Climate and Woodland Expansion in the Western Great Plains, USA

美国西部大平原的气候和林地扩张

• 批准号: 0418166
• 负责人: Margot Kaye
• 金额: $ 0.72万
• 依托单位: Arizona State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-09-01 至 2005-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0418166&HistoricalAwards=false
• 关键词: Climate; Woodland; Expansion; Western; Great

The boundary between the western Great Plains and the Rocky Mountains is a prominent biogeographical feature of North America. Over the past century, woodland expansion into former grasslands has been documented in many areas of the west-central Great Plains. Current biogeographical and ecological knowledge indicate that the expansion of woodlands into grasslands can be driven by climate, human land use, and/or species migration, and none of these factors may be entirely independent of the others. This study will disentangle the factors related to this expansion and identify the role of climate. The timing of expansion will be investigated and how the expansion coincides with climate variability over the past three to six centuries across a spatial gradient that extends from western Nebraska to northeastern New Mexico. To do this, areas of woodland expansion with uniform land-use histories across the spatial gradient will be selected for study. Dendroecological techniques will be used to reconstruct the timing of ponderosa pine (Pinus ponderosa) woodland expansion. Then, climate analyses using modern and reconstructed paleoclimatic data will examine variations and trends in climate over annual to centennial time scales. Finally, the study area will be surveyed for woodrat (Neotoma) middens to investigate possible earlier Holocene expansions in the area. The role of climate in 19th and 20th century woodland expansion will be investigated by comparing the timing and location of the expansion to local climate variations and the onset of widespread human land use. The paleoecological and paleoclimatological records will be used to determine whether other expansions have occurred in the past or whether post-1850s vegetation movements are unprecedented in character.Human impacts on the landscape over the past century can obscure long-term relationships between vegetation and climate. This can lead to the assumption that any recent changes in vegetation dynamics are the result of human activity. Long-term data predating the onset of wide-spread human activity allow us to identify the long-term relationships between climate and woodland expansion and to determine if those relationships have changed over the past century. The results of this project will shed light on the possible role of climate in other cases of woodland expansion, as well as elucidating the potential affects of future climate change on woodland expansion in many regions. An interdisciplinary team will work closely with the U.S. Department of Agriculture and the Shortgrass Steppe Long-Term Ecological Research site to identify long-term management goals and research agendas for woodland areas.

西部大平原和落基山之间的边界是北美的重要生物地理特征。 在过去的一个世纪中，在中西大平原的许多地区都记录了林地扩展到以前的草原。 当前的生物地理和生态知识表明，林地向草原的扩展可以由气候，人类土地使用和/或物种迁移驱动，这些因素都不完全独立于其他因素。 这项研究将消除与这种扩展相关的因素，并确定气候的作用。 在过去三到六个世纪中，从内布拉斯加州西部到新墨西哥州东北部的空间梯度中，将研究扩张的时间以及扩张与气候变化之间的重合。 为此，将选择在整个空间梯度上具有统一土地利用历史的林地扩建区域进行研究。 树突生态技术将用于重建黄松（Pinus Ponderosa）林地扩张的时机。 然后，使用现代和重建的古气候数据进行气候分析将检查年度至百年纪念尺度的气候变化和趋势。最后，将调查研究区域的伍德拉特（Neotoma）中期，以调查该地区可能早期的全新世扩张。 将气候在19世纪和20世纪的林地扩张中的作用将通过比较扩展的时间和位置与当地气候变化的时间和位置以及广泛的人类土地使用的开始。 古生态和古气候记录将用于确定过去是否发生过其他扩张，或者1850年代后的植被运动是否在特征上是前所未有的。过去世纪对景观的影响会掩盖植被和气候之间的长期关系。 这可能导致以下假设，即植被动态的任何最近变化都是人类活动的结果。 长期数据早于广泛的人类活动的发作，使我们能够确定气候和林地扩张之间的长期关系，并确定过去一个世纪的这些关系是否发生了变化。 该项目的结果将阐明气候在其他林地扩张案例中的可能作用，并阐明了未来气候变化对许多地区林地扩张的潜在影响。 跨学科团队将与美国农业部和Shortgrass Steppe长期生态研究站点紧密合作，以确定伍德兰地区的长期管理目标和研究议程。