SGS-LTER Ecosystem Stress Area - Soil Carbon & Nitrogen in shortgrass steppe on the Central Plains Experimental Range in Nunn, Colorado, USA 1991, 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.

本数据包由开展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管理。SGS-LTER项目的长期数据集及背景资料（含研究提案、报告、影像照片等）均收录于科罗拉多数字馆藏的综合项目馆藏中，访问链接为：http://digitool.library.colostate.edu/R/?func=collections&collection_id=3429。本数据集的数据表及采用生态元数据语言（Ecological Metadata Language, EML）生成的关联元数据文档，也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整体项目馆藏的组成部分。
1971年至1975年间，研究人员向样地施加了超出短草草原群落常规耐受范围的水、氮肥以及水氮混合处理；1970年至1974年完成首轮植物密度采样，1977年终止该阶段采样，后于1982年恢复采样工作，采样频率从每年一次调整为每两年一次。首轮采样结果显示，水、水氮混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，且水氮混合处理样地中出现了外来杂草物种。1982年至1991年的后续采样表明，相较于对照组，水氮混合处理样地的外来杂草物种丰度增长了10倍（Milchunas与Lauenroth，1995）；由于植物组织-土壤有机质反馈机制引发的持续性土壤氮素富集，该样地的群落变化得以长期留存（Vinton与Burke，1995）。1998年，研究人员在该历史研究样地新增了6组处理：对照组、蔗糖、木质素、锯末、木质素+蔗糖以及锯末+蔗糖。2010年起，样地采样频率调整为每5年一次。本研究旨在探究植物群落随时间的演替规律，并探讨此类变化对受胁迫生态系统监测的参考价值。更多相关信息及参考文献可访问：http://hdl.handle.net/10217/83317。