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Ditching is a common practice to dewater wetlands, including peatlands, and ditch blocking is a common method for restoring wetlands because substrate is often unavailable for filling the ditches. However, filling has many advantages compared to blocking ditches. Our goal was to test whether ditches could be filled in a Colorado sloping fen (Chattanooga Fen) using bales created from shredded aspen (Populus tremuloides) tree‐fiber. We monitored water table levels before and after we filled two ditches (combined length of approximately 165 m × 3 m wide) as well as an undisturbed reference portion of Chattanooga fen. The reference site had stable water tables that rarely dropped more than 20 cm below the soil surface. The ditches had been dewatering large areas of the fen for at least 100 years. Filling the ditches with fiber bales resulted in a water table increase between 2 and 22 cm in an area up to 150 m below the ditch. Native sedges now cover the area where we filled the ditches, with no erosion or compression/settling of the ground observed and no water backing up behind the filled ditches. Filling the ditches with shredded fiber bales is a good option for restoration in wilderness areas, or areas lacking peat or mineral soil fill because it is a natural material that is easily transported and placed in the ditches.  相似文献   
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We examined patterns of dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) loading to a small urban stream during baseflow and stormflow. We hypothesized that lower DOC and TDN contributions from impervious surfaces would dilute natural hydrologic flowpath (i.e., riparian) contributions during storm events in an urban watershed, resulting in lower concentrations of DOC and TDN during storms. We tested these hypotheses in a small urban watershed in Portland, Oregon, over a 3-month period during the spring of 2003. We compared baseflow and stormflow chemistry using Mann–Whitney tests (significant at p<0.05). We also applied a mass balance to the stream to compare the relative significance of impervious surface contributions versus riparian contributions of DOC and TDN. Results showed a significant increase in stream DOC concentrations during stormflows (median baseflow DOC = 2.00 mg l−1 vs. median stormflow DOC = 3.46 mg l−1). TDN streamwater concentrations, however, significantly decreased with stormflow (median baseflow TDN = 0.75 mg l−1 vs. median stormflow TDN = 0.56 mg l−1). During storms, remnant riparian areas contributed 70–74% of DOC export and 38–35% of TDN export to the stream. The observed pattern of increased DOC concentrations during stormflows in this urban watershed was similar to patterns found in previous studies of forested watersheds. Results for TDN indicated that there were relatively high baseflow nitrogen concentrations in the lower watershed that may have partially masked the remnant riparian signal during stormflows. Remnant riparian areas were a major source of DOC and TDN to the stream during storms. These results suggest the importance of preserving near-stream riparian areas in cities to maintain ambient carbon and nitrogen source contributions to urban streams.  相似文献   
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Fens represent a large array of ecosystem services, including the highest biodiversity found among wetlands, hydrological services, water purification and carbon sequestration. Land‐use change and drainage has severely damaged or annihilated these services in many parts of North America and Europe; restoration plans are urgently needed at the landscape level. We review the major constraints on the restoration of rich fens and fen water bodies in agricultural areas in Europe and disturbed landscapes in North America: (i) habitat quality problems: drought, eutrophication, acidification, and toxicity, and (ii) recolonization problems: species pools, ecosystem fragmentation and connectivity, genetic variability, and invasive species; and here provide possible solutions. We discuss both positive and negative consequences of restoration measures, and their causes. The restoration of wetland ecosystem functioning and services has, for a long time, been based on a trial‐and‐error approach. By presenting research and practice on the restoration of rich fen ecosystems within agricultural areas, we demonstrate the importance of biogeochemical and ecological knowledge at different spatial scales for the management and restoration of biodiversity, water quality, carbon sequestration and other ecosystem services, especially in a changing climate. We define target processes that enable scientists, nature managers, water managers and policy makers to choose between different measures and to predict restoration prospects for different types of deteriorated fens and their starting conditions.  相似文献   
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Urban areas (especially cities) are challenged in meeting their direct water needs from local sources. They also exert strain on global water resources through their indirect (virtual) water use. Agencies concerned with urban water management have visions and goals for managing direct water use, but indirect use is only inferred in more global visions for sustainable consumption. There is limited quantification of “urban water performance” at the macro urban scale (whole of city) to monitor progress toward these goals. It is constrained by a lack of clarity about the evaluation approaches that best serve them. We ask, How can the evaluation approaches described in literature advance urban water management goals? We reviewed the utility of eight evaluation approaches, including urban water system modeling, urban metabolism (territorial and mass balance), consumption (life cycle assessment, water footprinting, and input‐output analysis), and complex systems (ecological network analysis and systems dynamics) approaches. We found that urban metabolism based on water mass balance is a core method for generating information to inform current goals for direct urban water use, with potential for being “coupled” with the other approaches. Consumption approaches inform the management of indirect water use. We describe this in a framework for urban water evaluation to give greater clarity to this field and flag the further research that would be needed to progress this. It includes the recommendation to differentiate the evaluation of direct and indirect urban water, but to also interpret them together.  相似文献   
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1. Local assemblage structure, from a deterministic perspective, is presumably dictated by the regional species pool as well as regulated by local factors. We examined the relationships of the regional species pool and local hydrological characteristics to local species richness of North American freshwater fishes using data sets collected during the National Water Quality Assessment program conducted by the United States Geological Survey. 2. We predicted that local species richness is ultimately constrained by the composition of the regional species pool and further associated with local hydrological factors. Moreover, we predicted that variation in local species richness within major families can be explained by different combinations of hydrological characteristics that represent lineage‐specific responses to the environment. 3. Daily discharge and regional and local species richness data were assembled from 41 stream localities across the United States. Multiple stepwise regressions were conducted to predict local species richness, based on regional species richness, mean discharge and hydrological characteristics quantified by nine variables characterising flow variability. Species richness at each site was calculated for the entire assemblage as well as within the four most species‐rich families in the data set (Catostomidae, Centrarchidae, Cyprinidae and Percidae). 4. Local species richness was best predicted by a combination of regional species richness and discharge magnitude when all species were considered. Regional species richness was a significant explanatory variable of local species richness for three of four families (Catostomidae, Centrarchidae, Cyprinidae), but not for Percidae. Local richness in Centrarchidae and Cyprinidae was positively correlated with temporal flow variability as well as high and low flow duration, respectively, while richness in Catostomidae and Percidae tended to be associated with discharge volume. In addition, local species richness for three of the four major families was positively correlated with species richness of the other families in the assemblage, potentially suggesting the influence of local habitat quality and heterogeneity. 5. Results suggest the importance of the combined influences of the regional species pool and local hydrological characteristics on local richness in freshwater fishes, with variation in richness within each family predicted by different characteristics of flow regimes.  相似文献   
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Despite many years of establishment of exclosures in the semi-arid environments of north Ethiopia for rehabilitation of degraded areas, its effectiveness is constrained by water deficit. There is lack of empirical data on the response of vegetation to additional water (spate irrigation) application. This study aimed to evaluate the effects of spate irrigation using storm runoff on the growth of trees in exclosures. Two exclosures (May Ba'ati and Adi Kolakol), in Dogu'a Temben district, Tigray, north Ethiopia, were used for this study. Each exclosure was divided in two blocks (irrigated and non-irrigated) to allow comparison of change of vegetation using several diversity indices as well as contrasts in tree ring widths. The amount of spate irrigation water diverted onto the exclosures (762 mm) was in the same order of magnitude as the direct rainfall on the sites (645 mm). The results show that the irrigated exclosures have larger species richness, Shannon–Weaver diversity index, tree density, abundance, evenness and basal area than the non-irrigated areas. Following low rainfall (353 mm) in 2015, these indices decreased in the non-irrigated area, whereas most indices remained much higher in the irrigated area. The findings indicate that diverting runoff to exclosures results in an average 15% increase in ring width as compared to non-irrigated trees. In addition, there is strong abstraction of storm runoff in gullies in the study area. Besides the promotion of forestry in washout semi-arid areas of existing spate irrigation systems, we suggest to apply spate irrigation to exclosures in order to improve their productivity.  相似文献   
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In a seminal study, Dawson and Ehleringer used deuterium measurements on water to show that boxelder (Acer negundo) and bigtooth maple (Acer grandidentatum) trees growing directly next to a perennial stream in a mountain meadow did not use the stream water for transpiration, nor could they identify any other potential water source. Since then, similar observations of plant water isotopic signatures that do not match any available water source have been reported from a range of ecosystems worldwide. Here, we use a combination of non‐destructive in situ isotopic soil water sampling along with destructive soil sampling and cryogenic water extraction to demonstrate that isotopically distinct water pools can be identified in soils at the same site as the 1991 study during parts of the summer growing season. Water extracted from xylem tissues shows that streamside boxelder and bigtooth maple at the sites were predominantly using soil water with an isotopic composition similar to that measured by the in situ soil measurement technique. We introduce the use of water vapour probes that were directly attached to intact tree roots in situ to measure the isotopic composition of root xylem water and how it varies through the growing season and evaluate their potential and utility.  相似文献   
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We investigated the effects of removing near-stream Rhododendron and of the natural blowdown of canopy trees on nutrient export to streams in the southern Appalachians. Transects were instrumented on adjacent hillslopes in a first-order watershed at the Coweeta Hydrologic Laboratory (35°03′N, 83°25′W). Dissolved organic carbon (DOC), K+, Na+, Ca2+, Mg2+, NO3 -N, NH4 +-N, PO4 3−-P, and SO4 2− were measured for 2 years prior to disturbance. In August 1995, riparian Rhododendron on one hillslope was cut, removing 30% of total woody biomass. In October 1995, Hurricane Opal uprooted nine canopy trees on the other hillslope, downing 81% of the total woody biomass. Over the 3 years following the disturbance, soilwater concentrations of NO3 -N tripled on the cut hillslope. There were also small changes in soilwater DOC, SO4 2−, Ca2+, and Mg2+. However, no significant changes occurred in groundwater nutrient concentrations following Rhododendron removal. In contrast, soilwater NO3 -N on the storm-affected hillslope showed persistent 500-fold increases, groundwater NO3 -N increased four fold, and streamwater NO3 -N doubled. Significant changes also occurred in soilwater pH, DOC, SO4 2−, Ca2+, and Mg2+. There were no significant changes in microbial immobilization of soil nutrients or water outflow on the storm-affected hillslope. Our results suggest that Rhododendron thickets play a relatively minor role in controlling nutrient export to headwater streams. They further suggest that nutrient uptake by canopy trees is a key control on NO3 -N export in upland riparian zones, and that disruption of the root–soil connection in canopy trees via uprooting promotes significant nutrient loss to streams. Received 30 January 2001; accepted 25 July 2002.  相似文献   
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