Tanada Lake Trail Integrated Terrain unit Mapping and Permafrost Surveys, Wrangell-St. Elias National Park and Preserve, Alaska, 2012

Well, Aaron

An Integrated Terrain Unit (ITU) approach to mapping ecosystem components is well suited for fine-scale (tens to hundreds of square kilometers), site specific management and planning, monitoring, and study design. We initiated a pilot study, including field surveys, to illustrate the utility of the Integrated Terrain Unit approach for classification, mapping, and analysis of landscape sensitivities, and to collect baseline data for potential future broader scale mapping and monitoring in the vicinity of the Tanada Lake Trail in Wrangell-St. Elias National Park and Preserve (WRST). We used the Ecological Land Survey of Jorgenson et al. (2008a) to classify and map ecotypes, which we used in conjunction with field data to evaluate land sensitivity in the TLT study area. The majority of the study area occurs in lowland, upland, and subalpine physiography where glaciolacustrine (lowlands) and younger till and glacial outwash deposits (subalpine and upland) predominated. Geomorphic units were aggregated into six generalized soil texture classes for mapping, including Gravelly, Fill, Loamy, Loamy-Organic, Rubbly, and Water. Thirteen vegetation types were mapped in the study area; the most common included Open Mixed Low Shrub–Sedge Tussock Tundra, Open Low Shrub Birch–Willow, White Spruce Woodland, Black Spruce–White Spruce Woodland, Open White Spruce Forest, and Tussock Tundra. Four disturbance classes were mapped in the study area, the greater portion of which was undisturbed. Wheeled Vehicle Summer trail accounted for the largest disturbed area and corresponded to braided areas of the TLT. Lacustrine (drainage) was the second most common disturbance class and corresponded with several small kettle lakes in the study area that have recently drained. Fourteen ecotypes were mapped in the study area including 11 classified and described in Jorgenson et al. (2008a) and four not previously described for WRST. The most common ecotypes included Boreal Lowland Tussock–Shrub Bog, Boreal Subalpine Willow– Birch Shrub, Boreal Upland White Spruce Forest, Boreal Lowland Black Spruce Forest, and Boreal Lowland Sedge–Shrub Fen. Landscape sensitivity represents a combination of permafrost and summer traffic sensitivity developed by assessing vegetation-soil-landscape relationships based on field surveys, and by summarizing a reduced set of variables (surface organic thickness, thaw depth, and depth to >15% rock fragments, dominant soil texture) by ecotype. The landscape sensitivity model classified the majority of the study area as highly sensitive, which include lowland and riverine areas with organic-rich, fine-textured, and frozen soils. Upland and subalpine areas with rocky soils were classified as low sensitivity, the second most common sensitivity class in the study area. Lacustrine and riverine areas with loamy soils were classified as moderately sensitivity. We assessed the effectiveness of the landscape sensitivity classification overlaying the NPS Trails layer over the landscape sensitivity map and calculating the distance across each of four trail type classes and disturbance ratings. Trail type classes and impact ratings indicative of greater damage occurred most often in areas classified as high sensitivity, while those indicative of less damage occurred most often in areas classified as low and moderate sensitivity. Despite a few minor inconsistencies, these results indicate that the landscape sensitivity classification is reasonably robust. Lastly, we provided recommendations for additional studies to inform future management decisions, and to rehabilitate and monitor the Tanada Lake Trail into the future.

Tanada Lake Trail Integrated Terrain unit Mapping and Permafrost Surveys, Wrangell-St. Elias National Park and Preserve, Alaska, 2012

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