Recovery of Active Layer following Vehicle Disturbance Near Barrow, Alaska
Dustin R. Bronson, Craig E. Tweedie, Steven P. Rewa, Robert D. Hollister, Patrick J. WebberMethods:
Fig 2 - CIR Aerial photography June 1979 showing the four track sites studied
- Four localities were chosen within or near the Barrow Environmental Observatory (BEO). Tracks at each site were created by either a Rolligon or M-29 Weasel (Fig 2, 3).
- Twenty-five grided plots (2 x 10 meters) were established at four sites. Each grided plot was divided into (0.5 x 0.5 meter) sub plots to assess the spatial distribution of active layer thickness .
- Active layer thickness was measured four times throughout the summer. Measurements were made by thrusting a calibrated metal probe into the earth on the north side of every grid point until the probe reached the permafrost.
- All plots were classified as either dry, mesic, wet or aquatic according to their vegetation composition particularly of the presence of indicator species.
- Moisture content data was collected after the final active layer measurement was made. A random number generator was used to preselect three subplots for on-track, between-track and off-track for every plot. A soil core was taken from the preselected subplots and a soil tin was plunged in the side of the soil core until the tin was fully immersed in the soil. Soil samples were weighed to attain fresh weight then put into an oven at sixty degrees Celsius for two weeks to get dry weight weighed. The difference between wet and dry weight was used to calculate relative soil moisture content.
Fig 3 - Picture of Weasel Track at CRREL Trail - Overlays presented have been ranked accordingly by their soil moisture and vegetation status.
- All data was managed in a Microsoft Access database and manipulated in a Geographical Information System (GIS) Arc View (V3.2) using 3D analysis extension for visualization.
- Visualizations showing depth of thaw as shaded contours were produced. They are arranged according to site moisture regime and date (Fig 4).
- Comparison of end-of-season relative thaw depth with track position was used to visually assess residual thaw effects of the tracks (Fig 5).
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| Fig 4 - A two-dimensional array of ArcView (3.2) visualization of plot active layer thickness. These are arranged by plot moisture regime and seasonal progression, which indicates that drier plots thaw quicker and deeper than wet plots. | Fig 5 - A two-dimensional array of ArcView (3.2) visualization of track position on plots and relative thaw depth. Plots that show residual thaw affect due to vehicular tracks are checkmark. |
- Beginning
- Introduction
- Methods
- Results
- Conclusion
- References