Fire and Ice: Surprises in a Warming Arctic Land Surface

The Arctic region has warmed significantly over the past 30 years and arctic plants and ecosystems are already changing in response, including a general 'greening' of the arctic landscape, changes in species distributions and abundance, and changes in biogeochemical processes and cycles at local and regional scales. Many of these responses to warming are limited or regulated by low inputs, turnover, and availability of essential elements like N and P, and thus one of the main research needs is to predict the effects of arctic warming on N and P cycles and their interactions with species composition and with the C cycle. This need has been met in recent decades by experimental manipulations of whole ecosystems, by long-term monitoring in relation to climate, and by comparisons among climatically different arctic sites. Increasingly, however, it is apparent that climatic warming in the Arctic is accompanied by dramatic changes in large-area disturbances, especially disturbances related to thawing of permafrost and a surprising increase in wildfire. These large-area disturbances also interact with N and P cycles, producing much more dramatic and rapid changes in vegetation and element cycling than in response to warming alone. In the long term, warming-related changes in disturbance regime may be more important than the direct effects of warming alone on arctic plants, ecosystems, and the entire Arctic.