Persistent changes to ecosystems following winter road construction and abandonment in an area of discontinuous permafrost, Nahanni National Park Reserve, Northwest Territories, Canada

Abstract

Subarctic 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.