Basic hydrologic studies for assessing impacts of flow diversions on riparian vegetation: Examples from streams of the eastern Sierra Nevada,California, USA

As the number of proposals to divert streamflow for power production has increased in recent years, interest has grown in predicting the impacts of flow reductions on riparian vegetation. Because the extent and density of riparian vegetation depend largely on local geomorphic and hydrologic setting, site-specific geomorphic and hydrologic information is needed. This article describes methods for collecting relevant hydrologic data, and reports the results of such studies on seven stream reaches proposed for hydroelectric development in the eastern Sierra Nevada, California, USA. The methods described are: (a) preparing geomorphic maps from aerial photographs, (b) using well level records to evaluate the influence of streamflow on the riparian water table, (c) taking synoptic flow measurements to identify gaining and losing reaches, and (d) analyzing flow records from an upstream-downstream pair of gages to document seasonal variations in downstream flow losses. In the eastern Sierra Nevada, the geomorphic influences on hydrology and riparian vegetation were pronounced. For example, in a large, U-shaped glacial valley, the width of the riparian strip was highly variable along the study reach and was related to geomorphic controls, whereas the study reaches on alluvial fan deposits had relatively uniform geomorphology and riparian strip width. Flow losses of 20% were typical over reaches on alluvial fans. In a mountain valley, however, one stream gained up to 275% from geomorphically controlled groundwater contributions.     

Some thoughts on using a landscape framework to address cumulative impacts on wetland food chain support

Problems of using food chain support as a functional attribute of a wetland are discussed. It is suggested that primary production may not be the metric that best evaluates food chain support. Environmental constructs of the wetland and resultant habitat variables appear to yield more information on life-support functions. A landscape-oriented approach is derived to separate hierarchically the wet-lands into ecological regions and landscape elements. This classification scheme allows for predetermination of environmental constraints and the possible natural limits of wetland food chain support. It is proposed that models derived from spatial location theory be used to determine the movement of animals from wetland patches experiencing impacts on food chain support. Patch size, distance between patches, habitat diversity, and environmental constraints are incorporated in these models.     

A STATISTICAL APPROACH TO ASSESS FACTORS AFFECTING WATER CHEMISTRY USING MONITORING DATA1

ABSTRACT: A method to partition the variation in concentrations of water chemistry parameters in a river is described. The approach consists of fitting a family of curves for each chemical parameter. Each curve indicates the response of the parameter to river flow for a particular time period or location. An analysis of covariance is then used to identify statistically significant differences between curves. Such differences result largely from two factors: (1) the discharge of effluents and (2) river flow-concentration relationships. The deviations from the fitted curves indicate month-to-month variations unrelated to river flow that are controlled by factors such as temperature-related seasonal patterns. Underlying statistical assumptions are discussed with respect to water chemistry data. The technique is applied to a data set consisting of monthly samples of 22 water chemistry parameters from the Sulphur River of Texas and Arkansas. Several patterns of response to river flow and to two effluent discharges were revealed.     

Impacts of Recreation Trails on Exotic and Ruderal Species Distribution in Grassland Areas Along the Colorado Front Range

This study examines the establishment patterns of exotic and ruderal species along trail corridors in grassland areas of the Colorado Front Range. The effects of trail presence, trail age, and trail traffic levels on exotic and ruderal species establishment are explored to ascertain the potential impacts of trails on surrounding vegetation. Established trails exhibited a greater presence of exotic and ruderal species along the immediate trailside, showing that disturbed trailsides tend to encourage the growth of these species over time. Furthermore, the established trails exhibited significantly less native, nonruderal, and overall species richness at the trailside. These trailside patterns did not show a significant spread away from the trail edge, even after prolonged time periods. Finally, higher trail use tended to hasten the establishment of exotic species along the trailside. The trails did not introduce new species to the recreation areas; rather they acted as reorganizational tools for species that were already present in the study sites.     

Socio-Ecological Impact and Risk Assessments in the Urban Environment: A Multidisciplinary Concept from Hong Kong

This paper discusses the increasing importance of the environment to social scientists. A multidisciplinary approach is highlighted and it is argued that the social sciences have a more significant role to play in understanding and responding to environmental deterioration than has hitherto been the case. The need for harmonizing multidisciplinarity in appreciating impact assessments is emphasized. A framework for analyzing and containing environmental impacts in Hong Kong is also proposed.     

Changes in attitudes about importance of and willingness to pay for salmon recovery in Oregon

Salmon are perhaps the quintessential icon of the Pacific Northwest, affecting the region's culture, politics, and economy. The importance Oregonians place on salmon recovery and their willingness to pay for salmon recovery efforts was assessed biennially between 1996 and 2002 through the Oregon Population Survey. Based on these data, we found that Oregonians appear to have become less supportive toward salmon recovery and salmon recovery efforts over that time period; they were less likely to say salmon recovery is important and chose lower willingness to pay responses in 2002 than in 1996.Attitudes do appear to be related to the economic conditions and demographic composition of residents of the state. In particular, we found that local unemployment rates, age of respondent, and rural county residence are significantly negatively correlated with the respondent's expressed support for salmon recovery efforts. Attributes positively correlated with expressions of support for salmon include male gender, graduate-level education, and American Indian identity. We found that a significant portion of the decline in support is unexplained by the variables included in the analysis.     

Comparing Onsite and Offsite Methods for Measuring Norms for Trail Impacts

This study examined the comparability of onsite and offsite methods for measuring norms for trail impacts using photo/survey techniques. A total of 449 subjects participated in a study of Mudeung-Mountain Provincial Park, Gwang-Ju, Korea. For the overall photo evaluation method (OPEM), respondents rated the acceptability of bare soil area for each of a series of photographs. For the specific photo evaluation method (SPEM), respondents selected a photograph that illustrated the largest acceptable proportion of bare soil area from a series of 10 photographs. Overall, there were no substantial differences in maximum acceptable impacts between onsite (onsite-I visitor group surveyed at the actual trail points and onsite-II departing visitor group surveyed at the exit area) and offsite (students surveyed in a laboratory setting) groups for the two norm measurement alternatives (OPEM and SPEM). Subjects’ difficulty ratings were low for both methods, and there were no substantial differences in norms between individuals with high and low levels of experience at the park. The offsite method appears to be substitutable for onsite methods in this particular study area, which is a frontcountry setting with a relatively simple range of recreation opportunities. Implications and further studies are discussed.     

沙尘暴对暴露儿童健康效应的研究

为了研究沙尘暴对儿童可能造成的急性危害,以沙尘暴源区——甘肃省武威市的某2所小学3～5年级的1040名学生(年龄8～14岁)为研究对象,在2004年和2005年的3～5月沙尘暴频发期间进行健康状况问卷调查,共调查4场沙尘暴事件,所调查的症状有咳嗽、咯痰、气短、肺部喘鸣、胸部憋闷、咽干口苦、眼睛干涩、流泪、流涕、打喷嚏、心情压抑等11种常见的症状.结果表明,沙尘暴发生当天(滞后0d)儿童各种所查症状发生的相对危险度(RR)均有不同程度地升高,沙尘暴过后(滞后1～5d),儿童各种症状的RR逐渐降低,沙尘暴过后4d(滞后4d),几乎所有症状均恢复正常.暴露儿童在沙尘暴发生当天,除肺部喘鸣和胸部憋闷发生的RR升高不显著外(p>0.05),其他所查症状发生的RR均有显著性升高(p<0.05,p<0.01,p<0.001).沙尘暴过后虽然各种症状RR均有所下降,但下降速度不同:在滞后1～2d,气短、眼睛干涩、流泪和心情压抑等4种症状RR仍显著高于沙尘暴前,直到滞后3d才恢复到正常水平;而咳嗽、咯痰、咽干口苦和打喷嚏等4种症状RR在滞后4d才恢复正常;流涕症状RR在滞后5d才基本恢复正常.不同年度和不同时期的沙尘暴事件对儿童健康症状的影响有所不同.从以上结果可以看出:沙尘暴对儿童的健康既有当日急性效应又有一定的短期滞后效应.     

Benthic Impacts of Intertidal Oyster Culture, with Consideration of Taxonomic Sufficiency

An investigation of the impacts from elevated intertidal Pacific oyster culture in a New Zealand estuary showed enhanced sedimentation beneath culture racks compared with other sites. Seabed elevation beneath racks was generally lower than between them, suggesting that topographic patterns more likely result from a local effect of rack structures on hydrodynamic processes than from enhanced deposition. Compared with control sites, seabed sediments within the farm had a greater silt/clay and organic content, and a lower redox potential and shear strength. While a marked trend in macrofaunal species richness was not evident, species composition and dominance patterns were consistent with a disturbance gradient, with farm effects not evident 35 m from the perimeter of the racks. Of the environmental variables measured, sediment shear strength was most closely associated with the distribution and density of macrofauna, suggesting that human-induced disturbance from farming operations may have contributed to the biological patterns. To evaluate the taxonomic sufficiency needed to document impacts, aggregation to the family level based on Linnean classification was compared with an aggregation scheme based on `general groups' identifiable with limited taxonomic expertise. Compared with species-level analyses, spatial patterns of impact were equally discernible at both aggregation levels used, provided density rather than presence/absence data were used. Once baseline conditions are established and the efficacy of taxonomic aggregation demonstrated, a `general group' scheme provides an appropriate and increasingly relevant tool for routine monitoring.     

Soil organic carbon storage in a mountain permafrost area of Central Asia (High Altai,Russia)

The thawing and subsequent decomposition of large stocks of soil organic carbon (SOC) currently stored in the northern circumpolar permafrost region are projected to result in a ‘positive’ feedback on global warming. The magnitude of this feedback can only be assessed with improved knowledge about the total size and geographic distribution of the permafrost SOC pool. This study investigates SOC storage in an under-sampled mountain permafrost area in the Russian High Altai. SOC stocks from 39 soil pits are upscaled using a GIS-based land cover classification. We found that the top 100 cm of soils in Aktru Valley and the adjacent Kuray Basin only holds on average 2.6 ± 0.6 kg C m⁻² (95% confidence interval), of which only c. 1% is stored in permafrost. Global warming will result in an upward shift of alpine life zones, with new plant cover and soil development at higher elevations. As a result, this type of mountain permafrost area might act as a net C sink in the future, representing a ‘negative’ feedback on global warming.Electronic supplementary materialThe online version of this article (10.1007/s13280-020-01433-6) contains supplementary material, which is available to authorized users.