Abstract
The Arctic tundra is undergoing many environmental changes in addition to increasing temperatures: these changes include permafrost degradation and increased shrubification. Disturbances related to infrastructure can also lead to similar environmental changes. The Trans-Alaska Pipeline System (TAPS) is an example of infrastructure that has made a major imprint on the Alaskan landscape. This paper assesses changes in shrub presence along the northernmost 255 km of the TAPS. We used historical satellite imagery from before construction of the TAPS in 1974 and contemporary satellite imagery from 2010 to 2016 to examine changes in shrub presence over time. We found a 51.8% increase in shrub presence adjacent to the pipeline compared to 2.6% in control areas. Additionally, shrub presence has increased significantly more in areas where the pipeline is buried, indicating that the disturbances linked to pipeline burial have likely created favorable conditions for shrub colonization. These results are important for predicting potential responses of tundra vegetation to disturbance, which will be crucial to forecasting the future of Arctic tundra vegetation.
Highlights
The Arctic is experiencing warming at more than two times the mean global rate (IPCC, 2007), a process known as “Arctic Amplification.” Increases in regional temperatures are expected to result in widespread permafrost degradation, especially in areas where ground temperatures are close to freezing (Jorgenson et al, 2006; Shur and Jorgenson, 2007; Grosse et al, 2011)
This study found that shrub presence increased by 58.1% in the vicinity of the pipeline, as opposed to 2.7% for the control transects, which suggests that the processes linked to the disturbance from the pipeline have facilitated shrub colonization
The percent increase in shrub presence along the control transects is relatively low compared to some of the rates published in the studies listed above, which indicates that local conditions play a major role in facilitating shrub expansion (e.g., Tape et al, 2006; Myers-Smith et al, 2011b; Naito and Cairns, 2011b, 2015; Ackerman et al, 2017)
Summary
The Arctic is experiencing warming at more than two times the mean global rate (IPCC, 2007), a process known as “Arctic Amplification.” Increases in regional temperatures are expected to result in widespread permafrost degradation (thermokarst), especially in areas where ground temperatures are close to freezing (Jorgenson et al, 2006; Shur and Jorgenson, 2007; Grosse et al, 2011). Increases in regional temperatures are expected to result in widespread permafrost degradation (thermokarst), especially in areas where ground temperatures are close to freezing (Jorgenson et al, 2006; Shur and Jorgenson, 2007; Grosse et al, 2011). If thermokarst is initiated on a large scale, it can take up to 30 years after the disturbance for stabilization to occur in ice-rich, unstable thaw areas (Lawson, 1986; Walker and Walker, 1991). Since the base of the active layer is impermeable to water and impenetrable to roots (NRC, 2003), permafrost warming and degradation changes the hydrological and nutritional characteristics of soils, which affect vegetation distribution, plant community structure, and productivity in Arctic and Subarctic regions
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