Ecological Land Classification of Mount Revelstoke and Glacie r ...

Some stable landscapes have weakly developed soils . Recently glaciated areas have predominantly OrthicRegosols where the till contains lime . These soils may have incipient Ah horizons and sho wweathering of some carbonates, especially in peripheral areas which have been ice-free longest .Recently glaciated areas with noncalcareous till have a mosaic of Regosolic and Brunisolic soils . Neoglaciallandscapes in MRNP and GNP are likely a maximum of 400 years old, based on an extrapolationof Heusser 's (1956) conclusions on the Rocky Mountains . This provides an estimate of the tim eover which these soils have developed . Orthic Regosols with little evidence of alteration occur closes tto the retreating glacier . Further away, Orthic Eutric Brunisols show weak B horizon developmen tand a strong pH gradient within the top few tens of centimeters . They are slightly acid at depth (pH6 .1-6 .5) and become strongly acid near the surface (pH 5 .1-5 .5) . Where quartzites are predominant ,there is little buffering capacity and pH rapidly becomes 40 cm, and develop where shallow water that lacks mineral sediment is ponded or flows slowl yacross the surface for most of the growing season . They are most common in the Interior Cedar- -Hemlock Ecoregion, but only because the flat, wet topography conducive to their development i sscarce at higher elevations . They are most extensive on flat valley bottomland (e .g. Beaver River andMountain Creek valleys) but occur locally in the troughs and depressions of hummocky glacial drif ton valley floors . In both settings, development is occasionally associated with beaver dams .The organic material is fen peat derived mainly from rushes, sedges, and mosses . The peat is mostl yfibric (i.e. weakly decomposed), especially in the upper horizons, and Fibrisols predominate . Mesic ,moderately decomposed horizons are common but Mesisols are less extensive . Humic, thoroughly de -composed horizons and Humisols are rare .The mean thickness of peat accumulation is not well known . The Terric subgroup (thickness 1 .2 m thick (Typic subgroups) may occur on the Beaver Rive rand Mountain Creek valley floors .Thin layers of fluvial and occasionally eolian material occur sporadically within the Organic soils .They usually have a high silt content and lack coarse fragments . Both they and the mineral materialsthat underlie the Organic soils are generally gleyed .Gleysols are mineral soils with dull colors or strong mottling within 50 cm of the surface . They occu rwith Organics, but have a broader distribution as well . Many are as wet as Organics and some eve nhave fen vegetation, but episodes of fluvial deposition in these preclude the buildup of thick organi clayers and the development of pedogenic horizons (Rego Gleysols) . Orthic Gleysols occur in bothfluvial and morainal, stable landscapes . They have B horizons with dull colors or mottles (Bg), andpeat or forest humus