Black spruce (Picea mariana) colonization of subarctic snowpatches in response to warmer climate

1. Snowpatches are disjunct arctic ecosystems scattered across the Subarctic, particularly on wind-protected lee slopes, where a thick snow cover accumulates during the winter. These snow-rich treeless ecosystems are affected by delayed snowmelt, causing shorter growing seasons. Snow-tolerant plants occupy the center of subarctic snowpatches whereas black spruce trees grow at the margins. Snowpatches have shown sporadic expansion and shrinkage phases from tree establishment and mortality linked to climatic trends. Field surveys in the Subarctic of eastern Canada are showing an afforestation process occurring in snowpatches. The origin and nature of this afforestation were investigated based on the hypothesis that tree colonization and growth were closely associated with recent changes in climate. 2. Snowpatches were categorized in three types based on border trees: forested, semi-forested and tundra-like. In eight randomly selected snowpatches of each type, snowpatch borders and ...