ARCTIC PLANT COMMUNITIES RISE WITH TEMPERATURE Plant functional traits as a tool to predict global climate change

Abstract: Global warming occurs at a rate at least three-fold in the arctic regions compared to the rest of the world. Here, plant community functional traits were assessed in response to experimental warming in three arctic areas of Fennoscandia (Latnajajure, Abisko and Kilpisjärvi). Temperature was manipulated using Open Top Chambers (OTCs) of 1 m2, which induced local temperature increases ranging between 1.5-3°C in randomly selected plots within each arctic site. Functional traits at a community level were compared between the temperature manipulated and control plots. The traits assessed were either associated with plant growth: height and leaf area, or with the economic resource spectrum: Leaf Dry Matter Content (LDMC), leaf nitrogen content (leafN) and Specific Leaf Area (SLA). Plant community height was significantly greater in temperature manipulated plots, indicating that exposure to increased temperature cause plant communities to become taller. To better understand the potential consequences of changes in functional traits for arctic ecosystem functioning, a thorough literature review on plant functional trait variations and their possible association with climate change feedback mechanisms was performed. This review revealed several potential feedback mechanisms associated with increased plant height that affect global warming in the arctic regions. However, whether taller plant communities cause global warming to accelerate, decelerate or stay the same in an even warmer future depends on the balance between these positive and negative feedback mechanisms. For example, reduced albedo due to taller plants create more heat absorption by the earth’s surface, accelerating global warming. Yet, at the same time, woody plants that grow taller have a larger capacity to store carbon, resulting in reduced atmospheric carbon and, thus, a deceleration of the temperature increase.