Patterns of shrub abundance and relationships with other plant types within the forest-tundra ecotone in northern Canada

We examined the role of distance to edges of water bodies and environmental factors (microtopography, pH) in determining the spatial pattern of the shrub layer, and the relationship of shrubs with trees and shorter plant types at different scales. We considered tall and prostrate shrubs in the shrub layer across two subarctic/Arctic landscapes in central Canada: tundra and forest-tundra ecotone. Our specific objectives for shrubs were: 1) to determine patterns across edges of water bodies, 2) to relate their abundance to pH and microtopography, and 3) to assess relationships with other plant types (trees, herbs, graminoids, bryophytes, ground cover lichens) at different scales. We compared our results between Arctic tundra and forest-tundra ecotone landscapes because we were particularly interested in determining the effect of tree cover in the forest-tundra ecotone on the relationships between shrubs and other plant types.本研究探讨了距水体边缘的距离与环境因子（微地形（microtopography）、pH值）对灌木层空间格局的调控作用，并分析了不同尺度下灌木与乔木、低矮植物类群之间的关联。研究覆盖加拿大中部两处亚寒带/北极景观中的灌木层，包含直立灌木与匍匐灌木两类，具体景观类型为苔原（tundra）与森林-苔原交错带（forest-tundra ecotone）。针对灌木类群，本研究设定了三项具体目标：1）明确灌木沿水体边缘的分布格局；2）厘清灌木多度与pH值、微地形的相关性；3）评估不同尺度下灌木与其他植物类群（乔木、草本植物、禾草类（graminoids）、苔藓植物（bryophytes）、地衣覆被（ground cover lichens））的相互关系。本研究对北极苔原与森林-苔原交错带两处景观的研究结果进行了对比，因我们尤为关注森林-苔原交错带内的乔木覆盖度对灌木与其他植物类群间相互关系的调控作用。