共查询到20条相似文献,搜索用时 15 毫秒
1.
L.A. Batten 《Bird Study》2013,60(4):213-217
Great Crested Grebe numbers in Britain continue to increase overall, by about 50% since the last complete census in 1965. It is now spreading into marginal habitats, such as lowland rivers, which will make it difficult to census the species in future using traditional methods. 相似文献
2.
Climate change and its impact on birch pollen quantities and the start of the pollen season an example from Switzerland for the period 1969–2006 总被引:2,自引:1,他引:1
As published by the Intergovernmental Panel on Climate Change (IPCC) global warming is a reality and its impact is huge like the increase of extreme weather events, glacier recession, sea level rise and also effects on human health. Among them allergies to airborne pollen might increase or change in pattern due to the invasion of new allergic plants or due to different behavior of plants like earlier flowering. In this study we used the longest Swiss airborne pollen data set to examine the influence of the temperature increase on the time of flowering. In the case of Basel, where pollen data for 38 years are available, it was shown that due to a temperature increase the start of flowering in the case of birch occurred about 15 days earlier. Apart from a shift of the start of the flowering there is also a trend towards higher annual birch pollen quantities and an increase of the highest daily mean pollen concentrations. Due to global warming and because symptoms may appear earlier in the year people suffering from a pollen allergy might face a new unaccustomed situation. 相似文献
3.
Deirdre Oakley 《Ethnic and racial studies》2013,36(9):1576-1598
One-third of public school students are racial and/or ethnic minorities. Yet only 14 per cent of teachers represent these groups. Frequently lost in broader debates concerning this disparity is the paradoxical contribution of the 1954 Brown v. Board of Education decision. Schools were mandated under Brown to desegregate the student body. But the law did not necessarily protect the jobs of black teachers and administrators. Using a unique database of court orders, we examine the impact of mandated desegregation on black teachers. Findings indicate regional differences. Mandated desegregation created conditions that resulted in decreases in the black teaching force in the South. The opposite occurred in the non-south, with mandated desegregation positively associated with increases (although small) in the black teaching force. Our findings suggest that the legacy of mandated desegregation may have created broader institutional conditions in which black and other minority teachers remain underrepresented in the teaching force. 相似文献
4.
A process-based model was built to describe the ecological processes of an alkalinized–salinized meadow steppe ecosystem, including the hydrological and alkalization–salinization processes in the soil, as well as the succession and growth dynamics of the grassland communities. A numerical integration model and a water and salt balance model were integrated into a physically-based model, describing the dynamics of soil moisture, salt concentration, exchangeable sodium percentage (ESP) and pH. Meteorological variables and soil characteristics were the main environmental factors used to estimate the growth dynamics of three herbaceous communities that were dominated by Aneurolepidium chinense, Chloris virgata, and Suaeda glauca, respectively. Model validation showed good agreement between the simulated results and the observed data. Simulation studies were conducted to evaluate the potential changes in hydrological and alkalization–salinization processes, succession and growth dynamics from 1991 to 1998, under five grazing intensities, namely 0%, 25%, 50%, 75% and 90% above-ground biomass removal (AGBR). The simulations show that soil moisture decreased markedly under the 50%, 75% and 90% AGBR, but increased slightly under the 25% AGBR. The de-alkalization and de-salinization processes would be predominant under the 0% AGBR, and the processes became a little slower under the 25% AGBR. In contrast, the 50%, 75% and 90% AGBR accelerated the degradation of soil properties. The grassland was dominated by A. chinense under the 0% AGBR, and by A. chinense and C. virgata under the 25% AGBR. C. virgata could grow on slightly alkalinized–salinized soil and became a dominant species after three years of 50% AGBR. The soil degraded quickly and only S. glauca could grow on the severe alkalinized–salinized soil if the grassland received 75% or 90% AGBR. The grassland grew well under the 0% AGBR, and the biomass stayed at moderate level under 25% AGBR. The 50%, 75% and 90% AGBR decreased the grassland growth greatly. After accumulating the grazed biomass for each year, the 25% AGBR would provide the highest production, and the grassland production would decrease sharply with the increasing of grazing intensities. The simulation results indicate that 25% AGBR is significant for preserving the soil from degradation, and maintaining high grassland production. 相似文献
5.
Stefanie Christmann 《Restoration Ecology》2019,27(4):720-725
Pollinators are key agents for ecosystems and humankind concerning biodiversity, agriculture, climate change adaptation, and all other ecosystem services. Particularly in industrialized countries pollinator diversity is in decline. The bulk of research is on entomological or plant‐pollinator network related topics, but the broad range of impacts of pollinator loss on coupled human and natural systems is not yet studied. As 87% of all flowering plants depend on pollinators, they are basic for all ecosystem services to some extent. Therefore, pollinator loss might cause simultaneous degradation of ecosystem services inducing counterproductive human responses and interlinked poverty spirals. The interaction of climate change, a main risk factor for pollinators, and unadvised human responses to pollinator decline are rarely studied. Tipping points of pollinator loss are not yet identified. Can counterproductive human responses to pollinator deficiency upscale pollinator decline toward a pollinator‐loss syndrome in the course of climate change? The article argues for research on the impacts of pollinator loss on other ecosystem services, useful and counterproductive human strategies on pollinator‐loss induced degradation, and the integration of pollinator protection into all terrestrial restoration efforts. 相似文献
6.
7.
Cormorants and other wildlife populations have come in real or perceived conflicts with humans over exploited fish stocks. From gut contents of cormorants, and using an extension of the Catch equation, we estimated the degree of short term competition between great cormorants and coastal fisheries in two areas along the Swedish Baltic Sea. Cormorants consumed 10 and 44%, in respective area, of the fish biomass of six fish species harvested by humans; eel, flounder, herring, perch, pike, and whitefish. On average, cormorants consumed smaller individuals than harvested in fisheries. But for perch, cod and flounder, cormorants consumed harvestable sized fish corresponding >20% of human catches. Our competition model estimated the direct decrease in fisheries catches due to cormorant predation to be <10% for all species except flounder (>30%) and perch (2–20%). When also including the indirect effects of cormorant predation on smaller fish that never reached harvestable size, the estimated decrease in fisheries catches at least doubled for perch (13–34%) and pike (8–19%). Despite large uncertainties, our model indicates that cormorants may locally have a direct impact on human catches of at least flounder, and when incorporating indirect effects also on perch and pike. The study indicates that the degree of competition between cormorants and humans varies substantially between areas. We also included economical values in the model and concluded that for the commercially most important species, eel and cod, the estimated economic impact of cormorants on fisheries was low. 相似文献
8.
Empirical evidence is beginning to show that predators can be important drivers of elemental cycling within ecosystems by propagating indirect effects that determine the distribution of elements among trophic levels as well as determine the chemical content of organic matter that becomes decomposed by microbes. These indirect effects can be propagated by predator consumptive effects on prey, nonconsumptive (risk) effects, or a combination of both. Currently, there is insufficient theory to predict how such predator effects should propagate throughout ecosystems. We present here a theoretical framework for exploring predator effects on ecosystem elemental cycling to encourage further empirical quantification. We use a classic ecosystem trophic compartment model as a basis for our analyses but infuse principles from ecological stoichiometry into the analyses of elemental cycling. Using a combined analytical‐numerical approach, we compare how predators affect cycling through consumptive effects in which they control the flux of nutrients up trophic chains; through risk effects in which they change the homeostatic elemental balance of herbivore prey which accordingly changes the element ratio herbivores select from plants; and through a combination of both effects. Our analysis reveals that predators can have quantitatively important effects on elemental cycling, relative to a model formalism that excludes predator effects. Furthermore, the feedbacks due to predator nonconsumptive effects often have the quantitatively strongest impact on whole ecosystem elemental stocks, production and efficiency rates, and recycling fluxes by changing the stoichiometric balance of all trophic levels. Our modeling framework predictably shows how bottom‐up control by microbes and top‐down control by predators on ecosystems become interdependent when top predator effects permeate ecosystems. 相似文献
9.
Arctic–alpine plants have enormous ranges in the Northern Hemisphere. Phylogeographic studies have provided insights into their glacial survival as well as their postglacial colonization history. However, our understanding of the population dynamics of disjunct alpine populations in temperate regions remains limited. During Pleistocene cold periods, alpine populations of arctic–alpine species in East Asia were either connected to an ice-free Beringia refugium or they persisted with prolonged isolation after their establishment. To estimate which of these scenarios is more likely, we elucidated the genetic structure of Phyllodoce caerulea (Ericaceae) in Beringia and northern Japan, East Asia. Sequence variation in multiple nuclear loci revealed that P. caerulea can be distinguished into northern and southern groups. A demographic analysis demonstrated that the north–south divergence did not predate the last glacial period and detected introgression from Phyllodoce aleutica, relative widely distributed in East Asia, exclusively into the southern group. Therefore, although there has been genetic divergence between northern Japan and Beringia in P. caerulea, the divergence is unlikely to have resulted from their prolonged geographic separation throughout several cycles of glacial and interglacial periods. Instead, our study suggests that the introgression contributed to the genetic divergence of P. caerulea and that the range of P. caerulea was plausibly connected between northern Japan and Beringia during the last glacial period. Overall, our study not only provides a biogeographic insight into alpine populations of arctic–alpine plants in East Asia but also emphasizes the importance of careful interpretation of genetic structure for inferring phylogeographic history. 相似文献
10.
Penguin colony is one of the Earth’s simplest ecosystems. As the seabird with the largest population in Antarctica, penguin is a unique indicator of Antarctic environment and climate changes. In this study, we collected an ornithogenic sediment core from Gardner Island in Vestfold Hills, East Antarctica, reconstructed an 8,500 years variation history of penguin population and vegetation abundance on this island, and examined the evolution of the penguin colony. We used the levels of two molecular markers cholesterol and cholestanol as the proxy indicators of penguin population size. Other molecular markers, including C24:0 alkenoic acid, C18 n-alkanol and phytol were used as the proxy indicators of aquatic moss, algae, and general vegetation, respectively. It is shown that the growth of algae was mainly affected by the nutritional supply from penguin droppings, so their abundance was positively linked with penguin population. The growth of aquatic moss, however, was controlled more by the degree of water body transparency than by nutrient availability. Because the pollution of water body increased as penguin population grew, aquatic moss abundance showed a seesaw-like relationship with penguin population. These results suggested that penguins played a dominant role in this simple ecosystem in the Antarctic environment. The reconstructed relationship between penguin population and vegetation abundance may offer new insights to understand ancient Antarctic environment and ecology. 相似文献
11.
Background
Few studies have investigated the associations between outdoor air pollution and outpatient visits for respiratory diseases (RDs) in general population.Methods
We collected daily outpatient data of primary RDs from five hospitals in Jinan during January 2012 and December 2016, as well as daily measurements of air pollutants from the Jinan Environmental Monitoring Center and daily meteorological variables from the China Meteorological Data Sharing Service System. A generalized additive model (GAM) with quasi-Poisson regression was constructed to estimate the associations between daily average concentrations of outdoor air pollutants (PM2.5,PM10, SO2, NO2, CO and O3) and daily outpatient visits of RDs after adjusting for long-time trends, seasonality, the “day of the week” effect, and weather conditions. Subgroup analysis stratified by gender, age group and the type of RDs was conducted.Results
A total of 1,373,658 outpatient visits for RDs were identified. Increases of 10?μg/m3 in PM2.5, PM10, NO2, CO and O3 were associated with0.168% (95% CI, 0.072–0.265%), 0.149% (95% CI, 0.082–0.215%), 0.527% (95% CI, 0.211–0.843%), 0.013% (95% CI, 0.003–0.023%), and 0.189% (95% CI, 0.032–0.347%) increases in daily outpatient visits for RDs, respectively. PM2.5 and PM10 showed instant and continuous effects, while NO2, CO and O3 showed delayed effects on outpatient visits for RDs. In stratification analysis, PM2.5 and PM10 were associated with acute RDs only.Conclusions
Exposure to outdoor air pollutants including PM2.5, PM10, NO2, CO and O3 associated with increased risk of outpatient visits for RDs.12.
We analysed migration strategies of the Osprey Pandion haliaetus on the poorly studied Eastern European–East African flyway. Four adult birds were equipped with GPS-based satellite-transmitters or data-loggers in their breeding sites in Estonia (north-eastern Europe) and tracked to their wintering grounds in Africa and back, during up to six migration cycles. Departure times, migration routes, as well as wintering and stopover sites varied remarkably between individuals but not much between years. Stopovers (2–30 days) were made mostly in Europe and less in the Middle East (Turkey) and north-eastern Africa (Egypt). The Ospreys did not avoid flying long distances over the sea, and the sea was crossed four times during the night. The current study adds to current knowledge on Osprey migration and should help to concentrate actions on protecting important flyways and stopover locations. 相似文献
13.
Transfer processes from a eutrophic ecosystem, the river Rhône, to an oligotrophic environment, the north-west Mediterranean Sea, were studied during the winter period, when inputs of dissolved and particulate matter are at their highest.During a cruise carried out in February 1987, salinity, temperature, turbidity, nutrients, pigments, suspended particulate matter and particulate carbon and nitrogen were measured in surface and subsurface waters near the Rhône outlet.For most of the parameters the results show that during this period a simple dilution process occurs in the river plume of the Rhône without adsorption, desorption, precipitation or biological uptake, contrary to recordings for some other rivers. All the nutrients discharged into the sea by the Rhône are available for utilization by marine phytoplankters. 相似文献
14.
Hanna Eriksson Marianna Pastuszak Stefan Löfgren Carl-Magnus Mörth Christoph Humborg 《Biogeochemistry》2007,85(2):153-168
The Oder and the Vistula rivers are responsible for about 25% of the total riverine nitrogen input to the Baltic Sea and of
this 60% have been estimated to originate from diffuse sources. In this study we have tested the hypothesis that changes in
agricultural practices in Poland have changed the riverine nitrogen export from the rivers Oder and Vistula to the Baltic
Sea. We calculated agricultural long-term nitrogen budgets (1960–2000) for the catchments of the Oder and the Vistula rivers.
Poland went through severe economical changes in the early 1990s, which led to a drastic decrease in fertilizer consumption.
The role of the calculated nitrogen surplus as an eutrophication capacitor and the potential to reduce this important capacitor
to improve the environmental state of the Baltic Sea is discussed. N surplus for the entire country showed a maximum in 1980
(58 kg ha−1 sown area−1) and it dropped to 39 kg ha−1 sown area−1 in 2000. The surplus was, however, up to two times lower than that in other transitional countries, and much lower than in
Western Europe with intensive agriculture. An observed decrease in nitrogen concentrations in both Polish rivers is not ascribed
to drop in fertilizer use, but it results from nutrient removal in municipal wastewater treatment plants with tertiary treatment
facilities. Comparison of trends in nitrogen concentrations in different transition countries indicates that factors other
than reduced fertilizer application influenced the inertia of the water quality response. Hence, the potential to reduce diffuse
nitrogen emissions from agriculture by reducing fertilization is constricted in areas with low-nitrogen surplus. In transitional
countries like Poland the largest potential for nutrient reductions seem to be in improving the connectivity to waste water
treatment plants with tertiary treatment. 相似文献
15.
Jeffrey J. Smith 《Ocean Development & International Law》2013,44(4):301-327
The decision of the International Court of Justice in the Australia/Japan Whaling Case marks an advance in the law of the sea and the obligation on states to cooperate in common ocean resource regimes. The Court found substantially for Australia, prohibiting Japan's long-running program to capture large cetaceans in the Southern Ocean around Antarctica for scientific research. The Court's discussion of the criteria for states to design and implement scientific research whaling programs is assessed, as is the obligation for cooperation in such research and ocean research generally. The result for whaling and for the future work of the International Whaling Commission is considered. 相似文献
16.
Habitats and the ecosystem services they provide are part of the world’s portfolio of natural capital assets. Like many components
of this portfolio, it is difficult to assess the full economic value of these services, which tends to over-emphasize the
value of extractive activities such as coastal development. Building on recent ecological studies of species–habitat linkages,
we use a bioeconomic model to value multiple types of habitats as natural capital, using mangroves, sea grass, and coral reefs
as our model system. We show how key ecological variables and processes, including obligate and facultative behaviors map
into habitat values and how the valuation of these ecological processes can inform decisions regarding coastal development
(habitat clearing). Our stylized modeling framework also provides a clear and concise road map for researchers interested
in understanding how to make the link between ecosystem function, ecosystem service, and conservation policy decisions. Our
findings also highlight the importance of additional ecological research into how species utilize habitats and that this research
is not just important for ecological science, but it can and will influence ecosystem service values that, in turn, will impact
coastal land-use decisions. While refining valuation methods is not necessarily going to lead to more rational coastal land-use
decisions, it will improve our understanding on the ecological–economic mechanisms that contribute to the value of our natural
capital assets.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
17.
18.
John L. Bengtson Lisa M. Hiruki-Raring Michael A. Simpkins Peter L. Boveng 《Polar Biology》2005,28(11):833-845
Aerial surveys were conducted in 1999 and 2000 to estimate the densities of ringed (Phoca hispida) and bearded (Erignathus barbatus) seals in the eastern Chukchi Sea. Survey lines were focused mainly on the coastal zone within 37 km of the shoreline, with
additional lines flown 148–185 km offshore to assess how densities of seals changed as a function of distance from shore.
Satellite-linked time-depth recorders were attached to ringed seals in both years to evaluate the time spent basking on the
ice surface. Haulout patterns indicated that ringed seals transitioned to basking behavior in late May and early June, and
that the largest proportion of seals (60–68%) was hauled out between 0830 and 1530 local solar time. Ringed seals were relatively
common in nearshore fast ice and pack ice, with lower densities in offshore pack ice. The average density of ringed seals
was 1.91 seals km−2 in 1999 (range 0.37–16.32) and 1.62 seals km−2 in 2000 (range 0.42–19.4), with the highest densities of ringed seals found in coastal waters south of Kivalina and near
Kotzebue Sound. The estimated abundance of ringed seals for the entire study area was similar in 1999 (252,488 seals, SE=47,204)
and 2000 (208,857 seals, SE=25,502). Bearded seals were generally more common in offshore pack ice, with the exception of
high bearded seal numbers observed near the shore south of Kivalina. Bearded seal densities were not adjusted for haulout
behavior, and therefore, abundance was not estimated. Unadjusted average bearded seal density was 0.07 seals km−2 in 1999 (range 0.011–0.393) and 0.14 seals km−2 in 2000 (range 0.009–0.652). Levels of primary productivity, benthic biomass, and fast ice distribution may influence the
distributions of ringed and bearded seals in the Chukchi Sea. Information on movement and haulout behavior of ringed and bearded
seals would be very useful for designing future surveys. 相似文献
19.
Are local plants the best for ecosystem restoration? It depends on how you analyze the data 下载免费PDF全文
Anna Bucharova Walter Durka Norbert Hölzel Johannes Kollmann Stefan Michalski Oliver Bossdorf 《Ecology and evolution》2017,7(24):10683-10689
One of the key questions in ecosystem restoration is the choice of the seed material for restoring plant communities. The most common strategy is to use local seed sources, based on the argument that many plants are locally adapted and thus local seed sources should provide the best restoration success. However, the evidence for local adaptation is inconsistent, and some of these inconsistencies may be due to different experimental approaches that have been used to test for local adaptation. We illustrate how conclusions about local adaptation depend on the experimental design and in particular on the method of data analysis. We used data from a multispecies reciprocal transplant experiment and analyzed them in three different ways: (1) comparing local vs. foreign plants within species and sites, corresponding to tests of the “local is best” paradigm in ecological restoration, (2) comparing sympatric vs. allopatric populations across sites but within species, and (3) comparing sympatric and allopatric populations across multiple species. These approaches reflect different experimental designs: While a local vs. foreign comparison can be done even in small experiments with a single species and site, the other two approaches require a reciprocal transplant experiment with one or multiple species, respectively. The three different analyses led to contrasting results. While the local/foreign approach indicated lack of local adaptation or even maladaptation, the more general sympatric/allopatric approach rather suggested local adaptation, and the most general cross‐species sympatric/allopatric test provided significant evidence for local adaptation. The analyses demonstrate how the design of experiments and methods of data analysis impact conclusions on the presence or absence of local adaptation. While small‐scale, single‐species experiments may be useful for identifying the appropriate seed material for a specific restoration project, general patterns can only be detected in reciprocal transplant experiments with multiple species and sites. 相似文献
20.
This paper addresses the use of impact indicators with respect to climate change in the 2007–2013 Rural Development Programme (RDP) of the European Union, with particular reference to the Scotland Rural Development Programme (SRDP). It concludes that the policy context has highlighted the need for the rural land use sector to respond to climate change but that the associated Common Monitoring and Evaluation Framework (CMEF) did not develop suitable indicators to assess the impact of SDRP measures on GHG emission mitigation. It suggests improved impact indicators based on the relationship between rural land use and greenhouse gas (GHG) emissions: first, an indicator based on net GHG emissions per holding; and a second based on net GHG emissions per unit volume of output. The paper points out the challenges in measuring land-based emissions accurately. It further proposes screening of RDP measures to ensure that climate change mitigation impacts are properly appraised. It is recognised that climate change policy in relation to rural land use is still at an early stage of development but greater sophistication of policy instrument design and evaluation will be required if the RDP is to contribute significantly to climate change policy objectives. 相似文献