Ecological land survey and soil landscapes map for Alagnak Wild River, Alaska, 2014

Wells, Aaron; Christopherson, Tracy; Kidd, Janet; Johnson, Erin

This study was conducted to inventory and classify soils and vegetation within the ecosystems of Alagnak Wild River (ALAG) using an ecological land survey (ELS) approach. The classifications identified by the ELS were then mapped across the park, using an archive of Geographic Information System (GIS) and Remote Sensing (RS) datasets pertaining to land cover and topography. The description and mapping of the landform-vegetation-soil relationships identified by the ELS offers tools to support the design and implementation of future field- and RS-based studies; facilitates further analysis and contextualization of existing data; and informs natural resource management decisions. We collected information on the geomorphic, topographic, hydrologic, pedologic, and vegetation characteristics of ecosystems within a network of 132 field plots, of which 96 were sampled by us in 2014, and 36 were sampled by the Alaska Natural Heritage Program (AKNHP) in 2010. The plot network encompassed all of the major environmental gra-dients and landscape histories present in ALAG. Individual state-factors (e.g., soil pH, slope-aspect) and other ecosystem components (e.g., geomorphic unit, vegetation species-cover data) were measured or categorized using standard clas-sification schemes developed for Alaska. We described and analyzed the hierarchical relationships among the ecosystem components to classify 26 ecotypes (local-scale ecosystems) that best partition the variation in soils, vegetation, and disturbance properties observed at field plots. From the 26 ecotypes, we developed classifications of soil landscapes and disturbance landscapes that could be mapped across the park. Detailed soil descriptions for the 132 field plots pertained to 7 soil orders: Alfisols (5% of plots), Andisols (4%), Entisols (18%), Gelisols (12%), Histosols (13%), Inceptisols (40%), and Spodosols (8%). Within these 7 soil orders, field plots corresponded to a total of 63 soil subgroups, the most common of which were Andic Haplocryepts, Fluventic Haplocryepts, Folistic Dystrocryepts, Andic Haplocryalfs, Histic Cryaquepts, Oxyaquic Cryofluvents, and Fluvaquentic Historthels. The field data, the classifications of ecotypes and soil land-scapes, a pre-existing land cover map developed by AKNHP, and ancillary GIS and RS data were used to produce a series of ecosystem maps for ALAG. Three physiographic units cap-turing broad-scale divisions in landscape position, microcliation of rule-based modeling related to topography and interpretation of satellite imagery. The ecotypes classified using field data were aggregated into a reduced set of 22 map ecotypes that could be mapped across the study domain; aggregation was based on similarities in vegetation structure, general soil texture, and successional processes. Three map ecotypes accounted for ~50% of the mapping area: Upland Ashy-Loamy-Rocky White Spruce Woodland (37.6% of mapping area), Upland Frozen Organic-rich Birch-Tussock Low Shrub (8.6%), and Riverine Circumneutral River Water (8.4%). The map ecotypes were further organized into 11 soil landscape, 7 disturbance landscape, and 8 great group classes.Two widespread soil landscapes accounted for >50% of the study area: Upland Ashy-Loamy-Rocky Low Shrub-lands, Forests, and Woodlands (39.8% of mapping area) and Riverine Silty-Sandy-Rocky Shrublands and Forests (13.2%). The disturbance landscapes were derived from map ecotypes with broadly similar disturbance regimes. Two disturbance landscapes, including Windthrow, Fire, Pests and Pathogens (48.3%) and Flooding, Sedimentation, Erosion (24.8%); encompass nearly three quarters of the mapping area. We prepared a map of soil Great Groups by aggregating ecotypes with similar Great Group classifications and naming the mapping classes after the most common Great Groups in each class.

Ecological land survey and soil landscapes map for Alagnak Wild River, Alaska, 2014

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