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11.
M. Schratzberger T. A. D. Maxwell K. Warr J. R. Ellis S. I. Rogers 《Marine Biology》2008,153(4):621-642
Spatial variation of populations and their assemblages is an important component of many aspects of ecology, including the
maintenance of species diversity. In nature, organisms are generally aggregated in patches or form gradients or other spatially
related patterns. This investigation quantified the degree of spatial structure in benthic invertebrate assemblages. It examined
the distribution of infaunal assemblages of different size, mobility and contrasting life-history strategies (i.e. meiofaunal
nematodes and macrofaunal polychaetes) in two offshore muddy habitats in the Celtic Deep and the NW Irish Sea off the west
coast of the United Kingdom. The more heterogeneous habitat in the NW Irish Sea was characterised by higher tidal stress and
bottom temperature while greater water depth, mean particle diameter and organic carbon content was typical for the comparatively
homogeneous environment in the Celtic Deep. In both habitats, the environmental conditions became increasingly dissimilar
with separation. A total of 125 nematode and 88 polychaete species were recorded with 69% of the nematode and 49% of polychaete
species present at both study sites. Occurrence frequency of species, species diversity and average similarity of assemblage
composition was higher in the Celtic Deep than in the NW Irish Sea. Results from correlation analyses revealed statistically
robust relationships of community similarity and sample distance. Given their small size and low mobility, nematodes were
more susceptible to within-habitat physical variability than larger-sized, more mobile polychaetes. This, coupled with limits
to long-distance dispersal and likely restrictions in gene flow, resulted in a significant decrease in community similarity
with distance at the spatial scales sampled (i.e. within 0.1–23 km). Polychaetes, in contrast, combined a higher dispersal
potential (>23 km) with a relatively high tolerance to within-habitat environmental variability and these were the most likely
causes for non-significant relationships between the similarity of their assemblages and sample distance. The potential mechanisms
causing the observed variation and implications of results for environmental management strategies are discussed.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
12.
Corruption is a threat to the purpose of humanitarian assistance. Until fairly recently, humanitarian assistance has not been considered an important arena in broader efforts aimed at curbing corruption, and corruption has not always been considered a particularly important concern for humanitarian assistance despite the obviously challenging nature of the context of humanitarian emergencies. Corruption, though, is a threat to humanitarian action because it can prevent assistance from getting to the people who most need it, and because it can potentially undermine public support for such assistance. This paper examines perceptions of corruption and its affects, documents best practices, and outlines gaps in understanding. It suggests recommendations for improving the capacity of humanitarian agencies to prevent and manage the risk of corruption. Agencies have taken steps to combat corruption and improve accountability--downwards and upwards--but scope remains for improvement and for greater sharing of learning and good practice. 相似文献
13.
Baer SG Engle DM Knops JM Langeland KA Maxwell BD Menalled FD Symstad AJ 《Environmental management》2009,43(2):189-196
Vast areas of arable land have been retired from crop production and “rehabilitated” to improved system states through landowner
incentive programs in the United States (e.g., Conservation and Wetland Reserve Programs), as well as Europe (i.e., Agri-Environment
Schemes). Our review of studies conducted on invasion of rehabilitated agricultural production systems by nontarget species
elucidates several factors that may increase the vulnerability of these systems to invasion. These systems often exist in
highly fragmented and agriculturally dominated landscapes, where propagule sources of target species for colonization may
be limited, and are established under conditions where legacies of past disturbance persist and prevent target species from
persisting. Furthermore, rehabilitation approaches often do not include or successfully attain all target species or historical
ecological processes (e.g., hydrology, grazing, and/or fire cycles) key to resisting invasion. Uncertainty surrounds ways
in which nontarget species may compromise long term goals of improving biodiversity and ecosystem services through rehabilitation
efforts on former agricultural production lands. This review demonstrates that more studies are needed on the extent and ecological
impacts of nontarget species as related to the goals of rehabilitation efforts to secure current and future environmental
benefits arising from this widespread conservation practice. 相似文献
14.
15.
Meadow Restoration Increases Baseflow and Groundwater Storage in the Sierra Nevada Mountains of California 下载免费PDF全文
Luke J.H. Hunt Julie Fair Maxwell Odland 《Journal of the American Water Resources Association》2018,54(5):1127-1136
In mountains of the western United States, channel incision has drawn down the water table across thousands of square kilometers of meadow floodplain. Here climate change is resulting in earlier melt and reduced snowpack and water resource managers are responding by investing in meadow restoration to increase springtime storage and summer flows. The record‐setting California drought (2012–2015) provided an opportunity to evaluate this strategy under the warmer and drier conditions expected to impact mountain water supplies. In 2012, 0.1 km2 of meadow floodplain was reconnected by filling an incised channel through Indian Valley in the central Sierra Nevada Mountains of California. Despite sustained drought conditions after restoration, summer baseflow from the meadow increased 5–12 times. Before restoration, the total summer outflow from the meadow was 5% more than the total summer inflow. After restoration, total summer outflow from the meadow was between 35% and 95% more than total summer inflow. In the worst year of the drought (2015), when inflow to the meadow ceased for at least one month, summer baseflow was at least five times greater than before restoration. Groundwater levels also rose at four out of five sites near the stream channel. Filling the incised channel and reconnecting the meadow floodplain increased water availability and streamflow, despite unprecedented drought conditions. 相似文献
16.
Chukwujindu Maxwell Azubuike Iwegbue 《毒物与环境化学》2013,95(7):1368-1374
The concentrations of cadmium, chromium, copper, lead, zinc, manganese, iron, cobalt, and nickel in some brands of canned beef in Nigerian markets were determined by atomic absorption spectrophotometry. The mean concentration ranges for these metals in mg?kg?1 were 0.02–0.37 for Cd, <0.04–0.75 for Cr, 1.1–2.4 for Cu, <0.001–1.5 for Pb, 1.1–8.0 for Zn, <0.04–0.57 for Mn, 13.8–28.8 for Fe, 0.05–0.26 for Co, and 0.8–5.9 for Ni. The estimated dietary intake of metals from these products did not indicate any risk since the values were far below the permissible dietary intakes. 相似文献
17.
Jeremy S. Simmonds Andres Felipe Suarez-Castro April E. Reside James E. M. Watson James R. Allan Scott C. Atkinson Pasquale Borrelli Nigel Dudley Stephen Edwards Richard A. Fuller Edward T. Game Simon Linke Sean L. Maxwell Panos Panagos Philippe Puydarrieux Fabien Quétier Rebecca K. Runting Talitha Santini Laura J. Sonter Martine Maron 《Conservation biology》2023,37(3):e14040
Global efforts to deliver internationally agreed goals to reduce carbon emissions, halt biodiversity loss, and retain essential ecosystem services have been poorly integrated. These goals rely in part on preserving natural (e.g., native, largely unmodified) and seminatural (e.g., low intensity or sustainable human use) forests, woodlands, and grasslands. To show how to unify these goals, we empirically derived spatially explicit, quantitative, area-based targets for the retention of natural and seminatural (e.g., native) terrestrial vegetation worldwide. We used a 250-m-resolution map of natural and seminatural vegetation cover and, from this, selected areas identified under different international agreements as being important for achieving global biodiversity, carbon, soil, and water targets. At least 67 million km2 of Earth's terrestrial vegetation (∼79% of the area of vegetation remaining) required retention to contribute to biodiversity, climate, soil, and freshwater conservation objectives under 4 United Nations’ resolutions. This equates to retaining natural and seminatural vegetation across at least 50% of the total terrestrial (excluding Antarctica) surface of Earth. Retention efforts could contribute to multiple goals simultaneously, especially where natural and seminatural vegetation can be managed to achieve cobenefits for biodiversity, carbon storage, and ecosystem service provision. Such management can and should co-occur and be driven by people who live in and rely on places where natural and sustainably managed vegetation remains in situ and must be complemented by restoration and appropriate management of more human-modified environments if global goals are to be realized. 相似文献
18.
With approximately 20 % of the world’s population living in its downstream watersheds, the Qinghai-Tibetan Plateau (QTP) is considered “Asia’s Water Tower.” However, grasslands of the QTP, where most of Asia’s great rivers originate, are becoming increasingly degraded, which leads to elevated population densities of a native small mammal, the plateau pika (Ochotona curzoniae). As a result pikas have been characterized as a pest leading to wide-spread poisoning campaigns in an attempt to restore grassland quality. A contrary view is that pikas are a keystone species for biodiversity and that their burrowing activity provides a critical ecosystem service by increasing the infiltration rate of water, hence reducing overland flow. We demonstrate that poisoning plateau pikas significantly reduces infiltration rate of water across the QTP creating the potential for watershed-level impacts. Our results demonstrate the importance of burrowing mammals as ecosystem engineers, particularly with regard to their influence on hydrological functioning. 相似文献
19.
Sacral agenesis was diagnosed sonographically in the fetus of a diabetic mother and pancreatic agenesis was found additionally at autopsy. 相似文献
20.