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Abstract:
In the forest-alpine ecotone at Stillberg (Dischmatal/Switzerland) the morphology
of humus forms and the spatial variability of organic layer properties were investigated.
At northeast-exposed gully sites mulls with high acidity in the Ahorizon
occur. They were classified after the Canadian classification of humus
forms as Rhizomulls. Mors occur on ridges and on their east- and north-exposed
aspects. They can be differentiated by the ratio between the thickness of the Fhorizon
and the combined thickness of the F- and H-horizon. The relative thickness
of the F-horizon increases significantly in the order: east aspects < ridges
< north aspect. The humus forms of the east aspects and the ridges were classified
as Humimors and those of the north aspects as Hemimors. The Canadian classification
was suitable to describe the properties of the horizons and to classify the
humus forms. The results of a grid sampling at the study sites and the computation
of nonergodic correlograms show that the spatial variability of organic-layer
thickness, bulk density, and moisture is high (CV around 50%), with a pronounced
small-scale heterogeneity (range usually below 2 m and more than 50% variability
occurs within 0.3 m). Only 33% of the variance of organic-layer thickness were
explained by site and vegetation structure, but in spite of the low percentage both
proved to be a significant factor. In the forest-alpine tundra ecotone about 30 to
35 soil samples per site are needed for a reliable estimation of the mean of the
organic-layer thickness.
