵加剧。本实验在塞维利塔国家野生动物保护区（Sevilleta National Wildlife Refuge, NWR）内的干旱草原开展，旨在模拟夜间增温、更高水平氮沉降以及增强的厄尔尼诺（El Niño）频率（厄尔尼诺可使冬季降水平均增加50%）。实验的核心目标是深入理解全球环境变化对草原群落组成，以及外来杂酚油灌木（Larrea tridentata）种子与幼苗生长的潜在影响。本研究聚焦于3种优势物种的响应——这三个物种均处于其分布范围的边缘地带，因此对环境变化尤为敏感。研究假设：夏季升温与蒸发加剧将有利于荒漠草本植物黑格兰马草（Bouteloua eriopoda）的生长，而冬季降水增加与/或有效氮供给提升则会促进短草草原物种蓝格兰马草（Bouteloua gracilis）的生长。此外，研究推测冬季降水增加、氮添加与夜间升温将促进外来杂酚油灌木（Larrea tridentata）种子与幼苗的生长及存活。本实验将测定不同处理对限制性资源（土壤湿度、氮矿化速率）、物种生长（光合速率、杂酚油灌木枝条伸长量）、物种多度以及净初级生产力（NPP）的影响，以明确关键全球变化驱动因子对干旱草原植物群落动态的交互效应。为测定地上净初级生产力（即随时间推移植物生物量的变化，生物量由茎秆、花、果实与叶片构成），本数据集的植被变量（包括物种组成、个体盖度与高度）将通过在永久1m×1m样地每年两次（春季与秋季）采样获取。研究人员将利用样地采集的数据，结合SEV157数据集《净初级生产力（NPP）重量数据》中获取的选定收获物种的生物量干重，构建生物量与体积的回归模型。该生物量数据已收录于SEV205数据集《增温-厄尔尼诺（El Niño）-氮沉降实验（WENNDEx）：季节性生物量与季节及年度净初级生产力》。