Effects of stream map resolution on measures of riparian buffer distribution and nutrient retention potential

Riparian ecosystems are interfaces between aquatic and terrestrial environments recognized for their nutrient interception potential in agricultural landscapes. Stream network maps from a broad range of map resolutions have been employed in watershed studies of riparian areas. However, map resolution may affect important attributes of riparian buffers, such as the connectivity between source lands and small stream channels missing in coarse resolution maps. We sought to understand the influence of changing stream map resolution on measures of the river network, near-stream land cover, and riparian metrics. Our objectives were: (1) to evaluate the influence of stream map resolution on measures of the stream network, the character and extent of near-stream zones, and riparian metrics; (2) to compare patterns of variation among different physiographic provinces; and (3) to explore how predictions of nutrient retention potential might be affected by the resolution of a stream map. We found that using fine resolution stream maps significantly increased our estimates of stream order, drainage density, and the proportion of watershed area occurring near a stream. Increasing stream map resolution reduced the mean distance to source areas as well as mean buffer width and increased the frequency of buffer gaps. Measures of percent land cover within 100 m of streams were less sensitive to stream map resolution. Overall, increasing stream map resolution led to reduced estimates of nutrient retention potential in riparian buffers. In some watersheds, switching from a coarse resolution to a fine resolution stream map completely changed our perception of a stream network from well buffered to largely unbuffered. Because previous, broad-scale analyses of riparian buffers used coarse-resolution stream maps, those studies may have overestimated landscape-level buffer prevalence and effectiveness. We present a case study of three watersheds to demonstrate that interactions among stream map resolution and land cover patterns make a dramatic difference in the perceived ability of riparian buffers to ameliorate effects of agricultural activities across whole watersheds. Moreover, stream map resolution affects inferences about whether retention occurs in streams or riparian zones.     

Common artefacts and pitfalls in equine computed and digital radiography and how to avoid them

Radiographic technology has rapidly advanced over the last decade with the use of both computed radiography and digital radiography now being common in equine practice. Image quality is critical for optimal diagnostic accuracy, so identification of factors that negatively influence quality is vital. The most commonly encountered problems include positioning errors, exposure anomalies, movement artefacts, labelling errors and image processing faults. The aim of this review is to describe common radiographic faults that will allow the equine practitioner to recognise and learn how to prevent these issues, thus improving image quality. This will aid in improving diagnostic accuracy and will enhance radiation safety by reducing the number of repeat exposures required.     

COMPUTED TOMOGRAPHIC APPEARANCE OF MELANOMAS IN THE EQUINE HEAD: 13 CASES

Melanomas are one of the most common neoplasms in the horse and are frequently found in the head region. There is a genetic predisposition in horses with a gray hair coat. Computed tomography (CT) is frequently used in referral practice to evaluate the equine head but there are few reports describing the CT appearance of melanomas in this location. The aim of this retrospective, case series study was to describe characteristics in a group of horses with confirmed disease. Case records from two referral hospitals were reviewed, and 13 horses were identified that had undergone CT of the head, with a diagnosis of melanoma based on cytology, histopathology, or visual assessment of black (melanotic) tissue. A median of 11 melanomas was identified per horse (range 3–60), with a total of 216 masses. Melanomas were found most frequently in the parotid salivary gland, guttural pouches, surrounding the larynx and pharynx and adjacent to the hyoid apparatus. In noncontrast CT images, all melanomas were hyperattenuating (median; 113.5 Hounsfield units (HU), IQR; 26 HU) compared to masseter musculature (median; 69 HU, IQR; 5.5 HU). Fifty‐six (25.9%) masses were partially mineralized and 41 (19.4%) included hypoattenuating areas. Histopathological assessment of these melanomas suggested that the hyperattenuation identified was most likely a result of abundant intracytoplasmic melanin pigment. Melanomas of the equine head appeared to have consistent CT features that aided detection of mass lesions and their distribution, although histopathological analysis or visual confirmation should still be obtained for definitive diagnosis .     

Effects of Precipitation and Air Temperature on Nitrogen Discharges from Rhode River Watersheds

We studied discharges of total-N, nitrate, ammonium, and total organic-N from seven contiguous small watersheds on the Atlantic Coastal Plain in Maryland for up to 25 yr. These watersheds have perched aquifers so all groundwater discharges as well as surface runoff were measured at V-notch weirs which included volume-integrating flow-proportional samplers. Interannual variations in annual and seasonal precipitation during this study spanned approximately the range of 160 yr weather records in the region. Annual total-N area yields from the overall watershed varied nine-fold, correlations of all N-parameter discharges with precipitation were highly significant, and power function regressions of precipitation vs N-discharge explained from 36 to 59% of the variance. Nitrogen fluxes from a cropland watershed were much higher and more variable with volume of precipitation, while fluxes from a forested watershed were much lower and were primarily composed of organic-N. Correlations of N-fluxes with precipitation were higher in the winter and spring. Annual and seasonal N-concentrations also often increased significantly with precipitation. Variations in seasonal air temperature sometimes explained significant amounts of variance in N-discharges, especially ammonium. A model composed of regressions was used to construct graphical and tabular summaries.     

Wet-milling Factors of Sorghum and Relationship to Grain Quality

Relationships of grain sorghum quality factors (proximate composition and physical properties) to laboratory wet-milling attributes (fraction yields, protein content of fractions and recovery values) of 24 grain sorghum commercial hybrids were determined. Initial water absorption rate was positively correlated with both starch and gluten recoveries (r>0·45), thus showing the greatest significance among all quality factors. The need to understand fully protein matrix breakdown relative to obtaining optimum separation of components was indicated. Positive correlations of residual protein in starch with density and percent abraded (r>0·45) were observed. Laboratory wet-milling attributes also were correlated among themselves. The highest positive correlations were observed among yield and recovery of starch and gluten (r>0·6). These four parameters had strong negative correlations with fiber/germ yield (r<−0·6). Principal component factor analysis identified five factors (named as matrix-breakdown effect, solids-leaching effect, protein-dispersion effect, protein content of gluten effect, and washing-solids effect) that explained 91% of the total variation among wet-milling attributes.