Peter Scull

Predictive soil mapping: a review

Predictive soil mapping (PSM) can be defined as the development of a numerical or statistical model of the relationship among environmental variables and soil properties, which is then applied to a geographic data base to create a predictive map. PSM is made possible by geocomputational technologies developed over the past few decades. For example, advances in geographic information science, digital terrain modeling, remote sensing, fuzzy logic has created a tremendous potential for improvement in the way that soil maps are produced. The State Factor soil-forming model, which was introduced to the western world by one of the early Presidents of the American Association of Geographers (C.F. Marbut), forms the theoretical basis of PSM. PSM research is being driven by a need to understand the role soil plays in the biophysical and biogeochemical functioning of the planet. Much research has been published on the subject in the last 20 years (mostly outside of geographic journals) and methods have varied widely from statistical approaches (including geostatistics) to more complex methods, such as decision tree analysis, and expert systems. A geographic perspective is needed because of the inherently geographic nature of PSM.

A Top-Down Approach to the State Factor Paradigm for Use in Macroscale Soil Analysis

This article explains the need for an alternative conceptual framework for conducting macroscale soil geographic research. A top-down approach to the classic state factor paradigm is then described and illustrated by revisiting the idea of soil zonality to investigate the relationship between climate and soil character across the contiguous United States. Although many macroscale soil maps suggest strong relationships between soil properties and climate, few studies have explicitly demonstrated those relationships using unclassified point observations. Data from 10,661 sample points were analyzed using geographically weighted regression (GWR) models to describe the geography of the relationship between A-horizon soil properties and climate. In addition, macroscale soil property surfaces were interpolated from measured point samples visually to assess the validity of the zonal soil concepts. Results suggest many interesting relationships between climate and surface soil character. Local-scale soil variability related to topography and parent material was not found to exceed macroscale variability related to climate. Three of the four surface soil properties analyzed exhibited strong zonality, thus lending support to the concept of zonal soils. GWR was found to be an excellent tool for use in macroscale geographic soil research because of the coefficient maps that the procedure yields.

A Comparison of Methods to Predict Soil Surface Texture in an Alluvial Basin

Abstract Surface soil texture controls many important ecological, hydrological, and geomorphic processes in arid regions and is therefore important from a land-management perspective. Soil survey efforts have traditionally fulfilled this need, but they are constrained by the size, remoteness, and inaccessibility of many arid regions, which renders simple field measurements prohibitively expensive. This article compares several different predictive soil-mapping techniques with a sparse data set in order to develop surficial soil texture maps. Our results suggest that data collected at the landscape scale can be used as input to predictive soil-mapping techniques to create maps of soil texture at higher fidelity and a fraction of the cost than would be required using traditional methods.

Spatial analysis of species richness of shrews (Soricomorpha: Soricidae) in North America north of Mexico

We used geographic ranges of North American shrews and environmental data to better understand spatial distribution of species richness in the Soricidae. Richness was examined as a function of latitude and longitude and was compared with climatic variables at random points (≥90 km apart). Latitudinal trend in richness was parabolic with a maximum near 48°N, consistent with the general hypothesis that diversity is limited by energy to the north and by moisture to the south. Precipitation, snowfall, and July heating degree days were positively related to shrew richness. Richness of North American Soricidae was high in areas where topographic relief allowed for a variety of forested habitats and precipitation was high, such as the Southern Appalachians and Pacific Northwest. This broad, geographic study supports the idea that environmental moisture importantly limits distributions of shrews, which has been

Changes in Soil Temperature Associated with Reforestation in Central New York State

Central New York State has experienced extensive reforestation during the past hundred years, significantly altering many natural systems. In order to begin to assess the impact of reforestation on soil organic carbon, soil temperature was measured within four different land cover types representing various stages of secondary succession following agricultural abandonment. Over forty thousand soil temperature observations were summarized by pedothermic period in order to characterize seasonal differences between cover types and to determine how mean annual temperature changes during reforestation. Forested sites were cooler during the spring and summer, and slightly warmer in the fall. During the winter field locations were significantly warmer that the forested sites, perhaps due to more complete snow cover, which acts to insulate the soil from cold winter air. In addition, soil temperature variability and vegetation were negatively correlated; as vegetation cover increased, variability in soil temperature decreased. Overall, results suggest that as succession proceeds average annual soil temperatures will decrease. Therefore, the succeeding forests will act as a carbon sink by both absorbing carbon directly from the atmosphere, thus increasing standing biomass, and decreasing soil temperature, which should increase the capacity of the soil landscape to store carbon.

Privacy and Ethics in Undergraduate GIS Curricula

The development of location-aware technologies, such as smartphones, raises serious questions regarding locational privacy and the ethical use of geographic data. The degree to which these concepts are taught in undergraduate geographic information science (GISci) courses is unknown. A survey of GISci educators shows that issues of privacy and ethics are important in a GISci education. However, a large proportion of GISci educators are not concerned about the loss of locational privacy and many do not devote classes to the subject. Those not teaching the subject cite lack of course time and the need for more information.