SGS-LTER Effects of grazing on ecosystem structure and function (GZTX): Vegetation density on the Central Plains Experimental Range, Nunn, Colorado, USA 1992-2008, ARS Study Number 32

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. When the CPER was established in 1939,
researchers constructed a .5-1 ha grazing
exclosure in each of the pastures. These areas
have remained protected from grazing for the past
70 years. The remaining areas have been grazed for
the past 20+ years. This collection of pastures
and exclosures provided an extraordinary
opportunity to reinitiate grazing and protection,
and evaluate the balance between degradation and
aggradation. We proposed to rearrange fences and
expose areas to grazing that have been protected
for 50 years, and protect areas from grazing that
had been grazed for 50 years. The combinations of
grazing conditions were: 1. Long-term protection
2. Long-term grazing (moderate) 3. 50 years of
protection followed by grazing 4. 50 years of
grazing followed by protection Net primary
production, nitrogen dynamics, cattle utilization,
and community dynamics of vegetation were
measured. Additional information and referenced materials can be found: http://hdl.handle.net/10217/85596.

本数据包由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背景资料（包括研究提案、项目报告、影像资料等）均收录于科罗拉多州数字馆藏（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。本数据集附带的数据表与采用生态元数据语言（Ecological Metadata Language）编写的元数据文档，可通过服务于生态研究共同体的其他仓储获取，属于SGS-LTER综合项目馆藏的组成部分。1939年CPER设立之初，研究人员在各牧场内搭建了0.5至1公顷的放牧排除区（grazing exclosure），这些区域在过去70年间始终免受放牧干扰，其余区域则已持续放牧20余年。该批牧场与禁牧围封区为重新调整放牧与保护措施提供了绝佳契机，同时也可用于评估生态系统退化与积进演替之间的平衡。本研究计划重新布设围栏，将已受50年保护的区域纳入放牧范围，并对已持续放牧50年的区域实施保护。本研究设置了四类放牧条件组合：1. 长期禁牧保护；2. 长期适度放牧；3. 先禁牧保护50年再转为放牧；4. 先放牧50年再转为禁牧保护。研究团队测定了净初级生产力、氮素动态、家畜利用率以及植被群落动态。更多相关信息及参考文献可通过以下链接获取：http://hdl.handle.net/10217/85596。