Soil Catena Sequences and Fire Ecology in the Boreal Forest of Alaska

Abstract

peak solar influx plays an important role in the ecological energy budget (Pé wé , 1975; Van Cleve et al., 1992). This paper is the first to provide chemical, physical, and morphological properties of the soils in the boreal region of Alaska and To quantify soil development under contrasting slopeto demonstrate the dominant effect of landscape attributes in soil influenced energy regimes in a boreal setting, individual formation. This study was conducted to characterize soils and landsoil profiles must be characterized as catena sequences scape relationships in the boreal forest of Alaska. Sites representing on slopes of similar topography but different aspects. major landform positions and vegetation communities were selected The empirical data can be used to build a model of for study. Well-drained, shallow to moderately deep Inceptisols occur topographically influenced subsoil variability in boreal on the drier and warmer south aspect slopes with thin (5-9 cm) organic horizons and loamy textures. Poorly drained Gelisols form on wet regions strongly affected by fire and may also help preand cold north aspect slopes and valley floors with thick (18-52 cm) dict changes brought about by prescribed burning. organic horizons and permafrost within 45 to 60 cm of the surface. The Caribou-Poker Creek Research Watershed (CPC On the latter, mineral horizons are reduced. Soils on the ridgetop RW), located 50 km northwest of Fairbanks, Alaska show features of relic, nonsorted circle (a type of pattern grounds) (Fig. 1), is within the discontinuous permafrost zone that indicate a previous periglacial environment. The mineral soil on that extends across central Alaska eastward into northbackslopes is shallow to moderately deep due to gelifluction and slope movement but deep toward toeslopes. Charcoal particles, commonly central Canada. The watershed is representative of found within the soil profiles, attest to frequent fire events in the past. non-glaciated upland headwater stream basins found Fire has the greatest impact on soil properties on south aspect slopes throughout interior Alaska. Forest communities in the because the organic horizons are thin and dry, and easily destroyed by watershed are representative of the boreal forest zone fire. The underlying mineral horizons often develop hydrophobicity in Alaska. Forest fire is a dominant ecological factor in resulted from moderately and severe burn. Slope, aspect, and slope this region (Kasischke and Stocks, 2000) and there has gradient are major controlling factors for the contrasting soil types along the catena sequences in the watershed.

Permafrost soils and carbon cycling

“…In this zone, Gelisols commonly form in lowlands with restricted drainage that favor near-surface permafrost, but Gelisols also form in welldrained upland sites where the permafrost is deeper (Rieger, 1983;Ping et al, 2004;Li et al, 2008). Within the discontinuous and sporadic permafrost zones of the boreal regions, the slope and aspect of uplands and mountains play a controlling role in distributions of permafrost and Gelisols (Péwé, 1975;van Cleve et al, 1983;Ping et al, 2005a). In the Southern Hemisphere, permafrost and Gelisols occur on the Antarctic continent, on the sub-Antarctic islands, and in mountain areas (Beyer et al, 1999(Beyer et al, , 2000Blume et al, 1997;Bockheim, 1990;Campbell and Claridge, 2004a, b;Simas et al, 2007;Gilichinsky et al, 2010).…”

“…Most of these mineral soils with cryoturbated SOM and broken surface organic horizons are classified as Turbels (Turbic Cryosols). But, in the poorly drained valleys or basins among the hilly uplands, thick organic horizons (> 40 cm) can build up due to fen or bog formation, and these soils are classified as Histels (Cryic Histosols) (Ping et al, , 2005a. Ping et al (2008b) measured SOC stores along a northsouth transect through five bioclimatic subzones from the High Arctic to the boreal regions in North America as part of a larger study investigating the interrelationships between patterned ground formation and vegetation zonation .…”

Genesis of Turbic Cryosols on north-facing slopes in a dissected, unglaciated landscape, west-central Yukon Territory

“…Previous work on the genesis of Cryosolic soils in similar sub-arctic environments in central Alaska have also demonstrated the importance of geomorphology, slope aspect, and slope position in controlling soil thermal regime and related attributes of internal drainage, surface organic matter accumulation and biological productivity (Swanson 1996a;Ping et al 2005). These and other studies have highlighted the importance of permafrost and cryoturbation in stabilizing large stores of soil organic carbon in arctic and sub-arctic environments (Ping et al 1997;Shur et al 2005;Zimov et al 2006;Bockheim 2007;Ping et al 2008).…”

Towards improved parameterization of a macroscale hydrologic model in a discontinuous permafrost boreal forest ecosystem

“…In both small-scale parameterization schemes, the top layer of the permafrost cell is also assumed to be the organic layer (Ping et al, 2005;Zhang et al, 2010b) while mineral soil, as obtained from FAO dataset, is assumed for permafrost-free grid cells.…”

“…The hydraulic conductivity of permafrost-affected soils is several orders of magnitude less than that of the overlying organic layers and the nearby permafrost-free soil (Rieger et al, 1972;Burt and Williams, 1976;Kane and Stein, 1983;Woo, 1986;Ping et al, 2005;Zhang et al, 2010a). The icerich permafrost is an impermeable layer at the permafrost surface that limits the hydraulic flow to the active layerthe thin, seasonally thawed soil layer above permafrost (Romanovsky and Osterkamp, 1995;Romanovsky et al, 2003).…”