 |
| Titel |
Soil development along elevational transects on granite, andesitic lahar and basalt in the western Sierra Nevada, California |
| VerfasserIn |
R. A. Dahlgren, C. Rasmussen, R. J. Southard |
| Konferenz |
EGU General Assembly 2009
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250019556
|
|
|
|
|
|
| Zusammenfassung |
| Soil development along three elevational transects, consisting of granite, andesitic lahar and
basalt, were investigated on the western slopes of the Sierra Nevada, California to assess the
effects of climate on soil properties and processes. The transects, each consisting of
four to seven soils, spanned elevations between 150 to 2900 m with mean annual
temperatures (3-17 C) decreasing and precipitation (33-150 cm) increasing with increasing
elevation. All sites were characterized by a Mediterranean climate with warm to
hot, dry summers and cool to cold, wet winters. Vegetation progressed from oak
woodland/annual grasslands at low elevations to mixed conifer forest at mid elevations
and subalpine mixed conifer forest at high elevations. Soil pH and base saturation
decreased with increasing elevation with the largest decrease found on granite.
Solum carbon pools ranged from 2 to 25 kg m-2 with the highest contents found in
soils formed on andesitic lahar and in mid-elevation soils corresponding to the
highest ecosystem net primary productivity. The degree of weathering and mineral
assemblages exhibited a strong threshold change at the elevation of the permanent winter
snowline (1200-1500 m). Measures of chemical weathering (e.g., clay and Fe oxide
production) increased in a near-linear fashion to the winter snowline where they
abruptly decreased by about 10-fold. The clay mineralogical assemblage in the
rain-dominated weathering zone was dominated by kaolin minerals and was remarkably
similar among all parent materials. Within the snow-dominated weathering zone, clay
mineralogy was dominated by allophanic materials (allophone/imogolite) on the
andesite and basalt compared to hydroxy-Al interlayered 2:1 layer silicates and
gibbsite on the granite. Clay translocation resulting in the formation of argillic
horizons was only found in the rain-dominated zone. With increasing elevation, soil
development followed the order: Alfisols → Ultisols → Inceptisols (granite)/Andisols
(andesite/basalt) → Inceptisols/Entisols. Weathering, mineralogical transformations, soil
development and net primary productivity are limited by water availability at low
elevations, whereas low soil temperature is the major limitation at high elevations. |
|
|
|
|
|
|