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681.
三江平原气候变暖的进一步认识:最高和最低气温的变化 总被引:16,自引:2,他引:16
利用三江平原17个站1951-2000年的平均最高、最低气温和气温日较差资料,采用线性倾向估计和几种突变检测方法,定量研究了最高、最低气温和气温日较差变化趋势的空间分布,比较了最高、最低气温变化特征的差异性。结合前期的相关研究结果,对研究区20世纪70年代中期以来的三江平原气候变暖过程和成因有了进一步的认识。1975—2000年的变暖时期主要由两个阶段构成:1975—1987年为第一阶段,以夜间升温为主要特征,相对应的是气温日较差明显减小,超过一定面积的湿地开垦是该阶段气候变暖的主要驱动力之一;1987-2000年为第二阶段,以白天和夜间同时升温且幅度相当,气温日较差没有明显的变化趋势为特点,这一阶段的升温是对全球气候变暖同步的区域响应。 相似文献
682.
Above and below-ground biomass and nitrogen and carbon composition ofSpartina maritima, Halimione portulacoides andArthrocnemum perenne, dominating species in plant communities of the lower, middle and higher salt marsh, respectively, were compared in an estuarine
salt marsh in Portugal. Plant and soil nitrogen and carbon pools were estimated. For all three species root biomass was significantly
higher (70–92% of total biomass) than above-ground biomass. The percentage of root biomass was related to the location of
the plants in the marsh: higher values were found in plants growing in the lower salt marsh where the sediment was more unstable
and subject to tidal action, which stresses the role of the roots as an anchor. For all three species nitrogen concentrations
were highest in leaves, reflecting the photosynthetic role of the tissue. For carbon higher concentrations were found in the
stems, with the exception ofS. maritima. In general, lower nitrogen concentrations were found in summer, which can be explained by dilution processes due to plant
growth. For both nitrogen and carbon, higher concentrations were found in the soil surface layers. Higher soil nitrogen and
carbon levels were associated with higher organic matter contents. Most of the nitrogen in the salt marsh occurred in the
sediments (0–40 cm) and only ca. 5.7–13.3% of the total was found in the plants. The greater portion (76.5%–86%) of carbon
was found in the sediment. 相似文献
683.
684.
湿地构成变化与湿地保护 总被引:1,自引:0,他引:1
湿地不合理的开发利用 ,对湿地构成诸如水文、土壤、水质、植被和动物都造成了不同程度的负面影响 ,这些影响相互作用 ,使得湿地生态系统极为脆弱 ;通过对它们的分析 ,提出了相应的湿地保护措施 相似文献
685.
Amphibian Breeding Distribution in an Urbanized Landscape 总被引:5,自引:0,他引:5
Abstract: Amphibians commonly use wetlands for breeding habitat, and given the concern about their ongoing global declines, the effects of urbanization on the breeding distribution of amphibians need to be quantified. Thus, we conducted a survey of the larval amphibian community in central Pennsylvania (U.S.A.) wetlands along an urbanization gradient. Wetlands in urban areas had less surrounding forest and wetlands and greater road density than rural wetlands. Urbanization was also associated with increases in hydroperiod (i.e., wetland permanency) and the presence of fish predators. Moreover, urban wetlands had lower larval amphibian species richness than rural wetlands. This decrease in richness was attributable to a decrease in occurrence of wood frogs ( Rana sylvatica ) and ambystomatid salamanders ( Ambystoma maculatum and A. jeffersonianum ) in urban sites. Wood frogs and ambystomatid salamanders were positively associated with the amount of forest surrounding sites and negatively associated with hydroperiod. As a result, we hypothesize that these species are sensitive to the effects of urban development. The remaining species in this study appear fairly resilient to the effects of urbanization. These data demonstrate the importance of quantifying both local and landscape attributes when describing the factors that limit the breeding distribution of amphibians. We recommend that to preserve amphibian biodiversity in urbanized landscapes, it is best to focus on regional diversity, which protects a variety of sites that encompass various hydroperiods, have adequate buffer habitat, and are connected by dispersal routes. 相似文献
686.
基质是潜流式人工湿地污水处理系统的重要组成部分,直接影响到系统的处理效果.本文研究了由沸石、页岩陶粒和碎石3种不同基质构建的潜流式人工湿地对磷的去除效果.结果表明,在设计水力停留时间3 d,连续进出水情况下,碎石单元对磷的去除效果最好,页岩陶粒单元次之,沸石单元效果最差,平均去除率分别为95%、60%和35%.在潜流式人工湿地污水处理系统运行初期观察到磷释放现象,沸石单元最为明显.进水磷浓度较低时,磷的去除率随浓度升高而升高,当正磷、总磷浓度分别升高到2.4~2.5和3.1~3.3 mg/L时,正磷、总磷的去除率开始迅速下降. 相似文献
687.
Roots of salt marsh plant speciesSpartina alterniflora, S. patens, Distichlis spicata, and others were examined for the presence of vesicular-arbuscular mycorrhizal (VAM) fungi. Samples were taken from introduced
planted material in a salt marsh restoration project and from native material in adjacent marsh areas along the Indian River,
Clinton, Connecticut, USA. After ten years the replanted area still has sites devoid of vegetation. The salt marsh plants
introduced there were devoid of VAM fungi, while high marsh species from the adjacent undisturbed region showed consistent
infection, leading the authors to suggest that VAM fungal infection of planting stocks may be a factor in the success of marsh
restoration. 相似文献
688.
Mirady Sebastiani Sara Elena González María Mercedes Castillo Pablo Alvizu María Albertina Oliveira Jorge Pérez Antonio Quilici Martín Rada María Carolina Yáber Miguel Lentino 《Environmental management》1994,18(5):647-661
In Venezuela, large-scale shrimp farming began in the 1980s. By 1987, the Ministry of Environment and Natural Resources (MARNR)
had received 14 proposals for approval. A developer illegally started the construction of ponds at the Píritu Lagoon in the
State of Anzoátegui before the authorization process was completed. This action triggered a land-use conflict. This study
identifies the causes for public protest and determines the consequences of this conflict for land-use management. The results
show that public protest was based on the impacts of the partial construction of ponds. These impacts were related to direct
removal of wetlands, interruption of natural patterns of surface flows, and alteration of feeding grounds of some bird species
with migratory status. Consequences were identified in relation to the role that nongovernmental organizations (NGOs) play
in land-use conflicts and the actions that MARNR could take in the future to prevent and solve similar situations. 相似文献
689.
A binary response estimation procedure using contingent valuation data is proposed for estimating the incremental environmental benefits associated with the use of constructed wetlands to control agricultural waste-water runoff. The model uses two binary responses per individual while circumventing the non-independence problems associated with follow-up valuation questions. Case study results suggest that the methodology provides a potentially effective means for measuring the non-market benefits of constructed wetlands in addition to water-quality maintenance.1998 Academic Press 相似文献
690.
Judy Z. Drexier Barbara L. Bedford Arthur T DeGaetano Donald I. Siegel 《Journal of the American Water Resources Association》1999,35(4):753-769
ABSTRACT: Few water budgets exist for specific types of wetlands such as peatlands, even though such information provides the basis from which to investigate linkages between wetlands and upland ecosystems. In this study, we first determined the water budget and then estimated nutrient loading from an upland farm field into a 1.5 ha, kettle-block peatland. The wetland contains highly anisotropic peat and has no distinct, active layer of groundwater flow. We estimated the depth of the active layer using Fick's law of diffusion and quantified groundwater flow using a chemical mass balance model. Evapotranspiration was determined using MORECS, a semi-physical model based on the Penman-Monteith approach. Precipitation and surface outflow were measured using physical means. Groundwater provided the major inflow, 84 percent (44,418 m3) in 1993 and 88 percent (68,311 m3) in 1994. Surface outflow represented 54 percent (28,763 m3) of total outflows in 1993 and 48 percent (37,078 m3) in 1994. A comparison of several published water budgets for wetlands and lakes showed that error estimates for hydrologic components in this study are well within the range of error estimates calculated in other studies. Groundwater inflow estimates and nutrient concentrations of three springs were used to estimate agricultural nutrient loading to the site. During the study period, nutrient loading into the peatland via groundwater discharge averaged 24.74 kg K ha-1, 1.83 kg total inorganic P had, and 21.81 kg NO3-N ha-1. 相似文献