Emily Ogden, Sharon L. Smith, Merritt R. Turetsky, Steven G. Cumming, Jennifer L. Baltzer (2022). Too much of a good thing: Permafrost thaw induces short term increase in vegetation productivity in the northwestern boreal forest. Proceedings of the GWF Annual Open Science Meeting, May 16-18, 2022.

Over the past several decades various trends in vegetation productivity, from greening to browning, have been observed throughout the northern boreal biome. While some of this variation can be explained by recent climate warming and increased disturbance, very little is known about the impacts of permafrost thaw on vegetation productivity. We used a time-series of active layer thickness from permafrost monitoring sites (n=135) established in 1984 by the Geological Survey of Canada along a 10° latitudinal transect of the Northwest Territories, Canada, paired with a Landsat time-series of normalized difference vegetation index from 1984-2019, to quantify the impacts of changing permafrost conditions on vegetation productivity. We found that active layer thickness could explain some of the variation in vegetation productivity that has been observed in recent decades in the northern boreal forests, such that the highest rates of greening were found at sites where there was newly thawed permafrost. However, the greening associated with permafrost thaw was not sustained after prolonged periods of thaw. This is highlighted by the highest rates of greening being found at the mid-transect sites, between 62.4°N and 65.2°N. Indicating that the southern sites may have already undergone a period of rapid thaw and were past the threshold of beneficial permafrost thaw, and the northern sites may have yet to undergo extensive permafrost thaw. These results indicate that the response of vegetation productivity to permafrost thaw is variable and highly dependent on the extent of active layer thickening.

First Author: Emily Ogden Biology Department, Wilfrid Laurier University, Waterloo, Ontario, Canada
Additional Authors: Sharon L. Smith; Geological Survey of Canada, Natural Resources Canada, 601 Booth Street, Ottawa, ON, K1A 0E8, Canada. Merritt R. Turetsky; Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO, USA. Ecology and Evolutionary Biology Department, University of Colorado, Boulder, CO, USA. Steven G. Cumming; Department of Wood and Forest Sciences, Laval University, Quebec City, Quebec, Canada. Jennifer L. Baltzer; Biology Department, Wilfrid Laurier University, Waterloo, Ontario, Canada.