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91.
四川彭州铜尾矿库植被特征分析与植物群落演替初探 总被引:2,自引:0,他引:2
本文分析了四川彭州铜矿尾矿库的植被特征、群落特征与演替。在该尾矿库上自然定居的高等植物共91种,隶属38科79属,以菊科(Compositae)和禾本科(Gramineae)植物为主。形成6种相对稳定的群落类型;在2003年弃耕后形成的地段分布有史蒿+小飞蓬群落(Artemisia argyi+Conyza conadensis Comm.)、艾蒿+打破碗花花群落(Artemisia argyi+Anemone hupehensis Comm.)、艾蒿群落(Artemisia argyi Comm.)和白车轴苹群落(Trifolium repens Comm.);在经过30~40年自然演替的地段分布有芭茅+羊耳菊群落(Miscanthus sinensis+Inula cappa Comm.)和羊耳菊+千里光+密蒙花群落(Inula cappa+Senecio scandens+Buddleja officinalis Comm.);在近十年内新形成的地段现主要覆盖地衣和葫芦藓(Funaria hygrometrica)。通过对群落结构和不同地段植被特征的对比,对本铜尾矿库的演替现状和规律进行了分析,井讨论了人为影响对演替进程的影响,提出了人工恢复措施的建议。 相似文献
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Christopher I. Thornton Steven R. Abt Warren P. Clary 《Journal of the American Water Resources Association》1997,33(6):1279-1288
ABSTRACT: A meandering stream channel was simulated in the Hydraulics Laboratory at Colorado State University and a series of tests was conducted using four types of vegetation to evaluate the potential effects of vegetation on sediment deposition and retention in a stream channel. The data collected included average flow velocity, flow depth, length of vegetation, density of vegetation, cross-sectional area of the vegetative stem, wetted perimeter of the vegetative stem, and injection and flushing time. The findings indicated that the vegetation could retain from 30 to 70 percent of the deposited sediments. The ability of vegetation to entrap and retain sediment is related to the length and cross-sectional area of the vegetation. The variables describing the flow and the vegetative properties were combined to form a predictive parameter, the sedimentation factor (Sd) that can be compared with the amount of sediment entrapped by vegetation in a stream system. A relation was developed correlating vegetation length to sediment retention after flushing for flexibility and rigid vegetation. 相似文献
95.
Lakes Manapouri and Te Anau, in Fiordland National Park, became the center of a major controversy after the New Zealand government offered their water resource to an overseas aluminum smelting consortium for electricity generation. Although the scheme proceeded, the lake levels were not raised as originally proposed. Rather, government sought guidelines to optimize hydroelectric potential while maintaining ecological stability of the vulnerable, largely forested, glaciated lakeshores. Guidelines were derived by relating the vegetation zonation to the natural lake-level fluctuations recorded daily for 37 years. Ahigh operating range in the upper third of the lakes' natural ranges, based on flood tolerances of the woody shoreline species, restricts both duration and frequency. Alow operating range (ca. lower third) safeguards stability of shoreline sediments by limiting drawn-down rates, duration, and frequency. Themain operating range (ca. middle third) has few limitations. These guidelines, which allow utilization of ca. 93% of the water resource, have now been verified by instances of flooding and draw-down rates that exceeded the natural rates recorded earlier. The guidelines were officially accepted by the government in 1977 as a basis for managing the valuable multiple resources of these two lakes and their environs, and they were formalized in legislation in 1981. The details and merits of the guideline approach are discussed. 相似文献
96.
Vegetation changes associated with barrier-dune construction on the outer banks of North Carolina 总被引:1,自引:0,他引:1
Manmade dunes are used to stabilize the barrier islands of the mid-Atlantic coast of the United States so that they are more amenable to development. Although this strategy has stabilized extensive sections of the barrier-island substrate, it has also caused significant ecological changes. The rate and pattern of the resulting vegetation changes along the Outer Banks of North Carolina were determined using sequential aerial photography. Successional trends have been altered in favor of more stable woody communities. 相似文献
97.
Vehicular and pedestrian traffic decreased top and root production, percent cover, and diversity of vegetation, and modified species composition on beach and foredune areas of Padre Island National Seashore and Nueces County Park. Degradation of vegetal cover was directly related to the type and intensity of traffic; species in heavily trafficked areas represented earlier successional stages than those in comparable undisturbed areas. 相似文献
98.
P. H. Anderson M. W. Lefor W. C. Kennard 《Journal of the American Water Resources Association》1980,16(2):248-255
ABSTRACT: The delineation of inland wetlands requires close field examination of the biological and physical gradients (transition zones) between wetlands and bordering uplands. As part of a study on the detection and delineation of inland wetlands in eastern Connecticut by remote sensing techniques, this effort was designed to investigate vegetation distribution and composition and selected physical and chemical properties of the soils of wetland to upland transition zones in deciduous wetland forests. Field research was conducted during the growing season of 1975 within a test area consisting of the 45 mi2 Town of Mansfield, Connecticut. Changes in vegetation composition and structure, soil pH, and soil water content were determined along line transects extended over wetland to upland transition zones. Differences in soil pH occurred along the transects but were of such magnitude that they probably have little impact on plant distribution. There were significant changes in soil water content along the wetland to upland gradients. Discriminant analysis applied to statistical “index of abundance” data describing vegetation distribution among the various zones (wetland, transition, upland) showed which plant species best distinguish wetlands from uplands. Of the criteria studied, vegetation composition and distribution, soil water content, and relief are the most useful criteria for delineating deciduous wetland forests. 相似文献
99.
Norman J. Thomson 《Environmental management》1986,10(5):591-597
The clearing of over 80% of the native vegetation from Australian agricultural areas has contributed significantly to the degradation classification applied to more than half this land. Soil erosion, siltation, and salinity damage continue to increase yearly. This situation not only threatens the productivity of the farm sector but has contributed to the estimated loss of 78 species of native flora, endangerment of an additional 2206 species, and the loss of 20 species of Australia's marsupials.Private returns diverge from social returns because the action (or inaction) of farmers has an impact upon others, both now and in the future. There is justification, therefore, for the public sector to intervene on behalf of society in an attempt to influence private decision making for the social good. This article argues for increased incentives from the public sector in Australia to encourage the voluntary cooperation of farmers to improve the balance between development and conservation. In contrast to the essentially temporary nature of man-made measures such as flood-mitigating capital works, increasing the area set aside to native bushland offers scope for the permanent stewardship of the resource—land. 相似文献
100.
Analysis of bank erosion on the Merced River,Yosemite Valley,Yosemite National Park,California, USA 总被引:1,自引:0,他引:1
Channel changes from 1919 to 1989 were documented in two study reaches of the Merced River in Yosemite National Park through
a review of historical photographs and documents and a comparison of survey data. Bank erosion was prevalent and channel width
increased an average of 27% in the upstream reach, where human use was concentrated. Here, trampling of the banks and riparian
vegetation was common, and banks eroded on straight stretches as frequently as on meander bends. Six bridges in the upper
reach constrict the channel by an average of 38% of the original width, causing severe erosion. In the downstream control
reach, where human use was minimal, channel widths both decreased and increased, with a mean increase of only 4% since 1919.
Bank erosion in the control reach occurred primarily on meander bends. The control reach also had denser stands of riparian
vegetation and a higher frequency of large woody debris in channels. There is only one bridge in the lower reach, located
at the downstream end. Since 1919, bank erosion in the impacted upstream reach contributed a significant amount of sediment
(74,800 tonnes, equivalent to 2.0 t/km2/yr) to the river. An analysis of 75 years of precipitation and hydrologic records showed no trends responsible for bank erosion
in the upper reach. Sediment input to the upper reach has not changed significantly during the study period. Floodplain soils
are sandy, with low cohesion and are easily detached by lateral erosion. The degree of channel widening was positively correlated
with the percentage of bare ground on the streambanks and low bank stability ratings. Low bank stability ratings were, in
turn, strongly associated with high human use areas. Channel widening and bank erosion in the upper reach were due primarily
to destruction of riparian vegetation by human trampling and the effect of bridge constrictions on high flow, and secondarily
to poorly installed channel revetments. Several specific recommendations for river restoration were provided to park management. 相似文献