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Community Size (community + size)

Distribution by Scientific Domains

Medical Sciences	40%

Selected Abstracts

Network structural properties mediate the stability of mutualistic communities

ECOLOGY LETTERS, Issue 3 2008
Toshinori Okuyama
Abstract Key advances are being made on the structures of predator,prey food webs and competitive communities that enhance their stability, but little attention has been given to such complexity,stability relationships for mutualistic communities. We show, by way of theoretical analyses with empirically informed parameters, that structural properties can alter the stability of mutualistic communities characterized by nonlinear functional responses among the interacting species. Specifically, community resilience is enhanced by increasing community size (species diversity) and the number of species interactions (connectivity), and through strong, symmetric interaction strengths of highly nested networks. As a result, mutualistic communities show largely positive complexity,stability relationships, in opposition to the standard paradox. Thus, contrary to the commonly-held belief that mutualism's positive feedback destabilizes food webs, our results suggest that interplay between the structure and function of ecological networks in general, and consideration of mutualistic interactions in particular, may be key to understanding complexity,stability relationships of biological communities as a whole. [source]

Species loss leads to community closure

ECOLOGY LETTERS, Issue 6 2000
P. Lundberg
Global extinction of a species is sadly irreversible. At a local scale, however, extinctions may be followed by re-invasion. We here show that this is not necessarily the case and that an ecological community may close its doors for re-invasion of species lost from it. Previous studies of how communities are assembled have shown that there may be rules for that process and that limitations are set to the order by which species are introduced and put together. Instead of focusing on the assembly process we randomly generated simple competitive model communities that were stable and allowed for two to 10 coexisting species. When a randomly selected single species was removed from the community, the cascading species loss was recorded and frequently the resulting community was more than halved. Cascading extinctions have previously been recorded, but we here show that the relative magnitude of the cascade is dependent on community size (and not only trophic structure) and that the reintroduction of the original species lost often is impossible. Hence, species loss does not simply leave a void potentially refilled, but permanently alters the entire community structure and consequently the adaptive landscape for potential re-invaders. [source]

Size and phenotypic structure of microbial communities within soil profiles in relation to different playing areas on a UK golf course

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 5 2008
M. D. Bartlett
Summary Amenity turf accounts for up to 4% of land-use in urban areas, providing key refuges for both above- and below-ground biodiversity. Golf courses occupy the largest surface area of all sports facilities; however, only a limited amount of microbial ecology has been carried out to investigate differences in the size and structure of microbial communities of the soil. The soil microbial community is a key agent in nutrient cycling and delivery of other ecosystem goods and services; however, there has been little work focused on amenity turf ecosystems in the UK. A study of soil microbial community size and structure, on the range of playing areas maintained for the game of golf at a single golf course in relation to depth through the soil profile, was carried out. Soil from different playing areas showed significant differences in the size (measured using chloroform fumigation extraction) of the microbial community (P < 0.01), with a greater concentration of microbial biomass at 0,75 mm from the surface, compared with deeper zones (P < 0.01). Principal component analysis of phospholipid fatty acid (PLFA) biomarkers indicated that the community structure was significantly different at 0,75 mm from the surface on all areas of the golf course investigated (P < 0.05, in all cases). The PLFA biomarkers consistently associated with such discrimination were 16:0 and 18:1,9 c. These findings suggest that there is a consistently larger and similarly structured microbial community associated with the surface thatch layer, commonly found in amenity turf. [source]

Hearing problems among a cohort of nationally certified EMS professionals

AMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 3 2010
Antonio R. Fernandez MS, NREMT-P
Abstract Purpose The objectives of this study were to estimate the prevalence of hearing problems among a national cohort of emergency medical service (EMS) professionals, determine factors associated with hearing problems, and estimate the percentage of EMS professionals who utilize hearing protection. Methods Utilizing results from a questionnaire, individuals who reported hearing problems were compared to individuals who had not. Multivariable logistic regression was performed to identify variables associated with hearing problems. Finally, items regarding use of hearing protection were assessed to estimate the percentage of usage among EMS professionals. Results In total, 1,058 (57%) participants responded to the questionnaire. Of those, 1,024 (97%) who completed the hearing problems question were utilized for analysis. There were 153 (14.9%) cases of self-reported hearing problems. The final logistic regression model included lifetime occupational noise exposure 0.99 (95% CI,=,0.9997,1.0002), report of previous back problems (odds ratio (OR),=,2.74, 95% CI,=,1.8340,4.1042), large community size (OR,=,1.67, 95% CI,=,1.1211,2.4843), and minority status (OR,=,0.61, 95% CI,=,0.3719,0.9867). Finally, 213 (20.8%) individuals reported utilizing some form of hearing protection at their main EMS job. Conclusion The results from this analysis are the first national estimates of the prevalence of self reported hearing problems among EMS professionals. This study was also the first to estimate the percentage of EMS professionals who self reported the utilization of hearing protection. Am. J. Ind. Med. 53:264,275, 2010. © 2009 Wiley-Liss, Inc. [source]

Urban-Rural Differences in Motivation to Control Prejudice Toward People With HIV/AIDS: The Impact of Perceived Identifiability in the Community

THE JOURNAL OF RURAL HEALTH, Issue 3 2008
Janice Yanushka Bunn PhD
ABSTRACT:,Context:HIV/AIDS is occurring with increasing frequency in rural areas of the United States, and people living with HIV/AIDS in rural communities report higher levels of perceived stigma than their more urban counterparts. The extent to which stigmatized individuals perceive stigma could be influenced, in part, by prevailing community attitudes. Differences between rural and more metropolitan community members' attitudes toward people with HIV/AIDS, however, have rarely been examined. Purpose: This study investigated motivation to control prejudice toward people with HIV/AIDS among non-infected residents of metropolitan, micropolitan, and rural areas of rural New England. Methods: A total of 2,444 individuals were identified through a random digit dialing sampling scheme, and completed a telephone interview to determine attitudes and concerns about a variety of health issues. Internal or external motivation to control prejudice was examined using a general linear mixed model approach, with independent variables including age, gender, community size, and perceived indentifiability within one's community. Findings: Results showed that community size, by itself, was not related to motivation to control prejudice. However, there was a significant interaction between community size and community residents' perceptions about the extent to which people in their communities know who they are. Conclusion: Our results indicate that residents of rural areas, in general, may not show a higher level of bias toward people with HIV/AIDS. The interaction between community size and perceived identifiability, however, suggests that motivation to control prejudice, and potentially the subsequent expression of that prejudice, is more complex than originally thought. [source]