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61.
62.
Henrik Hedenås Bengt Å. Carlsson Urban Emanuelsson Alistair D. Headley Christer Jonasson Brita M. Svensson Terry V. Callaghan 《Ambio》2012,41(3):187-196
Plant species distributions are expected to shift and diversity is expected to decline as a result of global climate change, particularly in the Arctic where climate warming is amplified. We have recorded the changes in richness and abundance of vascular plants at Abisko, sub-Arctic Sweden, by re-sampling five studies consisting of seven datasets; one in the mountain birch forest and six at open sites. The oldest study was initiated in 1977–1979 and the latest in 1992. Total species number increased at all sites except for the birch forest site where richness decreased. We found no general pattern in how composition of vascular plants has changed over time. Three species, Calamagrostis lapponica, Carex vaginata and Salix reticulata, showed an overall increase in cover/frequency, while two Equisetum taxa decreased. Instead, we showed that the magnitude and direction of changes in species richness and composition differ among sites. 相似文献
63.
This article gives an overview of the studies on the environment surrounding the Abisko Scientific Research Station in Swedish Lapland. The long-term monitoring of the Station on processes related to the climate, and to the physical, biotic, and chemical environmental conditions is particularly addressed. Some variables are recorded since more than 100 years. The obtained data in combination with results from short-term studies and manipulation experiments are important to understand past and future conditions of the ecosystems. This has practical applications for the planning of tourism, transports, reindeer herding, and for societal purposes. 相似文献
64.
65.
Camilla Andersson Robert Bergström Christer Johansson 《Atmospheric environment (Oxford, England : 1994)》2009,43(22-23):3614-3620
This paper presents the contribution to population exposure (PE) of regional background fine primary (PPM2.5) and secondary inorganic (SIA) particulate matter and its impact on mortality in Europe during 1997–2003 calculated with a chemistry transport model. Contributions to concentrations and PE due to emissions from shipping, Western (WEU), Eastern (EEU), and Northern Europe are compared.WEU contributes about 40% to both PPM2.5 and SIA concentrations, whereas the EEU contribution to PPM2.5 is much higher (43% of total PPM2.5) than to SIA (29% of total SIA). The population weighted average concentration (PWC) of PPM2.5 is a factor of 2.3 higher than average (non-weighted) concentrations, whereas for SIA the PWC is only a factor 1.6 higher. This is due to PPM2.5 concentrations having larger gradients and being relatively high over densely populated areas, whereas SIA is formed outside populated areas. WEU emissions contribute relatively more than EEU to PWC and mortality due to both PPM2.5 and SIA in Europe.The number of premature deaths in Europe is estimated to 301 000 per year due to PPM2.5 exposure and 245 000 due to SIA, despite 3.3 times higher average SIA concentrations. This is due to population weighting and assumed (and uncertain) higher relative risk of mortality for PPM2.5 components (2.8 times higher RR for PPM2.5). This study indicates that it might be more efficient, for the health of the European population, to decrease primary PM emissions (especially in WEU) than to decrease precursors of SIA, but more knowledge on the toxicity of different PM constituents is needed before firm conclusions can be drawn. 相似文献
66.
Durrant CJ Stevens JR Hogstrand C Bury NR 《Environmental pollution (Barking, Essex : 1987)》2011,159(12):3595-3603
The River Hayle in south-west England is impacted with metals and can be divided into three regions depending on the copper and zinc concentrations: a low-metal upper section; a highly-contaminated middle section and a moderately contaminated lower section. Hayle river water is toxic to metal-naive brown trout, but brown trout are found in the upper and lower regions. The study aimed to evaluate the population genetic structure of River Hayle brown trout and to determine if the highly-contaminated section acts as a chemical barrier to migration. Population genetic analysis indicated that metals were not a barrier to gene flow within the river, but there was a high level of differentiation observed between fish sampled at two sites in the upper region, despite being separated by only 1 km. The metal tolerance trait exhibited by this brown trout population may represent an important component of the species genetic diversity in this region. 相似文献
67.
Between 1850 and 1970, rivers throughout Sweden were channelized to facilitate timber floating. Floatway structures were installed
to streamline banks and disconnect flow to secondary channels, resulting in simplified channel morphologies and more homogenous
flow regimes. In recent years, local authorities have begun to restore channelized rivers. In this study, we examined the
effects of restoration on riparian plant communities at previously disconnected secondary channels of the Pite River. We detected
no increase in riparian diversity at restored sites relative to unrestored (i.e., disconnected) sites, but we did observe
significant differences in species composition of both vascular plant and bryophyte communities. Disconnected sites featured
greater zonation, with mesic-hydric floodplain species represented in plots closest to the stream and mesic-xeric upland species
represented in plots farthest from the stream. In contrast, restored sites were most strongly represented by upland species
at all distances relative to the stream. These patterns likely result from the increased water levels in reconnected channels
where, prior to restoration, upland plants had expanded toward the stream. Nonetheless, the restored fluvial regime has not
brought about the development of characteristic flood-adapted plant communities, probably due to the short time interval (ca.
5 years) since restoration. Previous studies have demonstrated relatively quick responses to similar restoration in single-channel
tributaries, but secondary channels may respond differently due to the more buffered hydrologic regimes typically seen in
anabranching systems. These findings illustrate how restoration outcomes can vary according to hydrologic, climatic and ecological
factors, reinforcing the need for site-specific restoration strategies. 相似文献
68.
Christer Hellner Richard A. Keller 《Journal of the Air & Waste Management Association (1995)》2013,63(12):959-963
The body of information presented in this paper is directed to photochemists and air pollution scientists interested in species which result from the interaction of SO2 and light. When SO2 at low pressures is subjected to an intense photolysis flash, the characteristic, very structured SO2absorption spectrum disappears immediately after the flash and is replaced by a continuous absorption. The continuous absorption gradually decays and the normal SO2 absorption spectrum returns. The initial absorbance of the continuous absorption is proportional to the square of the SO2 pressure and the square of the flash irradiance. From these facts we propose the formation of a metastable dimer of SO2 formed by the collision of two excited molecules. Some properties of this dimer are: natural lifetime = 2 sec; energy above separated monomers = 4 kcal; lifetime at atmospheric pressure = 1 sec (quenching coefficients with several foreign gases = 10-20 cm3/sec molecule); absorption of ultraviolet light results in photode-composition of the dimer into monomeric SO2. The long lifetime of this species and its low quenching cross section may make it an important intermediate in photochemical reactions of SO2. The relatively low excitation energy of the metastable species indicates it may also be an intermediate in thermally excited reactions and perhaps an important component of smoke stack effluent. 相似文献
69.
Jean-Michel Roberge Hjalmar Laudon Christer Björkman Thomas Ranius Camilla Sandström Adam Felton Anna Sténs Annika Nordin Anders Granström Fredrik Widemo Johan Bergh Johan Sonesson Jan Stenlid Tomas Lundmark 《Ambio》2016,45(2):109-123
The rotation length is a key component of even-aged forest management systems. Using Fennoscandian forestry as a case, we review the socio-ecological implications of modifying rotation lengths relative to current practice by evaluating effects on a range of ecosystem services and on biodiversity conservation. The effects of shortening rotations on provisioning services are expected to be mostly negative to neutral (e.g. production of wood, bilberries, reindeer forage), while those of extending rotations would be more varied. Shortening rotations may help limit damage by some of today’s major damaging agents (e.g. root rot, cambium-feeding insects), but may also increase other damage types (e.g. regeneration pests) and impede climate mitigation. Supporting (water, soil nutrients) and cultural (aesthetics, cultural heritage) ecosystem services would generally be affected negatively by shortened rotations and positively by extended rotations, as would most biodiversity indicators. Several effect modifiers, such as changes to thinning regimes, could alter these patterns. 相似文献
70.
Replacing monocultures with mixed-species stands: Ecosystem service implications of two production forest alternatives in Sweden 总被引:2,自引:0,他引:2
Adam Felton Urban Nilsson Johan Sonesson Annika M. Felton Jean-Michel Roberge Thomas Ranius Martin Ahlström Johan Bergh Christer Björkman Johanna Boberg Lars Drössler Nils Fahlvik Peichen Gong Emma Holmström E. Carina H. Keskitalo Maartje J. Klapwijk Hjalmar Laudon Tomas Lundmark Mats Niklasson Annika Nordin Maria Pettersson Jan Stenlid Anna Sténs Kristina Wallertz 《Ambio》2016,45(2):124-139
Whereas there is evidence that mixed-species approaches to production forestry in general can provide positive outcomes relative to monocultures, it is less clear to what extent multiple benefits can be derived from specific mixed-species alternatives. To provide such insights requires evaluations of an encompassing suite of ecosystem services, biodiversity, and forest management considerations provided by specific mixtures and monocultures within a region. Here, we conduct such an assessment in Sweden by contrasting even-aged Norway spruce (Picea abies)-dominated stands, with mixed-species stands of spruce and birch (Betula pendula or B. pubescens), or spruce and Scots pine (Pinus sylvestris). By synthesizing the available evidence, we identify positive outcomes from mixtures including increased biodiversity, water quality, esthetic and recreational values, as well as reduced stand vulnerability to pest and pathogen damage. However, some uncertainties and risks were projected to increase, highlighting the importance of conducting comprehensive interdisciplinary evaluations when assessing the pros and cons of mixtures. 相似文献