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11.
The pi?on (Pinus edulis Engelm.)-juniper [Juniperus monosperma (Engelm.) Sarg.] woodlands of Bandelier National Monument are experiencing accelerated erosion. Earlier studies suggest that causes of these rapidly eroding woodlands are related to an unprecedented rapid transition of ponderosa pine (Pinus ponderosa C. Lawson) savanna to pi?on-juniper woodlands as a result of cumulative historical effects of overgrazing, fire suppression, and severe drought. To study the effectiveness of slash treatment in reducing accelerated erosion, we used sediment check dams to quantify sediment yield from twelve paired microwatersheds (300-1100 m2) within an existing paired water-shed study. Six of the twelve microwatersheds were located in a 41-ha (treatment) watershed with scattered slash treatment, whereas six microwatersheds were located in an adjacent 35-ha untreated (control) watershed. The primary purpose of our research was to quantify the rates of sediment yield between the treated and control microwatersheds. Sediment yield was measured from 15 individual storms during the months of June-September (2000 and 2001). In response to slash treatment, mean seasonal sediment yield for 2000 equaled 2.99 Mg/ha in the control vs. 0.03 Mg/ha in the treatment and 2.07 Mg/ha in the control vs. 0.07 Mg/ha in the treatment in 2001. The practice of slash treatment demonstrates efficacy in reducing erosion in degraded pi?on-juniper woodlands by encouraging herbaceous recovery. Our data show that slash treatment increases total ground cover (slash and herbaceous growth) beyond a potential erosion threshold. Restored pi?on-juniper woodlands, as the result of slash treatment, provide a forest structure similar to pre-grazing and pre-fire suppression conditions and decrease catastrophic fire hazard. 相似文献
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G. Langhendries D. E. De Vos B. F. Sels I. Vankelecom P. A. Jacobs G. V. Baron 《Clean Products and Processes》1998,1(1):21-29
Liquid phase hydrocarbon oxidation is one of the principal routes towards industrial organic chemicals. However, low product
selectivity and associated by-product formation are major problems in several oxidation processes. As a result of the increasingly
stringent environmental regulations, the development of oxidation catalysts has been a major challenge in the last decade.
An overview of novel selective and clean oxidation catalysts and processes is presented.
Received: 27 July 1998 / Accepted: 8 September 1998 相似文献
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The difference conservation makes to extinction risk of the world's ungulates 总被引:1,自引:0,他引:1 下载免费PDF全文
Michael Hoffmann J.W. Duckworth Katharine Holmes David P. Mallon Ana S.L. Rodrigues Simon N. Stuart 《Conservation biology》2015,29(5):1303-1313
Previous studies show that conservation actions have prevented extinctions, recovered populations, and reduced declining trends in global biodiversity. However, all studies to date have substantially underestimated the difference conservation action makes because they failed to account fully for what would have happened in the absence thereof. We undertook a scenario‐based thought experiment to better quantify the effect conservation actions have had on the extinction risk of the world's 235 recognized ungulate species. We did so by comparing species’ observed conservation status in 2008 with their estimated status under counterfactual scenarios in which conservation efforts ceased in 1996. We estimated that without conservation at least 148 species would have deteriorated by one International Union for Conservation of Nature (IUCN) Red List category, including 6 species that now would be listed as extinct or extinct in the wild. The overall decline in the conservation status of ungulates would have been nearly 8 times worse than observed. This trend would have been greater still if not for conservation on private lands. While some species have benefited from highly targeted interventions, such as reintroduction, most benefited collaterally from conservation such as habitat protection. We found that the difference conservation action makes to the conservation status of the world's ungulate species is likely to be higher than previously estimated. Increased, and sustained, investment could help achieve further improvements. 相似文献
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The study was prepared in 1966 for the Bureau of Sport Fisheries and Wildlife, Department of the Interior, for presentation to the United States Army Corps of Engineers which had under study several routes for rediversion of the discharge from the Santee-Cooper Hydro Electric Plant, Steam Plant and Lock. Each rediversion was designed to by-pass the Charleston Harbor and this study and report was concerned with one of those routes–Rediversion Route “B.” The channel was to be designed for a maximum fresh-water flow of 27,500 cfs and a mean flow of 15,500 cfs. The objectives of the study and report were to make an estimate of: (1) the geographical extent of salt marsh waters of which the salinity will be measurably reduced, and (2) the probable accumulation of fresh-water borne sediments in those same waters. Special consultants were Dr. F. H. Kellogg, Memphis State University, and Mr. K. L. Drennan, Gulf Coast Research Laboratory, Mississippi. 相似文献
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This study presents the modelling approach and impact assessment of different strategies for managing wetland water resources and groundwater dynamics of landscapes which are characterised by the hydrological interactions of floodplains and the adjacent lowlands. The assessment of such impacts is based on the analysis of simulation results of complex scenarios of land-use changes and changes of the density of the drainage-network. The method has been applied to the 198 km2 Lower Havel River catchment as a typical example of a lowland–floodplain landscape. The model used consists of a coupled soil water and groundwater model, where the latter one is additionally coupled to the surface channel network. Thus, the hydrological processes of the variable saturated soil zone as well as lateral groundwater flow and the interactions between surface water and groundwater are simulated in an integrated manner. The model was validated for several years of significantly different meteorological conditions. The comparison of lateral and vertical water balance components showed the dominance of lateral flow processes and the importance of the interactions between surface water and groundwater for the overall water balance and the hydrological state of that type of landscape.The simulation of land-use change scenarios showed only minor effects of land-use change on the water balance and groundwater recharge. Changes of groundwater recharge were particularly small within the wetland areas being part of the floodplain where interactions between surface water and groundwater are most pronounced. Alterations in vertical groundwater recharge were counter-balanced by the lateral interaction between groundwater and surface water. More significant deviations in groundwater recharge and storage were observed in the more peripheral areas towards the catchment boundaries which are characterised by greater groundwater distance from the surface and less intense of ground water–surface water interactions.However, the simulation results assuming a coarsening of the drainage network density showed the importance of drainage structure and geometry for the water balance: The removal of the artificial draining ditches in the floodplain would result in significant alterations of total groundwater recharge, i.e., less recharge from winter to early summer and an increase of groundwater recharge during summer and autumn. Furthermore the different effects of groundwater recharge alterations on the dynamics of groundwater stages within the wetland areas close to the floodplains compared to the more peripheral areas could be quantified. Finally, it will be discussed that a well-adjusted co-ordination of different management measures is required to reach a sustainable water resources management of such lowland–floodplain landscapes. 相似文献
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András Bardossy Arne Färber Steffen Schönau Bernhard Westrich Thomas Jancke Gerhard Schmid Sven Wurms Karl Stahr Thomas Gaiser Harald Frauenknecht Thilo Streck Joachim Ingwersen Claudia Kreschnak Ulrich Kern Hilke Heppelmann Ekkehard Christoffels Ulrich Förstner Patrick Jacobs 《Environmental Sciences Europe》2006,18(1):67-69