Abstract
ABSTRACTSubarctic ecosystems are experiencing rapid changes as a result of climate warming and more frequent and severe disturbances. There is considerable uncertainty regarding ecological trajectories following disturbance in forested ecosystems underlain by permafrost because their structure and function is controlled by feedbacks among soil conditions, vegetation, and ground thermal regime. In this paper, we studied post-disturbance ecosystem recovery in an area of discontinuous permafrost 32 years after construction and abandonment of a winter access road in Nahanni National Park Reserve (NNPR). Ecosystem recovery was examined by comparing disturbed (road) and undisturbed (adjacent to the road) sites in the following terrain types: spruce peatland, black spruce parkland, deciduous forest, and alpine treeline terrain. Our field data show that disturbances to discontinuous permafrost terrain can lead to large and persistent changes to ecosystem composition and structure. Our findings indicate that the ecological response of discontinuous permafrost to disturbance and climate warming will depend on interactions between soil conditions and vegetation communities. In instances where disturbance to discontinuous permafrost fundamentally disrupts stabilizing interactions between soil conditions and vegetation communities, we should expect lasting changes to ecosystem structure and function.
Highlights
Recent temperature increases at high latitudes have been double the global average, and Canada’s western Arctic has experienced disproportionately more warming than other northern regions (Arctic Climate Impact Assessment, 2005; IPCC, 2007; Serreze et al, 2000)
Our findings indicate that the ecological response of discontinuous permafrost to disturbance and climate warming will depend on interactions between soil conditions and vegetation communities
The abandoned roadbed was characterized by higher cover of Picea glauca, moss, and Shepherdia canadensis, and lower cover of Populus tremuloides, litter, Vibernum edule, and Cornus canadensis compared with undisturbed sites
Summary
Recent temperature increases at high latitudes have been double the global average, and Canada’s western Arctic has experienced disproportionately more warming than other northern regions (Arctic Climate Impact Assessment, 2005; IPCC, 2007; Serreze et al, 2000). Permafrost degradation and range retractions are predicted to be most severe at the southern margin of discontinuous permafrost, where perennially frozen ground is maintained by surface conditions that insulate frozen ground from warmer air temperatures (Camill and Clark, 1998, 2000; Halsey et al, 1995; Jorgenson et al, 2010; Romanovsky et al, 2010; Shur and Jorgenson, 2007; Throop et al, 2012). In these environments, it is unclear how resilient permafrost will be to disturbance or increases in air temperatures. Ecological responses to disturbance depend on the nature and rate of post-disturbance vegetation succession, which varies with terrain type (Sannel and Kuhry, 2008; Calmels et al, 2012)
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