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81.
Habitat corridors, a common management strategy for increasing connectivity in fragmented landscapes, have experimentally validated positive influences on species movement and diversity. However, long-standing concerns that corridors could negatively impact native species by spreading antagonists, such as disease, remain largely untested. Using a large-scale, replicated experiment, we evaluated whether corridors increase the incidence of plant parasites. We found that corridor impacts varied with parasite dispersal mode. Connectivity provided by corridors increased incidence of biotically dispersed parasites (galls on Solidago odora) but not of abiotically dispersed parasites (foliar fungi on S. odora and three Lespedeza spp.). Both biotically and abiotically dispersed parasites responded to edge effects, but the direction of responses varied across species. Although our results require additional tests for generality to other species and landscapes, they suggest that, when establishing conservation corridors, managers should focus on mitigating two potential negative effects: the indirect effects of narrow corridors in creating edges and direct effects of corridors in enhancing connectivity of biotically dispersed parasites. 相似文献
82.
Duester L Prasse C Vogel JV Vink JP Schaumann GE 《Journal of environmental monitoring : JEM》2011,13(5):1204-1211
The pore water transport of antimony and titanium, applied as nanoparticles (NPs), was studied by spiking stable suspensions of two different nanomaterials on the surface of an undisturbed floodplain soil. For preparation of stable dispersions, two different strategies were followed. (i) Comparable to those used in industrial applications: titanium dioxide nanoparticles, with an average diameter of 99 nm, were prepared by high-energy ball milling in water, whereas for (ii) antimony trioxide (Sb(2)O(3); average diameter 121 nm) a dispersing agent (sodium salt of poly[(naphthaleneformaldehyde)sulfonate] (pNFS) in water) was used. The upper 17 cm of a floodplain soil (river Rhine, Germany) was sampled using the minimally invasive sediment or fauna incubation experiment (SOFIE? two compartment cell; 3 l volume each), which preserved the pore system of the soil. The cells were equipped with 450 and 100 nm filter probes at different depths providing a non-invasive sampling of the pore water. The pore water was sampled at different times (T = 0, 24, 48, 96 and 196 h) and analysed by inductively coupled plasma quadrupole mass spectrometry (ICP-QMS). Sb and Ti were transported via the pore water of the floodplain soil to a depth of 14 cm, corresponding to the maximum cell depth. The highest Sb concentration in the pore water was detected after 24 h at a depth of 5.5-8 cm. Although the spiked concentration was higher for Ti than for Sb, the total Ti concentration in the pore water of the spiked cell was lower. This indicates a stronger agglomeration of TiO(2) NPs or a more intensive interaction of Ti with the solid matrix and a faster transport of Sb towards deeper soil layers. The results show that metal(loid)s from metal oxide NPs are transported in the soil pore water and, hence, have the potential to act as the source of contamination of deeper soil layers after soil surface contamination. 相似文献
83.
Ellen Hollands Steffensen Lars Henning Pedersen Stina Lou Ida Vogel the Danish Fetal Medicine Study Group the Danish Cytogenetic Central Registry Study Group 《黑龙江环境通报》2023,43(1):51-61
Objective
To investigate if the Down syndrome phenotype differs according to the result of first-trimester combined screening (FTS).Method
We included all Down syndrome cases diagnosed by karyotype in pregnancy or after birth in Denmark during 2005–2018. We compared screen positive (odds ≥1:300) and screen negative (odds <1:300) cases as well as screen result subgroups with respect to anthropometrics, congenital malformations, childhood diseases, and hospitalization.Results
Absolute measures of fetal and birth anthropometrics were comparable between groups. A prenatal malformation diagnosis was more prevalent among screen positive than screen negative cases. Analyses suggested that this could reflect a detection bias. Cases with a screen result of 1:2–1:10 had a higher probability of being diagnosed with a malformation prenatally and with severe congenital heart disease (CHD) postnatally compared with a result of 1:11–1:300. Screen positive cases more often had non-severe CHD but less often a non-heart malformation compared with screen negative cases, while proportions of severe CHD were similar in these groups. Data on hospitalizations showed inconsistent results.Conclusion
The 1:300 screening threshold had limited or no value in predicting Down syndrome phenotype severity. In contrast, cases with a screen result between 1:2 and 1:10 may represent a more severe phenotype. 相似文献84.
Sander Bruun Trine Lund Hansen Thomas H. Christensen Jakob Magid Lars S. Jensen 《Environmental Modeling and Assessment》2006,11(3):251-265
Source separation, composting and anaerobic digestion, with associated land application, are increasingly being considered
as alternative waste management strategies to landfilling and incineration of municipal solid waste (MSW). Environmental life
cycle assessments are a useful tool in political decision-making about waste management strategies. However, due to the diversity
of processed organic MSW and the situations in which it can be applied, the environmental impacts of land application are
very hard to determine by experimental means. In the current study, we used the agroecosystem model Daisy to simulate a range
of different scenarios representing different geographical areas, farm and soil types under Danish conditions and legislation.
Generally, the application of processed organic MSW resulted in increased emissions compared with the corresponding standard
scenarios, but with large differences between scenarios. Emission coefficients for nitrogen leaching to the groundwater ranged
from 0.03 to 0.87, while those for nitrogen lost to surface waters through tile drains ranged from 0 to 0.30. Emission coefficients
for N2O formation ranged from 0.013 to 0.022 and for ammonia volatilization from 0.016 to 0.11. These estimates are within reasonable
range of observed values under similar conditions. Furthermore, a sensitivity analysis showed that the estimates were not
very sensitive to the mineralization dynamics of the processed organic MSW. The results show that agroecosystem models can
be powerful tools to estimate the environmental impacts of land application of processed MSW under different conditions. Despite
this, agroecosystem models have only been used to a very limited degree for this purpose. 相似文献
85.
Animals disperse in space through different movement behaviors, resulting in different displacement distances. This is often described with a displacement kernel where the long-distance dispersers are within the tail of the kernel. A displacement with a large proportion of long-distance dispersers may have impact on different aspects of spatial ecology such as invasion speed, population persistence, and distribution. It is, however, unclear whether the kurtosis of the kernel plays a major role since a fatter tail also influences the variance of the kernel. We modeled displacement in landscapes with different amounts and configurations of habitats and handled kurtosis and variance separately to study how these affected population distribution and transition time. We conclude that kurtosis is not important for any of these aspects of spatial ecology. The variance of the kernel, on the other hand, was of great importance to both population distribution and transition time. We argue that separating variance and kurtosis can cast new light on the way in which long-distance dispersers are important in ecological processes. Consequences for empirical studies are discussed. 相似文献
86.
Nyberg Lars Lundström Ulla Söderberg Ulf Danielsson Rolf van Hees Patrick 《Water, Air, & Soil Pollution: Focus》2001,1(1-2):241-263
In 1994, a large survey of soil chemistry was undertaken in thecounty of Värmland in central Sweden (Lundström et al., 1998).The southern part of the county was affected by soilacidification whereas there were no such indications in thenorthern part. To investigate the influence of soil chemistryon the trees at the specific sites, the survey was continued byan analysis of needle chemistry (Norway spruce) which wasundertaken at 150 of the 180 sites, and of tree growth at 65 ofthe 180 sites. Growth was expressed as a ratio between expectedgrowth, estimated with a national, empirical growth model, andthe growth observed in the field. In statistical analyses,using rank correlation, PCA and PLS, there were only weakindications of an influence of soil chemistry on needlechemistry and on tree growth. A moderate correlation betweennitrogen and sulphur in needles was found, which wasinterpreted as an effect of deposition and of processes in thetree canopy. No obvious regional pattern of the growth ratiowas found, in contrast to the clear pattern of soilacidification. The statistical analysis could not with anycertainty point out any of the soil chemistry variables asespecially important for the tree growth ratio. 相似文献
87.
Magne Friberg Namphung Vongvanich Anna-Karin Borg-Karlson Darrell J Kemp Sami Merilaita Christer Wiklund 《Behavioral ecology and sociobiology》2008,62(6):873-886
Animal courtship rituals are important for species recognition, and a variety of cues might be utilized to recognize conspecific
mates. In this paper, we investigate different species-recognition mechanisms between two sympatric butterfly sister species:
the wood white (Leptidea sinapis) and Real’s wood white (Leptidea reali). We show that males of both species frequently court heterospecific females both under laboratory and field conditions.
The long-lasting elaborate courtships impose energetic costs, since the second courtship of males that were introduced to
two subsequent conspecific females lasted on average only one fourth as long as the first courtship. In this paper, we demonstrate
that premating reproductive isolation is dependent on female unwillingness to accept heterospecific mates. We studied female
and male courtship behavior, chemical signaling, and the morphology of the sexually dimorphic antennae, one of the few male
traits visible for females during courtship. We found no differences in ultraviolet (UV) reflectance and only small differences
in longer wavelengths and brightness, significant between-species differences, but strongly overlapping distributions of male
L. sinapis and L. reali antennal morphology and chemical signals and minor differences in courtship behavior. The lack of clear-cut between-species
differences further explains the lack of male species recognition, and the overall similarity might have caused the long-lasting
elaborate courtships, if females need prolonged male courtships to distinguish between con- and heterospecific suitors. 相似文献
88.
Calculations of large-scale displacement distances were made to evaluate the combined effect of small-scale movement pattern of a Collembola, Protaphorura armata. The effect of presence of food and conspecific density on turning angle, step length and activity/motility was investigated. Calculations of net square displacement were made both by assuming correlated random walk (CRW) and by resampling data to account for correlation structures in movement patterns that violate the assumptions of CRW. 相似文献
89.
Christer Wiklund Adrian Vallin Magne Friberg Sven Jakobsson 《Behavioral ecology and sociobiology》2008,62(3):379-389
Insects that hibernate as adults have a life span of almost a whole year. Hence, they must have extraordinary adaptations
for adult survival. In this paper, we study winter survival in two butterflies that hibernate as adults and have multimodal
anti-predator defences—the peacock, Inachis io, which has intimidating eyespots that are effective against bird predation, and the small tortoiseshell, Aglais urticae, which does not have an effective secondary defence against birds. We assessed predation on wild butterflies hibernating
in the attic of an unheated house, as well as survival of individually marked butterflies placed by hand on different sites
in the attic. Our objectives were to assess (1) the number of butterflies that were killed during hibernation, (2) whether
survival differed between butterfly species, and (3) how predation was related to hibernation site and the identity of the
predator. There was a strong pulse of predation during the first 2 weeks of hibernation: 58% of A. urticae and 53% of I. io were killed during this period. Thereafter, predation decreased and butterfly survival equalled 98% during the final 16 weeks
of hibernation. There was no difference in survival between the two butterfly species, but predation was site-specific and
more pronounced under light conditions in locations accessible to a climbing rodent, such as the common yellow-necked mouse,
Apodemus flavicollis. We contend that small rodents are likely important predators on overwintering butterflies, both because rodents are active
throughout winter when butterflies are torpid and because they occur at similar sites. 相似文献
90.
Effects of grazer richness and composition on algal biomass in a closed and open marine system 总被引:1,自引:0,他引:1
Most natural local systems exchange organisms with a regional pool of species through migration and dispersal. Such metacommunity processes of interconnected multispecies assemblages are likely to affect local dynamics of both species and processes. We present results from an artificial marine outdoor rock pool system in which we investigated the factors of (1) local grazer richness and composition, and (2) connectivity of local patches to a regional species pool, and their effects on algal biomass. Local species richness of six grazers was manipulated in both open and closed pools, which were embedded in a regional species pool containing all six grazers. Grazer richness showed significant net biodiversity effects on grazing in the closed, but not in the open, system. Grazer composition, on the other hand, showed significant effects on grazing in both open and closed systems, depending on which species were initially present. The two most efficient grazers were able to compensate for less efficient grazers in species mixtures, hence ensuring the function of grazing. The efficiency of top-down control of algal biomass in open systems thus depends on which particular species are lost. Further, differences in grazing between the open and closed system changed over time due to temporal dynamics in grazer composition. The results emphasize the importance of including system connectivity in experimental designs to allow an extrapolation of biodiversity ecosystem-functioning relationships to natural systems. 相似文献