James C. Bell

A new model of topographic effects on the distribution of loess

A model of topographic influence on the regional transport and accumulation of loess in sparsely vegetated landscapes is proposed, based on the critical role played by saltating eolian sand in the entrainment and long-distance transport of finer-grained suspended dust. In this model, long-term accumulation of loess occurs mainly downwind of topographic obstacles that limit eolian transport of sand, and associated re-entrainment of dust. Regional and local patterns of distribution of late Wisconsinan loess in parts of the Upper Mississippi River basin are closely related to the distribution of topographic obstacles to sand transport. These cases of topographic influence occur in a region where evidence exists for sparse tundra-like vegetation during the deposition of loess in the late Wisconsinan. Similar topographic effects may not be evident further south in the Missouri and Mississippi River basins because vegetation density was generally sufficient to prevent the movement of eolian sand out of source valleys. Thus, topographic obstacles and dense vegetation may have similar effects on loess distribution under different environmental conditions.

Geographic Information Systems in Agronomy

Publisher Summary This chapter is intended to provide an introduction to geographic information system (GIS) and associated landscape tools and to illustrate the ways in which they are being used in various aspects of agronomy. GIS technology is bringing about rapid changes in the way that agronomic analysis and management are being conducted. GIS coupled with remote sensing, Global Positioning System (GPS), electronic sensors, and computer technologies is providing new methods for data acquisition, storage, processing, analysis, and modeling. These new tools allow us to quantitatively describe landscapes and processes. The chapter discusses site-specific farming (SSF)—that is, farm management based upon variable soil and microclimate conditions that occur within most fields. SSF reduces waste, because fertilizer and herbicide—for example—are applied only where needed. New and/or improved models need to be developed to fully take advantage of the spatial nature of the data provided by these tools. The development of these models will rely on spatial statistical analysis techniques to quantify the accuracy of input parameters and model output. Many new tools are being used in this rapidly evolving field of GIS. Three-dimensional scene simulation, visualization, and animation linked with remote sensing and image processing technologies, and real time data collection will be needed in the study of agronomic systems. The development and use of three-dimensional GIS and spatiotemporal GIS will be an increasingly important area of research. The agronomic community—including farmers, land managers, fellow scientists, policymakers, and the general public should benefit from this evolving and expanding field.

The practice of “approximate original contour” in the central Appalachians. I. Slope stability and erosion potential

Abstract Surface mining for coal disturbed hundreds of thousands of hectares in the Appalachians by the mid-1970s. The mined landscape created by typical “shoot-and-shove” mining methods during this era led to severe water-quality and land-use problems. Enacted in 1977, the Surface Mining Control and Reclamation Act (SMCRA) required that all mining spoil be stabilized and returned to “approximate original contour” (AOC) wherever possible. This requirement is controversial in the steeply sloping Appalachian (U.S.A.) mining region. The major goal of this research was to objectively evaluate the long-term slope stability and potential erosivity of central Appalachian AOC landforms. Many AOC backfills in this region face long-term stability problems. The major factors leading to backfill instability are: (1) excessively steep and/or convex fill configurations; (2) excessive seepage leading to loss of fill strength; and (3) inaccurate estimation of spoil shear strength parameters and fill safety factors. Slope failures may occur both within and beyond the five-year bond release period mandated by SMCRA. Steeply sloping siltstone spoils are particularly prone to erosion losses, and rapid revegetation is essential for the stabilization of AOC slopes. Widespread implementation of alternative landforms which utilize hollow fills for excess spoil disposal while still eliminating the highwall would greatly reduce the potential for slope failures and erosion by reducing total backfill slope areas and lengths.

Effects of Riparian Buffers on Hydrology of Northern Seasonal Ponds

Although seasonal ponds are common in northern, glaciated, forested landscapes, forest management guidelines are generally lacking for these systems. The objective of this study was to determine the effect of riparian buffer type on seasonal pond hydrology following harvest of the adjacent upland forest. A replicated block design consisting of four buffer treatments was established in north central Minnesota in 2000. Treatments included an uncut control (i.e., the upland and buffer were uncut) and three treatments in which the upland was clearcut but the buffer was either uncut, partially harvested, or clearcut. Hydrologic characteristics were examined for differences among buffer treatments. One year of pre-harvest data was collected followed by five years of post-harvest data. Regression analysis of water levels indicated that all buffer treatments had significantly higher pond water depth than the uncut control for four years following harvests. The fifth year following harvests showed no difference in water depth between buffer treatments and the uncut control. In the first post-treatment year, the clearcut buffer treatment had the highest mean annual water depth of the three buffer treatments. Changes in evapotranspiration and runoff due to altering upland and riparian vegetation are considered key factors in explaining these hydrological responses. The results of this study indicate that upland harvesting increases water tables in seasonal ponds, and it takes about five years before water tables are similar to predisturbance levels. Our results also suggest that the amount of vegetation harvested within a riparian buffer affects the hydrologic response, especially in the first year following harvest.

The Practice of "Approximate Original Contour" in the Central Appalachians. II. Economic and Environmental Consequences of an Alternative

Zipper, C.E., Daniels, W.L. and Bell, J. C., 1989. The practice of “approximate original contour” in the central Appalachians. II. Economic and environmental consequences of an alternative. Landscape Urban Plann., 18: