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421.
Maximum species richness at intermediate frequencies of disturbance: consistency among levels of productivity 总被引:2,自引:0,他引:2
Development of a mechanistic understanding and predictions of patterns of biodiversity is a central theme in ecology. One of the most influential theories, the intermediate disturbance hypothesis (IDH), predicts maximum diversity at intermediate levels of disturbance frequency. The dynamic equilibrium model (DEM), an extension of the IDH, predicts that the level of productivity determines at what frequency of disturbance maximum diversity occurs. To test, and contrast, the predictions of these two models, a field experiment on marine hard-substratum assemblages was conducted with seven levels of disturbance frequency and three levels of nutrient availability. Consistent with the IDH, maximum diversity, measured as species richness, was observed at an intermediate frequency of disturbance. Despite documented effects on productivity, the relationship between disturbance and diversity was not altered by the nutrient treatments. Thus, in this system the DEM did not improve the understanding of patterns of diversity compared to the IDH. Furthermore, it is suggested that careful consideration of measurements and practical definitions of productivity in natural assemblages is necessary for a rigorous test of the DEM. 相似文献
422.
Kallio ER Voutilainen L Vapalahti O Vaheri A Henttonen H Koskela E Mappes T 《Ecology》2007,88(8):1911-1916
The influence of pathogens on host fitness is one of the key questions in infection ecology. Hantaviruses have coevolved with their hosts and are generally thought to have little or no effect on host survival or reproduction. We examined the effect of Puumala virus (PUUV) infection on the winter survival of bank voles (Myodes glareolus), the host of this virus. The data were collected by monitoring 22 islands over three consecutive winters (a total of 55 island populations) in an endemic area of central Finland. We show that PUUV infected bank voles had a significantly lower overwinter survival probability than antibody negative bank voles. Antibody negative female bank voles from low-density populations living on large islands had the highest survival. The results were similar at the population level as the spring population size and density were negatively correlated with PUUV prevalence in the autumn. Our results provide the first evidence for a significant effect of PUUV on host survival suggesting that hantaviruses, and endemic pathogens in general, deserve even more attention in studies of host population dynamics. 相似文献
423.
Phytostabilization may limit the leakage of metals and As from submersed mine tailings, thus treatment of acid mine drainage with lime could be reduced. Tall cottongrass (Eriophorum angustifolium Honckeny) and white cottongrass (E. scheuchzeri Hoppe) were planted in pots with unlimed (pH 5.0) and limed (pH 10.9) tailings (containing sulfides) amended with sewage sludge (SS) or a bioashsewage sludge mixture (ASM). Effects of the amendments on plant growth and plant element uptake were studied. Also, effects of plant growth on elements (Cd, Cu, Pb, Zn, and As), pH, electrical conductivity (EC), and concentrations of SO4(2-), in the drainage water as well as dissolved oxygen in tailings, were measured. Both plant species grew better and the shoot element concentrations of white cottongrass were lower in SS than in ASM. Metal concentrations were lowest in drainage water from limed tailings, and plant establishment had little effect on metal release, except for an increase in Zn levels, even though SO4(2-) levels were increased. In unlimed tailings, plant growth increased SO4(2-) levels slightly; however, pH was increased and metal concentrations were low. Thus, metals were stabilized by plant uptake and high pH. Amendments or plants did not affect As levels in the drainage water from unlimed tailings. Thus, to reduce the use of lime for stabilizing metals, phytostabilization with tall cottongrass and white cottongrass on tailings is a sound possibility. 相似文献
424.
425.
426.
Cecilia Akselsson Olle Westling Harald Sverdrup Johan Holmqvist Gunnar Thelin Eva Uggla Gunnar Malm 《Water, Air, & Soil Pollution: Focus》2007,7(1-3):201-210
The effects of harvesting on the long-term mass balances of calcium (Ca), magnesium (Mg) and potassium (K) were evaluated
on a regional level in Sweden. A new high-resolution weathering database was used together with estimates of total deposition,
losses through harvest and leaching. Estimates were made for pine and spruce separately and for two harvesting intensity scenarios:
stem harvesting and whole-tree harvesting. The mass balance calculations showed net losses of Ca and Mg in almost the whole
country for both scenarios. The losses were smaller for pine than for spruce. The K balances were mainly positive for pine
but negative for spruce. Leaching was a main factor in the mass balances, especially for Ca and Mg. Whole-tree harvesting
in spruce forests led to substantially higher net losses of K and Ca than stem harvesting, according to the calculations.
In the whole-tree harvesting scenario in spruce forests the estimated yearly net losses of Ca, Mg and K corresponded to at
least 5%, 8% and 3% of the pools of exchangeable base cations, respectively, at 25% of the analysed sites. If losses of this
magnitude continue the depletion of the pools of Ca, Mg and K may lead to very low base saturation of the soils, possibly
accompanied by negative effects on soil fertility, runoff water quality, tree vitality and tree growth within a forest rotation
in parts of Sweden. Avoiding whole-tree harvesting can improve the situation substantially for K, but the losses of Ca and
Mg will still be significant. 相似文献
427.
Carlos Cerdan Cristina Gazulla Marco Raugei Eva Martinez Pere Fullana-i-Palmer 《Journal of Cleaner Production》2009,17(18):1638-1643
Eco-design is a valuable approach in order to reduce the environmental impact associated with a product system, by introducing environmental considerations early on in its design. Different strategies are possible for the implementation of eco-design, depending on the intended goals as well as the characteristics of the products. The present work proposes a series of eco-design indicators and tests to what extent the application of these simple indicators provides a reliable indication of the reduction of environmental impact, as measured by commonly employed Life Cycle Impact Assessment (LCIA) indicators. The product chosen for the case study was a water source heat pump. Two of the newly-developed indicators were applied and compared to LCIA indicators, focussing on design for disassembly and for recycling. A good and robust correlation was found, providing support to the thesis that these simple eco-design indicators can be used as a proxy to quickly and effectively gauge the environmental improvements introduced in a product system at the design stage. 相似文献
428.
A methodology for identifying volatile organic compounds (VOC) and determining air quality of indoor air has been developed. The air samples are collected using pump samplers by the inhabitants when they perceive odorous and/or discomfort episodes. Glass multi-sorbent tubes are connected to the pump samplers for the retention of VOC. The analysis is performed by automatic thermal desorption (ATD) coupled with gas chromatography-mass spectrometry (GC/MS). This methodology can be applied in cases of sick building syndrome (SBS) evaluation, in which building occupants experience a series of varied symptoms that appear to be linked to time spent in the building. Chemical pollutants concentrations (e.g., VOC) have been described to contribute to SBS. To exemplify the methodology, a qualitative determination and an evaluation of VOC present were performed in a dwelling where the occupants experienced the SBS symptoms. Higher total VOC (TVOC) value was detected in episodes in indoor air (1.33 ( 1.53 mg/m3) compared to outdoor air (0.71 ( 0.46 mg/m3). The concentrations of individual VOCs, such as ethanol, acetone, isopropanol, 1-butanol, acetic acid, acetonitrile and 1-metoxy-2-propanol, were also higher than the expected for a standard dwelling. The external source of VOC was found to be a not declared activity of storage and manipulation of solvents located at the bottom of a contiguous building. 相似文献
429.
Bo B. Bet Maartje C. Snoep Elisabeth van Leeuwen Ingeborg H. Linskens Monique C. Haak Lieke Rozendaal Ingmar Knobbe Joost van Schuppen Carlijn E. L. Hoekstra David R. Koolbergen Sally-Ann Clur Eva Pajkrt 《黑龙江环境通报》2023,43(5):629-638
Objectives
To determine the proportion of children that require surgery in the first year of life and thereafter in order to improve the counseling of parents with a fetus with a right aortic arch (RAA).Methods
Fetuses diagnosed with isolated RAA, defined as the absence of intra- or extracardiac anomalies, between 2007 and 2021 were extracted from the prospective registry PRECOR.Results
In total, 110 fetuses were included, 92 with a prenatal diagnosis of RAA and 18 with double aortic arch (DAA). The prevalence of 22q11 deletion syndrome was 5.5%. Six pregnancies were terminated and five cases were false-positive; therefore, the follow-up consisted of 99 neonates. Surgery was performed in 10 infants (10%) in the first year of life. In total, 25 (25%) children had surgery at a mean age of 17 months. Eight of these 25 (32%) had a DAA. Only one child, with a DAA, required surgery in the first week of life due to obstructive stridor.Conclusions
Children with a prenatally diagnosed RAA are at a low risk of acute respiratory postnatal problems. Delivery in a hospital with neonatal intensive care and pediatric cardiothoracic facilities seems only indicated in cases with suspected DAA. Expectant parents should be informed that presently 25% of the children need elective surgery and only incidentally due to acute respiratory distress. 相似文献430.
Fleur Zwanenburg Arend D. J. Ten Harkel Maartje C. Snoep Bo B. Bet Ingeborg H. Linskens Ingmar Knobbe Eva Pajkrt Nico A. Blom Sally-Ann B. Clur Monique C. Haak 《黑龙江环境通报》2023,43(5):620-628