No description available.

No description available.

The study aimed to determine the interrelationship between aggregate stability and microbial biomass in restored soils, and to investigate if the development of the two parameters in soils disturbed by opencast mining could be influenced by the application of slow release organic amendments. These objectives were tested using two microbiological methods; determination of adenosine triphosphate and dehydrogenase activity, and three structural measurements; determination of aggregate stability by wet-sieving, shear vane and bulk density. Soil carbon and nitrogen were also determined. The first part of the study involved a survey of 16 field areas located in Britain, 12 disturbed and four not disturbed by opencast coal mining. The areas were all grasslands which varied in the time since restoration, which was between 0-16 years. A log linear relationship between the soil biomass and stable aggregates > 2 mm was found for all field areas (y = 38 In x - 69, r = 0.51). The variation in both properties was also affected by the restoration practices at the individual sites. A cluster analysis of the measured soil properties separated the restored areas into "good" restorations, involving progressive restoration, topsoil replacement and early underdrainage, and "poor" restorations, restored without topsoil or with soil forming material. The second part of the study reported on the first 16 months of a field trial set up on a recently restored opencast coal site situated near Denby in Derbyshire in 1991. A 3 x 4 factorial design involved two organic amendments (straw and wood), and four vegetation covers. The treatment effects were obscured by natural fluctuations in the soil properties over the period studied. However, the presence of the organic amendments alleviated some of the physical problems of the soil, such as waterlogging and frost damage, which drastically affected the results in 1992. The soil properties generally improved in the order straw>wood>no amendment for the majority of soil parameters (structure, C and N), the notable exception being the soil microbiological parameters which varied substantially throughout the experiment. Differences between the vegetation covers (a MAFF, a ruderal and a species rich seed mixture) were small.

No description available.

No description available.

No description available.

Most documented investigations of the effects of land-use change on hydrological systems have considered the modification of forest areas. In this thesis, a headwater area in the North York Moors is used to examine the consequences of maintaining a land management regime which has received comparatively little observation in this context: controlled heather burning (muirburn). The effects of coniferous afforestation are also evaluated for selected variables. Particular attention is given to the responses of soil, moisture and evapotranspiration and the relationship between these two components.Simulated soil moisture deficits derived from empirical models are tested against measured values. Predictions based on Penman-Monteith evapotranspiration and 'layer' moisture deficits, along with an optimised soil-drying parameter, were found to simulate observed conditions most closely. A land-use change from open heather moorland to burnt ground promoted reductions both in evapotranspiration levels, especially at potential demando and in moisture deficits. In contrast, following afforestation, deficits were maintained or enhanced throughout the year, with higher moisture losses to interception than found under heather, due to the higher aerodynamic resistance of the latter. Predictions of actual evapotranspiration, determined from soil moisture models, were generally found to be reliable estimates of those 'observed' from the moorland water balance.Antecedent catchment conditions and storm characteristics were used in analysis of runoff distribution over time, quantified in terms of 'unit hydrographs' and linear regression models. Land-use effects were manifested most significantly in a doubling of hydrograph peak discharge following muirburn, the lower measured soil moisture deficits under a burnt catchment rendering more water available for storm runoff. A secondary, underlying control, that of a slower response from a wet catchment, lent 'support to evidence for the existence of variable source areas.

This study, the first of its kind undertaken in Saudi Arabia, investigates and evaluates the condition of soil and vegetation and the relationship between them, as well as their relationship with slope components in the Upper Wadi Bishah basin, south-west Saudi Arabia. It is based mainly on quantitative and laboratory analysis, and provides a scientific basis for exploitation of the basin's slopes and conservation of its soil and vegetation. The findings reveal that floristic diversity of the research area is low. Only 62 perennial species belonging to 49 genera and 28 families were recorded in the upper Wadi Bishah basin. Of these, only 8 species or 12.9% of all species recorded, account for 89% of the absolute frequency of species in the basin. Although the vegetation density in this basin is low (2.71/ 100 m²), it is considered relatively high compared with other areas in Saudi Arabia. However, great diversities in density and distribution of vegetation were found between slope segments, and also generally between the south-west and north-east parts of the basin. The floristic composition and distribution of main plant groups were found to reflect the condition of soil and the topographical variety in the wadi basin. Also, it was found that over-grazing, particularly in north-east of the basin, is reflected in deterioration and degradation of vegetation and soil. In terms of soil properties, this study demonstrates quantitatively that the soil of south-west Wadi Bishah basin is generally loamy sand, shallow and somewhat rich in moisture, organic matter, organic carbon, nitrogen and phosphorus, and lacking in CaC0₃, potassium, electrical conductivity and pH, compared with the north-east of the basin. In the north-east of the Wadi Bishah basin, the soil is mostly sandy loam to sand, deep and very lacking in moisture, organic matter, organic carbon, nitrogen and phosphorus. Also, this region is affected by salinity problems. On the vertical level, deeper soils were found in the lower slopes and shallow soils found in the middle and upper slopes. Soil moisture, potassium and electrical conductivity increase down-slope and decrease in the middle and upper slopes. Soil organic matter, CaC0₃ and pH decrease going along the slope units from the top to the bottom. This study has revealed that slope angle and slope gradient have negative significant relationships with soil depth, sand content, potassium, soil pH and electrical conductivity, and positive significant relationships with moisture, silt content, organic matter, organic carbon and nitrogen. Slope length has inverse significant relationships with organic matter, organic carbon and nitrogen, and positive significant relationships with soil depth and potassium. None of the soil properties are associated significantly with slope form. Vegetation cover value and vegetation density are significantly correlated with almost all soil properties. Only electrical conductivity and clay content are not significantly associated with vegetation density. It is clearly demonstrated by this study that 51%, 27%,14%,56%,56%,12%, 45%, 6%, 6%, 31 % and 1 % of the variation in soil depth, moisture, texture, organic matter, organic carbon, CaC0₃, nitrogen, phosphorus, potassium, soil pH and electrical conductivity respectively relate to the function (or to the variation) of slope angle, slope gradient, slope length, vegetation cover value and vegetation density.

No description available.

No description available.