bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydra effects in stable communities and their implications for system dynamics
Authors: Cortez Michael H. , Abrams Peter A. 
Published: May 2016

AbstractA hydra effect occurs when the mean density of a species increases in response to greater mortality. We show that, in a stable multispecies system, a species exhibits a hydra effect only if maintaining that species at its equilibrium density destabilizes the system. The stability of the original system is due to the responses of the hydra‐effect species to changes in the other species’ densities. If that dynamical feedback is removed by fixing the density of the hydra‐effect species, large changes in the community make‐up (including the possibility of species extinction) can occur. This general result has several implications: (1) Hydra effects occur in a much wider variety of species and interaction webs than has previously been described, and may occur for multiple species, even in small webs; (2) conditions for hydra effects caused by predators (or diseases) often differ from those caused by other mortality factors; (3) introducing a specialist or a switching predator of a hydra‐effect species often causes large changes in the community, which frequently involve extinction of other species; (4) harvest policies that attempt to maintain a constant density of a hydra‐effect species may be difficult to implement, and, if successful, are likely to cause large changes in the densities of other species; and (5) trophic cascades and other indirect effects caused by predators of hydra‐effect species can exhibit amplification of effects or unexpected directions of change. Although we concentrate on systems that are originally stable and models with no stage‐structure or trait variation, the generality of our result suggests that similar responses to mortality will occur in many systems without these simplifying assumptions. In addition, while hydra effects are defined as responses to altered mortality, they also imply counterintuitive responses to changes in immigration and other parameters affecting population growth.
Connectivity from a different perspective: comparing seed dispersal kernels in connected vs. unfragmented landscapes
Authors: Herrmann John D. , Carlo Tomás A. , Brudvig Lars A. , Damschen Ellen I. , Haddad Nick M. , Levey Douglas J. , Orrock John L. , Tewksbury Joshua J. 
Published: May 2016

AbstractHabitat fragmentation can create significant impediments to dispersal. A technique to increase dispersal between otherwise isolated fragments is the use of corridors. Although previous studies have compared dispersal between connected fragments to dispersal between unconnected fragments, it remains unknown how dispersal between fragments connected by a corridor compares to dispersal in unfragmented landscapes. To assess the extent to which corridors can restore dispersal in fragmented landscapes to levels observed in unfragmented landscapes, we employed a stable‐isotope marking technique to track seeds within four unfragmented landscapes and eight experimental landscapes with fragments connected by corridors. We studied two wind‐ and two bird‐dispersed plant species, because previous community‐based research showed that dispersal mode explains how connectivity effects vary among species. We constructed dispersal kernels for these species in unfragmented landscapes and connected fragments by marking seeds in the center of each landscape with 15N and then recovering marked seeds in seed traps at distances up to 200 m. For the two wind‐dispersed plants, seed dispersal kernels were similar in unfragmented landscapes and connected fragments. In contrast, dispersal kernels of bird‐dispersed seeds were both affected by fragmentation and differed in the direction of the impact: Morella cerifera experienced more and Rhus copallina experienced less long‐distance dispersal in unfragmented than in connected landscapes. These results show that corridors can facilitate dispersal probabilities comparable to those observed in unfragmented landscapes. Although dispersal mode may provide useful broad predictions, we acknowledge that similar species may respond uniquely due to factors such as seasonality and disperser behavior. Our results further indicate that prior work has likely underestimated dispersal distances of wind‐dispersed plants and that factors altering long‐distance dispersal may have a greater impact on the spread of species than previously thought.
Modularity, pollination systems, and interaction turnover in plant‐pollinator networks across space
Authors: Carstensen Daniel W. , Sabatino Malena , Morellato Leonor Patricia C. 
Published: May 2016

AbstractMutualistic interaction networks have been shown to be structurally conserved over space and time while pairwise interactions show high variability. In such networks, modularity is the division of species into compartments, or modules, where species within modules share more interactions with each other than they do with species from other modules. Such a modular structure is common in mutualistic networks and several evolutionary and ecological mechanisms have been proposed as underlying drivers. One prominent explanation is the existence of pollination syndromes where flowers tend to attract certain pollinators as determined by a set of traits. We investigate the modularity of seven community level plant‐pollinator networks sampled in rupestrian grasslands, or campos rupestres, in SE Brazil. Defining pollination systems as corresponding groups of flower syndromes and pollinator functional groups, we test the two hypotheses that (1) interacting species from the same pollination system are more often assigned to the same module than interacting species from different pollination systems and; that (2) interactions between species from the same pollination system are more consistent across space than interactions between species from different pollination systems. Specifically we ask (1) whether networks are consistently modular across space; (2) whether interactions among species of the same pollination system occur more often inside modules, compared to interactions among species of different pollination systems, and finally; (3) whether the spatial variation in interaction identity, i.e., spatial interaction rewiring, is affected by trait complementarity among species as indicated by pollination systems. We confirm that networks are consistently modular across space and that interactions within pollination systems principally occur inside modules. Despite a strong tendency, we did not find a significant effect of pollination systems on the spatial consistency of pairwise interactions. These results indicate that the spatial rewiring of interactions could be constrained by pollination systems, resulting in conserved network structures in spite of high variation in pairwise interactions. Our findings suggest a relevant role of pollination systems in structuring plant‐pollinator networks and we argue that structural patterns at the sub‐network level can help us to fully understand how and why interactions vary across space and time.
Reproducing static and dynamic biodiversity patterns in tropical forests: the critical role of environmental variance
Authors: Fung Tak , O'Dwyer James P. , Rahman Kassim Abd. , Fletcher Christine D. , Chisholm Ryan A. 
Published: May 2016

AbstractEcological communities are subjected to stochasticity in the form of demographic and environmental variance. Stochastic models that contain only demographic variance (neutral models) provide close quantitative fits to observed species‐abundance distributions (SADs) but substantially underestimate observed temporal species‐abundance fluctuations. To provide a holistic assessment of whether models with demographic and environmental variance perform better than neutral models, the fit of both toSADs and temporal species‐abundance fluctuations at the same time has to be tested quantitatively. In this study, we quantitatively test how closely a model with demographic and environmental variance reproduces total numbers of species, total abundances,SADs and temporal species‐abundance fluctuations for two tropical forest tree communities, using decadal data from long‐term monitoring plots and considering individuals larger than two size thresholds for each community. We find that the model can indeed closely reproduce these static and dynamic patterns of biodiversity in the two communities for the two size thresholds, with better overall fits than corresponding neutral models. Therefore, our results provide evidence that stochastic models incorporating demographic and environmental variance can simultaneously capture important static and dynamic biodiversity patterns arising in tropical forest communities.
Native fungal endophytes suppress an exotic dominant and increase plant diversity over small and large spatial scales
Authors: Afkhami Michelle E. , Strauss Sharon Y. 
Published: May 2016

AbstractUnderstanding community dynamics and processes, such as the factors that generate and maintain biodiversity, drive succession, and affect invasion susceptibility, is a central goal in ecology and evolution. While most studies of how species interactions affect communities have focused on highly visible macroorganisms, we show that mutualistic microfungal endophytes have community‐level effects across their host plant's range and provide the first example of fungal endophytes enhancing plant diversity. A three‐year field study in which we experimentally manipulated endophyte abundance in a native Californian grass showed that despite their minute biomass, endophytes dramatically increased plant community diversity (~110% greater increase with endophytes) by suppressing a dominant invasive grass, Bromus diandrus. This effect was also detectable, but smaller, across five additional common gardens spanning ecologically diverse habitats, different climates, and >400 km of the host grass’ range as well as at microspatial scales within gardens. Our study illustrates that mutualistic microbes, while often hidden players, can have unexpectedly large ecological impacts across a wide range of habitats and scales and may be important for promoting diverse communities and ecosystems.
Failed and successful intentional introductions of fish species into 821 Swedish lakes
Authors: Henriksson Anna , Rydberg Cecilia , Englund Göran 
Published: May 2016

AbstractIntroductions of fish into lakes can be viewed as whole system experiments, which can be used to study the principles of community assembly and factors determining the outcome of species invasions. Freshwater fish species have been translocated by humans for centuries in Sweden, and this activity has been documented by national and regional authorities starting at the end of the 19th century. Based on this documentation and additional interviews with local fishermen, we have compiled a data set that includes 1157 intentional introductions of 26 freshwater fish species into 821 Swedish lakes. The data include both successful and failed introductions; where a successful introduction means that the introduced fish species was present in the lake for ≥20 yr or that reproduction was observed earlier than that. The oldest introduction is from 1658 and the latest from 2002. Additionally, the data set includes species composition, water temperature sum, maximum water temperature, lake area, elevation, longitude, and latitude for all lakes. These data have been used to test hypotheses about biotic resistance and invasion success in three papers. We found the presence or absence of specific species predicted invasion success better than the species richness of the lakes. We also found that species with high invasion success tend to make a large contribution to biotic resistance, which will make communities more resistant in the future as they are invaded by additional species.
Stoichiometry of microbial carbon use efficiency in soils
Authors: Sinsabaugh Robert L. , Turner Benjamin L. , Talbot Jennifer M. , Waring Bonnie G. , Powers Jennifer S. , Kuske Cheryl R. , Moorhead Daryl L. , Follstad Shah Jennifer J. 
Published: May 2016

AbstractThe carbon use efficiency (CUE) of microbial communities partitions the flow of C from primary producers to the atmosphere, decomposer food webs, and soil C stores. CUE, usually defined as the ratio of growth to assimilation, is a critical parameter in ecosystem models, but is seldom measured directly in soils because of the methodological difficulty of measuring in situ rates of microbial growth and respiration. Alternatively, CUE can be estimated indirectly from the elemental stoichiometry of organic matter and microbial biomass, and the ratios of C to nutrient‐acquiring ecoenzymatic activities. We used this approach to estimate and compare microbial CUE in >2000 soils from a broad range of ecosystems. Mean CUE based on C:N stoichiometry was 0.269 ± 0.110 (mean ± SD). A parallel calculation based on C:P stoichiometry yielded a mean CUE estimate of 0.252 ± 0.125. The mean values and frequency distributions were similar to those from aquatic ecosystems, also calculated from stoichiometric models, and to those calculated from direct measurements of bacterial and fungal growth and respiration. CUE was directly related to microbial biomass C with a scaling exponent of 0.304 (95% CI 0.237–0.371) and inversely related to microbial biomass P with a scaling exponent of −0.234 (95% CI −0.289 to −0.179). Relative to CUE, biomass specific turnover time increased with a scaling exponent of 0.509 (95% CI 0.467–0.551). CUE increased weakly with mean annual temperature. CUE declined with increasing soil pH reaching a minimum at pH 7.0, then increased again as soil pH approached 9.0, a pattern consistent with pH trends in the ratio of fungal : bacteria abundance and growth. Structural equation models that related geographic variables to CUE component variables showed the strongest connections for paths linking latitude and pH to β‐glucosidase activity and soil C:N:P ratios. The integration of stoichiometric and metabolic models provides a quantitative description of the functional organization of soil microbial communities that can improve the representation of CUE in microbial process and ecosystem simulation models.
Ethos e Pathos na constituição do gênero testemunho religioso na mídia
Authors: Souza Ronivaldo Moreira de 
Published: May 2016

Resumo: Dado ao lugar central que o Testemunho Religioso ocupa na liturgia das igrejas neopentecostais e o evidente uso que fazem do gênero no contexto midiático como forma de persuasão e adesão de novos fiéis, esta pesquisa se propõe à investigação de como se dá a construção das imagens de si neste gênero de discurso. Para investigação do fenômeno recorre-se aos estudos sobre ethose pathos nos teóricos da Escola Francesa de Análise do Discurso aplicando-os aos testemunhos que a Igreja Universal do Reino de Deus publica em sua página na internet: www.eucreioemmilagres.com.br. Palavras-chave: Ethos.Pathos. Igreja Universal do Reino de Deus. Testemunho religioso. Abstract:Religious Testimony occupies a central place in the liturgy of neo-Pentecostal churches and the genre is widely used in the media context as a form of persuasion and accession of new believers. So, this article aims to investigate how is the construction of the images of themselves in this kind of discourse. In order to do that, it investigates the phenomenon through the study of ethos and pathos in theorists of the French School of Discourse Analysis by applying them to the testimonies the Universal Church of the Kingdom of God published on its websitewww.eucreioemmilagres.com.br. Keywords: Ethos. Pathos. Universal Church of the Kingdom of God. Religious Testimony
An Integrated Software Technology Based on Research and Field Application for Completion, Stimulation and Fluid Placement Design in Complex Wells
Authors: Sau Rajes , Goodrow Anthony , Rockwell Marcus , Mayer Christian Sebastian Jakob , Shuchart Chris E. , Grubert Marcel Andre 
Published: May 2016

Abstract
Today, many wells all over the world are being completed with long intervals and complex completion equipment, such as limited-entry liners (LEL) and inflow control devices (ICDs). Accurate predictions and understanding of fluid placement during stimulation or injection operations through these complex completions can be quite challenging. This paper presents an integrated software technology based on research and field application for advanced completion, stimulation and fluid placement design of complex wells. The crux of the software is a novel and robust computational modeling simulator. Using innovative computational algorithms, this simulator models numerous challenging physics of acid stimulation and transient injection of multiple fluids through openhole complex completions, e.g. LEL and ICDs in long wells. LEL hole or ICD nozzle diameter, hole distributions, and packers are modeled as part of the completion while explicitly tracking multiple fluid concentrations and accounting for completion and formation pressure drops along the lateral and transient reservoir dynamics. Fundamental understanding of fluid placement is achieved through this stable and accurate computational model supported by experiments. Large-scale experiments have been performed to validate the model and understand the annular fluid displacement of multiple fluids through complex liner designs. Fluid invasion and stimulation distribution (wormhole and skin) along the lateral are computed by the simulator, which is coupled with a dynamic wormhole model. In addition to acid stimulation design, the software also provides capabilities to model various well injection processes in sandstone and carbonate reservoirs, such as scale squeezes, solvent treatments, and HF acid treatments along with corresponding productivity uplift estimates.
The integration of the computational model into proprietary subsurface software is achieved through an accelerated technology delivery process involving engineering researchers, software developers/computational scientists, and end-users in the field. The software creates a distinct advantage by giving engineers in the field the capability to quickly perform these analyses, which can lead to reduced overall development and operation costs, increased individual well productivity, and most importantly the capture of additional reserves.
A case history of the model application will be presented. The model was used to design a limited-entry liner with 4 mm holes distributed non-uniformly among 12 compartments. The liner enabled successful high-rate bullhead stimulation of an 11,500-ft lateral, resulting in reduced cost, limited risk, and elimination of the need for coiled tubing. The field data is used to validate the model predictions and calibrate model parameters.
An Alternate Mud Proposal to Minimise Borehole Instability
Authors: Altun Gursat , Osgouei Ali Ettehadi , Ozyurtkan Mustafa Hakan 
Published: May 2016

Abstract
There exists a strong relationship between mud and borehole stabilities. Mud instability is associated with flocculation that is primarily caused by high active solids, high electrolyte concentration, and high temperature. Drilling in hot environments coupled with active or reactive solid contamination results in severe operational problems which get worse with the presence of salt intrusion. Therefore, drilling engineers search for alternate drilling fluids to eliminate and/or minimize instability problems such as stuck pipes, circulation loss, excessive torque and drag, inadequate cuttings transport, and sloughing borehole. Such mud should tolerate for accumulation of high amount of reactive solids and mitigate diffetential pressure sticking to avoid stuck pipe.
This study is an experimental work to investigate and remediate the rheological and fluid loss properties of both unweighted and barite-weighted sepiolite muds heavily contaminated with active solid. Sepiolite muds were formulated in a certain mixing order of additives. Bentonite clay with API specifications (OCMA) at a rate of 80-lbm/bbl was used to simulate active solid. Rheological properties of mud samples were tested at varying temperatures ranging from ambient to 400oF along with a sodium chloride content of 260,000-ppm (120-lbm/bbl). The filtration loss properties were determined at 300oF. Methylene blue test was also performed to determine the tolerance of sepiolite mud for reactive solid contamination. Sepiolite mud was also investigated for tendency to cause wall sticking to consider incidence of differential pressure sticking of drill pipe. Bulk Sticking Coefficient (Ksc) of sepiolite based mud was determined as indicator parameters under high pressure (500 psi) and high temperature (up to 400oF).
Sepiolite mud samples resulted in appropriate yield point, plastic viscosity, and water loss values. More importantly, Methylene Blue values lower than 13-lb/bbl and appropriate sticking coefficient were the concrete usability indicator of sepiolite muds against heavily reactive-clay contamination. In other words, sepiolite muds might be a good alternative to drill wells experiencing instability problems resulting from active solid contamination and differential sticking.
Reversing the Production Decline and Maximizing Late-life Value of a Mature Oilfield in Offshore South China – A Brownfield Re-Development Project Success Story
Authors: Luo Donghong , Li Lin , Tao Bin , Halomoan Parlindungan Monris , Bisain Amarjit Singh , Wang Chao 
Published: May 2016

Abstract
A brownfield new horizontal wells re-development project was initiated in mid-2012 to arrest the production decline rate of Panyu oilfield with average field water cut of 91% and to further increase its reserve recovery.
The new horizontal wells campaign were targeting at the remaining less than 5m thin oil column with strong bottom water drive and the previously unexploited 2m thin layers reserves. However, the re-development and exploiting these targets present operational challenges with increasing complexity. Not only the horizontal well needs to be optimally placed within complex target zone, the lateral also needs to be placed as close as possible to the reservoir top to keep it away from the unknown current fluid contact.
This paper features the best practices implemented to optimize the standoff between horizontal section and oil water contact that is very sensitive to well performance and reserve recovery. This includes precise landing with low incident angle and lateral placement within less than 0.5m window below the reservoir top utilizing the directional electromagnetic and wellbore imaging applications for detail reservoir profiles description and current OWC level identification while drilling.
Multiple wells' field cases will be discussed in the paper based on 25 horizontal wells completed during the course of the project. Several key outcomes that have been observed during the execution and upon the completion of the well will be highlighted, including:- Clear identification of the reservoir geo-bodies and their interfaces including the current fluid contact level- Optimum lateral placement in the best position to drain the remaining hydrocarbon- Reversing the production decline trend and exceeding the cumulative incremental oil by 45% over the forecast.
Finally, the authors conclude that significant oil reserve can remain in mature fields and be recovered through re-entry horizontal wells drilling program. The implementation of the best practices in operation is the key enabler to effectively place the trajectory in the best place to drain the remaining hydrocarbon that lead to maximizing the late-life value of a mature oilfield.