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Since Iceland was settled 1100 y ago, declines in vegetated land cover has been accompanied by severe wind and water erosion. Interaction of
 

Summary: Since Iceland was settled 1100 y ago, declines in vegetated land cover
has been accompanied by severe wind and water erosion. Interaction of
four reinforcing factors appears to have contributed to the erosion
problem: soil (Andisol) properties, cold climate, vegetation poorly
adapted to herbivory, and livestock grazing. Andisols, with their low bulk
density and particle cohesion, are intrinsically susceptible to erosion
(Figure 1). The high soil water holding capacity causes them to expand
when soils freeze, thus destabilizing soil surfaces. We hypothesized
that grazing, by reducing plant biomass, root growth, and sward
thickness, would magnify these instabilities and increase Andisol
susceptibility to erosion. To test this hypothesis, soil surface movement
was quantified in treatments simulating grazing. Results indicate that
grazing exacerbates soil surface instability, the magnitude varying with
vegetative ground cover properties. Properties of degraded landscapes
were also studied on sites randomly selected from satellite imagery.
These landscapes were grouped based on NDVI values and stage of
erosion, and species abundance, vegetation cover, microtopography
and sward thickness, -strength and ­type quantified. Preliminary results
show that low sward strength was positively correlated with low NDVI
values and rougher microtopography (i.e. hummock shape and size).

  

Source: Archer, Steven R. - Savanna/Woodland Ecology Lab., School of Natural Resources and the Environment, University of Arizona

 

Collections: Environmental Sciences and Ecology