SGS-LTER Graduate Student Research: Aboveground Net Primary Production as Biochemical Responses of US Great Plains Grasslands to Regional and Interannual Variability in Precipitation (1999-2001)

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. Additional information and referenced materials can be found: http://hdl.handle.net/10217/85531. Carbon (C) sequestration potential in grasslands is thought to be high due to the large soil organic carbon pools characteristic of these ecosystems. Inputs of C (aboveground net primary productivity) are highly correlated to precipitation across the Great Plains region; however, changes in C pool size at a specific site are governed by the relative input and output rates across time. Our objective was to quantify the ecosystem C response of three grassland community types (shortgrass steppe, mixed grass and tallgrass prairie) to interannual variation in precipitation. At five sites across a precipitation gradient in the Great Plains, we measured net primary production (NPP), soil respiration (SRESP), and litter decomposition rates for three consecutive years. NPP, SRESP, and litter decomposition increased from shortgrass steppe (175, 454, and 47 g C m-2 yr-1) to tallgrass prairie (408, 1221, and 348 g C m-2 yr-1 for NPP, SRESP, and litter decomposition respectively). Increased growing season precipitation between study years resulted in increased NPP, SRESP, and litter decomposition at almost all sites. However, the regional patterns of the interannual NPP, SRESP, and litter decomposition responses differ from each other. This data suggests NPP and SRESP are more sensitive to interannual changes in precipitation than litter decomposition, and that shortgrass steppe sites are more responsive to interannual variability in precipitation than mixed grass and tallgrass prairie.

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负责管理。有关SGS-LTER项目的长期数据集与背景资料（包括研究方案、报告、影像资料等），均收录于科罗拉多州数字馆藏（Digital Collections of Colorado）旗下的综合项目馆藏中，访问链接为：http://digitool.library.colostate.edu/R/?func=collections&collection_id=3429。本数据表及配套的元数据文档以生态元数据语言（Ecological Metadata Language）生成，可通过服务于生态研究共同体的其他仓储获取，同时也是SGS-LTER综合项目馆藏的组成部分。更多信息与参考资料可通过以下链接获取：http://hdl.handle.net/10217/85531。

由于草原生态系统普遍拥有规模庞大的土壤有机碳库，学界普遍认为草原具备较高的碳固存潜力。北美大平原地区的碳输入（即地上净初级生产力）与降水量呈高度相关；但特定站点的碳库规模变化，取决于跨时间尺度的碳输入与输出相对速率。本研究旨在量化三种草原群落类型（短草草原、混合草原与高草草原）的生态系统碳响应，以应对降水量的年际变化。研究团队在大平原地区沿降水梯度设置的5个样地中，连续三年开展了净初级生产力（Net Primary Production, NPP）、土壤呼吸（Soil Respiration, SRESP）与枯落物分解速率的测定工作。

三种群落的NPP、SRESP与枯落物分解速率均呈现从短草草原到高草草原的递增趋势：短草草原分别为175、454与47 g C m⁻² yr⁻¹，高草草原则分别为408、1221与348 g C m⁻² yr⁻¹（对应NPP、SRESP与枯落物分解速率）。研究年度内生长季降水量的增加，使得几乎所有样地的NPP、SRESP与枯落物分解速率均有所提升。但三者的年际响应区域模式存在显著差异。本研究数据表明，NPP与SRESP对降水量年际变化的敏感性高于枯落物分解，且短草草原样地对降水量年际波动的响应程度强于混合草原与高草草原。