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591.
Floodplain forests are flood-dependent ecosystems. They rely on well-timed, periodic floods for the provision of regeneration sites and on tapered flood recession curves for the successful establishment of seedlings. These overbank flood events are described as regeneration flows. Once floodplain forest trees are established, in order to grow they also require adequate, although variable, river stage levels or maintenance flows throughout the year. Regeneration flows are often synonymous with flood flows and only occur periodically. There is a disparity between this need for varied interannual flows over the decadal time frame and the usual annual cycle of flow management currently used by most river management agencies. Maintenance flows are often closer to established minimum flows and much easier to provide by current operational practices.A number of environmental flow methodologies, developed in North America, Australia, and South Africa are described in this review. They include the needs of the floodplain environment in the management and allocation of river flows. In North America, these methodologies have been put into practice in a number of river basins specifically to restore floodplain forest ecosystems. In Australia and South Africa, a series of related holistic approaches have been developed that include the needs of floodplain ecosystems as well as in-channel ecosystems. In most European countries, restoration of floodplain forests takes place at a few localized restoration sites, more often as part of a flood-defense scheme and usually not coordinated with flow allocation decisions throughout the river basin. The potential to apply existing environmental flow methodologies to the management of European floodplain forests is discussed. 相似文献
592.
There are numerous demands for the limited water supplies in the Rocky Mountain (USA) region, and controversies surrounding
instream flows abound. A specific problem involves water diversions (i.e., small dams that shunt water out of stream channels)
during the summer irrigation season. We developed an approach to assess the effects of restoration of natural or less-than-natural
summer flows on trout that accounts for variation in habitat over long segments of low-gradient, alluvial-valley streams.
The approach has utility for managers because it can be conducted with hydologic data, aerial photographs, topographic maps,
and a spreadsheet without extensive fieldwork. We applied the approach by assessing the effects of different summer flows
on abundance of brown trout (Salmo trutta) in several streams annually dewatered in the Salt River Valley of western Wyoming. The assessment approach can be calibrated
for other trout species and areas of the Rocky Mountain region. 相似文献
593.
We applied the Theory of Planned Behavior to help understand the relationships between environmental beliefs, support for
ecosystem restoration actions, and willingness to pay (WTP) for restoration and protection goals in the Hudson River estuary,
New York State, USA. We conducted a mail survey with 3,000 randomly-chosen local residents of the Hudson River estuary in
the fall of 1999. As hypothesized, the broad ecosystem restoration goals of the Hudson River Estuary Action Plan were more
strongly supported than the corresponding specific implementation actions. We found that beliefs and past behavior were better
explanatory variables than sociodemographic characteristics for explaining people's support for ecosystem restoration actions
and WTP for restoration and protection goals. Because ecosystem restoration goals appear to be more generally acceptable than
specific restoration actions, proponents of restoration programs should not become complacent about the need for active public
outreach and involvement even if initial restoration program discussions have been low in controversy. Efforts to assess and
foster support for ecosystem restoration should be targeted toward audiences identified on the basis of beliefs and past behaviors
rather than on sociodemographic characteristics. 相似文献
594.
Riparian livestock exclosure research in the western United States: a critique and some recommendations 总被引:1,自引:1,他引:0
Sarr DA 《Environmental management》2002,30(4):516-526
Over the last three decades, livestock exclosure research has emerged as a preferred method to evaluate the ecology of riparian
ecosystems and their susceptibility to livestock impacts. This research has addressed the effects of livestock exclusion on
many characteristics of riparian ecosystems, including vegetation, aquatic and terrestrial animals, and geomorphology. This
paper reviews, critiques, and provides recommendations for the improvement of riparian livestock exclosure research. Exclosure-based
research has left considerable scientific uncertainty due to popularization of relatively few studies, weak study designs,
a poor understanding of the scales and mechanisms of ecosystem recovery, and selective, agenda-laden literature reviews advocating
for or against public lands livestock grazing. Exclosures are often too small (<50 ha) and improperly placed to accurately
measure the responses of aquatic organisms or geomorphic processes to livestock removal. Depending upon the site conditions
when and where livestock exclosures are established, postexclusion dynamics may vary considerably. Systems can recover quickly
and predictably with livestock removal (the “rubber band” model), fail to recover due to changes in system structure or function
(the “Humpty Dumpty” model), or recover slowly and remain more sensitive to livestock impacts than they were before grazing
was initiated (the “broken leg” model). Several initial ideas for strengthening the scientific basis for livestock exclosure
research are presented: (1) incorporation of meta-analyses and critical reviews. (2) use of restoration ecology as a unifying
conceptual framework; (3) development of long-term research programs; (4) improved exclosure placement/design; and (5) a stronger
commitment to collection of pretreatment data. 相似文献
595.
The natural Park of Peñalara consists of a small mountainousarea near Madrid and includes a series of water bodies (fromsmall mountain lakes to temporary ponds and peat bogs), the mostknown of them being the so-called `Laguna Grande dePeñalara'. Due to growing numbers of visitors theenvironmental conditions of this lake started to decline in theearly 1970s because of: (1) the start of severe soil erosionprocesses; (2) the increase of nutrient load; and (3) theintroduction of a non-native fish species. Since the area wasprotected in 1990, several conservation and restoration projectsincluded in an integrated management plan have been developed. Here we summarise some of the results of these efforts: (1) controlled access of livestock and visitors to the area; (2) palaeolimnology studies aimed at inferring recent changes in thewatershed; and (3) monitoring of the limnological features of thesystem. Restoration of this lake and its watershed is intendedto serve as a model for the management of other severely alteredhigh mountain lakes. 相似文献
596.
Economic evaluations of restored or enhanced lakes in Florida indicated gravity drawdown was the least expensive action, whereas effluent diversion was 10,000 times more costly on a per hectare basis, with the other lake treatment costs occurring in the following order: gravity drawdown < grass carp introduction < mechanical drawdown < aeration < stormwater control = drawdown-dredging < effluent diversion. Within a particular treatment category, the costs spanned approximately one and one half orders of magnitude. Contrary to the abundant cost data, which permitted an economic analysis, inappropriate statistical design and lack of commitment toward sampling Florida's restored lakes undermines attempts to understand long-term water quality responses to various enhancement techniques. Using Lake Tohopekaliga as a case study, ordinary statistical tests produced contradictory and unreliable interpretations on the effectiveness of drawdown and phosphorus removal at sewage treatment plants in improving the trophic state index. This emphasizes the need for more robust statistical approaches and more detailed data collection in evaluating lake restoration activities It is unfortunate for Florida's lake restoration program that quantitative conclusions based on inferential statistics, replete with tests of assumptions, is limited to very few lakes 相似文献
597.
Hydrologic modeling as a predictive basis for ecological restoration of salt marshes 总被引:4,自引:0,他引:4
Roads, bridges, causeways, impoundments, and dikes in the coastal zone often restrict tidal flow to salt marsh ecosystems.
A dike with tide control structures, located at the mouth of the Herring River salt marsh estuarine system (Wellfleet, Massachusetts)
since 1908, has effectively restricted tidal exchange, causing changes in marsh vegetation composition, degraded water quality,
and reduced abundance of fish and macroinvertebrate communities. Restoration of this estuary by reintroduction of tidal exchange
is a feasible management alternative. However, restoration efforts must proceed with caution as residential dwellings and
a golf course are located immediately adjacent to and in places within the tidal wetland. A numerical model was developed
to predict tide height levels for numerous alternative openings through the Herring River dike. Given these model predictions
and knowledge of elevations of flood-prone areas, it becomes possible to make responsible decisions regarding restoration.
Moreover, tidal flooding elevations relative to the wetland surface must be known to predict optimum conditions for ecological
recovery. The tide height model has a universal role, as demonstrated by successful application at a nearby salt marsh restoration
site in Provincetown, Massachusetts. Salt marsh restoration is a valuable management tool toward maintaining and enhancing
coastal zone habitat diversity. The tide height model presented in this paper will enable both scientists and resource professionals
to assign a degree of predictability when designing salt marsh restoration programs. 相似文献
598.
Mark J. Hanson Heinz G. Stefan 《Journal of the American Water Resources Association》1984,20(6):889-900
The shallow Fairmont Lakes in southern Minnesota have been treated with copper sulfate for 58 years to reduce excessive algal growth. Copper sulfate was applied to five lakes at cumulative rates upo to 1647 kg/ha (1470 1b/acre), totaling 1.5 million kilograms. Data collected since treatment of the Fairmont Lakes began in 1921 provide alarming insights into lake responses to sustained chemical treatment with copper sulfate. Short-term and long-term effects have occurred. Short-term effects include: a) the intended temporary killing of algae, b) dissolved oxygen depletion by decomposition of dead algae, c) accelerated phosphorus recycling from the lake bed and recovery of the algal population within 7 to 21 days, and d) occasional fish kills due to oxygen depletion or copper toxicity or both. Long-term effects are shown to include: a) copper accumulation in the sediments, b) tolerance adjustments of certain species of algae to higher copper sulfate dosages, c) shift of species from green to blue-green algae and from game fish to rough fish, d) disappearance of macrophytes, and e) reductions in benthic macroinvertebrates. The conclusion is that while copper sulfate treatments enjoy great popularity because they kill and remove algae almost instantaneously, other immediate or cumulative side effects can be harmful to many other aquatic organisms. 相似文献
599.
生态保护的基础是生态监测与生态调查,生态保护的关键则是生态系统健康评价,生态系统健康评价因素有组织、结构、活力、恢复力、系统对相邻系统的影响、投入、对人类健康的影响等,其类型有健康、较健康、亚健康、不健康、患病五级;其相应的生态恢复为生态预防、自然恢复、生态修复、生态重建;其相应的生态工程有建立自然保护区、封育、补播与放流、人工林、人工草场、人工湿地等。 相似文献
600.