SGS-LTER Ecosystem Stress Area - long-term point-frame (percent basal cover) dataset following nutrient enrichment stress on the Central Plains Experimental Range in Nunn, Colorado, USA 1982-2011, ARS Study Number 3 (Reformatted to a Darwin Core Archive)

This data package is formatted as a Darwin Core Archive (DwC-A, event core). For more information on Darwin Core see https://www.tdwg.org/standards/dwc/. This Level 2 data package was derived from the Level 1 data package found here: https://pasta.lternet.edu/package/metadata/eml/edi/331/2, which was derived from the Level 0 data package found here: https://pasta.lternet.edu/package/metadata/eml/knb-lter-sgs/521/7. The abstract below was extracted from the Level 0 data package and is included for context: This data package was produced by researchers working on the Shortgrass Steppe Long Term Ecological Research (SGS-LTER) Project, administered at Colorado State University. Long-term datasets and background information (proposals, reports, photographs, etc.) on the SGS-LTER project are contained in a comprehensive project collection within the Digital Collections of Colorado (http://digitool.library.colostate.edu/R/?func=collections&collection_id=3429). The data table and associated metadata document, which is generated in Ecological Metadata Language, may be available through other repositories serving the ecological research community and represent components of the larger SGS-LTER project collection. Water, nitrogen, and water-plus-nitrogen at levels beyond the range normally experience by shortgrass steppe communities were applied from 1971 through 1975, plant densities were sampled through 1977, and then sampling resumed in 1982, with sampling frequencies changing from annually to every other year. The initial sampling from 1970 to 1974 showed that the water and water plus nitrogen treatments had the strongest effect on plant community structure, both treatments increased biomass, and exotic weed species were noted on the water plus nitrogen treatment. Later sampling from 1982 to 1991 showed a ten-fold increase in exotic weed species on the water plus nitrogen plots as compared to the controls (Milchunas and Lauenroth 1995), a community change that has persisted on this site due to a chronic elevation of soil nitrogen caused by a plant tissue/soil organic matter feedback mechanism (Vinton and Burke 1995). In 1998, Six new treatments were superimposed on the historic study site. The six new treatments were: control, sugar, lignin, sawdust, lignin and sugar, and sawdust and sugar.In 2010, plots will be sampled every 5 years. Our objective in this study is to examine how plant communities change through time and explore implications of these changes for monitoring potentially stressed ecosystems. Additional information and referenced materials can be found: http://hdl.handle.net/10217/83317. The Shortgrass Steppe Long Term Ecological Research (SGS-LTER) project was funded by National Science Foundation as one of the first sites in the US LTER Network in 1982. This collaborative, interdisciplinary research project was established in the Natural Resource Ecology Lab at Colorado State University by ecosystem scientists who learned novel approaches to study grassland ecosystems during the International Biome Program (IBP) (1968-1974). The SGS-LTER project was built upon the foundation of data and information obtained during IBP, as scientists sought to identify and follow, and often manipulate in experiments, important ecosystem processes over the long-term. The objectives of the SGS-LTER project were to investigate what mechanisms regulate processes in the shortgrass steppe. Research questions focused on how biotic and abiotic components of the ecosystem are coupled, where and when ecosystem components are most vulnerable to perturbations, disseminating information that would be helpful for rangeland management and assessing impacts of climate change. Scientists explored variations in the structure and function of the ecosystem over space and time and sought to understand how these aspects are governed by climate, natural disturbance, biota, physiography, and human use. Scientists at the SGS-LTER integrated long-term monitoring data, designed experimental studies, performed and advanced modeling techniques, and synthesized data to conduct innovative research, education, and outreach. The core SGS-LTER research site was established on the Central Plains Experimental Range (CPER) in Nunn, Colorado, part of the United States Department of Agriculture’s Agricultural Research Service. The research site sits in the rain shadow of the Rocky Mountains at the western edge of the shortgrass steppe of North America. The shortgrass steppe ecosystem evolved with grazing by the American bison, which has now been replaced by cattle. Grazing by domestic livestock is the primary land use of native grassland, which occupies about 60% of the land area of the shortgrass steppe. Short grasses dominate the vegetation community, which have adapted to grazing and less than 400 mm of annual rainfall. The topography is characterized by gently rolling hills, broad ephemeral stream courses and low flat-topped terraces. Aspects of physiography regulate the shortgrass steppe ecosystem, including landscape position, soil age, water holding capacity, soil depth and surface texture which, in turn, determine such properties as soil moisture storage, net primary productivity and the distribution of small mammals such as prairie dogs and pocket gophers. SGS-LTER scientists have expanded their research studies beyond the CPER to identify similar or different patterns in ecosystem structure and function in North American grasslands; across the Great Plains region and along the latitudinal gradient from Wyoming to Mexico. They also conducted cross-site collaborative research and compared their results and tested theories in grasslands located in South America, Asia and Africa. Funding from NSF for the SGS-LTER project ends in 2014, but over thirty years of research has resulted in a scientific team with diverse expertise, which produced over 1200 journal publications, almost 400 book chapters and over 200 theses. Data, products and other information produced from the SGS-LTER are available through the LTER Network Information System, Digital Collections of Colorado at CSU or upon request through [e-mail].本数据包采用达尔文核心档案（Darwin Core Archive, DwC-A）事件核心格式。有关达尔文核心标准的详细信息，请参阅https://www.tdwg.org/standards/dwc/。本二级数据包源自以下一级数据包：https://pasta.lternet.edu/package/metadata/eml/edi/331/2，而该一级数据包又源自以下零级数据包：https://pasta.lternet.edu/package/metadata/eml/knb-lter-sgs/521/7。以下摘编自零级数据包的摘要用于提供背景信息： 本数据包由参与短草草原长期生态研究（Shortgrass Steppe Long Term Ecological Research, SGS-LTER）项目的研究人员编制，该项目由科罗拉多州立大学负责管理。有关SGS-LTER项目的长期数据集及背景资料（包括研究提案、报告、影像资料等），均收录于科罗拉多数字馆藏（http://digitool.library.colostate.edu/R/?func=collections&collection_id=3429）中的综合项目馆藏中。本数据表及采用生态元数据语言（Ecological Metadata Language）生成的关联元数据文档，可通过其他服务于生态研究社群的仓储平台获取，亦属于SGS-LTER项目整体馆藏的组成部分。 1971年至1975年间，研究人员向样地施加了超出短草草原群落自然耐受范围的水、氮及水氮复合处理；1977年之前持续监测植物密度，1982年恢复监测，监测频率从每年一次调整为每两年一次。1970年至1974年的初始监测结果显示，水和水氮复合处理对植物群落结构影响最为显著：两类处理均提升了生物量，且水氮复合处理样地出现了外来杂草物种。1982年至1991年的后续监测显示，与对照组相比，水氮复合处理样地的外来杂草物种丰度提升了10倍（Milchunas与Lauenroth，1995）；由于植物组织/土壤有机质反馈机制导致土壤氮素长期富集，该样地的群落结构变化至今仍在持续（Vinton与Burke，1995）。1998年，研究人员在该历史研究样地增设了6组新处理：对照组、蔗糖组、木质素组、锯末组、木质素+蔗糖组以及锯末+蔗糖组。2010年起，样地监测频率调整为每5年一次。本研究旨在探究植物群落随时间的变化规律，并分析此类变化对受胁迫生态系统监测的启示。更多相关信息及参考文献可参阅：http://hdl.handle.net/10217/83317。 短草草原长期生态研究（SGS-LTER）项目于1982年由美国国家科学基金会（National Science Foundation, NSF）资助，是美国LTER网络首批设立的站点之一。该跨学科合作研究项目由科罗拉多州立大学自然资源生态实验室的生态学家发起，这些研究者曾在国际生物群系计划（International Biome Program, IBP，1968-1974）期间掌握了研究草原生态系统的创新方法。SGS-LTER项目依托IBP期间获取的数据与信息基础展开研究，旨在长期识别、追踪并通过实验操控关键生态过程。 本项目的研究目标为解析调控短草草原生态过程的机制，具体研究问题包括：生态系统的生物与非生物组分如何耦合？生态系统组分在何时、何地最易受到扰动？以及产出可为牧场管理提供参考的信息、评估气候变化的影响。研究者探索了生态系统结构与功能在时空尺度上的变异，旨在阐明气候、自然干扰、生物群落、地貌特征及人类活动对生态系统的调控机制。SGS-LTER团队整合长期监测数据、设计受控实验、运用先进建模技术并开展数据综合分析，以推进创新性研究、教育与科普工作。 项目核心研究场地设立于科罗拉多州努恩市的中央平原实验牧场（Central Plains Experimental Range, CPER），该场地隶属于美国农业部农业研究服务局。研究场地位于北美短草草原西缘的落基山脉雨影区，其原生植被以短草为主，这类植物已适应放牧环境与年均降雨量不足400毫米的气候条件。该区域的地貌以缓坡丘陵、季节性宽河道和平顶低阶地为主要特征。地貌属性（包括景观位置、土壤龄期、持水能力、土层深度及地表质地）调控着短草草原生态系统，进而决定了土壤水分储量、净初级生产力以及草原犬鼠、囊鼠等小型哺乳动物的分布格局。 SGS-LTER的研究范围已从CPER扩展至北美草原的其他区域：涵盖大平原地区以及从怀俄明州到墨西哥的纬度梯度样带。团队还与南美、亚洲及非洲的草原研究机构开展跨站点合作，对比研究结果并验证相关理论。NSF对SGS-LTER项目的资助于2014年终止，但历经三十余年的研究已打造出一支专业背景多元的科研团队，累计发表期刊论文1200余篇、图书章节近400部、学位论文200余篇。SGS-LTER产出的数据、研究成果及其他相关信息，可通过LTER网络信息系统、科罗拉多州立大学科罗拉多数字馆藏获取，或通过邮件[e-mail]申请获取。