Assessment, Description, and Delineation of Soil Spatial Variability at Hillslope
to Landscape Scales (10m2 to 100m2)
J. C. Bell
Department of Soil, Water, and Climate
University of Minnesota
St. Paul, MN
e-mail: jay.bell@soils.umn.edu
Bioiophysical processes operating through time differentiate the soil-landscape continuum into repeating
patterns of variability that can be observed at multiple spatial scales. These patterns of variability for spatial resolutions
in the range of 10 m2 to 100 m2 may be largely determined by hillslope and other geomorphic processes resulting
in the redistribution of soil components. Mapping scales appropriate for this level of variability roughly
corresponds to map scales of 1:10,000 to 1:100,000. Soil maps of these scales are typically used to make land-use decisions
for individual and local governmental planning purposes documenting variability from within fields to within
minor watersheds. These maps usually contain sufficient detail for making specific land-use decisions, yet are still
cost-effective to produce. As such, considerable resources have and will continue to be dedicated to mapping
soil variability at these scales. Feasible sampling densities for these spatial scales are generally too dispersed to
map variability from one soil observation to another. Hence, relationships with observable landscape features
(topography, vegetation, etc.) are used to infer the variability of soil properties. Both qualitative and quantitative
approaches have been used to formulate these soil-landscape models. Traditional methods of describing and
mapping soil variability within this range rely on conceptual soil-landscape models formulated by field soil
scientists. These conceptual models are based on accumulated experience of soil-landscape observations. While these
models are the mainstay of many soil survey activities, the specific decision criteria used to map soil variability
is seldom documented and often is difficult for field scientists to articulate. Legends are based on multivariate
soil taxa which define the composition of spatial mapping units and are used as the basis for making soil
interpretations. More recent research has focused on quantifying empirical soil-landscape relationships based on
observational data coupled with an understanding of local pedogenic and geomorphic processes. Many efforts at
quantitative soil-landscape modeling have focused on mapping specific soil properties, rather than soil taxa. The use
of multivariate statistical procedures permits assessments of class uncertainty, while other spatial modeling
techniques have been used to map gradients of change for continuous soil variables. The success of
quantitative modeling efforts relies heavily on the quality of ancillary spatial data, such as digital maps of topographic,
land-cover, or climatic attributes.
Back to the Abstracts Page
|