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Climate and vegetation change in the Newberry mountains, Southern Clark County, Nevada.

机译：内华达州南克拉克县纽伯里山的气候和植被变化。

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摘要

Ecological studies have shown worldwide that vegetation is being affected by climate change. Species are shifting to new elevations and physiographic positions to adapt to changes in their environment. More specifically, paleoecology studies in the Mojave Desert have shown shifting vegetation patterns in response to past warming and precipitation changes. Recent studies have shown mortality among desert plants related to extended drought and warming. However, few studies have shown how the geographic distribution of Mojave Desert species has changed during this most recent period of warming. This study addresses this gap in the literature by focusing on several plant species in the Newberry Mountains, which are located at the southeastern boundary of the Mojave Desert in a transitional area to the Sonoran Desert. The study area is co-managed by the Bureau of Land Management and the National Park Service, and as a result, has been relatively undisturbed.;A 1979 dataset utilized for analysis includes 111 vegetation transects from the Newberry Mountains. 107 of these transects were re-surveyed over 2007-2008 to allow for direct comparison over a 30-year period. Using Parameter-elevation Relationships on Independent Slopes Model (PRISM) data, I found that average annual minimum temperature in the Newberry Mountains has increased 1.5° C over the last 30 years, with the greatest increases seen in the higher elevations. Precipitation has also declined across the study area by three centimeters on average, with the greatest decreases in the high elevations. Maxent uses species presence locations, along with environmental and climate variables, to predict the probability of species' occurrences across the study area. A past weakness of Maxent has been a lack of on-the-ground data. This 30-year dataset allows for "ground-truthing" the model. Maxent is used to predict species locations in 1979, project locations in 2008 given climatic change, and then results are compared to actual locations in 2008. Using ArcGIS, projected occurrence rasters for 2008 are subtracted from actual 2008 rasters to evaluate the effectiveness of projecting changes with Maxent. Additionally, the 1979 probability maps are subtracted from 2007-2008 maps to determine actual change over the last 30-years.;Findings are that Maxent does a poor job of projecting 2008 species distributions when using 1979 locations with 2008 climate data. However, when using locations and climate variables from the sample period, Maxent accurately represents species' realized niches. The 2008 projection models over-predict species habitat when compared to 2008 models using actual locations. Species found at higher elevations that are more reliant on precipitation as a predictor variable show decreasing suitable habitat within the Newberries. Species widely distributed across the study area show little to no change. Since the only model variables that changed are species presence locations, 1970's climate variables, and 2000's climate variables, I conclude that the species in the Newberry Mountains that are most reliant on higher precipitation levels are migrating to higher elevations in order to adapt to the current climate change.
机译：生态学研究表明，世界范围内的植被正在受到气候变化的影响。物种正在转移到新的海拔高度和地理位置，以适应其环境的变化。更具体地说，莫哈韦沙漠的古生态研究表明，植被模式随着过去的变暖和降水变化而变化。最近的研究表明，荒漠植物的死亡率与长期干旱和变暖有关。但是，很少有研究表明在最近的变暖时期莫哈韦沙漠物种的地理分布是如何变化的。本研究通过集中研究纽伯里山的几种植物来解决文献中的空白，纽伯里山位于莫哈韦沙漠东南边界的索诺兰沙漠过渡地区。该研究区域由土地管理局和国家公园管理局共同管理，因此相对不受干扰。1979年用于分析的数据集包括来自纽伯里山的111个植被样带。在2007年至2008年间对107个样带进行了重新调查，以便在30年内进行直接比较。使用独立坡度模型上的参数高程关系（PRISM）数据，我发现在过去30年中，纽伯里山的年平均最低气温增加了1.5°C，在较高的海拔高度上增幅最大。研究区域的降水量平均下降了三厘米，高海拔地区的降水量下降最大。 Maxent使用物种存在的位置以及环境和气候变量来预测整个研究区域中物种出现的可能性。 Maxent过去的弱点是缺乏实地数据。这个长达30年的数据集允许对模型进行“实际研究”。用Maxent预测1979年的物种位置，并根据气候变化预测2008年的项目位置，然后将结果与2008年的实际位置进行比较。使用ArcGIS，从2008年的实际栅格中减去2008年的预测发生栅格，以评估预测变化的有效性与Maxent。此外，从2007-2008年的地图中减去1979年的概率图以确定最近30年的实际变化。结果发现，当使用1979年的位置和2008年的气候数据时，Maxent在预测2008年物种分布方面做得不好。但是，当使用采样期间的位置和气候变量时，Maxent可以准确地表示物种的已实现生态位。与使用实际位置的2008年模型相比，2008年预测模型高估了物种栖息地。在高海拔地区发现的物种更多地依赖于降水作为预测变量，表明该物种在新莓中的适宜栖息地正在减少。在研究区域广泛分布的物种几乎没有变化。由于唯一改变的模型变量是物种存在的位置，1970年代的气候变量和2000年代的气候变量，因此我得出结论，纽伯里山区最依赖较高降水水平的物种正在向更高海拔迁移，以适应当前气候变化。

著录项

  • 作者

    Guida, Ross Joseph.;

  • 作者单位

    University of Nevada, Las Vegas.;

  • 授予单位 University of Nevada, Las Vegas.;
  • 学科 Biology Ecology.;Environmental Sciences.;Climate Change.
  • 学位 M.S.
  • 年度 2011
  • 页码 120 p.
  • 总页数 120
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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