A method to generate soilscapes from soil maps

Abstract

Digital soil mapping for large areas is challenging if mapping resolution should be as high as possible and sampling should be as sparse as possible. Generally, the more complex the soil associations in a landscape, the more samples are required to systematically cover the entire feature space. Moreover, regions should be modeled separately if the patterns of spatial variation vary on subregion level. A systematic segmentation of a landscape into soilscapes is additionally important for a feasible application of soil‐sensing approaches. In this paper, we introduce a semiautomated approach to segment nominal spatial datasets based on the local spatial frequency distribution of the mapping units. The aim is to provide homogeneous and nonfragmented segments with smoothed boundaries. The methodological framework for the segmentation comprises different spatial and nonspatial techniques and focuses mainly on a moving‐window analysis of the local frequency distribution and a k‐means cluster analysis. Based on an existing soil map (1:50,000), we derived six segments for the Nidda catchment (Central Hesse, Germany), comprising 1600 km2. As segmentation is based on a soil map, soilscapes are derived. In terms of the feature space, these soilscapes show a higher homogeneity compared to the entire landscape. Advantages compared to an existing map of landscape units are discussed. Segmenting a landscape as introduced in this study might also be of importance for other disciplines and can be used as a first step in biodiversity analysis or setting up environmental‐monitoring sites.

Method development to extract spatial association structure from soil polygon maps

“…Recent fi ndings provide more and more quantitative results on how soil bodies are associated (Behrens, T. et al 2009;Hewitt, A.E. et al 2010;Schmidt, K. et al 2010). The latest nationwide digital soil mapping projects in New Zealand (Hewitt, A.E.…”

“…They provide us a path through the almost infinite number of theoretically possible combinations to the most probable outcome. In countries where small or medium scale soil maps exist their statistical analysis may help to defi ne homogenous soil regions or soilscapes and representative areas for detailed soil surveys (Behrens, T. et al 2009;Schmidt, K. et al 2010).…”

“…et al 1991;Lagarcherie, P. et al 2001;Schmidt, K. et al 2010). Soilscape is a term introduced by Buol, S.W.…”

“…Very often, mapping soilscapes from soil forming factor maps is more realistic than mapping soil classes. The primary task in mapping larger areas should be to account for these spatial soil-association patt erns as a basis to segment landscapes (Schmidt, K. et al 2010). McSweeny, K. et al (1994) proposed to set up a hierarchical multistage strategy to explain the variability of soils and soil properties in space.…”

“…SOTER has become widely evaluated in European and broader context (Dobos, E. et al 2001(Dobos, E. et al , 2005(Dobos, E. et al , 2010. However, these terrain-based approaches are more appropriate for fi ner scales as they mainly focus on deriving terrain facets instead of deriving larger homogeneous geomorphological or pedological regions (Schmidt, K. et al 2010).…”