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301.
Jonathan W. Long Aregai Tecle Benrita M. Burnette 《Journal of the American Water Resources Association》2003,39(6):1345-1359
ABSTRACT: To prioritize sites for riparian restoration, resource managers need to understand how recovery processes vary within landscapes. Complex relationships between watershed conditions and riparian development make it difficult to predict the outcomes of restoration treatments in the semiarid Southwest. Large floods in 1993 scoured riparian areas in the Carrizo watershed on the White Mountain Apache Reservation in east‐central Arizona. We evaluated recovery at three of these sites using repeated photographs and measurements of channel cross sections and stream‐side vegetation along permanent transects. The sites were mapped as lying on the same soil type, had similar streamside vegetative communities, and were similarly treated through livestock exclusion and supplemental seeding. However, the sites and individual reaches within the sites followed strikingly different development paths. Dramatic recovery occurred at a perennial reach where cover of emergent wetland plants increased from 4.7 percent (standard error = 0.8 percent) in October 1995 to 55.5 percent (standard error = 2.7 percent) in September 2001. At several other reaches, geologic and hydro geomorphic characteristics of the sites limited inputs of fine sediment or surface water, resulting in modest or negligible increases in emergent cover. Recovery efforts for highly valued marshlands in this region should prioritize perennial reaches in low gradient valleys where salty sediments are abundant. 相似文献
302.
微塑料污染对水生态系统及人类健康危害大,为探究微塑料在不同环境介质中的赋存特征,选择长江一级支流玛瑙河为研究区域,通过现场采样、显微镜观察和傅里叶红外光谱测定等,对玛瑙河表层水体、沉积物、河岸带土壤和底栖动物铜锈环棱螺中微塑料的丰度、粒径、形状、颜色和组成类型进行了分析.结果表明,玛瑙河表层水体的微塑料平均丰度为(5.9±0.26)n·L-1;上层沉积物中微塑料丰度(以干重计)为(1.35±0.1)n·g-1,下层沉积物中微塑料丰度(以干重计)为(0.93±0.12)n·g-1;近河岸带土壤中微塑料丰度(以干重计)为(0.68±0.16)n·g-1,远河岸带土壤中微塑料丰度(以干重计)为(0.69±0.14)n·g-1;铜锈环棱螺体内微塑料丰度为(2.06±0.25)n·g-1.分析发现,上层沉积物和下层沉积物中微塑料丰度呈正相关;铜锈环棱螺体内微塑料丰度分别与上、下层沉积物中微塑料丰度呈正相关;近、远河岸带土壤中微塑料丰度具有相关性.各环境介质和铜锈环棱螺体内微塑料粒径大多<0.1mm,主要形态为纤维状和碎片状,颜色以蓝色和黑色为主,成分主要是聚丙烯(PP)和聚乙烯(PE).研究发现,河岸带土壤中微塑料主要来源于农用塑料薄膜的破碎和分解.通过多环境介质调查和铜锈环棱螺体内微塑料的分析,探明了大型底栖动物体内微塑料的累积效应,可为全面了解微塑料潜在生态风险提供依据. 相似文献
303.
Kathleen L. Wolf Elizabeth Housley 《Journal of Environmental Planning and Management》2017,60(10):1853-1870
Decades of research studies demonstrate links between healthy environment, healthy lifestyles, and healthy people. This study evaluated the correlations between young adult conservation workers' perceived stress, personal effectiveness, and nature experience using quantitative and qualitative social science methods. The study cohort numbered nearly 300 individuals serving on small crews for an entire year, and were dispersed across Washington State (USA) to participate in conservation projects in rural to urban landscapes. Pre- and post-test surveys, using validated measures of perceived stress, health dimensions, and personal resiliency, were further informed by mid-year, field-based interviews. Overall, the young adults expressed fatigue with the physical work but were quite healthy when compared to national benchmarks. They indicated a reduction in perceived stress, and indicated social function influences based on the conservation work. Conclusions address the importance and implications of expanding this work opportunity to a more diverse cohort and future research needs. 相似文献
304.
305.
306.
A lidar-based assessment of riparian shade and large wood potential in the Skagit River watershed,WA
Tim Hyatt 《Journal of the American Water Resources Association》2023,59(4):743-761
Wild salmon stocks in the Pacific Northwest are imperiled by a variety of declining habitat factors, including riparian shade and in-channel large wood. In this paper, a relatively simple lidar model of the riparian canopy was used along anadromous streams in the Skagit River watershed in western Washington State, United States, to delineate where riparian trees were most lacking, and where restoration efforts would have the greatest benefit in terms of shade and large wood recruitment potential. Within a 45-m riparian buffer, 61% of riparian zones were currently incapable of delivering large wood to the stream. Current potential for large wood recruitment is greatest adjacent to stream edges and falls off rapidly with distance from the channel. Approximately 99% of large wood recruitment potential lies within 45 m of the channel edge, and 50% of the wood potential is within 9 m. A hypothetical canopy model in which all trees mature to a 100-year height would provide 18% more shade distributed over the entire watershed, and 90% more shade in the tributaries. Most of the potential gains in improved shade and large wood contributions are in agricultural areas, as opposed to forestry or urban land uses. The shade and large wood models were constructed from widely available geographic information system tools and are readily transferable to other watersheds with similar characteristics. Model outputs are intended for use in planning restoration projects, as an input to stream temperature models, and to inform policy on restoration priorities and regulatory buffer widths. 相似文献
307.
Managers need measurements and resource managers need the length/width of a variety of items including that of animals, logs,
streams, plant canopies, man-made objects, riparian habitat, vegetation patches and other things important in resource monitoring
and land inspection. These types of measurements can now be easily and accurately obtained from very large scale aerial (VLSA)
imagery having spatial resolutions as fine as 1 millimeter per pixel by using the three new software programs described here.
VLSA images have small fields of view and are used for intermittent sampling across extensive landscapes. Pixel-coverage among
images is influenced by small changes in airplane altitude above ground level (AGL) and orientation relative to the ground,
as well as by changes in topography. These factors affect the object-to-camera distance used for image-resolution calculations.
‘ImageMeasurement’ offers a user-friendly interface for accounting for pixel-coverage variation among images by utilizing
a database. ‘LaserLOG’ records and displays airplane altitude AGL measured from a high frequency laser rangefinder, and displays
the vertical velocity. ‘Merge’ sorts through large amounts of data generated by LaserLOG and matches precise airplane altitudes
with camera trigger times for input to the ImageMeasurement database. We discuss application of these tools, including error
estimates. We found measurements from aerial images (collection resolution: 5–26 mm/pixel as projected on the ground) using
ImageMeasurement, LaserLOG, and Merge, were accurate to centimeters with an error less than 10%. We recommend these software packages as a means for expanding
the utility of aerial image data. 相似文献
308.
309.
大型水利水电工程扰动区植被的生态恢复 总被引:1,自引:0,他引:1
大型水利水电工程具有防洪、发电、航运等综合效益,是开发治理江河的骨干工程.水利水电工程建设常对项目区自然生态环境带来影响,施工中所产生的岩质边坡、土质边坡、弃土和弃渣等扰动可能导致项目区的生态系统退化、生物多样性丧失、水土流失和地质灾害加剧.扰动区植被生态恢复关系到工程安全运行和其所在区域的可持续发展.以向家坝水电工程为例,研究了大型水利水电工程扰动区植被生态恢复的目标、原则及方法.按生产、生态和社会功能,向家坝水电工程扰动区可划分为工程核心区、服务区和过渡区等3个功能区来系统规划其生态恢复.结合各自的功能需求和干扰特征,各功能区可采取相应的生态恢复技术和配置适宜物种来构建植物群落,形成结构稳定、多样性丰富、具有复合功能的植被景观.还简要评价了向家坝水电工程植被恢复现状,提出一些完善其生态恢复的建议. 相似文献
310.
Linking Theory and Practice for Restoration of Step-Pool Streams 总被引:1,自引:0,他引:1
Chin A Anderson S Collison A Ellis-Sugai BJ Haltiner JP Hogervorst JB Kondolf GM O'Hirok LS Purcell AH Riley AL Wohl E 《Environmental management》2009,43(4):645-661
Step-pools sequences are increasingly used to restore stream channels. This increase corresponds to significant advances in
theory for step-pools in recent years. The need for step-pools in stream restoration arises as urban development encroaches
into steep terrain in response to population pressures, as stream channels in lower-gradient areas require stabilization due
to hydrological alterations associated with land-use changes, and as step-pools are recognized for their potential to enhance
stream habitats. Despite an increasingly voluminous literature and great demand for restoration using step-pool sequences,
however, the link between theory and practice is limited. In this article, we present four unique cases of stream restoration
using step-pools, including the evolution of the approaches, the project designs, and adjustments in the system following
restoration. Baxter Creek in El Cerrito, California demonstrates an early application of artificial step-pools in which natural
adjustments occurred toward geomorphic stability and ecological improvement. Restoration of East Alamo Creek in a large residential
development near San Ramon, California illustrates an example of step-pools increasingly used in locations where such a channel
form would not naturally occur. Construction of a step-pool channel in Karnowsky Creek within the Siuslaw National Forest,
Oregon overcame constraints posed by access and the type and availability of materials; the placement of logs allowed natural
scouring below steps. Dry Canyon Creek on the property of the Mountains Restoration Trust in Calabasas, California afforded
a somewhat experimental approach to designing step-pools, allowing observation and learning in the future. These cases demonstrate
how theories and relationships developed for step-pool sequences over the past two decades have been applied in real-world
settings. The lessons from these examples enable us to develop considerations useful for deriving an appropriate course of
design, approval, and construction of artificial step-pool systems. They also raise additional fundamental questions concerning
appropriate strategies for restoration of step-pool streams. Outstanding challenges are highlighted as opportunities for continuing
theoretical work. 相似文献