Canadian Forest Service Publications
Barren‐ground caribou (Rangifer tarandus groenlandicus) behaviour after recent fire events; integrating caribou telemetry data with Landsat fire detection techniques. 2016. Global Change Biology.
Issued by: Pacific Forestry Centre
Catalog ID: 37657
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Fire regimes are changing throughout the North American boreal forest in complex ways. Fire is also a major factor governing access to high-quality forage such as terricholous lichens for barren-ground caribou (Rangifer tarandusgroenlandicus). Additionally, ﬁre alters forest structure which can affect barren-ground caribou’s ability to navigate ina landscape. Here, we characterize how the size and severity of ﬁres are changing across ﬁve barren-ground caribou herd ranges in the Northwest Territories and Nunavut, Canada. Additionally, we demonstrate how time since ﬁre,ﬁre severity, and season result in complex changes in caribou behavioural metrics estimated using telemetry data.Fire disturbances were identiﬁed using novel gap-free Landsat surface reﬂectance composites from 1985 to 2011 across all herd ranges. Burn severity was estimated using the differenced normalized burn ratio. Annual area burned and burn severity were assessed through time for each herd and related to two behavioural metrics: velocity and relative turning angle. Neither annual area burned nor burn severity displayed any temporal trend within the study period. However, certain herds, such as the Ahiak/Beverly, have more exposure to ﬁre than other herds (i.e. Cape Bathurst had a maximum forested area burned of less than 4 km2). Time since ﬁre and burn severity both signiﬁcantly affected velocity and relative turning angles. During fall, winter, and spring, ﬁre virtually eliminated foraging-focused behaviour for all 26 years of analysis while more severe ﬁres resulted in a marked increase in movement-focused behaviour compared to unburnt patches. Between seasons, caribou used burned areas as early as 1-year post-ﬁre, demonstrating complex, nonlinear reactions to time since ﬁre, ﬁre severity, and season. In all cases, increases in movement-focused behaviour were detected post ﬁre. We conclude that changes in caribou behaviour immediately post ﬁre are primarily driven by changes in forest structure rather than changes in terricholous lichen availability.
Plain Language Summary
The objective of this study is to document changes in barren ground caribou habitat, specifically vegetation productivity, and assess how these changes are affecting caribou behavior using a vegetation productivity index generated from comprehensive, annual, Landsat-derived 30 m data. Recent work has demonstrated that at a broad scale (i.e. using MODIS 1 km pixels), the lower Arctic and Boreal forests are increasing in productivity. However, this has been difficult to assess at finer scales (i.e. 30 m Landsat pixels) owing to data acquisition challenges. Here, we apply a newly developed Landsat compositing and proxy infilling technique to estimate vegetation productivity changes across 700 000 km2 of barren ground caribou habitat from 1984 to 2012. Additionally, we relate how these changes are influencing caribou behavior by incorporating these data with behavioral metrics derived from GPS telemetry data collected on 258 individual barren ground caribou from 2006 to present.