Ninth International Conference on Permafrost ... - IARC Research

Ni n t h In t e r n at i o n a l Co n f e r e n c e o n Pe r m a f r o s ton the ice-poor gravel substrates of riparian areas (DryasRiver Terrace and Riparian Shrublands) did not subside,and vegetation recovered steadily even after severe initialdamage.Tussock Tundra and Sedge-Willow Tundra plotsrecovered well except for a few that subsided into troughs.Sedge-Dryas Tundra frequently subsided, even when initialdisturbance was not high, and over two-thirds of the plotswere still disturbed in 2005, with substantial changes inplant community composition (Fig. 1). Low Shrub Tundraand Dryas River Terrace had some low-level disturbanceremaining in 2005–2007, mainly patchy subsidence andvehicle ruts that did not subside, with more subtle plantcommunity composition changes.Camp-move trails were made by vehicles with higherground pressure than seismic lines and had more initialdamage and slower recovery. By 1989, 32% of seismictrails were still disturbed compared to 64% of camp trails,including 41% at medium- and high-level disturbance. By2005, all seismic trail plots had recovered to a negligibledisturbance level, whereas 10% of the camp trail plots werestill disturbed and one-half of those had medium- and highleveldisturbance. Overall, 5% of plots were still disturbed in2005. This translates to 200 km of disturbed trail, out of theoriginal 4000 km of trails.Previous studies of winter seismic vehicle disturbance inthe Arctic predicted only short-term and mostly aestheticimpacts. Long-term monitoring showed that most of thedisturbance disappeared gradually, but that impacts to tundravegetation persisted on a small percentage of the trails up to23 years after disturbance (Fig. 2).ReferencesEmers M. & Jorgenson, J.C. 1997. Effects of winter seismicexploration on the vegetation and soil thermal regimeof the Arctic National Wildlife Refuge. In: R.M.M.Crawford (ed.), Disturbance and Recovery in ArcticLands: an Ecological Perspective. Dordrecht, theNetherlands: Kluwer Academic Publishers.Felix, N.A. & Raynolds, M.K. 1989. The effects of winterseismic trails on tundra vegetation in northeasternAlaska, U.S.A. Arctic and Alpine Res. 21(2): 188-202.Raynolds, M.K. & N.A. Felix. 1989. Airphoto analysis ofwinter seismic disturbance in northeastern Alaska.Arctic 42(4): 362-367.Figure 2. Repeat photographs of trail on Moist Sedge-WillowTundra in 1985 (top) and 2007 (bottom). An undisturbed referenceplot adjacent to this trail had a mean of 28% excess ice content nearthe surface of the permafrost. Trail subsidence caused increases inhydrophytic sedges and decreases in all other plants.120