CORE-PERIPHERY STRUCTURE IN NETWORKS ROMBACH, M. PUCK; PORTER, MASON A.; FOWLER, JAMES H. ...
SIAM journal on applied mathematics,
01/2014, Letnik:
74, Številka:
1
Journal Article
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Intermediate-scale (or "meso-scale") structures in networks have received considerable attention, as the algorithmic detection of such structures makes it possible to discover network features that ...are not apparent either at the local scale of nodes and edges or at the global scale of summary statistics. Numerous types of meso-scale structures can occur in networks, but investigations of such features have focused predominantly on the identification and study of community structure. In this paper, we develop a new method to investigate the meso-scale feature known as core-periphery structure, which entails identifying densely connected core nodes and sparsely connected peripheral nodes. In contrast to communities, the nodes in a core are also reasonably well connected to those in a network's periphery. Our new method of computing core-periphery structure can identify multiple cores in a network and takes into account different possible core structures. We illustrate the differences between our method and several existing methods for identifying which nodes belong to a core, and we use our technique to examine core-periphery structure in examples of friendship, collaboration, transportation, and voting networks.
As investments are made to engage communities in childhood obesity prevention efforts, an approach to better understand local communities’ readiness to implement evidence-based strategies is needed. ...The Community Readiness Model (CRM) was used to assess the readiness of 15 communities in Georgia actively working to prevent childhood obesity. Seventy-nine key informant interviews were conducted assessing six dimensions of readiness. Data were analyzed and scored using the CRM protocol. Overall community readiness scores ranged from 2.8 to 5.1 on a 9-point scale. The mean readiness score, 4.3 (SD = 0.5) corresponds with a preplanning level of readiness. Findings suggest that communities are recognizing the problem, organizing stakeholders, and beginning to develop solutions. There is a need for funders to match their community-based funding initiatives with the readiness levels of the communities being supported. Communities should focus their attention to the six dimensions of readiness while utilizing evidence-based frameworks and guidance on prevention.
Household food insecurity is a serious public health concern in high-income countries. Canada and the USA regularly monitor household food insecurity, while in other countries, such as the UK, it has ...been the rapid rise of food bank usage that has drawn increased attention to this longstanding, but largely overlooked, problem. This review evaluates evidence on interventions intended to reduce household food insecurity in high-income countries. Research on social protection interventions suggests both cash transfers and food subsidies (e.g. the US Supplement Nutrition and Assistance Programme) reduce household food insecurity. In contrast, research on community-level interventions, such as food banks and other food programmes, suggests limited impacts. Although food banks have become a common intervention for food insecurity in high-income countries, evidence suggests their reliance on donations of volunteer time and food make them inevitably limited in the assistance they are able to provide. The stigma people feel using food banks may also make them untenable. Alternatives to, or enhanced, food banks such as community shops or community kitchens, have become common, but evidence also suggests they may be limited in effectiveness if they do not reach people experiencing food insecurity. This review highlights the difficulty of trying to address household food insecurity with community-based food interventions when solutions likely lie upstream in social protection policies.
Summary
Climate change and land‐use intensification are increasing productivity in subarctic lakes. Simultaneously, fish and invertebrate species adapted to temperate conditions are expanding their ...range northwards into subarctic habitats. Community level studies are required to predict long‐term effects of these dual stressors on subarctic freshwater ecosystems.
We conducted a space‐for‐time study examining the fish, benthic invertebrate and pelagic zooplankton communities in littoral, profundal and pelagic habitats in 19 subarctic lakes situated on a temperature, land‐use and productivity gradient in northern Europe.
Fish density (ranging between 0.5 and 150.5 fish per net series h−1) and biomass (range between 92 and 5,147 g per net series h−1) increased significantly with increasing lake temperature and productivity. This was associated with significantly decreasing body size (26 to 12 cm total length; 174 to 19 g body mass) and a shift in fish community structure from salmonid (Arctic charr Salvelinus alpinus, whitefish Coregonus lavaretus), to percid (ruffe Gymnocephalus cernua, perch Perca fluviatilis) and ultimately cyprinid (roach Rutilus rutilus, bleak Alburnus alburnus) dominance. Changes in fish community composition were most apparent in littoral and pelagic zones.
Benthic macroinvertebrate density peaked in mesotrophic lakes, zooplankton density was highest at either end of the gradient, indicating habitat specific differences in predation pressure and top‐down control. Body size of zooplankton and benthic macroinvertebrates was negatively related to temperature and productivity.
These results suggest that climate change and intensification of land‐use practices are gradually turning subarctic lakes into warmer, less transparent and more productive systems harbouring abundant, small‐sized and warmer adapted communities.
•35 years of inorganic fertilizer and manure amendment alter the soil bacterial and archaeal community.•pH and NO3− concentration played important roles in shaping the community structures.•Inorganic ...fertilizers decrease soil bacterial and archaeal diversity.•The incorporation of inorganic fertilizer and manure increase soil bacterial and archaeal diversity.
Black soil is common in northeast China and plays an important role in Chinese crop production. However, in the past three decades, inappropriate use of fertilizer has caused a sequence of agroecological issues. The objective of this research was to evaluate the effect of long-term fertilizer on the microbial communities in black soil. The soil was subjected to four fertilization regimes: without fertilizer (CK); manure (M); nitrogen, phosphorus and potassium inorganic fertilizer (NPK); and inorganic fertilizers with manure (MNPK). The soil pH was decreased by inorganic fertilizers and increased by manure. Quantitative PCR analysis of microbial community size and Illumina platform-based analysis of the V4 16S rRNA gene region were performed to characterize soil microbial abundance and to compare community structure and diversity. Microbial community size was enhanced by the incorporation of inorganic fertilizer and manure. Microbial diversity was decreased by inorganic fertilizer and increased by the incorporation of inorganic fertilizer and manure. The predominate phyla in all samples were Proteobacteria (29.39–33.48%), Acidobacteria (13.14–16.25%) and Actinobacteria (9.32–10.77%). The relative abundance of different classes significantly differed among the different treatments, especially MNPK and NPK. Acidobacteria and Deltaproteobacteria were relatively stable in organic fertilizer treated soil. Gammaproteobacteria, Alphaproteobacteria and Betaproteobacteria were sensitive to all the fertilization regimes. Comparatively, Spartobacteria was stable in response to fertilization practices. Principal coordinate analysis indicated that microbial communities were primarily clustered into three groups: CK and M were clustered together; MNPK was improved by manure and separated from NPK. Shannon and Simpson indexes were significantly correlated with soil pH and the concentrations of available phosphorus and total phosphorus. Redundancy analysis indicates that microbial communities were closely positively correlated with soil nitrate nitrogen concentration (P=0.002) and pH (P=0.002). These results indicate that inorganic fertilizer plus manure increased microbial size and diversity and changed microbial composition.
This volume studies local priests as central players in small communities of early medieval Europe. On the one hand, manuscript evidence shows their knowledge, expertise and potential to teach, ...whereas charter collections shed light on local priests as active members of networks of the locally powerful. By combining both approaches and covering most of early medieval Europe, this book is the first to offer a comprehensive overview of the subject.
From Roots to Results Wolf, Lesley; Vigna, Abra J.; Inzeo, Paula Tran ...
Health education & behavior,
10/2019, Letnik:
46, Številka:
1_suppl
Journal Article
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Policy, systems, and environmental change are now widely accepted as critical to sustaining improvements in community health. Evidence suggests that such systems-level change is most effective when ...driven by community-based partnerships. Yet, after more than three decades of building community-based partnership work, health inequities have continued to deepen. To address health inequities, current and historical distributions of power are increasingly recognized as important considerations in efforts to ensure all individuals have the opportunity to attain their full health potential (i.e., achieving health equity). Building on social determinants of health literature, social injustice and powerlessness are put forth as fundamental causes of health inequities. Focusing on power as a root cause of health and health equity through application of Wolff and colleagues’ six principles requires substantial changes in contemporary public health practice. This case study uses document analysis of a single case, the Community Teams Program, to assess the evolution of a statewide public health leadership program’s efforts to build the capacity of coalition-based teams to catalyze community change in line with Wolff and colleagues’ principles. Deductive, selective coding of the materials surface four themes in the program adaptations: (1) the need to focus on power as a root cause, (2) shifting power through relationship building, (3) storytelling as a way to shift narrative, and (4) building mechanisms into the curriculum that hold coalitions accountable for applying and sustaining learned skills. The themes demonstrate philosophical, pedagogical, and organizational changes to center power building approaches in health promotion. Findings are triangulated by reflections from the program director and recorded reflections of participants captured in existing evaluation data.
Seed dispersal by frugivores plays a key role in structuring and maintaining tree diversity in forests. However, little is known about how the spatial legacy of seed dispersal and early recruitment ...shapes spatial patterns and the spatial interaction network of plant species in mature forest communities.
We analysed two fully mapped mixed Pine–Oak forest communities using spatial point pattern analysis to determine (a) the detailed structure of the intraspecific spatial patterns of saplings and adults, (b) the intra‐ and interspecific spatial interaction of saplings, adults and saplings relative to adults, (c) the spatial patterns of species richness at the community level and (d) whether seed dispersal mechanisms affect the plant–plant interaction networks and the ratio of adult to sapling neighbourhood densities used as surrogate for spatial self‐thinning.
The intraspecific spatial patterns of saplings and adults showed in general complex nested cluster structures that were similar for sapling and adult stages, despite substantial self‐thinning in some dry‐fruited species. The spatial network of saplings was characterized by positive spatial interactions. Adults of several tree species facilitated saplings in their proximity; however, adults of dry‐fruited species, but not those of fleshy‐fruited ones, lost almost all positive interactions that occurred at the sapling stage. Besides, interaction strength between adults was positive and often significantly stronger if both species were fleshy‐fruited. At the community level, the forests were structured into multispecies clumps across all life stages.
Synthesis. Our analyses highlight the importance of the spatial legacy of seed dispersal and early recruitment in the assembly of plant communities. Particularly, animal seed dispersal can lead to multispecies clusters and positive spatial associations across life stages in Mediterranean forests, with surprisingly little signatures of negative interactions. Our analysis suggests that changes of the spatial structure across plant life stages are driven by seed dispersal mechanisms and subsequent spatial self‐thinning, generating a spatial footprint at the sapling stage that conditions the long‐term interactions between adult plants. Combining spatial point pattern analysis with network analysis and species traits is a promising way to disentangle the processes underlying observed patterns of local diversity.
Our analyses highlight the importance of the spatial legacy of seed dispersal and early recruitment in the assembly of plant communities. Particularly, animal seed dispersal can lead to multispecies clusters and positive spatial associations across life stages in Mediterranean forests, with surprisingly little signatures of negative interactions. Our analysis suggests that changes of the spatial structure across plant life stages are driven by seed dispersal mechanisms and subsequent spatial self‐thinning, generating a spatial footprint at the sapling stage that conditions the long‐term interactions between adult plants. Combining spatial point pattern analysis with network analysis and species traits is a promising way to disentangle the processes underlying observed patterns of local diversity.
1. There is increasing evidence that species diversity enhances the temporal stability (TS) of community productivity in different ecosystems, although its effect at the population and tree levels ...seems to be negative or neutral. Asynchrony in species responses to environmental conditions was found to be one of the main drivers of this stabilizing process. However, the effect of species mixing on the stability of productivity, and the relative importance of the associated mechanisms, remain poorly understood in forest communities. 2. We investigated the way mixing species influenced the TS of productivity in Pinus sylvestris L. and Fagus sylvatica L. forests, and attempted to determine the main drivers among overyielding, asynchrony between species annual growth responses to environmental conditions, and temporal shifts in species interactions. We used a network of 93 experimental plots distributed across Europe to compare the TS of basal area growth over a 15-year period (1999-2013) in mixed and monospecific forest stands at different organizational levels, namely the community, population and individual tree levels. 3. Mixed stands showed a higher TS of basal area growth than monospecific stands at the community level, but not at the population or individual tree levels. The TS at the community level was related to asynchrony between species growth in mixtures, but not to overyielding nor to asynchrony between species growth in monospecific stands. Temporal shifts in species interactions were also related to asynchrony and to the mixing effect on the TS. 4. Synthesis. Our findings confirm that species mixing can stabilize productivity at the community level, whereas there is a neutral or negative effect on stability at the population and individual tree levels. The contrasting findings regarding the relationships between the temporal stability and asynchrony in species growth in mixed and monospecific stands suggest that the main driver in the stabilizing process may be the temporal niche complementarity between species rather than differences in species' intrinsic responses to environmental conditions.
It is widely argued that increased community participation in government decision making produces many important benefits. Dissent is rare: It is difficult to envision anything but positive outcomes ...from citizens joining the policy process, collaborating with others and reaching consensus to bring about positive social and environmental change. This article, motivated by contextual problems encountered in a participatory watershed management initiative, reviews the citizen-participation literature and analyzes key considerations in determining whether community participation is an effective policy-making tool. We list conditions under which community participation may be costly and ineffective and when it can thrive and produce the greatest gains in effective citizen governance. From the detritus of an unsuccessful citizen-participation effort, we arrive at a more informed approach to guide policy makers in choosing a decision-making process that is appropriate for a community's particular needs.
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