Abstract: Increased bulk density of a clay loam soil on logging skid trails in the Oregon Coast Ranges was most highly correlated with the logarithm of the number of turns with a low-ground pressure (FMC) skidder. The surface 15 cm of soil was impacted more by uphill than by downhill yarding. Downhill skid trails with three or fewer turns had small increases in bulk density, usually < 10%. The regression relationship (r² = 0.411; Sy·ₓ = 23.16) developed for the 7.5-cm depth indicated that nine turns with an FMC skidder would increase soil bulk density approximately 25 and 45% for downhill and uphill yarding, respectively. After approximately 18 turns with an FMC skidder, the predicted bulk density increase at the 22.5-cm soil depth was 25% (±5% at α = 0.1). Modified 10-blow Proctor tests slightly overestimated increases of soil bulk density on high-use downhill skid trails. The 15- and 10-blow Proctor tests very closely estimated these density increases for the 7.5- and 15-cm depths, respectively, for uphill skidding.

Abstract: Information on soil changes under various forms of land use in poplar box (Eucalyptus populnea) lands on solodic soils is summarized and generalizations on the effects of management practices on the soil resource are made. The implications of the results for land use are considered and problems seen as requiring further research are outlined. Crazing by domestic livestock results in soil compaction which, through decreasing the infiltration rates, causes an increase in the surface run-off of water. These effects are enhanced by the killing of trees, and the associated changes in soil water content profiles are accompanied by changes in the distribution of soluble soil salts. Scalds develop in some areas. Tnese deleterious changes are reversed where there is shrub growth and livestock are excluded. The reasons for the development and persistence of scalds require further elucidation. In particular, the conditions requited for the recruitment of grass and shrub species, and the relative importance of the various pathways for salt movement in these systems, should be defined.

Abstract: Soil physical conditions of a Levin silt loam were examined after five years of continuous cropping. Areas of normal cultivation, no-tillage, and an uncropped, heavily wheel-tracked area were compared. A good soil tilth resulted from both the cultivation and no-tillage treatments, although no-tillage maintained more stable aggregation and slightly higher organic matter levels. Soil strengths tended to be lower in the cultivated soil. In contrast, wheel-induced compaction resulted in large aggregates, higher bulk densities, greater mechanical strengths, and a severe loss of macroporosity to a depth of 15 cm. Results showed the ability of soils containing weathered volcanic ash to withstand repeated cultivation and, therefore, indicated their high physical potential for intensive cropping.

Abstract: Physical characteristics were determined for 5 potting media composed of varying ratios of Florida sedge peat and pine bark subjected to compaction pressures of 0.0, 0.1, 0.2, or 0.3 kg/cm2. Percent noncapillary pore space decreased as compaction pressure and amount of peat in the mixture increased, while water holding capacity by volume increased with peat addition and compaction pressure. Top growth of Pilea pubescens ‘Silver Tree’ in compacted media was generally as good as in noncompacted media, but root growth was restricted.

Abstract: Intensive visitor use of scenic view areas at Bryce Canyon National Park, Utah, has resulted in damage to vegetation, soil compaction, accelerated erosion, and reduced aesthetic quality. An assessment of the degree of disturbance at selected scenic viewpoints showed vegetal cover and soil infiltration rates to be consistently lower on high-use areas than on low-use areas. Soil bulk density and sediment production were consistently higher on high-use areas than on low-use areas. More effective management of visitor use is necessary to protect soil and plant resources.

Abstract: Results are summarized for a number of separate studies which investigated the effects of killing the trees, and of grazing by domestic livestock on herbage biomass, densities of grasses, forbs and woody plants and some surface soil properties in poplar box woodlands. Some temporal changes in vegetation and spatial patterns in soil properties occurred in all treatments. Forb and grass densities increased from 1966 to 1970 and 1972 respectively and then declined. Surface soil pH, micro-relief, salt content and litter biomass were generally higher at the tree bole than between the tree canopies. Herbage biomass was highest where trees had been killed but the killing of trees did not have a direct effect on the densities of either grasses or shrubs. The increased growth of herbage is attributed to an increase in the availability of water and nitrogen. The vegetation changes following tree killing with livestock excluded are summarized in the form of changes in the proportions of the grasses, shrubs and trees; grass proportion increased for the first six years following tree killing after which grasses tended to be replaced by shrubs. The density of shrubs increased following the exclusion of livestock. Shrub densities were less in experimental grazed plots than in ungrazed plots but still increased with time. With grazing by livestock, herbage biomass was highest adjacent to trees and the percentage of bare soil increased away from trees. Changes resulting from interactions between the grazing and killing treatments mainly related to soil compaction and water infiltration. It is suggested that shrub encroachment in the poplar box lands may arise because of fluctuations in grazing pressure resulting from large paddock and property sizes and variability in rainfall. Little of the available herbage is grazed during abnormally wet years, thus there is an effective release from grazing at a time when germination of shrubs is likely to occur.

Abstract: The term shale encompasses materials displaying different responses during excavation, compaction and service life. A soft, non-durable shale is easily broken down and may be Compacted as a soil fill. A hard, durable shale may perform satisfactorily when placed as a rock fill. An intermediate shale may be mechanically hard during excavation and compaction but may prove to be non-durable over the service life of a compacted embankment. The New Providence shale used in this study is classified as a medium hard, non-durable shale. Shale samples were compacted from shale aggregate by a California kneading compactor. Conventional oedometer tests were performed on a group of as-compated samples to investigate the compressibility behavior and the compactive prestress induced in the samples. At pressures above the prestress the compressibility of the compacted soil markedly increases. The effect of the compaction variables on the observed behavior of the samples was of interest. These variables were: compacted dry density, molding moisture content, initial void ratio, initial degree of saturation, and nominal compactive pressure. It was found that the prestress was equal to the compaction pressure for the low and intermediate compactive efforts at the dry-of-optimum and near-optimum moisture conditions. Increasing the compaction pressure or the moisture condition resulted in a decrease in the ratio of prestress to compaction pressure to less than unity. Increasing moisture reduces the air permeability and permits the buildup of pore air and pore water pressures during compaction which results in less of the compaction pressure being applied to the soil skeleton. Increasing compaction pressure causes greater aggregate degradation during compaction. Some of the compaction effort is spent breaking aggregates which results in the reduction in the number of large pores. Statistical analysis of the accumulated test data permitted a descriptive model to be developed for the estimation of the compactive prestress for samples of compacted New Providence shale. The most influential variables affecting the level of compactive prestress appear to be the nominal compaction pressure and the molding moisture content.

Abstract: Results are summarized for a number of separate studies which investigated the effects of killing the trees, and of grazing by domestic livestock on herbage biomass, densities of grasses, forbs and woody plants and some surface soil properties in poplar box woodlands. Some temporal changes in vegetation and spatial patterns in soil properties occurred in all treatments. Forb and grass densities increased from 1966 to 1970 and 1972 respectively and then declined. Surface soil pH, micro-relief, salt content and litter biomass were generally higher at the tree bole than between the tree canopies. Herbage biomass was highest where trees had been killed but the killing of trees did not have a direct effect on the densities of either grasses or shrubs. The increased growth of herbage is attributed to an increase in the availability of water and nitrogen. The vegetation changes following tree killing with livestock excluded are summarized in the form of changes in the proportions of the grasses, shrubs and trees; grass proportion increased for the first six years following tree killing after which grasses tended to be replaced by shrubs. The density of shrubs increased following the exclusion of livestock. Shrub densities were less in experimental grazed plots than in ungrazed plots but still increased with time. With grazing by livestock, herbage biomass was highest adjacent to trees and the percentage of bare soil increased away from trees. Changes resulting from interactions between the grazing and killing treat- ments mainly related to soil compaction and water infiltration. It is suggested that shrub encroachment in the poplar box lands may arise because of fluctuations in grazing pressure resulting from large paddock and property sizes and variability in rainfall. Little of the available herbage is grazed during abnormally wet years, thus there is an effective release from grazing at a time when germination of shrubs is likely to occur.