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691.
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Altitudinal and horizontal shifts of the upper boundaries of open and closed forests in the Polar Urals in the 20th century 总被引:2,自引:0,他引:2
S. G. Shiyatov M. M. Terent’ev V. V. Fomin N. E. Zimmermann 《Russian Journal of Ecology》2007,38(4):223-227
In the Polar Urals (the Rai-Iz massif and Mounts Tchernaya and Malaya Tchernaya), altitudinal and horizontal shifts of the upper boundary of open and closed larch forests in the 20th century have been studied. Spatiotemporal parameters of these shifts have been assessed with the aid of the ARC/INFO geographic information system (ESRI Inc., United States), using our original large-scale geobotanical maps showing the distribution of different types of forest-tundra communities in the early 1910s and 2000s. The results show that tree vegetation has been actively expanding to higher elevations over the past 90 years. On average, the upper boundaries of open and closed forests have ascended 26 and 35 m and shifted horizontally 290 and 520 m, respectively. These shifts have been conditioned by climate warming and increasing humidity observed since the 1920s. 相似文献
695.
The results of a discrete choice experiment (DCE) as a part of a survey among the urban riverbank residents on the Red River in Winnipeg, Manitoba, Canada, indicated that the risk of over-dike flooding, set at 2ft above the 1997 flood water level, was a significant determinant of both voluntary and mandatory evacuation, compared to those set at the 1996 or 1997 levels. Mandatory evacuation was more preferred over voluntary evacuation when the likelihood of flooding was at its most severe, and the opposite relationship was the case when the likelihood was low. The notification time for evacuation, suggested as 1, 2, and 4 days, proved to be an insignificant attribute, whereas the respondents indicated significant preference for full flood compensation over an offer of either 80% or 90% flood relief, irrespective of the alternatives of voluntary or mandatory evacuation. 相似文献
696.
Nicole Geberzahn Wolfgang Goymann Christina Muck Carel ten Cate 《Behavioral ecology and sociobiology》2009,64(2):193-204
Birdsong serves to attract mates and to deter territorial rivals. Even though song is not restricted to males, this dual function
has almost exclusively been demonstrated for male song. To test the generality of hypotheses on birdsong, we investigated
female song in the sex-role reversed, classically polyandrous African black coucal (Centropus grillii) in the context of female–female competition. We compared spontaneously vocalizing females with females vocally responding
to a playback simulating a conspecific intruder. Females changed vocal parameters in response to playbacks: They lowered the
pitch of their vocalizations and enhanced the duration of song elements when being challenged. Also, the composition of the
vocalizations was altered. There was no significant correlation between pitch and body size parameters in spontaneous song,
but there was for response songs, with larger females having a lower pitch. These changes in vocal properties suggest that
the vocalizations are important for mutual assessment of competitive abilities in females. Our findings confirm the general
role of intrasexual competition in vocal communication of birds. 相似文献
697.
Wolfgang H. Höll 《Environmental geochemistry and health》2010,32(4):287-290
In this review paper, various methods for arsenic removal from water have been described by explaining the related mechanisms
of each methods. Advantages and drawbacks were discussed. Membrane methods were suggested as reliable methods for elimination
of arsenic from water in addition to other conventional separation methods. 相似文献
698.
Bernard D. Roitberg Karen Zimmermann Thomas S. Hoffmeister 《Behavioral ecology and sociobiology》2010,64(4):627-637
Despite the multitude of work on patch time allocation and the huge number of studies on patch choice in the face of danger,
the patch leaving response of foragers perceiving cues of danger has received relatively little attention. We investigated
the response of parasitoid insects to cues of danger both theoretically and experimentally. Using stochastic dynamic theory,
we demonstrate that patch-leaving responses in response to the detection of danger should be seen as a dynamic decision that
depends upon reproductive options on the current host patch and on alternative patches that might be found after leaving the
current patch. Our theory predicts a sigmoidal response curve of parasitoids, where they should accept the danger and stay
on the patch when patch quality is high and should increasingly avoid the risk and emigrate from the patch with decreasing
patch quality and decreasing costs of traveling to an alternative host patch. Experiments with females of the drosophilid
parasitoid Asobara tabida that were exposed to a puff of formic acid (a danger cue) at different times through their patch exploitation confirmed the
theoretical predictions (i.e., a sigmoid response curve); however, the predicted curve was significantly steeper than observed.
We discuss the impact of dynamic patch-exit decisions of individual foragers on population and community dynamics. 相似文献
699.
Nuclear magnetic resonance imaging (NMRI) methods for visualization of fluid flow and transport in porous media are reviewed in this paper. They are illustrated with experiments showing applications of velocity imaging, NMRI measurements of multiphase flow, and NMRI measurements of density flow. The latter two are compared with numerical simulations. The examples show the capacity of NMRI to give structural information both of the medium and the fluid distributions as well as their temporal development. The resulting data can be used in a black box-white box comparison and as benchmarks for numerical models. 相似文献
700.
Removal efficiencies on xenobiotics from polluted water in a twin-shaped constructed wetland consisting of a vertical flow chamber with the crop plant Colocasia esculenta L. Schott and a reverse vertical flow one with Ischaemum aristatum var. glaucum Honda, were assessed by chemical analysis and bioassays. After a four-month period of application, removal efficiencies of the applied pesticides parathion and omethoate were 100% with no detectable parathion and omethoate in the effluent. For the applied herbicides, the decontamination was less efficient with removal efficiencies of 36% and 0% for 4-chloro-2-methyl-phenoxyacetic acid and dicamba, respectively. As shown by toxicity assay with duckweed Lemna minor L., growth retardation may occur if the water treated for herbicide removal is used in irrigation of sensitive cultivars in agriculture or horticulture. In contrast to I. aristatum var. glaucum Honda, the crop C. esculenta L. Schott has a high yield in biomass production as a valuable source of renewable energy. 相似文献