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81.
PHILLIP CASSEY TIM M. BLACKBURN RICHARD P. DUNCAN STEVEN L. CHOWN 《Austral ecology》2005,30(4):475-480
Abstract Biological invasions have commonly occurred, and to a lesser degree continue to do so, without human assistance. It is, however, a combination of the rate and magnitude, as well as the distances and agency involved, that separates human‐driven invasion processes from self‐perpetuated colonization events. Exotic species are a pervasive and major component of human‐induced global change. Decisions to manage invasive species will require judgements to be communicated from scientists to policy makers, because scientists may often be the only ones in the position to make them. 相似文献
82.
Hydraulic microhabitats and the distribution of macroinvertebrate assemblages in riffles 总被引:6,自引:0,他引:6
1. The influence of hydraulic conditions on the spatial distribution of macroinvertebrate assemblages was investigated in three riffles in a perennial Australian river. 2. Velocity, depth and variability of substrate roughness were measured at each of 56 macroinvertebrate sampling locations. Complex hydraulic variables (roughness Reynolds number, shear velocity, Froude number) were calculated from combinations of two or three of the directly measured variables. The biological significance of directly measured and complex hydraulic variables was determined by a combination of univariate and multivariate statistical procedures. 3. Macroinvertebrate abundance, number of taxa and community composition were significantly different between the identified roughness Reynolds number, Froude number, velocity and shear velocity microhabitats throughout the studied riffles. 4. Regression analysis showed macroinvertebrate abundance and number of taxa were negatively related to roughness Reynolds number, shear velocity, velocity and Froude number. Depth was negatively related to abundance. In general, the majority of the macroinvertebrate community preferred the areas of riffles with the lowest near‐bed turbulence. 5. Roughness Reynolds number explained more of the spatial variation in invertebrate abundance, number of taxa and community composition than the other hydraulic variables, either directly measured or calculated. Of the directly measured variables, velocity had the greatest explanatory power, which was marginally less than roughness Reynolds number and shear velocity. 6. This study demonstrated that small‐scale differences in hydraulic conditions created by combinations of velocity, depth and substrate roughness have an important role in the spatial distribution of macroinvertebrate assemblages in riffle habitats. 相似文献
83.
TIM C. G. RICH DAVID MARDON IAN CURTIS STAN J. HEYWARD VERA G. HEYWARD DOUGLAS R. MCKEAN TONY HALL STACEY HARRIS ANTONY O'ROURKE ROBYN S. COWAN MICHAEL F. FAY fls 《Botanical journal of the Linnean Society. Linnean Society of London》2005,147(2):203-211
Sagina boydii F. B. White (Caryophyllaceae), Boyd's pearlwort, is an enigmatic taxon of unknown geographical origin which is only known in cultivation and is of uncertain taxonomic status. Morphological, cytological and geographical evidence suggests that it is most similar to S. procumbens L. and S. saginoides (L.) H. Karst., but it differs in its compact growth form. Genetically, AFLP analysis shows that it can be included as part of the variation in S. procumbens . In cultivation, it will grow true from seed. Other compact growth forms occur in S. procumbens but do not grow true from seed. As S. boydii is part of the variation in S. procumbens , is of uncertain geographical origin, is known only in cultivation, and grows true from seed, it is best treated as a new cultivar, Sagina procumbens 'Boydii'. A neotype and standard specimen is designated. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 147 , 203–211. 相似文献
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86.
TIM L. KING MICHAEL S. EACKLES ANNE P. HENDERSON CAROL I. BOCETTI DAVE CURRIE JOSEPH M. WUNDERLE 《Molecular ecology resources》2005,5(3):569-571
We document the isolation and characterization of 23 microsatellite DNA markers for the endangered Kirtland's warbler (Dendroica kirtlandii), a Nearctic/Neotropical migrant passerine. This suite of markers revealed moderate to high levels of allelic diversity (averaging 7.7 alleles per locus) and heterozygosity (averaging 72%). Genotypic frequencies at 22 of 23 (95%) markers conformed to Hardy–Weinberg equilibrium expectations, and no linkage disequilibrium was observed in blood samples taken from 14 warblers found on the wintering grounds in the Bahamas archipelago. Multilocus genotypes resulting from this suite of markers should reduce the amount of resources required for initiating new genetic studies assessing breeding structure, parentage, demographics, and individual‐level ecological interactions for D. kirtlandii. 相似文献
87.
TIM J. CLOUGH KELLY ADDY† DOROTHY Q. KELLOGG† BARBARA L. NOWICKI† ARTHUR J. GOLD† PETER M. GROFFMAN‡ 《Global Change Biology》2007,13(7):1528-1537
Few data are available to validate the Intergovernmental Panel on Climate Change's (IPCC) emission factors for indirect emissions of nitrous oxide (N2O). In particular the N2O emissions resulting from nitrogen leaching and the associated groundwater and surface drainage (EF5-g) are particularly poorly characterized. In situ push–pull methods have been used to identify the fate of NO3− in the groundwater. In this study, we adapted a previously published in situ denitrification push–pull method to examine the fate of 15N2O introduced into the subsoil–groundwater matrix. Enriched 15N2O was manufactured, added to groundwater via a closed system in the laboratory, and then introduced into the groundwater–subsoil matrix in an upland-marsh transition zone of a salt marsh and a forested alluvial riparian zone. Conservative tracers (SF6 and Br−) and 15N2O were injected into the groundwater and left for 1–4 h after which the groundwater was sampled. Added 15N2O behaved in a conservative manner at one site while the other site showed variability with some injections showing significant consumption (3–8 μg N2O-15N kg−1 soil day−1) of 15N2O. Our results show that the fate and dynamics of N2O in groundwater are complex and variable and that these dynamics should be considered in the development of improved IPCC inventory calculations. 相似文献
88.
How landscape structure, land-use intensity and habitat diversity affect components of total arthropod diversity in agricultural landscapes 总被引:13,自引:1,他引:13
FREDERIK HENDRICKX† JEAN-PIERRE MAELFAIT† WALTER VAN WINGERDEN‡ OLIVER SCHWEIGER§ MARJAN SPEELMANS† STÉPHANIE AVIRON¶ ISABEL AUGENSTEIN REGULA BILLETER†† DEBRA BAILEY¶ ROMAN BUKACEK‡‡ FRANÇOISE BUREL§§ TIM DIEKÖTTER†† JOLANDA DIRKSEN‡ FELIX HERZOG¶ JAAN LIIRA¶¶ MARTINA ROUBALOVA VIKI VANDOMME ROB BUGTER‡ 《Journal of Applied Ecology》2007,44(2):340-351
89.
ANNETTE MENZEL TIM H. SPARKS NICOLE ESTRELLA ELISABETH KOCH ANTO AASA REIN AHAS KERSTIN ALM‐KÜBLER PETER BISSOLLI OL'GA BRASLAVSK AGRITA BRIEDE FRANK M. CHMIELEWSKI ZALIKA CREPINSEK YANNICK CURNEL SL
G DAHL CLAUDIO DEFILA ALISON DONNELLY YOLANDA FILELLA KATARZYNA JATCZAK FINN MGE ANTONIO MESTRE
YVIND NORDLI JOSEP PE
UELAS PENTTI PIRINEN VIERA REMIOV HELFRIED SCHEIFINGER MARTIN STRIZ ANDREJA SUSNIK ARNOLD J. H. VAN VLIET FRANS‐EMIL WIELGOLASKI SUSANNE ZACH ANA ZUST 《Global Change Biology》2006,12(10):1969-1976
Global climate change impacts can already be tracked in many physical and biological systems; in particular, terrestrial ecosystems provide a consistent picture of observed changes. One of the preferred indicators is phenology, the science of natural recurring events, as their recorded dates provide a high-temporal resolution of ongoing changes. Thus, numerous analyses have demonstrated an earlier onset of spring events for mid and higher latitudes and a lengthening of the growing season. However, published single-site or single-species studies are particularly open to suspicion of being biased towards predominantly reporting climate change-induced impacts. No comprehensive study or meta-analysis has so far examined the possible lack of evidence for changes or shifts at sites where no temperature change is observed. We used an enormous systematic phenological network data set of more than 125 000 observational series of 542 plant and 19 animal species in 21 European countries (1971–2000). Our results showed that 78% of all leafing, flowering and fruiting records advanced (30% significantly) and only 3% were significantly delayed, whereas the signal of leaf colouring/fall is ambiguous. We conclude that previously published results of phenological changes were not biased by reporting or publication predisposition: the average advance of spring/summer was 2.5 days decade−1 in Europe. Our analysis of 254 mean national time series undoubtedly demonstrates that species' phenology is responsive to temperature of the preceding months (mean advance of spring/summer by 2.5 days°C−1 , delay of leaf colouring and fall by 1.0 day°C−1 ). The pattern of observed change in spring efficiently matches measured national warming across 19 European countries (correlation coefficient r =−0.69, P <0.001). 相似文献
90.
TIM R. MOORE PETER M. LAFLEUR† DIANE M. I. POON BENJAMIN W. HEUMANN J. W. SEAQUIST NIGEL T. ROULET 《Global Change Biology》2006,12(12):2323-2335
In northern ecosystems, the onset and growth of spring photosynthesis may have an important influence on the annual carbon (C) budget, yet the controls have not been clearly identified, especially for peatlands. We used a 5‐year set of daily carbon dioxide (CO2) exchange measurements derived from an eddy covariance tower located at Mer Bleue, an ombrotrophic bog near Ottawa, Canada, from March to May [day‐of‐year (DOY) 60–150], 1999–2003. We used half‐hourly measured net ecosystem exchange minus modelled ecosystem respiration to estimate daily photosynthesis, as gross ecosystem production (GEP). The onset of GEP in each year was closely related to the thinning and disappearance of the snow cover, occurring between DOY 86 and 101. GEP increased during the spring, reaching 10‐day average values of between 5 and 9 g CO2 m?2 day?1 by the end of May. This increase was initially associated with moss activity (Sphagnum and Polytrichum), followed by the evergreen shrubs. Peat temperatures in the rooting zone (10–20 cm depth) and increases in shrub leaf nitrogen and chlorophyll a concentrations contributed to this rapid increase in GEP. Examination of moderate‐resolution imaging spectroradiometer (MODIS) images over several years revealed that the temporal resolution (16‐day composites) was inadequate to capture the onset of GEP but estimates of gross primary productivity and photosynthesis from MODIS 8‐day composites for the most part followed the pattern and magnitude of CO2 exchange observed at the tower. 相似文献