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411.
We assessed the relationship between riparian management and stream quality along five southeastern Minnesota streams in 1995
and 1996. Specifically, we examined the effect of rotationally and continuously grazed pastures and different types of riparian
buffer strips on water chemistry, physical habitat, benthic macroinvertebrates, and fish as indicators of stream quality.
We collected data at 17 sites under different combinations of grazing and riparian management, using a longitudinal design
on three streams and a paired watershed design on two others. Continuous and rotational grazing were compared along one longitudinal
study stream and at the paired watershed. Riparian buffer management, fenced trees (wood buffer), fenced grass, and unfenced
rotationally grazed areas were the focus along the two remaining longitudinal streams. Principal components analysis (PCA)
of water chemistry, physical habitat, and biotic data indicated a local management effect. The ordinations separated continuous
grazing from sites with rotational grazing and sites with wood buffers from those with grass buffers or rotationally grazed
areas. Fecal coliform and turbidity were consistently higher at continuously grazed than rotationally grazed sites. Percent
fines in the streambed were significantly higher at sites with wood buffers than grass and rotationally grazed areas, and
canopy cover was similar at sites with wood and grass buffers. Benthic macroinvertebrate metrics were significant but were
not consistent across grazing and riparian buffer management types. Fish density and abundance were related to riparian buffer
type, rather than grazing practices. Our study has potentially important implications for stream restoration programs in the
midwestern United States. Our comparisons suggest further consideration and study of a combination of grass and wood riparian
buffer strips as midwestern stream management options, rather than universally installing wood buffers in every instance.
RID=" ID=" The Unit is jointly sponsored by the US Geological Survey, Biological Resources Division; the Minnesota Department
of Natural Resources; the University of Minnesota; and the Wildlife Management Institute. 相似文献
412.
/ For regional analyses of species imperilment patterns, data on species distributions are available from the U.S. Fish and Wildlife Service and from the state heritage programs. We compared these two different databases as sources of best available information for regional analyses of patterns of aquatic species imperilment for 132 counties in the southern Appalachians and examined patterns produced from the databases. The heritage program database contained information about a greater number of imperiled species because species need not be federally listed as threatened or endangered to be included in this database. In the southern Appalachians, about half of imperiled molluscs and about one-fourth of imperiled fish were listed as threatened or endangered; much smaller proportions of other taxonomic groups were federally listed. Most threatened and endangered species appeared on both lists, but for about 40% of the species inconsistencies exist, notably a lack of recent records in the heritage program dataset. Numbers of species in each county were significantly different between the two datasets for Georgia, Tennessee, and Virginia, where the largest number of threatened and endangered species reside. Nevertheless, some counties always appeared as centers of imperilment, and the general spatial patterns of imperilment were similar. 相似文献
413.
The Aquatic Macrophyte Community Index (AMCI) is a multipurpose tool developed to assess the biological quality of aquatic
plant communities in lakes. It can be used to specifically analyze aquatic plant communities or as part of a multimetric system
to assess overall lake quality for regulatory, planning, management, educational, or research purposes. The components of
the index are maximum depth of plant growth; percentage of the littoral zone vegetated; Simpson's diversity index; the relative
frequencies of submersed, sensitive, and exotic species; and taxa number. Each parameter was scaled based on data distributions
from a statewide database, and scaled values were totaled for the AMCI value. AMCI values were grouped and tested by ecoregion
and lake type (natural lakes and impoundments) to define quality on a regional basis. This analysis suggested that aquatic
plant communities are divided into four groups: (1) Northern Lakes and Forests lakes and impoundments, (2) North-Central Hardwood
Forests lakes and impoundments, (3) Southeastern Wisconsin Till Plains lakes, and (4) Southeastern Wisconsin Till Plains impoundments,
Driftless Area Lakes, and Mississippi River Backwater lakes. AMCI values decline from group 1 to group 4 and reflect general
water quality and human use trends in Wisconsin. The upper quartile of AMCI values in any region are the highest quality or
benchmark plant communities. The interquartile range consists of normally impacted communities for the region and the lower
quartile contains severely impacted or degraded plant communities. When AMCI values were applied to case studies, the values
reflected known impacts to the lakes. However, quality criteria cannot be used uncritically, especially in lakes that initially
have low nutrient levels. 相似文献
414.
/ The management of riverine wetlands, recognized as a major component of biodiversity in fluvial hydrosystems, is problematic. Preservation or restoration of such ecosystems requires a method to assess the major ecological processes operating in the wetlands, the sustainability of the aquatic stage, and the restoration potential of each riverine wetland. We propose a method of diagnosis based on aquatic macrophytes and helophytes. Plant communities are used because they are easy to survey and provide information about (1) the origin of a water supply (i.e., groundwater, seepage, or surface river water) and its nutrient content, (2) effects of flood disturbances, and (3) terrestrialization processes. The novelty of the method is that, in contrast to available typologies, it is based on the interference of gradients resulting from several processes, which makes it possible to predict wetland sustainability and restoration potential. These predictions result from knowledge of the processes involved in terrestrialization, i.e., the influence of flood disturbances, occurrence of groundwater supplies, trophic degree, and water permanency of the habitat during a yearly cycle. The method is demonstrated on five different river systems. 相似文献
415.
在伊春红山水电站枢纽工程建设前对汤旺河干流红山电站坝址段(上甘岭河段),即淹没区上游、淹没区和坝区以及坝区下水生生物进行实地监测调查,并根据调查结果对项目区河段水生生物现状进行评价,为项目建设的环境影响提供基础数据。 相似文献
416.
依兰航电枢纽的建设,不仅改善了当地乃至松花江流域的航运条件、旅游环境,而且促进了松花江航道及区域经济可持续发展.同时,项目的建设也产生了一些环境问题.施工期作业区水文条件的改变对水生生物及渔业资源造成了影响.营运期库区水域生态环境的改变,使得浮游生物和底栖生物种类发生变化,鱼类组成将由复杂变为简单.因此,本文提出适宜的... 相似文献
417.
418.
419.
超声波控藻及对水生生态安全的影响 总被引:1,自引:1,他引:0
通过恒温培养实验(250L培养基)表征了低强度 (发射功率20W) 定向发射超声波对惠氏微囊藻、孟氏浮游蓝丝藻、四尾栅藻以及菱形藻的生长影响,并通过超声波对大草履虫、大型蚤、稀有鮈鲫以及蜈蚣草的作用研究了其对水生生态的安全性.结果表明,超声波对蓝藻惠氏微囊藻的生长有较好的抑制作用,6d后生物量仅为对照组的32%;超声波对蓝藻孟氏浮游蓝丝藻、绿藻四尾栅藻以及硅藻菱形藻的生长也有一定的抑制作用,超声波作用10~13 d后,藻细胞密度比对照组低30%~33%.结果还表明,该强度的超声波对浮游动物草履虫和大型蚤、鱼类稀有鮈鲫以及沉水植物蜈蚣草的生长没有受到明显的影响.研究结果说明,低强度定向超声波可以对藻类生长产生抑制作用,而对水体中浮游动物、鱼类以及沉水植物等其它主要水生生物不产生明显影响. 相似文献
420.
Impacts of atrazine in aquatic ecosystems 总被引:26,自引:0,他引:26
A portion of all herbicides applied to forests, croplands, road sides, and gardens are inevitably lost to water bodies either directly through runoff or indirectly by leaching through groundwater into ephemeral streams and lakes. Once in the aquatic environment, herbicides may cause stress within aquatic communities and radically alter community structure. Atrazine is one of the most effective and inexpensive herbicides in the world and is consequently used more frequently than any other herbicide. Atrazine is frequently detected in aquatic waters, and has been known to affect reproduction of aquatic flora and fauna, which in turn impacts on the community structure as a whole. This paper presents a summary of the reported direct and indirect impacts of atrazine on aquatic organisms and community structure. The information can be used for developing improved management guidelines and legislation. It is concluded that a single universal maximum limit on the atrazine application in catchments, as suggested by many regulatory authorities, does not provide adequate protection of the aquatic environment. Rather, it is advocated that flexible limits on the application of atrazine be developed in line with the potential risk of contamination to surface and subsurface water and fragility of the aquatic environment. 相似文献