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Abstract: Although numerous factors influence soil-water content, it is considered a key indicator of rangeland health. This paper investigates the effect of grazing on soil-water content using three treatments within the same soil association. The treatments, simulated holistic planned grazing (SHPG), rest-rotation (RESTROT), and total rest (TREST) applied stocking rates of 36, 6, and 0 animal days/hectare respectively. Soil-water content was measured continuously from 2006 to 2008 using 36 capacitance sensors. Statistical analyses revealed differences in percent volumetric-water content (%VWC) and in all treatments, the SHPG pasture had the highest %VWC. Mixed procedures models indicate strong environmental and treatment effects as explanatory variables for the observed difference in %VWC. Although results of vegetation cover analyses indicated no difference in percent shrub cover in the two production pastures (SHPG and RESTROT), percent litter cover differed in the latter years of this study. It was concluded that in addition to a variety of other factors, management decisions (grazing and rest) can have substantial influence upon soil-water content and that soil-water content can vary substantially as a result of animal impact and the duration of grazing. [Copyright &y& Elsevier]

Abstract: In the highlands of northern Ethiopia, degraded hillslopes are closed for grazing and agriculture for environmental rehabilitation. In order to assess the effect of these exclosures on water balances, a correct assessment of evapotranspiration is needed. A common method for calculating evapotranspiration employs the reference evapotranspiration in combination with a crop coefficient. However, for natural vegetation, these crop coefficients are not readily available. Therefore, the objective of this study was to derive crop coefficients for semiarid natural vegetation using two different approaches. The crop coefficients were assessed with the dual crop coefficient approach as outlined in the FAO Irrigation and Drainage Paper n°56 and compared with crop coefficients derived from a simple soil water balance. A good agreement between both methods was found. The mid-season crop coefficients ranged from 0.50 to 0.85 for open vegetation with small shrubs and from 0.85 to 0.95 for well developed shrubland. Vegetation with a closed tree canopy was characterized by a mid-season crop coefficient between 0.95 and 1.1. Additionally, a significant logarithmic relation between vegetative soil cover and crop coefficient was found. Using this relation, crop coefficients can be easily derived for semiarid shrub savannahs in similar environments and used for the calculation of evapotranspiration. [Copyright &y& Elsevier]

Abstract: In the Tarim River Basin, the desert riparian forest vegetation is under high-temperature and aridity stress. However, the vegetation can grow continuously because of deep rooting that can reach groundwater, which can thus redistribute water into the upper soil profile. This paper describes patterns of hydraulic lift by Populus euphratica Oliv. and discusses its ecological effects. Our results show that the tap root sap velocity of P. euphratica Oliv. is positive during the day and night. However, a reverse sap flow was observed in the lateral roots during the night. The soil water content of the subsoil was higher than that of the topsoil at depths of 0–120cm. When the sap flow of the lateral roots was reversed at night, the soil water content clearly increased. In particular, at depths of 60–120cm, the soil water content at 4:00 was 28–38% greater than that at 16:00. The vapor pressure deficit was a factor that predominantly affected the root sap velocity, and the smaller vapor pressure deficit often facilitated a reverse sap flow in the lateral roots. Our findings demonstrate the hydraulic lift characteristics and ecological effects that occur in the desert riparian forest in extremely arid regions of middle Asia [Copyright &y& Elsevier]

Abstract: Riparian zones are deemed significant due to their interception capability of non-point source impacts and the maintenance of ecosystem integrity region wide. To improve classification and change detection of riparian buffers, this paper developed an evolutionary computational, supervised classification method – the RIparian Classification Algorithm (RICAL) – to conduct the seasonal change detection of riparian zones in a vast semi-arid watershed, South Texas. RICAL uniquely demonstrates an integrative effort to incorporate both vegetation indices and soil moisture images derived from LANDSAT 5 TM and RADARSAT-1 satellite images, respectively. First, an estimation of soil moisture based on RADARSAT-1 Synthetic Aperture Radar (SAR) images was conducted via the first-stage genetic programming (GP) practice. Second, for the statistical analyses and image classification, eight vegetation indices were prepared based on reflectance factors that were calculated as the response of the instrument on LANDSAT. These spectral vegetation indices were then independently used for discriminate analysis along with soil moisture images to classify the riparian zones via the second-stage GP practice. The practical implementation was assessed by a case study in the Choke Canyon Reservoir Watershed (CCRW), South Texas, which is mostly agricultural and range land in a semi-arid coastal environment. To enhance the application potential, a combination of Iterative Self-Organizing Data Analysis Techniques (ISODATA) and maximum likelihood supervised classification was also performed for spectral discrimination and classification of riparian varieties comparatively. Research findings show that the RICAL algorithm may yield around 90% accuracy based on the unseen ground data. But using different vegetation indices would not significantly improve the final quality of the spectral discrimination and classification. Such practices may lead to the formulation of more effective management strategies for the handling of non-point source pollution, bird habitat monitoring, and grazing and live stock management in the future. [Copyright &y& Elsevier]

Abstract: Establishing forest cover in arid or drought-stricken regions is a challenging task facing countries with a high degree of desertification or risk of desertification. China''s Loess Plateau is one such area, an extremely dry climate, especially in spring, and that has a highly dissected topography. A new tree-planting technique to improve drought resistance, in which planting holes are lined with biodegradable plastic to reduce drainage and evaporation, was tested in an arid, erosion-prone, hilly area of the Loess Plateau between 1997 and 2006, during a period of lower-than-normal precipitation. In this paper, we report the survival and growth of 15 tree species grown with and without the new plastic lining. The new tree-planting technique promoted root growth in the topsoil by keeping the soil moisture than the surrounding soil evident during the first 4 months after planting. Tree survival rates, branch growth increment per year, tenth-year canopy area, and tenth-year canopy density in trees planted using the new method increased by an average of 41.4%, 29.0%, 16.9%, and 65.3%, respectively, compared with the values for the conventional planting technique. This suggests that the new planting technique is more suitable than the conventional method for the study area''s soil environment and climate, and may prove suitable for similar areas elsewhere in the world where survival and growth rates are low. The results of our study thus represent a potentially valuable alternative for forest restoration and soil conservation in arid zones. [Copyright &y& Elsevier]

Abstract: This paper describes and compares the hydrological responses of runoff, soil moisture and groundwater levels to rainfall events for two small semi-arid catchments over a 2-year period. Romwe received 1430 and 756mm of rainfall in the 19999/00 and 2000/01 season, respectively. Mutangi received 756 and 615mm of rainfall in the same years. Romwe generated 520 and 102mm of runoff in the 19999/00 and 2000/01 seasons, respectively, while Mutangi generated 82 and 69mm of runoff in the same years. The runoff response of the catchments was dominated by a relatively quick response to rainfall and with little or no significant contribution from regional groundwater or ‘old water’ sources. Total soil moisture storage to a depth of 120cm was higher at Romwe than Mutangi for the entire study period reflecting the differences in the soil types. The groundwater level was closer to the surface and responded more quickly to rainfall at Romwe compared to Mutangi where water levels were between 12 and 16m below the surface. There was a significant relationship between profile soil moisture and water table level at Romwe and none was observed at all in Mutangi. Significant (p<0.05) monthly rainfall runoff relationships were observed at both Romwe and Mutangi. At Romwe and Mutangi 91% and 76% of the runoff variation was accounted for by rainfall in the 1999/00 season, respectively. The rainfall–runoff relationship were different at Romwe for the two seasons, it was higher in the 1999/00 season than the 2000/01 season when 91% and 49% of the runoff variation was due to rainfall, respectively. The relationships were almost similar at Mutangi during the two seasons. [Copyright &y& Elsevier]