Ecosystems on the edge: the ecology of deciduous forest ecosystems near their northern limit in Quebec

了解控制森林生态系统在其北部边界附近如何运作的因素，对于预测森林将如何应对气候变化至关重要。本研究旨在加深对魁北克北部詹姆斯湾地区以颤杨为主的森林分布的气候、土壤和生物因素的相对控制作用的认识。我们最近在魁北克北部的白杨林和黑云杉林所做的研究表明，树木的建立和生长取决于植被、土壤有机质分解和积累、土壤营养和立地干扰的相互作用。我们开发了一种新的空间格局多变量分析方法，改进了野外生态关系的检测。这项新的研究将建立在这些调查路线的基础上。拟议的计划将研究气候、地点以及碳和养分循环在控制从魁北克中部到其范围北部极限的气候样带上白杨林分布方面的作用。将制定以生物为中心的气候指数，以确定1300公里的样带。白杨林的特点是树木生长速度、养分循环和土壤性质。随着纬度的增加，这些变量的变化模式将与气候指数的变化模式进行比较，以检验气候是主要控制因素的假设。由于树木以综合的方式对多种胁迫做出反应，气候的影响取决于其他因素的影响；有利的场地条件或土壤因素可以使杨树在不利的气候条件下生长。这一点将在使用靠近其北部边界的白杨林的景观模式时得到验证。我们将使用碳和氮同位素特征来更好地了解白杨林的分布是否随着气候的变化而变化。总体而言，这项研究将增加对气候和非气候因素在决定北方落叶森林生态系统分布方面的相对作用的认识，并将为预测气候变化的影响提供更好的基础。

Understanding the factors that control how forest ecosystems function near their northern limits is critical to predicting how forests will respond to climate change. This research aims to increase understanding of the relative role of climate, soil and biotic factors in controlling the distribution of forests dominated by trembling aspen (Populus tremuloides) in the James Bay region of northern Quebec. Our recent work in aspen and black spruce forests in the northern Quebec have shown that establishment and growth of trees depends on the interacting effects of vegetation, soil organic matter decomposition and accumulation, soil nutrition, and site disturbance. We have developed a new approach for multivariate analysis of spatial pattern that improves detection of ecological relationships in the field. The new research will build on these lines of enquiry. The proposed program will study the roles of climate, site, and carbon and nutrient cycling in controlling the distribution of aspen forests across a climatic transect from central Quebec to the northern limit of their range. 'Biocentric' climatic indices will be developed to define the 1300 km transect. Aspen stands will be characterized by tree growth rates, nutrient cycling and soil properties. Patterns of change in these variables with increasing latitude will be compared to patterns of change in climatic indices to test the hypothesis that climate is the dominant control. Since trees respond in an integrated way to multiple stresses, the effect of climate depends on the effects of other factors; favorable conditions in site or soil factors can allow aspen to grow in unfavorable climate. This will be tested in using landscape patterns of aspen forests near their northern limit. We will use C and N isotopic signatures to better gain a better understanding of whether the distribution of aspen forests in changing with changing climate. Overall, the research will increase knowledge of the relative roles of climatic and non-climatic factors in determining the distribution of deciduous forest ecosystems in the north and will provide a better foundation for predicting the effects of climate change.