Doctoral Dissertation Research: The Effects of Climate and Disturbance Variation on Post-Fire Regeneration of Madrean Pine-Oak Forests in Mexico's Sierra Madre Occidental

博士论文研究：气候和干扰变化对墨西哥西马德雷山脉马德雷松橡树林火灾后再生的影响

• 批准号: 0201807
• 负责人: Thomas Veblen
• 金额: $ 1万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-06-01 至 2003-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0201807&HistoricalAwards=false
• 关键词: Doctoral; Dissertation; Research; Effects; Climate

The ecological effects of anthropogenic global climate change are of increasing concern for understanding and predicting climate driven vegetation change. Global circulation models exist that predict future climates and changes in coarse scale vegetation patterns. However, the efficacy of these models is limited by temporal and spatial scale problems and a poor understanding of how climate variation and human land use changes influence disturbance regimes and subsequent vegetation patterns. This doctoral dissertation research project will help to understand how annual to decadal scale climatic variation interacts with human influences on the landscape in north-central Mexico to effect changes in the fire regime and subsequently affect the regeneration success and species distributions of Madrean pine-oak ecosystems after fire. The specific objectives are: 1) to assess how climate variation and changes in human land use practices influence the fire regime in Madrean pine-oak ecosystems, 2) how climate variation and alterations to the fire regime interact to regulate seedling establishment and success, and 3) to test if ecosystem/community responses to climate and land use identified in other regions of North America are general ecological responses or are dependent on the life history traits of specific taxa. Standard tree-ring study techniques will be used to derive tree establishment dates, tree age frequencies, and reconstruct past fire regimes in a set of study sites that have been repeatedly disturbed by humans within a context of pronounced climatic variability. A combination of correlation analysis and regression analysis techniques will be used to identify temporal patterns of tree establishment at different spatial and temporal scales. The results of this study will be used to test the general hypothesis that seedling establishment in Madrean pine-oak ecosystems is related to climate variation and variations in the fire regime. Seedling establishment is predicted to occur during multi-annual to decadal periods of above average precipitation that follow widespread, biologically severe fires. Widespread fire years are predicted to occur during annual to multi-annual periods of below-average precipitation and above-average temperature. Humans are predicted to influence the occurrence and severity of fires by altering fuel quantity and continuity and serving as ignition sources. Ultimately, the site specific ecosystem/community responses to climate and land use variation identified in north-central Mexico will be compared with previous results from studies in other regions to test if these are general ecological responses, or if they are dependent on the life history traits of specific taxa. The study of how climate variation and human land use affect the fire regime and subsequent vegetation patterns has important consequences for predicting the ecological effects of global change. This study will provide basic information concerning how climate and human interactions with the fire regime affect the success of seedling establishment after fires in north-central Mexico. This research has broad ecological significance in that it will test previous hypotheses of climatic influences on fire, tree establishment, and tree mortality that were developed in other regions of North America with taxonomically different ecosystems under different precipitation and temperature trends. This study will also provide additional information to clarify the roles of climatic and human influences on vegetation change due to the climatic differences, and the differences in the timing of human migrations and subsequent land use practices throughout North America. Moreover, the differences in ecosystem characteristics between our sites in Mexico and other areas of North America will allow us to test whether the ecosystem responses to climate and land use changes identified in previous studies are general ecological responses or are if they dependent on the life history traits of specific taxa. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.

人类活动对全球气候变化的生态影响是理解和预测气候驱动的植被变化的一个重要方面。全球环流模型可以预测未来的气候和粗尺度植被模式的变化。然而，这些模型的效力是有限的时间和空间尺度的问题，以及对气候变化和人类土地利用变化如何影响干扰制度和随后的植被格局的认识不足。这个博士论文研究项目将有助于了解年度到十年尺度的气候变化如何与人类对墨西哥中北部景观的影响相互作用，以影响火灾状况的变化，并随后影响火灾后Madrean松栎生态系统的再生成功和物种分布。具体目标是：1）评估气候变化和人类土地利用方式的变化如何影响Madrean松树-橡树生态系统的火灾状况，2）气候变化和火灾状况的变化如何相互作用，以调节幼苗的建立和成功，3）测试生态系统/在北美其他地区确定的群落对气候和土地利用的反应是一般的生态反应，或取决于生活史特定类群的特征。标准的树木年轮研究技术将被用来获得树的建立日期，树的年龄频率，并重建过去的火灾制度，在一组研究地点，已多次受到人类干扰的背景下，明显的气候变化。相关分析和回归分析技术相结合，将用于确定在不同的空间和时间尺度的树木建立的时间模式。本研究的结果将被用来测试的一般假设，即在Madrean松栎生态系统的幼苗建立与气候变化和火灾制度的变化。幼苗建立预计发生在多年到十年的平均降水量以上的时期，随后广泛的，生物严重的火灾。据预测，大面积火灾年将发生在降水量低于平均水平和温度高于平均水平的年度至多年期。预测人类通过改变燃料量和连续性以及作为点火源来影响火灾的发生和严重程度。最终，网站特定的生态系统/社区的气候和土地利用变化的反应，在墨西哥中北部地区确定将与以前的研究结果在其他地区进行比较，以测试这些是一般的生态反应，或者如果他们依赖于特定类群的生活史特征。 研究气候变化和人类土地利用如何影响火灾状况和随后的植被格局，对于预测全球变化的生态影响具有重要意义。这项研究将提供有关如何气候和人类相互作用与火政权影响幼苗建立后，在墨西哥中北部火灾的成功的基本信息。这项研究具有广泛的生态意义，因为它将测试以前的假设，气候对火灾，树木建立，树木死亡率，在北美其他地区开发的分类不同的生态系统下，不同的降水和温度趋势。这项研究还将提供更多的信息，以澄清气候和人类的影响对植被变化的作用，由于气候的差异，以及人类迁移的时间和随后的土地使用做法在整个北美的差异。此外，我们在墨西哥和北美其他地区的网站之间的生态系统特征的差异将使我们能够测试是否在以前的研究中确定的气候和土地利用变化的生态系统响应是一般的生态响应，或者如果他们依赖于特定类群的生活史特征。 作为博士论文研究改进奖，该奖项还将提供支持，使有前途的学生建立一个强大的独立的研究生涯。