Unravelling the effects of climate, composition and disturbance on forest productivity in the eastern boreal forest

气候变化、干扰制度及其相互作用正在改变生态系统动态，特别是在高纬度森林；我的长期目标是评估东部北方森林大片地区优势树种几十年来的生长、种群和群落动态变化。具体来说，我将结合全省范围内树木年轮核心的生长模式，研究北方树木在大环境梯度下生长的气候敏感性。我们将调查物种和地点水平的物种响应。另一个短期目标是评估这些相同物种沿东西（降水）和南北（温度）梯度的长期种群变化（死亡vs补充）和群落（组成变化）动态。由于昆虫是变温动物，它们也应该对变暖做出强烈反应，并可能与水分压力相互作用，使树木的死亡率增加。云杉budworm是一种爆发性昆虫，随着其活动范围的扩大，在其传统活动范围内罕见的混合物种将受到越来越多的攻击。在不同空间尺度的北方森林系统中，关联关系（增强的抗性vs易感性）的影响将被用作对非生物（气候）和生物（昆虫）压力的恢复力的代理。为了回答这些问题，我和我的研究生将把从全省收集的36.5万多棵树核的大型数据库与1945年以来每十年系统拍摄的航空照片相结合。我们还将使用在当前云杉芽虫爆发之初建立的永久样地的落叶和物种混合数据。结合过去70年的地貌数据库和气候数据，我们将按地点类型评估气候对每个物种生长和种群动态的影响。结合树木变化的时空分析将使我们能够更好地解释近期气候变化对森林组成和生产力的影响，然后预测未来的变化。通过探索多种树种在大时间和尺度尺度上的物种响应，这项工作还将使我进一步了解树木对气候变化的响应中物种之间与物种内部的现场水平变异性。目前大多数方法一次只评估一个响应变量（如生长或死亡率）。将多管齐下的方法应用于北方森林，将使我们能够更全面地评估气候变化对经历了一些最大气候变化的生态系统生产力的实际影响。

Changing climate, disturbance regimes and their interactions are modifying ecosystem dynamics especially in high latitude forests; my long-term objective is to evaluate changes in decades of growth, population and community dynamics of the dominant tree species across a large region of the eastern boreal. Specifically, I will combine growth patterns derived from a province wide collection of tree ring cores to study climate sensitivity of the growth of boreal trees across large environmental gradients. We will investigate both species and site-level within species responses. Another short-term objective is to evaluate long-term changes in population (mortality vs recruitment) and community (changes in composition) dynamics of these same species along east-west (precipitation) and north-south (temperature) gradients. As insects are ectotherms they should also react strongly to warming and may interact with moisture stresses that predispose trees to increased mortality. With range expansion of the spruce budworm, an outbreaking insect, mixes of species that are rare in its traditional range will be increasing under attack. The effects of associational relationships (increased resistance vs susceptibility) in different mixes of boreal tree species will be used as a proxy for resilience to abiotic (climate) and biotic (insects) stresses in boreal forest systems at different spatial scales.To answer these questions, my graduate students and I will combine a large data base of more than 365 000 tree cores collected from across the province with a temporal series of aerial photos taken systematically every decade since 1945. We will also use defoliation and species mixing data from permanent sample plots established at the beginning of the current spruce budworm outbreak. Coupled with geomorphological data bases and climatic data for the last 70 years we will evaluate the effect of climate by site type on the growth and population dynamics of each speciesCombining temporal and spatial analyses of tree changes will allow us to better explain the influence of recent changes in climate on forest composition and productivity and to then predict future change. By exploring species responses over large temporal and scale scales with multiple tree species this work will also allow me to further our understanding of between species vs within species site-level variability in tree responses to climate change. Most current approaches evaluate one response variable at a time (i.e. growth, or mortality). A multi-pronged approach applied to the boreal forest will permit us to more fully evaluate the real effects of climate change on the productivity of an ecosystem that has undergone some of the largest climatic changes.