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Physical Disturbance (physical + disturbance)
Selected AbstractsThe Effect of Repeated Physical Disturbance on Soft Tissue Decomposition,Are Taphonomic Studies an Accurate Reflection of Decomposition?,JOURNAL OF FORENSIC SCIENCES, Issue 5 2007Rachel E. Adlam M.Sc. Abstract:, Although the relationship between decomposition and postmortem interval has been well studied, almost no studies examined the potential effects of physical disturbance occurring as a result of data collection procedures. This study compares physically disturbed rabbit carcasses with a series of undisturbed carcasses to assess the presence and magnitude of any effects resulting from repetitive disturbance. Decomposition was scored using visual assessment of soft tissue changes, and numerical data such as weight loss and carcass temperature were recorded. The effects of disturbance over time on weight loss, carcass temperature, soil pH and decomposition were studied. In addition, this study aimed to validate some of the anecdotal evidence regarding decomposition. Results indicate disturbance significantly inversely affects both weight loss and carcass temperature. No differences were apparent between groups for soil pH change or overall decomposition stage. An insect-mediated mechanism for the disturbance effect is suggested, along with indications as to why this effect may be cancelled when scoring overall decomposition. [source] Effects of physical disturbance and granivory on establishment of native and alien riparian trees in Colorado, U.S.A.DIVERSITY AND DISTRIBUTIONS, Issue 1-2 2001Gabrielle L. Katz In western North America, the alien Elaeagnus angustifolia L. invades riparian habitats usually dominated by pioneer woody species such as Populus deltoides Marshall ssp. monilifera (Aiton) Eckenwalder. We conducted manipulative field experiments to compare the importance of physical disturbance and granivory for seedling establishment of these two species. We planted seeds of both species in disturbed and undisturbed study plots, and used exclosures, seed dish trials and live-trapping to assess the role of granivory. Seedling establishment of both species was increased by physical disturbance and seeds of both species were subject to granivory. However, the relative importance of these two factors differed between species. For P. deltoides, lack of physical disturbance prevented seedling establishment in uncleared subplots, but granivory did not prevent seedling establishment outside of exclosures. For E. angustifolia, granivory prevented seedling establishment outside of exclosures, but lack of physical disturbance did not prevent establishment in uncleared subplots. The lesser dependence on disturbance may enable E. angustifolia to invade areas characterized by low levels of fluvial disturbance, such as floodplains along regulated rivers, where P. deltoides recruitment does not occur. Populations of granivorous rodents may affect the susceptibility of riparian ecosystems to invasion by E. angustifolia. [source] Effects of plant diversity, plant productivity and habitat parameters on arthropod abundance in montane European grasslandsECOGRAPHY, Issue 4 2005Jörg Perner Arthropod abundance has been hypothesized to be correlated with plant diversity but the results of previous studies have been equivocal. In contrast, plant productivity, vegetation structure, abiotic site conditions, and the physical disturbance of habitats, are factors that interact with plant diversity, and that have been shown to influence arthropod abundance. We studied the combined effect of plant species diversity, productivity and site characteristics on arthropod abundance in 71 managed grasslands in central Germany using multivariate statistics. For each site we determined plant species cover, plant community biomass (productivity), macro- and micronutrients in the soil, and characterized the location of sites with respect to orographic parameters as well as the current and historic management regimes. Arthropods were sampled using a suction sampler and classified a priori into functional groups (FGs). We found that arthropod abundance was not correlated with plant species richness, effective diversity or Camargo's evenness, even when influences of environmental variables were taken into account. In contrast, plant community composition was highly correlated with arthropod abundances. Plant community productivity influenced arthropod abundance but explained only a small proportion of the variance. The abundances of the different arthropod FGs were influenced differentially by agricultural management, soil characteristics, vegetation structure and by interactions between different FGs of arthropods. Herbivores, carnivores and detritivores reacted differently to variation in environmental variables in a manner consistent with their feeding mode. Our results show that in natural grassland systems arthropod abundance is not a simple function of plant species richness, and they emphasize the important role of plant community composition for the abundance patterns of the arthropod assemblages. [source] The specialist seed predator Bruchidius dorsalis (Coleoptera: Bruchidae) plays a crucial role in the seed germination of its host plant, Gleditsia japonica (Leguminosae)FUNCTIONAL ECOLOGY, Issue 2 2002K. Takakura Summary 1,This paper describes the germination mechanism of hard seeds of a species of honey locust, Gleditsia japonica, which can germinate only when externally damaged, in relation to four germinating factors: feeding damage by two specialist seed predators, a bean weevil (Bruchidius dorsalis) and a cydid bug (Adrisa magna); feeding damage by a generalist seed predator, a wild mouse (Apodemus speciosus); and physical damage. 2,In laboratory experiments, both the bean weevil and physical damage facilitated germination, while damage by the cydid bug and wild mouse did not. 3,In contrast to laboratory findings, field censuses of G. japonica seed survival revealed that more than 99% were damaged either by B. dorsalis or A. magna. Therefore, less than 0·5% of the seeds remained intact, preventing formation of a seed bank. 4,In addition, all germinating seeds found in the field contained B. dorsalis larvae. 5,These results strongly suggest that damage by B. dorsalis is a prerequisite for G. japonica germination, in contrast to the conventional view that physical disturbance, possibly flooding, is the primary germinating factor for hard seeds. [source] Will increased storm disturbance affect the biodiversity of intertidal, nonscleractinian sessile fauna on coral reefs?GLOBAL CHANGE BIOLOGY, Issue 11 2008S. J. WALKER Abstract Relatively little is known about how the future effects of climatic change, including increases in sea level, temperature and storm severity and frequency, will impact on patterns of biodiversity on coral reefs, with the notable exception of recent work on corals and fish in tropical reef ecosystems. Sessile invertebrates such as ascidians, sponges and bryozoans occupying intertidal rubble habitats on coral reefs contribute significantly to the overall biodiversity and ecosystem function, but there is little or no information available on the likely impacts on these species from climate change. The existing strong physical gradients in these intertidal habitats will be exacerbated under predicted climatic change. By examining the distribution and abundance of nonscleractinian, sessile invertebrate assemblages exposed to different levels of wave action and at different heights on the shore around a coral reef, we show that coral reef intertidal biodiversity is particularly sensitive to physical disturbance. As physical disturbance regimes increase due to more intense storms and wave action associated with global warming, we can expect to see a corresponding decrease in the diversity of these cryptic sessile assemblages. This could impact negatively on the future health and productivity of coral reef ecosystems, given the ecosystem services these organisms provide. [source] Asymmetric coexistence: bidirectional abiotic and biotic effects between goose barnacles and musselsJOURNAL OF ANIMAL ECOLOGY, Issue 4 2006TAKASHI KAWAI Summary 1Species coexistence depends on the net effect of interacting species, representing the sum of multiple interaction components that may act simultaneously and vary independently depending on ambient environmental conditions. Consequently, for a comprehensive understanding of the compound nature of species interactions and coexistence, a mechanistic approach that allows a separate evaluation of each interaction component is required. 2Two sessile filter-feeders, the goose barnacle Capitulum mitella and the mussel Septifer virgatus, coexist on moderately wave-exposed rocky shores in south-western Japan. In the upper intertidal, Capitulum positively influenced Septifer survivorship and growth through amelioration of thermal stress and of physical disturbance. On the other hand, these species are potential competitors as they have similar body sizes and modes of resource utilization. These opposite processes, facilitation and competition, are based on abiotic characteristics and biotic functions of the two species, respectively. 3In order to quantify the bidirectional abiotic, biotic and net effects, a series of experimental manipulations was conducted involving the use of living neighbours with both abiotic and biotic effects, and artificial mimics to simulate abiotic effects without biotic effects. 4Capitulum had strong positive abiotic effects on the mussel survivorship in most experimental periods, while the biotic effect was negligible or weakly negative, suggesting that the net effect of Capitulum on mussel survival was largely attributable to the abiotic effect. In contrast, a significantly negative biotic effect on the mussel growth rate was always present, though this was cancelled out by the larger, positive abiotic effect. In the case of Septifer, its abiotic and biotic effects on the survivorship of goose barnacles were negligible, while those on the growth rate showed temporal variation. 5With respect to the relationship between species interaction and environmental conditions, the strength of abiotic facilitative effect of Capitulum on mussel survival increased with increasing abiotic stress, while the strength of biotic effect was negligible or weakly negative. As regards the effects of mussels on goose barnacles, our study indicated no obvious relationship. These results point to the importance of decomposing interaction for an accurate, mechanistic understanding of species relations and coexistence. [source] Chronic fishing disturbance has changed shelf sea benthic community structureJOURNAL OF ANIMAL ECOLOGY, Issue 3 2000M. J. Kaiser Summary 1.,Bottom fishing using towed nets and dredges is one of the most widespread sources of physical disturbance to the continental shelf seas throughout the world. Previous studies suggest that degradation and ecosystem changes have occurred in intensively fished areas. Nevertheless, to date it has been difficult to attribute habitat and benthic community changes to fishing effort at a spatial scale that is truly representative of commercial fishing activities. 2.,In this study we present convincing evidence that chronic bottom-fishing disturbance has caused significant and widespread changes in the structure of two distinct soft-sediment benthic assemblages and habitats. 3.,Our study compared the benthic fauna found in areas that have been exposed to either high or low levels of bottom-fishing disturbance over the past 10 years. We were able to validate the fishing effort data in some areas using scars in the shells of a long-lived bivalve mollusc (Glycymeris glycymeris) which result from fishing disturbance. Shell scars occurred most frequently in bivalves collected from the area of highest fishing effort. 4.,Multivariate analyses and the response of abundance/biomass curves indicated that chronic fishing has caused a shift from communities dominated by relatively sessile, emergent, high biomass species to communities dominated by infaunal, smaller-bodied fauna. Removal of emergent fauna has thus degraded the topographic complexity of seabed habitats in areas of high fishing effort. The communities within these areas currently may be in an alternative stable state. [source] Assessing and predicting the relative ecological impacts of disturbance on habitats with different sensitivitiesJOURNAL OF APPLIED ECOLOGY, Issue 2 2007J. G. HIDDINK Summary 1Methods for assessing habitat sensitivity to human impacts are needed to gauge the sustainability of existing impacts, develop spatial management plans and support meaningful environmental impact assessments. These methods should be quantitative, validated, repeatable and applicable at the scales of impact and management. 2Existing methods for assessing the sensitivity of marine habitats to human impacts have tended to rely on expert judgement and/or scoring systems. They are neither validated, quantitative nor repeatable. 3We have developed a method that meets the criteria for assessing the sensitivity of seabed habitats to physical disturbance, and delineating and mapping habitat sensitivity at large spatial scales (>105 km2). The method assumes that sensitivity is related to the recovery time of production or biomass, as predicted using a size-based model that takes account of the effects of natural disturbance. 4As trawling disturbance is a major and widespread direct human impact on shelf seas, this was used as an example of anthropogenic physical disturbance. We mapped habitat sensitivity to trawling in 9-km2 boxes across an area of 125 000 km2 in the North Sea. 5Habitat sensitivities varied widely, and a trawling frequency of 5 year,1 in the least-sensitive habitat had the same ecological effect as a trawling frequency of 0·3 year,1 in the most-sensitive habitat (based on production). When trawling effort was held constant but redirected to the least-sensitive habitats, the existing impacts on production and biomass were reduced by 36% and 25%, respectively. 6Synthesis and applications. The method described in this paper enables managers to predict the implications of changing patterns of human impact on seabed habitats when establishing spatial management plans. In the context of fisheries management, this will support the identification and selection of fishing grounds that minimize the adverse ecological effects of fishing; the selection of closed areas (both representative and highly sensitive); the comparison of management options that might reduce the overall environmental impacts of fishing; and any future steps towards the application of environmental impact assessment in advance of fishery development. [source] Offshore renewable energy: ecological implications of generating electricity in the coastal zoneJOURNAL OF APPLIED ECOLOGY, Issue 4 2005ANDREW B. GILL Summary 1Global-scale environmental degradation and its links with non-renewable fossil fuels have led to an increasing interest in generating electricity from renewable energy resources. Much of this interest centres on offshore renewable energy developments (ORED). The large scale of proposed ORED will add to the existing human pressures on coastal ecosystems, therefore any ecological costs and benefits must be determined. 2The current pressures on coastal ecology set the context within which the potential impacts (both positive and negative) of offshore renewable energy generation are discussed. 3The number of published peer-review articles relating to renewable energy has increased dramatically since 1991. Significantly, only a small proportion of these articles relate to environmental impacts and none considers coastal ecology. 4Actual or potential environmental impact can occur during construction, operation and/or decommissioning of ORED. 5Construction and decommissioning are likely to cause significant physical disturbance to the local environment. There are both short- and long-term implications for the local biological communities. The significance of any effects is likely to depend on the natural disturbance regime and the stability and resilience of the communities. 6During day-to-day operation, underwater noise, emission of electromagnetic fields and collision or avoidance with the energy structures represent further potential impacts on coastal species, particularly large predators. The wider ecological implications of any direct and indirect effects are discussed. 7Synthesis and applications. This review demonstrates that offshore renewable energy developments will have direct and, potentially, indirect consequences for coastal ecology, with these effects occurring at different scales. Ecologists should be involved throughout all the phases of an ORED to ensure that appropriate assessments of the interaction of single and multiple developments with the coastal environment are undertaken. [source] Documenting hurricane impacts on coral reefs using two-dimensional video-mosaic technologyMARINE ECOLOGY, Issue 2 2007Arthur C. R. Gleason Abstract Four hurricanes impacted the reefs of Florida in 2005. In this study, we evaluate the combined impacts of hurricanes Dennis, Katrina, Rita, and Wilma on a population of Acropora palmata using a newly developed video-mosaic methodology that provides a high-resolution, spatially accurate landscape view of the reef benthos. Storm damage to A. palmata was surprisingly limited; only 2 out of 19 colonies were removed from the study plot at Molasses Reef. The net tissue losses for those colonies that remained were only 10% and mean diameter of colonies decreased slightly from 88.4 to 79.6 cm. In contrast, the damage to the reef framework was more severe, and a large section (6 m in diameter) was dislodged, overturned, and transported to the bottom of the reef spur. The data presented here show that two-dimensional video-mosaic technology is well-suited to assess the impacts of physical disturbance on coral reefs and can be used to complement existing survey methodologies. [source] Survival rate, abundance, and residency of long-finned pilot whales in the Strait of GibraltarMARINE MAMMAL SCIENCE, Issue 3 2009P. Verborgh Abstract Long-finned pilot whales in the Strait of Gibraltar are distributed over the main shipping routes. This exposes them to risks of collisions and probable acoustic and physical disturbance. This species is also the target of whale-watching operations. The aim of this study was to estimate the annual population size, survival rate, and population growth rate of pilot whales occurring in the Strait and their inter-annual variation using photo-identification. A robust design was used to estimate all three parameters. A total of 10,784 individual pilot whale fins were photographed and analyzed. The population size estimation in summer ranged from a low of 147 individuals in 1999 to a high of 265 individuals in 2003. The annual population growth rate was estimated from mark recapture models to be 5.5%. The survival rate of adults was estimated at 0.982 (95% CI: 0.955,0.993). The same individuals have been observed between years. This suggests that this population is resident in the Strait, at least during summer. This study provides baseline knowledge prior to a predicted increase in shipping traffic throughout the main foraging area due to the opening in 2007 of a major shipping harbor along the Moroccan coast of the Strait. [source] A method to assess the sensitivity of sedimentary communities to fishing activitiesAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 3 2009Harvey Tyler-Walters Abstract 1.Methods of sensitivity assessment to identify species and habitats in need of management or protection have been available since the 1970s. 2.The approach to sensitivity assessment adopted by the Marine Life Information Network (MarLIN) assumes that the sensitivity of a community or biotope is dependent on the species within it. However, the application of this approach to sedimentary communities, especially offshore, is complex because of a lack of knowledge of the structural or functional role of many sedimentary species. 3.This paper describes a method to assess the overall sensitivity of sedimentary communities, based on the intolerance and recoverability of component species to physical disturbance. A range of methods were applied to identify the best combinations of abundant, dominant or high biomass species for the assessment of sensitivity in the sedimentary communities examined. 4.Results showed that reporting the most frequent species' sensitivity assessment, irrespective of the four methods used to select species, consistently underestimated the total sensitivity of the community. In contrast, reporting the most sensitive assessment from those species selected resulted in a range of biotope sensitivities from very low to very high, that was better able to discriminate between the sensitivities of the communities examined. 5.The assumptions behind the methodology, its limitations and potential application are discussed. © Crown copyright 2008. Reproduced with permission of Her majesty's stationery office. Published by John Wiley & Sons, Ltd. [source] | |||||||||||||||||||