Mountain Soils - Mountain Geography: Physical and Human Dimensions - page 310

dry and support a scanty cover of lichens, mosses, and cushion plants. Organic material
may darken the surface, but there is little other evidence of horizons. Some Entisols
may be simply accumulations of fine or rocky material rather than true soils. The ending
“-ent” denotes an entisol. A “cryorth ent ,” for example, is an Entisol developed where
the mean annual temperature at 50 cm depth is 0-8°C.
INCEPTISOLS
Inceptisols are soils in early stages of profile development or soils with diagnostic hori-
zons that fail to meet the criteria for other orders (Soil Survey Staff 2010). They occur
from the tropics to tundra regions, but do not include soils of arid environments. In-
ceptisols comprise most of the soils found above timberline in the Pyrenees, Caucasus,
Rockies, and Alps (Retzer 1974). The ending “-ept” denotes an Inceptisol. The alpine-
turf subgroup (cryumbrept) is well-drained and occurs on upper slopes and exposed
areas. Turf stabilizes these surfaces. Once the turf is destroyed, however, the soil be-
comes highly susceptible to erosion (Bouma 1974; Byers 2005). Consequently, protec-
tion of turf is essential for the preservation of alpine landscapes.
Cryumbrepts may be relatively deep, extending to 30-80 cm. They show distinct hori-
zon development and are weakly to strongly acidic, characteristics that represent some
downward movement of water through the profile (Bäumler and Zech 1994). The finest
particles occur at the surface, reflecting the greater weathering and biological activity
near the soil/atmosphere interface (Fig. 6.6). Eolian (wind) deposition may also contrib-
ute to the finer surface texture. The “A” horizon is dark brown to black, with a high or-
ganic content, but nutrient status is fairly low.
MOLLISOLS
Mollisols are relatively deep subalpine and alpine grassland soils with distinct horizons
and neutral to slightly alkaline pH. Compared to Inceptisols, Mollisols contain more ex-
changeable bases and, therefore, more plant nutrients. Mollisols characteristically have
an organic-rich “A” horizon at least 25 cm thick. Mollisols develop under grass vegeta-
tion in environments that are neither humid nor dry. They occur in midlatitude prairie
regions, and at high and low latitudes and high altitudes.
SPODOSOLS
Spodosols, or subalpine-forest soils, are moderately deep, well-drained, acidic soils with
well-developed and distinct horizons. They form under a complete cover of conifer-
ous forest on many types of parent material, predominantly on crystalline rocks. The
primary soil-forming process involves leaching of the “A” horizon and translocation of
bases and clays to the “B” horizon (Lundström et al. 2000). Rates of decomposition and
incorporation of organic matter into the soil are slow, owing to the low temperatures
and heavy snowpack of many high mountain forests. Under these conditions, a layer of
litter and partially decomposed organic material accumulates above the mineral soil.
Water moving down through the profile carries humic acid from the decomposing hu-
mus, creating an acidified profile in which oxides of iron and aluminum can be mobil-