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

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.

Resources in this dataset:
Resource Title: Website Pointer to html file.
File Name: Web Page, url: https://portal.edirepository.org/nis/mapbrowse?scope=knb-lter-sgs&identifier=521
Webpage with information and links to data files for download

本数据集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。SGS-LTER项目的长期数据集及相关背景资料（包含项目提案、研究报告、影像资料等）均收录于科罗拉多数字馆藏（Digital Collections of Colorado）的综合项目馆藏中，访问链接为：http://digitool.library.colostate.edu/R/?func=collections&collection_id=3429。本数据集包含的数据表及配套元数据文档采用生态元数据语言（Ecological Metadata Language, EML）编制，可通过服务于生态研究共同体的其他仓储平台获取，属于SGS-LTER项目整体馆藏的组成部分。

1971年至1975年，研究人员向样地施加了超出短草草原群落正常耐受范围的水、氮肥以及水氮复合处理；1977年完成植物密度采样后，于1982年恢复采样，采样频率从每年一次调整为每两年一次。1970年至1974年的初始采样结果显示，水、水氮复合处理对植物群落结构的影响最为显著：两类处理均提升了群落生物量，且水氮复合处理样地中出现了外来杂草物种。1982年至1991年的后续采样结果显示，相较于对照组，水氮复合处理样地的外来杂草物种数量增长了10倍（Milchunas & Lauenroth, 1995）；由于植物组织与土壤有机质间的反馈机制导致土壤氮素长期升高，该样地的群落变化得以持续（Vinton & Burke, 1995）。1998年，研究人员在该历史研究样地增设了6组新处理，分别为：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，样地采样频率调整为每5年一次。本研究的目标为探究植物群落随时间的变化规律，并探讨此类变化对潜在受胁迫生态系统监测的启示。更多相关信息及参考资料可通过以下链接获取：http://hdl.handle.net/10217/83317。

本数据集包含的资源如下：
资源标题：指向HTML文件的网站指针
文件名称：网页，访问链接：https://portal.edirepository.org/nis/mapbrowse?scope=knb-lter-sgs&identifier=521
该网页包含相关研究信息并提供数据文件的下载链接。