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1.
Hypsographs are graphic depictions of the vertical distributions of volumes or masses of water in lakes, ponds, or reservoirs. Quantitative limnological science or engineering must use a hypsograph, or a more complex equivalent system, to undertake calculations of water constituent concentration data by mathematical weighting. Construction of the graph is simple and described. Exemplary uses of the hypsograph are presented. 相似文献
2.
Sediment cores were collected from two remote subalpine lakes: the rather shallow (1.5 m) Little Ghost Lake at 2040 m elevation and the deeper, Great Ghost Lake (40 m) at 2150 m elevation. Different early diagenesis of metals were observed. the seasonally anoxic hypolimnion drives the annual iron redox cycle and causes the remobilization of metals in the mobile fractions of sediments in the Great Ghost Lake. These result in the redistribution of metals in the mobile fractions of sediment and poor correlation between metal concentrations. in the Little Ghost Lake, the shallow water column is always oxic with less change of metals in the mobile fractions of sediments. As a result, most metals have strong positive correlations with each other.
The distributions of metal/Al ratios, total metal contents and acid-leached metal concentrations in the near-surface sediments of these two lakes suggest that the anthropogenic inputs from the atmospheric fallouts in recent decades are one of the major factors affecting the distributions of metals such as cadmium, lead and, to a lessor extent, zinc. the Pb-206/Pb-207 ratios confirm the anthropogenic lead input in these surface sediments. 相似文献
The distributions of metal/Al ratios, total metal contents and acid-leached metal concentrations in the near-surface sediments of these two lakes suggest that the anthropogenic inputs from the atmospheric fallouts in recent decades are one of the major factors affecting the distributions of metals such as cadmium, lead and, to a lessor extent, zinc. the Pb-206/Pb-207 ratios confirm the anthropogenic lead input in these surface sediments. 相似文献
3.
Lake Erie water quality has improved dramatically since the degraded conditions of the 1960s. Additional gains could be made,
but at the expense of further investment and reductions in fishery productivity. In facing such cross-jurisdictional issues,
natural resource managers in Canada and the United States must grapple with conflicting objectives and important uncertainties,
while considering the priorities of the public that live in the basin. The techniques and tools of decision analysis have
been used successfully to deal with such decision problems in a range of environmental settings, but infrequently in the Great
Lakes. The objective of this paper is to illustrate how such techniques might be brought to bear on an important, real decision
currently facing Lake Erie resource managers and stakeholders: the choice of new phosphorus loading targets for the lake.
The heart of our approach is a systematic elicitation of stakeholder preferences and an investigation of the degree to which
different phosphorus-loading policies might satisfy ecosystem objectives. Results show that there are potential benefits to
changing the historical policy of reducing phosphorus loads in Lake Erie. 相似文献
4.
Callaghan TV Tweedie CE Akerman J Andrews C Bergstedt J Butler MG Christensen TR Cooley D Dahlberg U Danby RK Daniëls FJ de Molenaar JG Dick J Mortensen CE Ebert-May D Emanuelsson U Eriksson H Hedenås H Henry H R G Hik DS Hobbie JE Jantze EJ Jaspers C Johansson C Johansson M Johnson DR Johnstone JF Jonasson C Kennedy C Kenney AJ Keuper F Koh S Krebs CJ Lantuit H Lara MJ Lin D Lougheed VL Madsen J Matveyeva N Mcewen DC Myers-Smith IH Narozhniy YK Olsson H Pohjola VA Price LW Rigét F Rundqvist S 《Ambio》2011,40(6):705-716
Understanding the responses of tundra systems to global change has global implications. Most tundra regions lack sustained environmental monitoring and one of the only ways to document multi-decadal change is to resample historic research sites. The International Polar Year (IPY) provided a unique opportunity for such research through the Back to the Future (BTF) project (IPY project #512). This article synthesizes the results from 13 papers within this Ambio Special Issue. Abiotic changes include glacial recession in the Altai Mountains, Russia; increased snow depth and hardness, permafrost warming, and increased growing season length in sub-arctic Sweden; drying of ponds in Greenland; increased nutrient availability in Alaskan tundra ponds, and warming at most locations studied. Biotic changes ranged from relatively minor plant community change at two sites in Greenland to moderate change in the Yukon, and to dramatic increases in shrub and tree density on Herschel Island, and in subarctic Sweden. The population of geese tripled at one site in northeast Greenland where biomass in non-grazed plots doubled. A model parameterized using results from a BTF study forecasts substantial declines in all snowbeds and increases in shrub tundra on Niwot Ridge, Colorado over the next century. In general, results support and provide improved capacities for validating experimental manipulation, remote sensing, and modeling studies. 相似文献
5.
6.
Sediment cores were collected from two remote subalpine lakes: the rather shallow (1.5 m) Little Ghost Lake at 2040 m elevation and the deeper, Great Ghost Lake (40 m) at 2150 m elevation. Different early diagenesis of metals were observed. the seasonally anoxic hypolimnion drives the annual iron redox cycle and causes the remobilization of metals in the mobile fractions of sediments in the Great Ghost Lake. These result in the redistribution of metals in the mobile fractions of sediment and poor correlation between metal concentrations. in the Little Ghost Lake, the shallow water column is always oxic with less change of metals in the mobile fractions of sediments. As a result, most metals have strong positive correlations with each other. The distributions of metal/Al ratios, total metal contents and acid-leached metal concentrations in the near-surface sediments of these two lakes suggest that the anthropogenic inputs from the atmospheric fallouts in recent decades are one of the major factors affecting the distributions of metals such as cadmium, lead and, to a lessor extent, zinc. the Pb-206/Pb-207 ratios confirm the anthropogenic lead input in these surface sediments. 相似文献
7.
8.
Polar and alpine environments are changing rapidly due to increases in temperature, which are amplified in the Arctic, as
well as changes in many local factors. The impacts on ecosystems and their function have potential consequences for local
residents and the global community. Tundra areas are vast and diverse, and the knowledge of geographical variation in environmental
and ecosystem change is limited to relatively few locations, or to remote sensing approaches that are limited mostly to the
past few decades. The International Polar Year, IPY, provided a context, stimulus and timely opportunities for re-visiting
old research sites and data sets to collate data on past changes, to pass knowledge from old to new generations of researchers
and to document environmental characteristics of sites to facilitate detection and attribution of future changes. Consequently,
the project “Retrospective and Prospective Vegetation Change in the Polar Regions: Back to the Future,” BTF, was proposed
and endorsed as an IPY activity (project #512). With national funding support, teams of researchers re-visited former sites
and data sets throughout the Arctic and some alpine regions. These efforts have amounted to a gamut of “BTF” studies that
are collectively geographically expansive and disciplinary diverse. A selection of these studies are introduced and presented
in the current issue together with a brief synthesis of their findings. 相似文献
9.
Integrating limnological characteristics of high mountain lakes into the landscape of a natural area 总被引:1,自引:0,他引:1
Gary L. Larson Andy Wones C. David McIntire Barbara Samora 《Environmental management》1994,18(6):871-888
A general conceptual watershed-lake model of the complex interactions among climatic conditions, watershed location and characteristics,
lake morphology, and fish predation was used to evaluate limnological characteristics of high mountain lakes. Our main hypothesis
was that decreasing elevation in mountainous terrain corresponds to an increase in diversity of watershed size and lake area,
depth, temperature, nutrient concentrations, and productivity. A second hypothesis was that watershed location and aspect
relative to climatic gradients within mountainous terrain influences the limnological characteristics of the lakes. We evaluated
these hypotheses by examining watershed location, aspect and size; lake morphology; water quality; and phytoplankton and zooplankton
community characteristics among high mountain forest and subalpine lakes in Mount Rainier National Park.
Although many of the comparisons between all forest and subalpine lakes were statistically insignificant, the results revealed
trends that were consistent with our hypotheses. The forest lake group included more lakes with larger watersheds, larger
surface areas, greater depths, higher concentrations of nutrients, and higher algal biovolumes than did the group of subalpine
lakes. Deep lakes, which were mostly of the forest lake type, exhibited thermal stratification and relatively high values
of some of the water-quality variables near the lake bottoms. However, the highest near-surface water temperatures and phytoplankton
densities and the taxonomic structures of the phytoplankton and zooplankton assemblages were more closely related to geographical
location, which corresponded to a west-east climate gradient in the park, than to lake type. Some crustacean and rotifer taxa,
however, were limited in distribution by lake type.
Fish predation did not appear to play an important role in the structure of the crustacean zooplankton communities at the
genus level with the exception of Mowich Lake, where crustacean taxa were absent from the zooplankton community. This was
the only lake inhabited by a true zooplanktivourous species of fish. 相似文献
10.
A. J. Plater J. F. Boyle C. Mayers S. D. Turner R. W. Stroud 《Regional Environmental Change》2006,6(1-2):71-85
The limnological record of human impact on catchment land cover and on lake sedimentation during the historical period has
been established for Pinto Lake in Central Coastal California. In addition, the sedimentary record of the ‘pre-impact’ condition
preserves evidence of a climatic control on the nature of lake sedimentation. Chronological marker horizons have been determined
using pollen data in combination with the documented land-use history and introductions of exotic species. Further chronological
data have been determined using 14C and 137Cs. The impact of Mexican and Euro-American immigrants and their ‘imported’ land-use practices is clearly reflected in an
order of magnitude increase in the rate of lake sedimentation to c. 9 kg m−2 year−1 (c. 2 cm year−1) between 1770 and 1850. Here, the occurrence of exotic plant species indicates disturbance as early as c. 1769–1797, whilst
redwood deforestation between 1844 and 1860 represents the most significant human impact. Changes in the nature of sedimentation
prior to this reveal a high degree of sensitivity to changes in precipitation where subtle decreases in lake level and the
supply of runoff-derived mineral matter have resulted in two periods of organic lake sedimentation c. 650–900 and 1275–1750. Set against this background condition of high sensitivity, the dramatic impacts of Euro-American settlement
are unsurprising.
An erratum to this article can be found at 相似文献