PPS Arctic Canada (Present processes, Past changes, Spatio-temporal variability in the Arctic delimitation zone, Canada)

In the summers of 2007-09, we collected data at over a dozen locations in the Yukon, Northwest Territories, Nunavut, northern Manitoba, northern Québec and Labrador. The results from these studies contribute to our short-term objectives: 1) an analysis of recent change in tree and shrub distributions; 2) the collection of environmental and microclimate data to accompany tree line change; 3) an investigation of the mechanisms of vegetation change at tree line; 4) the mapping of the spatial pattern of tree and non-tree species at tree line and in tundra islands within the boreal forest to predict future changes as tree line migrates; 5) an assessment of the role of disturbance; and 6) the development of models of the long-term relationship between environmental change, resource availability and human health and well-being in the forest-tundra ecotone. Data were collected regarding the impacts of changes in climatic conditions on tree line and their consequences on ecosystems and communities. Other data were collected on trees of all ages, seeds, vegetation, snow and ice, microclimate, spatial pattern, soil and socioeconomic indicators across the forest tundra ecotone at sites across northern Canada. Our key finding continues to be the large amount of variability in tree growth, regeneration and spatial pattern among tree species, regions across Canada and even sites within the same region. Evidence of change in and movement of the forest-tundra ecotone is evident in some site s but not in others despite increasing temperatures. Seed viability or seedling recruitment may be hindering tree line movement at these sites. This variation in tree line response may be extremely challenging to outline general strategies for climate change adaptation in Arctic environments. Our long-term objectives are: 1) to model temporal and spatial tree line dynamics and to situate these processes within a comprehensive conceptual framework of environmental change that addresses ecological, social and cultural factors; 2) to assess the impact of climate change on processes within the tree line ecotone; 3) to determine ecosystem services of the tree line ecotone and their vulnerability with climate change and land use impacts; and 4) to develop conceptual models of the long term relationship of environmental change and human health and well-being in the Arctic and Sub-Arctic.2007至2009年夏季，研究团队于加拿大育空地区（Yukon）、西北地区（Northwest Territories）、努纳武特地区（Nunavut）、曼尼托巴省北部、魁北克省北部以及拉布拉多的十余处采样点开展数据采集工作。 本研究的相关成果服务于六项短期目标： 1. 分析树木与灌丛分布的近期变化； 2. 采集配套于林线（tree line）变化的环境与微气候数据； 3. 探究林线植被变化的驱动机制； 4. 绘制林线及寒温带森林内苔原岛中树木与非树木物种的空间分布格局，以预测林线迁移下的未来变化； 5. 评估干扰因素的作用； 6. 构建森林-苔原生态交错带（forest-tundra ecotone）内环境变化、资源可获得性与人类健康福祉之间的长期关系模型。 研究团队采集了气候条件变化对林线的影响，以及此类影响对生态系统与社区所造成后果的相关数据。此外，还在加拿大北部各采样点的森林-苔原生态交错带内，采集了全龄级树木、种子、植被、冰雪、微气候、空间格局、土壤以及社会经济指标等多类数据。 本研究的核心发现始终为：不同树木物种、加拿大不同区域乃至同一区域内不同采样点间，树木生长、更新与空间格局存在显著差异。尽管气温持续上升，但部分采样点已观测到森林-苔原生态交错带发生变化并出现迁移的迹象，另一部分采样点则未出现此类现象。在这些采样点中，种子活力或幼苗定植过程可能阻碍了林线的迁移。这种林线响应的差异性，可能为北极地区气候变化适应通用策略的制定带来极大挑战。 本研究的四项长期目标如下： 1. 构建林线时空动态模型，并将这些过程置于涵盖生态、社会与文化因素的综合环境变化概念框架中进行阐释； 2. 评估气候变化对林线交错带内各类过程的影响； 3. 明确林线交错带的生态系统服务功能及其在气候变化与土地利用影响下的脆弱性； 4. 构建北极与亚北极地区环境变化与人类健康福祉长期关系的概念模型。