Doctoral Dissertation Research: Factors Determining Geographical Range Limits of Boreal and Temperate Tree Species

博士论文研究：决定北方和温带树种地理范围限制的因素

• 批准号: 0802729
• 负责人: Eric Kruger
• 金额: $ 1.2万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-04-15 至 2011-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0802729&HistoricalAwards=false
• 关键词: Doctoral; Dissertation; Research; Factors; Determining

Forecasts regarding influences of anticipated climate change on geographical distributions of trees and other plant species have been criticized for lacking a sufficiently mechanistic basis. To help address this shortcoming, this doctoral dissertation research project will compare influences of climate on the growth and physiology of boreal versus temperate tree species. This comparison will be accomplished by exposing trees to climates they may face in the future (owing to forecasted warming) through use of a latitudinal gradient extending from northern Wisconsin to central Mississippi. Based on preliminary data gathered along a roughly 1,800-km-long transect, the doctoral candidate will test two major hypotheses: (1) South of their current ranges, boreal species grow more slowly in terms of height and biomass than temperate endemics. (2) Comparatively slow net growth of boreal species is attributable primarily to negative influences of temperature on carbon-use efficiency (the efficiency with which plants use assimilated carbon to produce biomass) mediated by the pronounced temperature sensitivity of respiratory metabolism. In each of four common gardens along the established transect over a two-year period, the doctoral candidate will monitor saplings of target boreal and temperate tree species, trembling aspen (Populus tremuloides) and tulip-poplar (Liriodendron tulipifera). The following variables will be compared across gardens and species (and among geographic provenances within species): growth and its physiological determinants (i.e. photosynthetic traits, biomass allocation, leaf morphology, dark respiration and carbon-use efficiency); and dormant season dynamics in tissue carbohydrate reserves. This research project will address long-standing questions regarding intrinsic and extrinsic constraints on current and future species distributions and will culminate in the calibration of physiological subroutines in a landscape model simulating forest responses to climate change.The geographical range limits of terrestrial plant species are expected to shift considerably in response to climate warming. In eastern North America, for example, boreal tree species are predicted to retreat northward, while temperate species are expected to fill in behind them. The factors governing a particular species' southern range boundary likely will dictate the extent of its northward retreat. To date, however, the specific factors shaping southern range limits remain unclear. This project will directly address this issue, thereby providing input for models forecasting the responses of tree species distributions to global climate change. The data gathered during the conduct of this project also will provide insight into the competitive interactions occurring within new species assemblages that may result from tree migrations. The project will help the scientific community improve its ability to generate credible forecasts concerning the impacts of global change for the structure and function of terrestrial ecosystems in North America and elsewhere. These predictions are important products used by policymakers at the state, regional, national and international levels, addressing global change impacts as well as potential mitigation strategies. 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.

关于预期气候变化对树木和其他植物物种地理分布的影响的预测因缺乏足够的机制基础而受到批评。为了帮助解决这一不足，本博士论文研究项目将比较气候对北方和温带树种生长和生理的影响。通过利用从威斯康辛州北部延伸到密西西比州中部的纬度梯度，将树木暴露在它们未来可能面临的气候中（由于预测的变暖），从而实现这种比较。根据沿着大约1800公里长的样带收集的初步数据，这位博士候选人将测试两个主要假设：(1)在它们目前的分布范围以南，北方物种在高度和生物量方面比温带特有物种生长得更慢。(2)北方植物净生长相对缓慢，主要是由于呼吸代谢的温度敏感性导致温度对碳利用效率（植物利用同化碳产生生物量的效率）的负面影响。在两年的时间里，博士候选人将沿着已建立的样带在四个普通花园中监测目标北方和温带树种，颤杨（杨树）和郁金香杨树（Liriodendron tulipifera）的树苗。以下变量将在花园和物种之间（以及物种内的地理种源之间）进行比较：生长及其生理决定因素（即光合特性、生物量分配、叶片形态、暗呼吸和碳利用效率）；冬眠季节组织碳水化合物储备的动态变化。该研究项目将解决关于当前和未来物种分布的内在和外在限制的长期问题，并将最终在模拟森林对气候变化反应的景观模型中校准生理子程序。随着气候变暖，陆生植物物种的地理分布范围将发生显著变化。例如，在北美东部，预计北方树种将向北撤退，而温带树种将填补它们的空缺。控制一个特定物种南部范围边界的因素可能会决定其向北撤退的程度。然而，到目前为止，形成南部范围限制的具体因素仍不清楚。该项目将直接解决这一问题，从而为预测树种分布对全球气候变化的响应的模型提供输入。在这个项目中收集的数据也将提供对新物种组合中发生的竞争性相互作用的见解，这些相互作用可能是由树木迁移引起的。该项目将帮助科学界提高其就全球变化对北美和其他地区陆地生态系统的结构和功能的影响作出可靠预测的能力。这些预测是国家、区域、国家和国际各级决策者使用的重要产品，用于处理全球变化影响以及潜在的缓解战略。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研究生涯。