Identification of Landscape Elements Related to Local Declines of a Boreal Grey-sided Vole Population     

Frauke Ecke  Pernilla Christensen  Per Sandström  Birger Hörnfeldt 《Landscape Ecology》2006,21(4):485-497

Several studies indicate a long-term decline in numbers of different species of voles in northern Fennoscandia. In boreal Sweden, the long-term decline is most pronounced in the grey-sided vole (Clethrionomys rufocanus). Altered forest landscape structure has been suggested as a possible cause of the decline. However, habitat responses of grey-sided voles at the landscape scale have never been studied. We analyzed such responses of this species in lowland forests in Västerbotten, northern Sweden. Cumulated spring densities representing 22 local time series from 1980–1999 were obtained by a landscape sampling design and were related to the surrounding landscape structure of 2.5×2.5 km plots centred on each of the 22 1-ha trapping plots. In accordance with general knowledge on local habitat preferences of grey-sided voles, our study supported the importance of habitat variables such as boulder fields and old-growth pine forest at the landscape scale. Densities were negatively related to clear cuts. Habitat associations were primarily those of landscape structure related to habitat fragmentation, distance between habitat patches and patch interspersion rather than habitat patch type quantity. Local densities of the grey-sided vole were positively and exponentially correlated with spatial contiguity (measured with the fragmentation index) of old-growth pine forest, indicating critical forest fragmentation thresholds. Our results indicate that altered land use might be involved in the long-term decline of the grey-sided vole in managed forest areas of Fennoscandia. We propose two further approaches to reveal and test responses of this species to changes in landscape structure.  相似文献   

Urban forests as compensation measures for infrastructure development     

Erik Skrbck 《Urban Forestry & Urban Greening》2007,6(4):279-285

Sustainable development requires, among other things, that development projects not result in the degradation of natural resources for outdoor recreation. There has been a rapid increase in knowledge regarding the importance of the external environment to our health and well-being. Stress is reduced significantly when people are exposed to health-promoting nature and landscape values. Many people are actively choosing to reduce their stress. Doctors today prescribe outdoor walks in peaceful environments for the same purpose. A high level of traffic noise increases stress. This paper discusses the application of silent values in an infrastructure development project, the extension of Sturup Airport, east of Malmö, Sweden and Copenhagen, Denmark. Through estimating the change in noise resulting from the development, it is possible to integrate mitigating and compensating measures in the planning process discussions. Such measures can be negotiated as conditions for authorization of the project. The airport is situated in an area rich in nature values for recreation. The airport expansion will mean both new noise impacting "silent" areas and increasing noise levels in already noise-affected areas. In this study, we have taken a positive stand on the silent areas, mostly agriculture land, where compensation measures could be taken, thus balancing the loss of silent nature values for recreation. Silent areas that will not be affected are suitable and feassible for compensation measures thus can be called compensation areas. In this way the development of new recreational areas, preferably designed as urban forests, are critical preconditions for the negotiations for the airport extension. The conclusion is that urban forest investments for health and well-being can be an important part of strategic decisions in spatial planning. As preconditions for a permit, the development and financing of new urban forests and green areas can be part of the total development plan. This is an issue of global interest, as many countries are in a process of rapid urbanization, and urban greening and urban forestry have an important role to play in the process of promoting quality of life and improving environmental quality.  相似文献   

Suppression of Rice Blast by Preinoculation with Avirulent Pyricularia oryzae and the Nonrice Pathogen Bipolaris sorokiniana     

Manandhar HK  Lyngs Jørgensen HJ  Mathur SB  Smedegaard-Petersen V 《Phytopathology》1998,88(7):735-739

ABSTRACT Avirulent isolates of Pyricularia oryzae and isolates of Bipolaris sorokiniana, a nonrice pathogen, were used to suppress rice blast caused by P. oryzae. In greenhouse experiments, both fungi substantially reduced leaf blast when applied 24 h or more before the pathogen. B. sorokiniana, but not avirulent isolates of P. oryzae, systemically reduced disease in leaf 5 when applied to whole plants at the four-leaf stage. In field experiments, both fungi were able to reduce neck blast significantly. No increase in grain yield was obtained by using avirulent isolates of P. oryzae, whereas five sprays with B. sorokiniana from seedling to heading stages increased the grain yield in two of three experiments conducted at two locations in Nepal. The significant increase in yield was observed under high inoculum pressure of P. oryzae. Induced resistance is suggested to be involved in the suppression of disease.  相似文献   

Valerenic acid derivatives and valepotriates among individuals, varieties and species of Valeriana.     

X Q Gao  L Bj?rk 《Fitoterapia》2000,71(1):19-24

To investigate the variations of active compounds between species, varieties and individuals of Valeriana cultivated under the same environmental condition, the contents of valerenic acid derivatives and valepotriates in rhizomes and roots of different plant material were analysed by a HPLC method. Different species or varieties of Valeriana yielded 11.65-0.15 mg/g of valerenic acid derivatives, and 1.81-0.03 mg/g of valepotriates. The variation between individuals of one commercial cultivar of V. officinalis ranged from 12.34 to 3.01 mg/g of valerenic acid derivatives, and 3.67-0.92 mg/g of valepotriates. Individuals from self-pollinated mother plants, normal or regenerated, showed a similar variation. The variation of micropropagated plants was much less than the seed propagated plants. The ratio of mean values between valerenic acid derivatives and valepotriates was similar in all groups (3 < ratio < 8) except one group of micropropagated plants (ratio > 20).  相似文献   

Einfluss assoziativer rhizosphärenbakterien auf die äHrstoffaufnahme und den Ertrag von Mais     

Gisela Höflich  Erik Tappe  Günter Kühn  Wolfgang Wiehe 《Archives of Agronomy and Soil Science》2013,59(4):323-333

In mehrjährigen Feldversuchen (1990–1995) in Nordostdeutschland wurde der Einfluß selektierter assoziativer Rhizosphärenbakterien auf den Ertrag und die Nährstoffaufnahme bei Mais untersucht.

Der Trockenmasse‐ und Kolbenertrag zur Siloreife bzw. der Samenertrag wurde durch die Bakterienstämme Pseudomonas fluorescens (PsIA12), Agrobacterium rhizogenes (A1A4), Rhizobium trifolii (R39) und z.T. durch Stenotrophomonas maltophilia (PsIB2) in den Jahren 1990 bis 1995 auf lehmigen Sandböden wiederholt signifikant, auf sandigem Lehm zum Teil signifikant erhöht. Maissorten können unterschiedlich auf die Bakterieninokulation reagieren. Die Bakterien stimulierten insbesondere bei Jungpflanzen die Wurzelentwicklung und die Nährstoffaufnahme (N, P, K) aus dem Boden. Sie bildeten Phytohormone (Auxine und z.T. Cytokinine) und überlebten, auch unter Feldbedingungen, im Rhizosphärenraum von Mais während der gesamten Vegetation.  相似文献   

Effects of grazing strategy on limiting nitrate leaching in grazed grass‐clover pastures on coarse sandy soil     

E. M. Hansen  J. Eriksen  K. Søegaard  K. Kristensen 《Soil Use and Management》2012,28(4):478-487

Urinations of ruminants on grazed pastures increase the risk of nitrate leaching. The study investigated the effect of reducing the length of the grazing season on nitrate leaching from a coarse sandy, irrigated soil during 2006–2007 and 2007–2008. In both years, precipitation was above the long‐term mean. The experiment was initiated in a 4‐yr‐old grass‐clover sward in south Denmark. Three treatments were as follows grazing only (G), spring cut followed by grazing (CG) and both spring and autumn cuts with summer grazing (CGC). Nitrate leaching was calculated by extracting water isolates from 80 cm depth using ceramic suction cups. Because of considerable variation in measured nitrate concentrations, the 32 installed suction cups per treatment were insufficient to reveal differences between treatments. However, weighted nitrate leaching estimations for G, CG and CGC showed estimated mean nitrate N concentrations of 23, 19 and 13 mg/L for an estimated proportion area occupied by urine patches of 0.33, 0.26 and 0.16, respectively. Thus, N concentrations in G and CG exceeded the EU limit of 11.3 mg N/L. Under the prevailing conditions, the time of urination did not appear important. The estimated background leaching calculated from suction cups presumably not situated under urine patches resulted in mean nitrate N concentrations of 2.6 mg/L.  相似文献   

Studies on uptake and intracellular processing of infectious pancreatic necrosis virus by Atlantic cod scavenger endothelial cells     

Martin-Armas M  Sommer AI  Smedsrød B 《Journal of fish diseases》2007,30(11):701-710

Previous work in our group has identified the scavenger endothelial cells (SECs) of heart endocardium in cod, Gadus morhua L., as the major site for elimination of both physiological and foreign macromolecular waste from the circulation. The present study was undertaken to establish the role of cod SECs in the clearance of virus. We focused on infectious pancreatic necrosis virus (IPNV) as it is a well-known virus with a broad host range, and causes significant economic losses in the salmon industry. Our results showed that cod SEC cultures infected by the IPNV produce high titres of new virus. Ligand-receptor inhibition experiments suggested that the virus did not enter the cells through any of the major endocytosis receptors of cod SECs. Yet, the infection lowered the capacity of the cells to endocytose ligands via the scavenger receptor. Inhibitors of receptor recycling and vesicle acidification did not affect virus infectivity. The finding that SEC cultures prepared from 25% of the cod produced high titres of IPNV without being infected in the laboratory, suggests that SECs of cod may serve as reservoirs for IPNV in persistently infected cod.  相似文献   

Identification of Francisella sp. from Atlantic salmon, Salmo salar L., in Chile     

Birkbeck TH  Bordevik M  Frøystad MK  Baklien A 《Journal of fish diseases》2007,30(8):505-507

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Microsomal Drug Oxidation: Function,Induction, And Inhibition Of The Cytochrome P450-System     

Erik Dybing 《Acta veterinaria Scandinavica》1973,14(1):11

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Announcement     

Jens Havskov  S?ren Alexandersen  Poul Astrup  Knud Erik Christensen  Torben Mikkelsen  et al. 《Tropical animal health and production》1990,22(1):62-43

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