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械基础而受到批评。 为了帮助解决这一缺点，该博士学位论文研究项目将比较气候对北方树种与温带树种的生长和生理学的影响。 通过将树木暴露于将来可能面临的环境（由于预测的变暖）来实现这种比较，该比较将通过使用从威斯康星州北部到密西西比州中部的纬度梯度来实现。 基于沿大约1800公里长的样带收集的初步数据，博士候选人将检验两个主要的假设：（1）在当前范围以南，北方物种在身高和生物量方面的生长速度较慢。 （2）北方物种的净生长相对较慢，主要归因于温度对碳使用效率的负面影响（植物使用同化碳产生生物量的效率）介导的，这是由呼吸代谢的明显温度敏感性介导的。 在两年内，在沿着已建立的样带的四个普通花园中的每个花园中，博士候选人将监测目标北方和温带树种的树苗，颤抖的Aspen（Populus tremuloides）和Tulip-Poplar（liriodendendron tulipifera）。 将在花园和物种（物种内的地理促销中）进行以下变量：生长及其生理决定因素（即光合特征，生物量分配，叶片形态，黑暗呼吸和碳use效效率）；组织碳水化合物储量中的休眠季节动态。 该研究项目将解决有关当前和未来物种分布的固有和外在约束的长期问题，并将在景观模型中对生理亚列端进行校准，模拟森林对气候变化的反应。陆生植物物种对气候变化的地理范围的限制有望大大转移，以响应对气候变暖的响应。 例如，在北美东部，预计北方树种将向北撤退，而预计温带物种将在其后面填充。 管理特定物种南部范围边界的因素可能决定其北向撤退的程度。 然而，迄今为止，塑造南部范围限制的特定因素尚不清楚。 该项目将直接解决此问题，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。 在该项目进行期间收集的数据还将洞悉新物种组合中可能导致的竞争相互作用，这可能导致树木迁移。 该项目将帮助科学界提高其产生有关全球变化对北美和其他地方陆地生态系统结构和功能的影响的可信预测的能力。 这些预测是国家，地区，国家和国际层面的政策制定者使用的重要产品，涉及全球变化的影响以及潜在的缓解策略。 作为博士学位论文研究改进奖，该奖项还将提供支持，使有前途的学生能够建立强大的独立研究职业。