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171.
This article demonstrates the importance of obtaining high response rates for surveys of the general population while illustrating that survey design and procedures that adopt and modify factors known to positively affect survey returns can lead to high response rates, even for a lengthy survey of the general population. Using an expanded version of Dillman's “tailored design method,” we achieved an 82.8% response rate for a general population survey of landowners. When comparing early respondents to late respondents we found significant differences on several sociodemographic variables as well as a number of attitudinal measures central to the research project. In addition, costs are compared between this methodology and a more typical four-wave mailing. Our survey further highlights the importance of improving our understanding of the social changes taking place in rural communities and the implications these changes can have on natural resources management. This article originally published in Society & Natural Resources, Vol. 17, Issue 5, pages 431–442, 2004. DOI: 10.1080/08941920490430223 相似文献
172.
Ravindra Dwivedi Thomas Meixner Jennifer C. McIntosh P.A. Ty Ferr Christopher J. Eastoe Guo‐Yue Niu Rebecca L. Minor Greg A. Barron‐Gafford Jon Chorover 《水文研究》2019,33(4):476-494
High‐elevation mountain catchments are often subject to large climatic and topographic gradients. Therefore, high‐density hydrogeochemical observations are needed to understand water sources to streamflow and the temporal and spatial behaviour of flow paths. These sources and flow paths vary seasonally, which dictates short‐term storage and the flux of water in the critical zone (CZ) and affect long‐term CZ evolution. This study utilizes multiyear observations of chemical compositions and water residence times from the Santa Catalina Mountains Critical Zone Observatory, Tucson, Arizona to develop and evaluate competing conceptual models of seasonal streamflow generation. These models were tested using endmember mixing analysis, baseflow recession analysis, and tritium model “ages” of various catchment water sources. A conceptual model involving four endmembers (precipitation, soil water, shallow, and deep groundwater) provided the best match to observations. On average, precipitation contributes 39–69% (55 ± 16%), soil water contributes 25–56% (41 ± 16%), shallow groundwater contributes 1–5% (3 ± 2%), and deep groundwater contributes ~0–3% (1 ± 1%) towards annual streamflow. The mixing space comprised two principal planes formed by (a) precipitation‐soil water‐deep groundwater (dry and summer monsoon season samples) and (b) precipitation‐soil water‐shallow groundwater (winter season samples). Groundwater contribution was most important during the wet winter season. During periods of high dynamic groundwater storage and increased hydrologic connectivity (i.e., spring snowmelt), stream water was more geochemically heterogeneous, that is, geochemical heterogeneity of stream water is storage‐dependent. Endmember mixing analysis and 3H model age results indicate that only 1.4 ± 0.3% of the long‐term annual precipitation becomes deep CZ groundwater flux that influences long‐term deep CZ development through both intercatchment and intracatchment deep groundwater flows. 相似文献
173.
Greg G. Sass Stephen R. Carpenter Jereme W. Gaeta James F. Kitchell Tyler D. Ahrenstorff 《Aquatic Sciences - Research Across Boundaries》2012,74(2):255-266
Lakeshore residential development (LRD) reduces coarse woody habitat (CWH) in lakes resulting in negative effects on fishes.
We tested whether the addition of CWH could reverse those effects. We added CWH to Camp Lake, a lake with CWH abundances similar
to developed lakes, following 2 years of study of the fish populations in the reference and treatment basins. Both basins
were monitored for 4 years following the manipulation. Specifically, we tested for changes in the population dynamics (densities,
size-structure, growth), diet, and behavior (habitat use) of bluegill (Lepomis macrochirus) and largemouth bass (Micropterus salmoides). CWH addition had no discernible effect on fish population dynamics. Diet and behavioral responses were more pronounced
in the treatment basin. Prey diversity and availability increased. Piscivory increased, with decreased reliance upon terrestrial
prey, for largemouth bass. Habitat use was positively correlated with CWH branching complexity and abundance. Our study suggests
that negative effects observed in fish populations through CWH reductions cannot be reversed in the short-term by adding CWH.
We recommend that regulations governing the LRD process be protective of CWH. 相似文献
174.
Although the importance of the subsurface saturated interstitial zone (hyporheic zone) to the ecological functioning and maintenance of water quality of stream ecosystems is well known, there is little information on the impacts of different forms of land use upon this zone. Hyporheic physico‐chemistry and invertebrates were compared among small streams draining hill‐country catchments under pasture, exotic pine forest, and native forest near Hamilton, New Zealand. In streams draining native forest, the hyporheic zone harboured a relatively diverse invertebrate fauna comprising mostly taxa common in the surface benthos, although a few apparently obligate hyporheic taxa (ostracods, blind amphipods) were collected. Few individuals and taxa occupied the hyporheic zones of streams draining pasture with some groups such as water mites conspicuously absent. The hyporheos of the stream in exotic pine forest was similar in richness and abundance to that of the pasture streams. Hyporheic water temperatures were significantly higher in the pasture streams than those in pine or native forest. There were strong positive correlations between percentage saturation of dissolved oxygen in the hyporheic zones of all streams and both species richness and total invertebrate abundance. We suggest that land clearance for pasture leads to hill slumping and siltation that bury the lateral bars along the stream channels, rendering this habitat unsuitable for hyporheic invertebrates. Channel narrowing and incision may physically remove further hyporheic habitat, and the reduction of flushing flows to remove interstitial silt and clay leads to low hyporheic dissolved oxygen concentrations and reduced colonisation by surface benthos. 相似文献
175.
Stockmann KD Anderson NM Skog KE Healey SP Loeffler DR Jones G Morrison JF 《Carbon balance and management》2012,7(1):1
Background
Global forests capture and store significant amounts of CO2 through photosynthesis. When carbon is removed from forests through harvest, a portion of the harvested carbon is stored in wood products, often for many decades. The United States Forest Service (USFS) and other agencies are interested in accurately accounting for carbon flux associated with harvested wood products (HWP) to meet greenhouse gas monitoring commitments and climate change adaptation and mitigation objectives. This paper uses the Intergovernmental Panel on Climate Change (IPCC) production accounting approach and the California Forest Project Protocol (CFPP) to estimate HWP carbon storage from 1906 to 2010 for the USFS Northern Region, which includes forests in northern Idaho, Montana, South Dakota, and eastern Washington. 相似文献176.
177.
Vegetative remains of three coalified Lower Devonian vascular plants (Zosterophyllum, Psilophyton, Renalia) were analyzed using flash pyrolysis-gas chromatography-mass spectrometry. The distributions of pyrolysis products are compared with those from younger vascular plant fossil xylem (Cordaixylon, Callixylon) and cuticle (Pachypteris). The likelihood of the chemical preservation of characteristic higher plant macromolecules (e.g., lignin and cutan) in the Lower Devonian plant fossils is considered in light of this comparison and associated thermal maturity assessments. Reflectance values from vitrinite-like macerals, which may not be vitrinite sensu stricto in the Lower Devonian host rocks for the fossils selected for this study, are shown to provide a reasonable assessment of the thermal maturity of these early vascular plant fossils. Although lignin altered through burial maturation is the most likely source of the prominent alkylphenols and aromatic hydrocarbons in the Lower Devonian tracheophyte flash pyrolysates, a contribution from thermally modified tannins cannot be ruled out. Comparison of the highly aliphatic pyrolysates from the Zosterophyllum and Psilophyton axes with that of a thermally mature fossil gymnosperm leaf revealed that cutan was an important component in the Devonian plant remains. This is the earliest chemical evidence for the presence of cutan in vascular plants. 相似文献
178.
Recurring issues in the social sciences concern the distribution of public facilities such as parks and equity of access to them. Geographers have observed that access has perceptual as well as physical dimensions and that perceptions of difference can affect use of public space. This study explores the nature of greenways as public space and a set of issues related to equity of access to greenway trails in Indianapolis, Indiana. The study uses proximity as a measure of access and simple GIS analyses of census and other data to assess equality of access. Evidence is provided that suggests that minorities and the poor have disproportionate access to trails. It is also shown that populations adjacent to the trails differ and that the populations along particular trails are segregated. Spatial differences in trail populations are associated with historic land use patterns and population movements within the city. The implications of the findings of difference for use of the greenways system are explored. Implications for management of the greenways system—including achievement of the goal of linking neighborhoods—are also discussed. 相似文献
179.
Numerical simulations show that inclusion of meso-scale bathymetry can enhance poleward eastern boundary undercurrents. 相似文献
180.
In part of a large abandoned mining complex, electromagnetic geophysical surveys were used along with data derived from cores and monitoring wells to infer sources of contamination and subsurface hydrologic connections between acidic refuse deposits and adjacent undisturbed geologic materials.Electrical resistivity increases sharply along the boundary of an elevated deposit of pyritic coarse refuse, which is highly contaminated and electrically conductive, indicating poor subsurface hydrologic connections with surrounding deposits of fine refuse and undisturbed glacial material. Groundwater chemistry, as reflected in values of specific conductance, also differs markedly across the deposit's boundary, indicating that a widespread contaminant plume has not developed around the coarse refuse in more than 40 yr since the deposit was created. Most acidic drainage from the coarse refuse is by surface runoff and is concentrated around stream channels.Although most of the contaminated groundwater within the study area is concentrated within the surficial refuse deposits, transects of apparent resistivity and phase angle indicate the existence of an anomalous conductive layer at depth (>4 m) in thick alluvial sediments along the northern boundary of the mining complex. Based on knowledge of local geology, the anomaly is interpreted to represent a subsurface connection between the alluvium and a flooded abandoned underground mine. 相似文献