首页> 外文学位 >Using eddy covariance, remote sensing, and in situ observations to improve models of springtime phenology in temperate deciduous forests.
【24h】

Using eddy covariance, remote sensing, and in situ observations to improve models of springtime phenology in temperate deciduous forests.

机译:利用涡度协方差,遥感和原位观测来改善温带落叶林的春季物候模型。

获取原文
获取原文并翻译 | 示例

摘要

Phenological events in temperate forests, such as bud burst and senescence, exert strong control over seasonal fluxes of water, energy and carbon. The timing of these transitions is influenced primarily by air temperature and photoperiod, although the exact nature and magnitude of these controls is poorly understood. In this dissertation, I use in situ and remotely sensed observations of phenology in combination with surface meteorological data and measurements of biosphere-atmosphere carbon exchanges to improve understanding and develop models of canopy phenology in temperate forest ecosystems. In the first element of this research I use surface air temperatures and eddy covariance measurements of carbon dioxide fluxes to evaluate and refine widely used approaches for predicting the onset of photosynthesis in spring that account for geographic variation in thermal and photoperiod constraints on phenology. Results from this analysis show that the refined models predict the onset of spring photosynthetic activity with significantly higher accuracy than existing models. A key challenge in developing and testing these models, however, is lack of adequate data sets that characterize phenology over large areas at multi-decadal time scales. To address this need, I develop a new method for estimating long-term average and interannual dynamics in the phenology of temperate forests using time series of Landsat TM/ETM+ images. Results show that estimated spring and autumn transition dates agree closely with in-situ measurements and that Landsat-derived estimates for the start and end of the growing season in Southern New England varied by as much as 4 weeks over the 30-year record of Landsat images. In the final element of this dissertation, I use meteorological data, species composition maps, satellite remote sensing, and ground observations to develop models of springtime leaf onset in temperate deciduous forests that account for geographic differences in how forest communities respond to springtime climate forcing. Results demonstrate important differences in cumulative heating requirements and photoperiod cues among forest types and that regional differences in species composition explain substantial geographic variation in springtime phenology of temperate forests. Together, the results from this dissertation provide an improved basis for observing and modeling springtime phenology in temperate forests.
机译:温带森林中的物候事件,例如芽破裂和衰老,对水,能量和碳的季节性通量具有很强的控制力。这些转换的时间主要受空气温度和光周期的影响,尽管对这些控制的确切性质和大小知之甚少。在本文中,我结合对物候的原位和遥感观测,结合表面气象数据和对生物圈-大气碳交换的测量,以增进对温带森林生态系统冠层物候模型的理解和发展。在这项研究的第一部分中,我使用地面空气温度和二氧化碳通量的涡度协方差测量来评估和完善广泛使用的方法,以预测春季光合作用的开始,从而说明热和光周期对物候学约束的地理变化。该分析的结果表明,改进后的模型预测春季光合作用活动的开始的准确性明显高于现有模型。然而,开发和测试这些模型的一个关键挑战是缺乏足够的数据集,这些数据集在数十年的时间尺度上描述了大范围的物候特征。为了满足这一需求,我开发了一种使用Landsat TM / ETM +图像的时间序列估算温带森林物候的长期平均和年际动态的新方法。结果表明,估计的春季和秋季过渡日期与原位测量值非常吻合,而Landsat得出的对新英格兰南部生长季节开始和结束的估计在Landsat的30年记录中相差多达4周。图片。在本文的最后一部分中,我将使用气象数据,物种组成图,卫星遥感和地面观测来开发温带落叶林中春季叶片起病的模型,这些模型解释了森林群落对春季气候强迫的响应方式的地理差异。结果表明,森林类型之间在累积供暖需求和光周期提示方面存在重要差异,物种组成的区域差异解释了温带森林春季物候的重大地理差异。总之,本论文的结果为温带森林春季物候的观测和建模提供了改进的基础。

著录项

  • 作者

    Melaas, Eli Kellen.;

  • 作者单位

    Boston University.;

  • 授予单位 Boston University.;
  • 学科 Physical Geography.;Remote Sensing.;Biology Ecology.
  • 学位 Ph.D.
  • 年度 2014
  • 页码 167 p.
  • 总页数 167
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱:kefu@zhangqiaokeyan.com

京公网安备:11010802029741号 ICP备案号:京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有
  • 客服微信

  • 服务号