SGS-LTER Impact of Labile and Recalcitrant Carbon Treatments on Plant Communities (Density) in a Semiarid Ecosystem on the Central Plains Experimental Range, Nunn, Colorado, USA 1997-2012, 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. Additional information and referenced materials can be found: http://hdl.handle.net/10217/85547.
In a 10-year study, we assessed the influence of five carbon (C) treatments on the labile C and nitrogen (N) pools of historically N enriched plots on the Shortgrass Steppe Long Term Ecological Research site located in northeastern Colorado. For eight years, we applied sawdust, sugar, industrial lignin, sawdust + sugar, and lignin + sugar to plots that had received N and water additions in the early 1970s. Previous work showed that past water and N additions altered plant species composition and enhanced rates of nutrient cycling; these effects were still apparent 25 years later. We hypothesized that labile C amendments would stimulate microbial activity and suppress rates of N mineralization, whereas complex forms of carbon (sawdust and lignin) could enhance humification and lead to longer-term reductions in N availability. Results indicated that of the five carbon treatments, sugar, sawdust, and sawdust + sugar suppressed N availability, with sawdust + sugar being the most effective treatment to reduce N availability. The year after treatments stopped, N availability remained less in the sawdust + sugar treatment plots than in the high-N control plots. Three years after treatments ended, reductions in N availability were smaller (40-60%). Our results suggest that highly labile forms of carbon generate strong short- term N sinks, but these effects dissipate within one year of application, and that more recalcitrant forms reduce N longer. Sawdust + sugar was the most effective treatment to decrease exotic species canopy cover and increase native species density over the long term. Labile carbon had neither short- nor long-term effects on exotic species. Even though the organic amendments did not contribute to recovery of the dominant native species Bouteloua gracilis, they were effective in increasing another native species, Carex eleocharis. These results indicate that organic amendments may be a useful tool for restoring some native species in the shortgrass steppe. 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=541 Webpage with information and links to data files for download

本数据包由在科罗拉多州立大学管理的短草草原长期生态研究（SGS-LTER）项目的研究人员制作。包含SGS-LTER项目长期数据集和背景信息（提案、报告、照片等）的综合性项目收藏集，可在科罗拉多数字收藏馆（http://digitool.library.colostate.edu/R/?func=collections&collection_id=3429）中找到。生态元语言生成的数据表及其相关元数据文档可能通过服务于生态研究社区的其它数据存储库获得，并代表SGS-LTER项目收藏集的组成部分。更多信息和参考材料可查阅：http://hdl.handle.net/10217/85547。在为期十年的研究中，我们对位于科罗拉多州东北部的短草草原长期生态研究站上历史富氮地块的易变碳和氮库受五种碳（C）处理的影响进行了评估。在过去的八年中，我们对1970年代初接受过氮和水分添加的地块施加了锯末、糖、工业木质素、锯末+糖以及木质素+糖。先前的研究表明，过去的水和氮添加改变了植物物种组成并增强了养分循环的速度；这些影响在25年后仍然明显。我们假设，易变碳的添加将刺激微生物活性并抑制氮矿化速率，而碳的复杂形式（锯末和木质素）可以增强腐殖化作用，从而导致氮可用性的长期降低。结果显示，在五种碳处理中，糖、锯末以及锯末+糖抑制了氮的可用性，其中锯末+糖是降低氮可用性最有效的处理。在处理停止后的第二年，锯末+糖处理地块的氮可用性仍然低于高氮对照地块。在处理结束三年后，氮可用性的降低幅度较小（40-60%）。我们的结果表明，高度易变的碳形式能够生成强大的短期氮汇，但这些效果在应用一年后就会消失，而较难分解的碳形式则能降低氮的可用性更长时间。锯末+糖处理是降低外来物种冠层覆盖并长期增加本地物种密度的最有效处理。易变碳对外来物种既无短期也无长期影响。尽管有机改良物并未促进优势本地物种糙草（Bouteloua gracilis）的恢复，但它们在增加另一种本地物种——长叶薹草（Carex eleocharis）方面是有效的。这些结果表明，有机改良物可能是恢复短草草原某些本地物种的有用工具。本数据集包含资源：资源标题：指向html文件的网站指针。文件名：网页，url：https://portal.edirepository.org/nis/mapbrowse?scope=knb-lter-sgs&identifier=541 提供信息和数据文件下载链接的网页。