CRP Targeting for Wildlife Habitat: A New Indicator Using the 1992 National Resources Inventory
Congress has wrestled with the issue of which land should be enrolled in a renewal of the Conservation Reserve Program (CRP), considering that benefits to wildlife from CRP are substantial. This paper evaluates the amount of land that may qualify for CRP enrollment in order to provide high-value wildlife habitat and to present the potential enrollment costs. The assessment is based on a wildlife habitat indicator developed from the National Resources Inventory conducted by the Natural Resources Conservation Service.
Wetland Soils of the Prairie Potholes
Publisher Summary The chapter discusses the wetlands of the prairie pothole region (PPR). The two important hydrologic factors are climate and topography that explain the existence of wetlands in any landscape. PPR wetland soil development is based on hydrologic processes and conditions created by a climatic gradient as impacted by topography, sediment lithology, and stratigraphy. The most important systems used to classify wetlands in the PPR include the United States Fish and Wildlife system; the Stewart and Kantrud system; and an extension of the Stewart and Kantrud system that incorporates hydrology and landscape position. The dominant water quality considerations for wetlands in the PPR are increased sedimentation from cultivation; and salinity associated with hydric soils, groundwater, and surface water. Wetland soil properties that have the greatest influence on current land use include soil moisture dynamics, soil aeration, and salinity. Using principal components analysis (PCA), Richardson and Bigler found that principal component factors reflecting salinity, organic matter accumulation, calcium carbonate dynamics, and texture, respectively in order of importance, explained most of the observed variations in PPR wetlands. In the PPR, three soil types have been observed in nonfen wetland edges: the Calciaquoll without salinity and gypsum; the Calciaquoll with salinity and gypsum; and the Natraquoll.
Monte Carlo Study of the Effect of Backscatter Materail Thickness on 99 mTc Source Response in Single Photon Emission Computed Tomography
Introduction SPECT projections are contaminated by scatter radiation, resulting in reduced image contrast and quantitative errors. Backscatter constitutes a major part of the scatter contamination in lower energy windows. The current study is an evaluation of the effect of backscatter material on FWHM and image quality investigated by Monte Carlo simulation. Materials and Methods SIMIND program was used for simulation of a Siemen’s dual-head variable angle scintillation gamma camera. Planar and SPECT scanning of a 99m Tc source and a Jaszczak phantom for varying thicknesses of Perspex slabs, as a backscatter media, were analyzed using the photopeak and scatter windows. Simulated planar images and reconstructed tomographic images were evaluated qualitatively, by two nuclear medicine specialists, and quantitatively, by Structural Similarity (SSIM) Index. Results In the 99m Tc photopeak window, no significant change in total counts due to backscatter material was measured. In the scatter windows, scattering was overestimated compared with a simulated backscatter free SPECT system. For instance, at a thickness of 10 cm, total counts of a 99m Tc source detected in the 72 keV windows eventually doubled with increasing backscatter material, compared with the situation without backscatter material. The backscatter contribution plateaued when more than 7 cm of scatter material was placed but there were optimized results for a backscatter thickness of 4.5 cm. Better image quality for the thickness was confirmed by the results of eye interpretation and also by SSIM algorithm. Conclusion Backscatter should be taken into account, particularly in model-based scatter correction methods in SPECT for an accurate simulation system optimization.