bluuebunny/crossref_metadata_2025 huggingface dataset:
Crane overlap and operational flexibility: balancing utilization, duration, and safety
Authors: Al Hattab Malak , Zankoul Emile , Barakat Mohammad , Hamzeh Farook
Published: December 2017

Purpose

With tower cranes being the site hubs, thoroughly planning and managing their operations can result in better construction performance. As urban spaces become more constricted, overlapping working radii of tower cranes becomes inevitable. While project planners are concerned with safety hazards, research has not comprehensively addressed workload distribution and synchronization of overlapping cranes. Therefore, this study aims at exploring the impact of overlapping cranes, used on high-rise buildings, on operational flexibility which is the balance between schedule duration, crane utilization and safety.

Design/methodology/approach

A simulation model was developed and applied on a real project to analyze and compare the impacts of different overlap sizes. Seven scenarios of different overlap sizes, i.e. different number of tasks falling in the overlap space, were executed in the model; their results were plotted and analyzed.

Findings

The outcomes result from several compounded factors such as the experience of planners and crane operators, the sequencing of critical versus non-critical activities and the overall effort and care taken when planning operations of overlapping cranes. Increasing overlap size can be beneficial or unfavorable depending on how properly planners allocate overlapping cranes to workload demand, keeping in mind that there are certain trade-offs while achieving operational flexibility.

Originality/value

While project planners are concerned with safety hazards associated with crane overlaps, research has not been comprehensively nor proactively addressing the workload distribution and synchronization of overlapping crane processes. This study contributes to science by addressing the need to harness the flexibility in using overlapping tower cranes while minimizing the resulting interruptions and safety risks. This study sheds light on the potential benefits of allowing cranes to overlap while considering their collision free operations. Operational flexibility is seen as the balance between achieving shorter schedule durations and higher crane utilizations while maintaining collision free motion paths.
Penalty mechanisms for enforcing concessionaire performance in public–private partnership contracts in Nigeria
Authors: Opawole Akintayo
Published: December 2017

Purpose

The purpose of this study is to develop penalty measures against concessionaires’ defaults as a mechanism for protecting the interests of parties (public and private) in public–private partnership (PPP) contracts for enhancing project delivery.

Design/methodology/approach

The research methodology is a mixed qualitative and quantitative approach. This study commenced with an in-depth literature review, which provided the basis for identification of penalty measures in construction contract management. The qualitative assessment was based on semi-structured face-to-face interviews, which were aimed at identifying the underlying pattern of the penalty measures, and the quantitative assessment was based on a structured questionnaire. In both cases, respondents were stakeholders’ organizations that had been involved in PPP contracts in the southwestern region of Nigeria. These include industrial practitioners from government-based organizations (ministries, agencies, corporations/parastatals, etc.), private developers/concessionaires, law firms, banks, etc. The sample size was selected using a respondent-driven sampling approach, as the comprehensive lists of the participants in PPP contracts are not readily available in the Nigerian construction industry. Responses from the interview were analysed using interpretative phenomenal analysis via ATLAS.ti7. The quantitative data were analysed using percentile for flexibility between “most” and “more” preferred mechanisms.

Findings

This study developed mechanisms that defined the rights of the public party to redress underperformance of PPP contracts consequent to the defaults of the private party. “Step-in-right” and “termination of the contracts” were preferred against specific cases of “delayed execution”, “abandonment of the project”, “bankruptcy of the concessionaire” and “non-compliance with design and specifications”. With respect to “shortfall in performance against established dates”, the results converged on “monetary fine” and diverged on “step-in-right” and “termination of the contracts”.

Practical implications

The study contributes to literature on mechanisms for enforcing PPP project performance. Besides, defining rights and obligations of the parties in specific events of underperformance of the concessionaires in PPP contracts is a significant step towards the development of standard conditions of contract for managing PPP projects in which the model is being newly adopted.

Originality/value

Project management studies on PPP were extended by defining the liabilities that are consequent to the defaults of the private party and the mechanisms for their enforcement.
Development and validation of disability management indicators for the construction industry
Authors: Quaigrain Rhoda Ansah , Issa Mohamed H.
Published: December 2017

Purpose

Support at the organizational and managerial levels defines the degree to which construction workplaces can accommodate disabled and injured workers. There is little empirical evidence about the indicators and practices that can be used by construction organizations to evaluate disability management (DM). This paper aims to develop and validate key indicators and practices of disability/injury management within construction.

Design/methodology/approach

To achieve this, the research used a two-phase sequential exploratory review of literature, followed by a quantitative phase, using analytic hierarchy process. The analytical hierarchy process (AHP) involved recruiting eight health and safety and DM experts to conduct pairwise comparisons of these indicators.

Findings

The results found return-to-work and disability and injury management practices to be the most important indicators and physical accessibility and claims management practices to be the least important.

Practical implications

The development of these indicators should help construction organizations develop DM programs that better meet their needs, and benchmark and improve related performance.

Social implications

The results could also be useful for all stakeholders in general and decision makers in particular involved within construction.

Originality/value

Such prioritization helps organizations to prioritize their DM practices thereby optimizing performance.
Infrastructure procurement skills gap amongst procurement personnel in Nigeria’s public sector
Authors: Mahamadu Abdul-Majeed , Manu Patrick , Booth Colin , Olomolaiye Paul , Coker Akinwale , Ibrahim Ahmed , Lamond Jessica
Published: December 2017

Purpose

Procurement of public infrastructure that is fit for purpose partly depends on the competencies of procurement personnel. In many developing countries in Sub-Saharan Africa, including Nigeria, there is a deficit in the quantity and quality of infrastructure and their procurement is further riddled with deficiencies in the capacity of public procuring entities. The purpose of this study was to ascertain the critical skills development needs of public personnel involved in the procurement of infrastructure in Nigeria.

Design/methodology/approach

Based on a quantitative research strategy, this study sought to address the knowledge gap through a survey of public infrastructure procurement personnel (n = 288) in different tiers of government (i.e. state and local government) and geopolitical contexts (north and south) in Nigeria.

Findings

Of the 45 procurement skill areas operationalised, there is need for further development in 38 of them including: computing/ICT; problem-solving; communication; decision-making; health and safety management; quality management; relationship management; team building; project monitoring and evaluation; time management and procurement planning.

Originality/value

A key implication of this study is for policymakers in state and local government to formulate and implement infrastructure procurement capacity development reforms that address the competency gaps of procurement personnel. Such reforms need to take into account the suitable methods for developing procurement competencies. Additionally, the procurement skill areas operationalised in this capacity assessment study could serve as a useful blueprint for studying capacity deficiencies amongst public infrastructure procurement personnel in other developing countries.
Behaviour of geosynthetic reinforced column supported embankments
Authors: Yapage Namal , Liyanapathirana Samanthika
Published: December 2017

Purpose

This paper aims to investigate the behaviour of geosynthetic reinforced deep cement mixed (DCM) column-supported embankments constructed over soft soils.

Design/methodology/approach

Coupled consolidation analyses based on the finite element method are carried out assuming that the soil and DCM columns are fully saturated porous mediums. In the first part of the paper, a case study of an embankment constructed over a very soft soil deposit in Finland is presented. Two- and three-dimensional finite element models for the case study are developed including isolated and attached DCM columns beneath the embankment to capture the arching mechanism between DCM columns. The model simulations were carried out considering the actual staged construction procedure adopted in the field. Finite element predictions show good agreement with field data and confirm that the load transfer is mainly between attached columns beneath the embankment. Next, the significance of geosynthetic reinforcement on the load transfer mechanism is investigated. Finally, the influence of permeability of columns and soft soil on the performance of geosynthetic reinforcement column-supported embankments is studied.

Findings

Results demonstrate that the excess pore pressure dissipation rate is fast in DCM column-improved ground compared to the same case without any columns, although the same permeability is assigned to both DCM columns and surrounding soft soil. When DCM column permeability exceeds soil permeability, excess pore pressure dissipation rate shows a remarkable increase compared to that observed when the DCM column permeability is less than or equal to the permeability of surrounding soft soil. [ ]

Originality/value

This paper investigates the contribution of permeability and geosynthetic layer on the vertical load transfer mechanism of the embankment and modelling issues related to application of the embankment load and the properties of the cement-improved columns.
The role of IT in automotive supplier supply chains
Authors: Fuchs Christoph , Beck Daniel , Lienland Bernhard , Kellner Florian
Published: December 2017

Purpose

The purpose of this paper is to explore the impact of information technology (IT) on supply chain performance in the automotive industry. Prior studies that analyzed the impact of IT on supply chain performance report results representing the situation of the “average industry.” This research focuses on the automotive industry because of its major importance in many national economies and due to the fact that automotive supply chains do not represent the supply chain of the average industry.

Design/methodology/approach

A research model is proposed to examine the relationships between IT capabilities, supply chain capabilities, and supplier performance. The model divides IT capabilities into functional and data capabilities, and supply chain capabilities into internal process excellence and information sharing. Data have been collected from 343 automotive first-tier suppliers. Structural equation modeling with partial least squares is used to analyze the data.

Findings

The results suggest that functional capabilities have the greatest impact on internal process excellence, which in turn enhances supplier performance. However, frequent and adequate information sharing also contributes significantly to supplier performance. Data capabilities enable supply chain capabilities through their positive impact on functional capabilities.

Practical implications

The findings will help managers to understand the effect of IT implementation on company performance and to decide whether to invest in the expansion of IT capacities.

Originality/value

This research reports the impact of IT on supply chain performance in one of the most important industries in many industrialized countries, and it provides a new perspective on evaluating the contribution of IT on firm performance.
Business excellence via advanced manufacturing technology and lean-agile manufacturing
Authors: Ghobakhloo Morteza , Azar Adel
Published: December 2017

Purpose

The purpose of this paper is to contribute to the existing knowledge about the relationships between advanced manufacturing technology (AMT), lean manufacturing (LM), agile manufacturing (AM), and business performance.

Design/methodology/approach

A questionnaire-based survey was performed to collect data from 189 Iranian automobile part manufacturers. Statistical analysis of hypothesized relationships was conducted via partial least squares structural equation modeling.

Findings

AMT significantly contributes to the development of both LM and AM. These manufacturing systems can co-exist in one system, and LM is a precursor to AM. LM contributes to operational performance whereas AM improves marketing performance and financial performance.

Research limitations/implications

Relying on the cross-sectional data of this research, and lack of generalizability of findings are key limitations. An interesting direction for future research would be to empirically offer a hybrid lean-agile approach and further map the mechanism through which this hybrid approach can be achieved in practice.

Practical implications

Both LM and AM are information-intensive and highly supported by AMT. They contribute to different aspects of business performance. Pursuing both cost-leadership strategy and product mix flexibility is viable via hybridizing the lean and agile systems.

Originality/value

This study is among the first to address issues related to the lean-AM relationship among developing countries. This study is unique in the sense it shows the mechanism through which the value of AMT is truly transformed to performance improvement.
Exploring the key success factors of advanced manufacturing technology implementation in Indian manufacturing industry
Authors: Kumar Raman , Singh Harwinder , Chandel Rohit
Published: December 2017

Purpose

The purpose of this paper is twofold: first, to explore the relationship between success parameters and implementation of advanced manufacturing technology (AMT); and second, to examine the changes required in manufacturing system as a result of AMT implementation.

Design/methodology/approach

The first order confirmatory factor analysis was performed to validate the presence of observed variables on their respective latent variable. Structural equation modeling is used to test the considered eight hypotheses.

Findings

The finding indicates that all five success factors are positively related to the AMT implementation. The redesign in the production system and organization strategy is directly related to the AMT implementation. The notable finding is the AMT implementation has no direct impact on the redesign of human resource, but it has mediated impact through the production system.

Research limitations/implications

The originality and reliability of data collected for research purpose merely depends upon information and the accessible resources.

Originality/value

The outcome of the present work gives rise to meaningful implications for researchers and practitioners as well.
Reverse supply chain practices in developing countries: the case of Morocco
Authors: El Baz Jamal , Frei Regina , Laguir Issam
Published: December 2017

Purpose

The purpose of this paper is to investigate reverse supply chain (RSC) practices and their obstacles using case studies of Moroccan companies. The authors present the main findings of case studies’ analysis along with a discussion of an RSC framework for further directions of research.

Design/methodology/approach

A qualitative approach was adopted and semi-structured interviews with Moroccan companies were conducted using an interview guide.

Findings

The authors present an RSC model that encompasses remanufacturing, refurbishing and disposal processes. The authors believe that this model would constitute a promising framework for further research. The findings show that the successful implementation of RSC depends on many factors, but the company’s attitude (proactive or conservative) is one of the most critical determinants in RSC initiatives. Furthermore, the results of the case studies indicate two types of inhibitors: external and internal. These findings confirm the results of previous research on environmental sustainability obstacles in general and RSC obstacles in particular.

Research limitations/implications

This study has some limitations that provide future research opportunities. Because this study is qualitative, further statistical support is needed to justify wider generalisation of its findings. Further studies might therefore investigate RSC practices in developing countries other than Morocco to increase the external validity of the results.

Practical implications

The findings can help firms to gain better understanding of their RSC and particularly the link between forward and RSCs. Consequently, companies can upgrade their business models to better control their RSC activities.

Originality/value

The relevant literature about RSC practices has mainly targeted manufacturing sectors in developed countries, and few studies have been conducted on developing countries. Research on RSC practices in developing countries in general and African countries in particular is sparse. This is one of the first articles written to address this gap by investigating RSC practices in Morocco.
Additive manufacturing in the wood-furniture sector
Authors: Murmura Federica , Bravi Laura
Published: December 2017

Purpose

In the world economy there is the emergence of advanced manufacturing technologies that are enabling more cost and resource-efficient small-scale production. Among them, additive manufacturing, commonly known as 3D printing, is leading companies to rethink where and how they conduct their manufacturing activities. The purpose of this paper is to focus in the Italian wood-furniture industry to understand if the companies in this sector are investing in additive manufacturing techniques, to remain competitive in their reference markets. The research also attempts to investigate the potential sustainable benefits and limitations to the implementation of 3D printing in this specific sector, considering the companies that have already implemented this technology.

Design/methodology/approach

Data were collected using a structured questionnaire survey performed on a sample of 234 Italian companies in this sector; 76 companies claimed to use 3D printing in their production system. The questionnaire was distributed via computer-assisted web interviewing and it consisted of four sections.

Findings

The research has highlighted how Italian 3D companies have a specific profile; they are companies aimed at innovating through the search for new products and product features, putting design and Made in Italy in the first place. They pay high attention to the image they communicate to the market and are highly oriented to the final customer, and to the satisfaction of its needs.

Originality/value

The study is attempting to expand a recent and unexplored research line on the possible advantages and disadvantages of the implementation of emerging production technologies such as 3D printing.
The emergence and performance of German REITs
Authors: Newell Graeme , Marzuki Muhammad Jufri
Published: December 2017

Purpose

German real estate investment trusts (REITs) are a small but important property investment vehicle in the European REIT landscape, offering German commercial property investment exposure in a liquid format, compared to the more property development-focused German listed property companies and the popular German open-ended property funds. The purpose of this paper is to assess the emergence of the German REIT market and the risk-adjusted performance and portfolio diversification benefits of German REITs in a mixed-asset portfolio over 2007-2015. The post-global financial crisis (GFC) recovery of German REITs is highlighted. Enabling strategies for the ongoing development of the German REIT market are also identified.

Design/methodology/approach

Using monthly total returns, the risk-adjusted performance and portfolio diversification benefits of German REITs over 2007-2015 are assessed. Efficient frontier and asset allocation diagrams are used to assess the role of German REITs (and German property companies) in a mixed-asset portfolio. Sub-period analysis is used to assess the post-GFC recovery of German REITs.

Findings

German REITs delivered lesser risk-adjusted returns compared to German stocks over 2007-2015, with limited portfolio diversification benefits. However, since the GFC, German REITs have delivered strong risk-adjusted returns, but with continued limited portfolio diversification benefits with German stocks. German REITs also out-performed German property companies. Importantly, this sees German REITs as strongly contributing to the German mixed-asset portfolio across the portfolio risk spectrum in the post-GFC environment.

Practical implications

German REITs are a small but important market at a local, European and global REIT level. The results highlight the major role of German REITs in a German mixed-asset portfolio in the post-GFC context. The strong risk-adjusted performance of German REITs compared to German stocks sees German REITs contributing to the mixed-asset portfolio across the portfolio risk spectrum. This is particularly important, as many investors (e.g. small pension funds) use German REITs (and German listed property companies) to obtain their German property exposure in a liquid format, as well as the increased importance of blended property portfolios of listed property and direct property.

Originality/value

This paper is the first published empirical research analysis of the risk-adjusted performance of German REITs, and the role of German REITs as a listed property vehicle in a mixed-asset portfolio. This research enables empirically validated, more informed and practical property investment decision making regarding the strategic role of German REITs in a portfolio.
Does urban tourism attractiveness affect young adult migration in Germany?
Authors: Schäfer Philipp , Just Tobias
Published: December 2017

Purpose

The purpose of this paper is to analyze whether urban tourism attractiveness affects young adult migration within Germany. Currently, factors like urban attractiveness, environmental qualities or vicinity to amenities play a more important role for the migration of young adults than in the past. This has highly asymmetric implications for the housing (and commercial real estate) markets in cities with an abundance of urban attractiveness, compared to cities without such attractions.

Design/methodology/approach

This analysis focuses on the internal migration of young adults (18-30-year-olds). First, some stylized facts regarding migration patterns are presented by means of descriptive and cluster analyses (k-means methodology) with respect to the net immigration rate for the two years, 2004 and 2014. Second, ordinary least squares-regression analyses are used to estimate the connection between urban tourism attractiveness and migration.

Findings

Young adults in Germany predominantly migrate to cities. The authors find typical migration patterns, and the regression results indicate that young adult migration is highly correlated with the indicator measuring urban tourism attractiveness. This means that urban attractions matter for young adults. Finally, the authors also find that housing rents are correlated with urban tourism attractiveness.

Practical implications

Good city planning must not only be concerned with new industrial sites, but also about esthetic neighborhoods and, for example, attractive squares. Moreover, because city structures and urban amenities are both path dependent and expensive to change, it is likely that the winning cities of today will remain winners in the next decade, which is good news for risk-averse investors.

Originality/value

To the best of the authors’ knowledge, the paper provides the first empirical analysis of the connection between urban tourism attractiveness and the migration of young adults, in the context of German cities.
Green pay off in commercial real estate in Germany: assessing the role of Super Trophy status
Authors: Ott Christian , Hahn Jonas
Published: December 2017

Purpose

Based on a hedonic regression approach, the purpose of this paper is to relativize existing green pay off evidence by incorporating Super Trophy as a so far underrepresented determinant. The authors analyze a private panel database of 160 European office properties and confirm a significant green pay off; the positive impact of excellent environmental certification results on market values and net rents is significantly reduced when considering Super Trophy characteristics.

Design/methodology/approach

Based on a panel database of 160 European office properties, the survey applies a hedonic regression approach including an extensive set of control factors as, for example, location criteria, general property characteristics, climate adjustments, consumption data, refurbishment activities, green leases, sustainable certification and energy performance certificate figures.

Findings

Even though our database still confirms a significant green pay off, the positive impact of excellent environmental certification results on market values and net rents is significantly reduced when controlling for Super Trophy characteristics.

Practical implications

Especially, the question how sustainability can be integrated into real estate appraisal is of major interest. The paper at hand may help in two aspects: on the one hand, it provides further insight with regard to the quantitative impact of Super Trophy Buildings on rents and market values. On the other hand, a higher transparency in appraisals may result in structural specifications that help to consolidate appraisals and empirical evidence on a “green pay off.”

Originality/value

The study investigates a niche segment – landmark properties. The empirical analysis explicitly controls for potential Super Trophy status. It draws attention to the importance of a reasonable and complete set of control variables to increase statistical validity of future studies in that field.
How flood risk impacts residential rents and property prices
Authors: Hirsch Jens , Hahn Jonas
Published: December 2017

Purpose

The purpose of this paper is to quantify the impact of 100-year flood risk on both property rents and values in Germany, exemplified by the market of the historic city of Regensburg, and therefore supports investors in understanding market behavior patterns in both rental and investment context.

Design/methodology/approach

The authors construct two generalized additive models for rents and purchasing prices with spatial components and under inclusion of both typical property characteristics (as control variables) and a 100-year flood risk parameter in order to estimate its effect on the rents and property price structure. The authors apply the methodology to a four-year data set of more than 16,500 observations.

Findings

The analysis shows that flood risk is a highly significant parameter when estimating both the rent as well as the sales price model. The authors also find that purchase prices for one square meter of living area are, on average, EUR299 lower if the property is located in the flood risk zone. In addition, also rental markets come with a respective, but rather low, discount.

Practical implications

The authors provide transparency to investors in terms of the impact that a flood risk location has on property rents as well as purchasing prices. The study supports investors by providing evidence on reaction patterns in German real estate markets and helps quantifying the financial impact that comes with flood risk in Germany.

Originality/value

This is the first study that aims to empirically test and to quantify the impact of flood risk on property rents and purchasing prices in Germany. Related research has been performed for the USA, Ireland and New Zealand and largely refers to event-driven work or rather conceptual in the context of property valuation.
Thermodynamic analysis of hybrid nanofluid based solar flat plate collector
Authors: J.A. Ranga Babu , K. Kiran Kumar , S. Srinivasa Rao
Published: December 2017

Purpose

This paper aims to present an analytical investigation of energy and exergy performance on a solar flat plate collector (SFPC) with Cu-CuO/water hybrid nanofluid, Cu/water and CuO/water nanofluids as collector running fluids.

Design/methodology/approach

Heat transfer characteristics, pressure drop and energy and exergy efficiencies of SFPC working on these nanofluids are investigated and compared. In this study, a comparison is made by varying the mass flow rates and nanoparticle volume concentration. Thermophysical properties of hybrid nanofluids are estimated using distinctive correlations available in the open literature. Then, the influence of these properties on energy and exergy efficiencies of SFPC is discussed in detail.

Findings

Energy analysis reveals that by introducing the hybrid nanoparticles in water, the thermal conductivity of the working fluid is enhanced by 17.52 per cent and that of the individual constituents is enhanced by 15.72 and 15.35 per cent for Cu/water and CuO/water nanofluids, respectively. This resulted in 2.16 per cent improvement in useful heat gain for hybrid nanofluid and 1.03 and 0.91 per cent improvement in heat gain for Cu/water and CuO/water nanofluids, respectively. In line with the above, the collector efficiency increased by 2.175 per cent for the hybrid nanofluid and 0.93 and 1.05 per cent enhancement for Cu/water and CuO/water nanofluids, respectively. Exergy analysis elucidates that by using the hybrid nanofluid, exergy efficiency is increased by 2.59 per cent, whereas it is 2.32 and 2.18 per cent enhancement for Cu/water and CuO/water nanofluids, respectively. Entropy generation is reduced by 3.31, 2.35 and 2.96 per cent for Cu-CuO/water, Cu/water and CuO/water nanofluids, respectively, as compared to water.

Research limitations/implications

However, this is associated with a penalty of increment in pressure drop of 2.92, 3.09 and 2.74 per cent for Cu-CuO/water, Cu/water and CuO/water nanofluids, respectively, compared with water.

Originality/value

It is clear from the analysis that Cu-CuO/water hybrid nanofluids possess notable increment in both energy and exergy efficiencies to use them in SFPCs.
Fly ash-based green composite as pipe, gear and blade
Authors: MP Jenarthanan , Kumar S. Ramesh , Kumar Singh Akhilendra
Published: December 2017

Purpose

This paper aims to perform an experimental investigation on the impact strength, compressive strength, tensile strength and flexural strength of fly ash-based green composites and to compare with these polyvinyl chloride (PVC), high density polyethylene (HDPE) and low density polyethylene (LDPE).

Design/methodology/approach

Fly ash-based polymer matrix composites (FA-PMCs) were fabricated using hand layup method. Composites containing 100 g by weight fly ash particles, 100 g by weight brick dust particles and 50 g by weight chopped glass fiber particles were processed. Impact strength, compressive strength, tensile strength and flexural strength of composites have been measured and compared with PVC, HDPE and LDPE. Impact strength of the FA-PMC is higher than that of PVC, HDPE and LDPE. Structural analysis of pipes, gears and axial flow blade was verified using ANSYS. Barlou’s condition for pipes, Lewis–Buckingham approach for gears and case-based analysis for axial flow blades were carried out and verified.

Findings

Pipes, gears and axial flow blades made form fly ash-based composites were found to exhibit improved thermal resistance (i.e. better temperature independence for mechanical operations), higher impact strength and longer life compared to those made from PVC, HDPE and LDPE. Moreover, the eco-friendly nature of the raw materials used for fabricating the composite brings into its quiver a new dimension of appeal.

Originality/value

Experimental investigation on the impact strength, compressive strength, tensile strength and flexural strength of fly ash-based green composites has not been attempted yet.
Dynamic occupancy modelling reveals a hierarchy of competition among fishers, grey foxes and ringtails
Authors: Green David S. , Matthews Sean M. , Swiers Robert C. , Callas Richard L. , Scott Yaeger J. , Farber Stuart L. , Schwartz Michael K. , Powell Roger A.
Published: December 2017

Determining how species coexist is critical for understanding functional diversity, niche partitioning and interspecific interactions. Identifying the direct and indirect interactions among sympatric carnivores that enable their coexistence is particularly important to elucidate because they are integral for maintaining ecosystem function.

We studied the effects of removing nine fishers (Pekania pennanti) on their population dynamics and used this perturbation to elucidate the interspecific interactions among fishers, grey foxes (Urocyon cinereoargenteus) and ringtails (Bassariscus astutus). Grey foxes (family: Canidae) are likely to compete with fishers due to their similar body sizes and dietary overlap, and ringtails (family: Procyonidae), like fishers, are semi‐arboreal species of conservation concern. We used spatial capture–recapture to investigate fisher population numbers and dynamic occupancy models that incorporated interspecific interactions to investigate the effects members of these species had on the colonization and persistence of each other's site occupancy.

The fisher population showed no change in density for up to 3 years following the removals of fishers for translocations. In contrast, fisher site occupancy decreased in the years immediately following the translocations. During this same time period, site occupancy by grey foxes increased and remained elevated through the end of the study.

We found a complicated hierarchy among fishers, foxes and ringtails. Fishers affected grey fox site persistence negatively but had a positive effect on their colonization. Foxes had a positive effect on ringtail site colonization. Thus, fishers were the dominant small carnivore where present and negatively affected foxes directly and ringtails indirectly.

Coexistence among the small carnivores we studied appears to reflect dynamic spatial partitioning. Conservation and management efforts should investigate how intraguild interactions may influence the recolonization of carnivores to previously occupied landscapes.
More invaders do not result in heavier impacts: The effects of non‐native bullfrogs on native anurans are mitigated by high densities of non‐native crayfish
Authors: Liu Xuan , Wang Supen , Ke Zunwei , Cheng Chaoyuan , Wang Yihua , Zhang Fang , Xu Feng , Li Xianping , Gao Xu , Jin Changnan , Zhu Wei , Yan Shaofei , Li Yiming
Published: December 2017

With accelerating species introductions in an era of globalization, co‐occurring alien species have become increasingly common. Understanding the combined ecological impacts of multiple invaders is not only crucial for wildlife managers attempting to ameliorate biodiversity loss, but also provides key insights into invasion success and species coexistence mechanisms in natural ecosystems. Compared with much attentions given to single‐invader impacts, little is known about the impacts of multiple co‐occurring invaders.

The American bullfrog (Lithobates catesbeianus = Rana catesbeiana) and the red swamp crayfish (Procambarus clarkii) are two aquatic invasive species in many different areas of the globe. They coexist with native anurans in a variety of permanent lentic waters, which provide an ideal model system to explore the combined effects of multiple invaders from different trophic levels on native species.

Based on a global diet analysis covering 34 native and invasive bullfrog populations, and data from 10‐year field surveys across 157 water bodies in the Zhoushan Archipelago, China, we observed a reduced impact of bullfrogs on native anurans at high crayfish densities when the two invaders co‐occurred.

The global diet analysis showed that crayfish occurrence reduced the number of native anuran prey consumed by bullfrogs in both native and invasive populations. After accounting for pseudoreplication of different observations among water bodies, islands, and survey time, model averaging analyses based on GLMMs showed a negative relationship between bullfrog density and native anuran densities for field observations of invasive bullfrogs alone and co‐invaded observations with low crayfish density. However, this negative relationship disappeared when the two invaders co‐occurred with high crayfish density. Structural equation modelling (SEM) analyses further validated that the impacts of bullfrogs on native frogs were mitigated by the negative interactions between crayfish and bullfrogs.

Our results provide novel evidence of a density‐dependent antagonistic effect of two sympatric invaders from different trophic levels on native species. This study highlights the importance of considering complex interactions among co‐invaders and native species when prioritizing conservation and management actions and will facilitate the development of a more precise framework to predict invasion impacts.
Primary rainforest amount at the landscape scale mitigates bird biodiversity loss and biotic homogenization
Authors: Kormann Urs G. , Hadley Adam S. , Tscharntke Teja , Betts Matthew G. , Robinson W. Douglas , Scherber Christoph
Published: December 2017

Tropical conservation strategies traditionally focus on large tracts of pristine forests but, given rapid primary forest decline, understanding the role of secondary forest remnants for biodiversity maintenance is critical. Until now, the interactive effects of changes in forest amount, configuration and disturbance history (secondary vs. primary forest) on the conservation value of tropical landscapes have remained unknown, hampering the incorporation of these global change drivers into local and global conservation planning.

We disentangled effects of landscape‐wide forest amount, fragment size and forest age (old growth vs. secondary forest) on abundance, α‐diversity, β‐diversity (biotic homogenization) and community shifts of bird communities in human‐dominated landscapes of southern Costa Rica. Utilizing two complementary methods, yielding 6,900 individual detections and 223 species, we characterized bird communities in 49 forest fragments representing independent gradients in fragment size (<5 ha vs. >30 ha) and forest amount (5%–80%) in the surrounding landscape (within 1000 m).

Abundance and α‐diversity of forest specialists and insectivores declined by half in small fragments, but only in landscapes with little old‐growth forest. Conversely, secondary forest at the landscape scale showed no such compensation effect. Similarly, a null‐model approach indicated significant biotic homogenization in small vs. large fragments, but only in landscapes with little old‐growth forest, suggesting forest amount and configuration interactively affect β‐diversity in tropical human‐dominated landscapes. Finally, dramatic abundance‐based community shifts relative to intact forests are largely a result of landscape‐scale loss of old growth rather than changes in overall forest cover.

Policy implications. Our study provides strong evidence that retaining old growth within tropical human‐modified landscapes can simultaneously curb erosion of avian forest specialist α‐diversity, mitigate collapse of β‐diversity (biotic homogenization) and dampen detrimental avian community shifts. However, secondary forests play, at best, a subordinate role to mitigate these processes. To maintain tropical forest biodiversity, retaining old‐growth forest within landscapes should be first priority, highlighting a land‐sparing approach.
Admixture increases performance of an invasive plant beyond first‐generation heterosis
Authors: Li Yan , Stift Marc , van Kleunen Mark
Published: December 2017

Through its potential to enhance progeny performance, admixture (between‐population crossing) may promote invasiveness of alien plants. The few studies that tested this idea found evidence for heterosis (positive effects of admixture) in the first generation (F1), but have not considered further generations. In this paper, we test whether admixture benefits can be maintained in subsequent generations of an invasive plant.

We follow up on a previous study, in which we made crosses between plants of Mimulus guttatus from native‐ (western North America) and invaded‐range populations (New Zealand and Scotland), and showed that admixture increases F1 performance. Here, we performed further crosses to create non‐admixed progeny, F1 progeny resulting from within‐ and between‐range admixture, and subsequent F2 progeny both through outcrossing and through self‐fertilization. As heterosis, out‐ and inbreeding depression may depend on the environment, we assessed progeny performance under benign (well‐watered) and drought‐stress conditions in a greenhouse experiment.

We found that non‐admixed progeny of M. guttatus were outperformed by admixed progeny (averaged across F1 and F2), particularly by progeny from between‐range admixture. However, the benefit of admixture was stronger in F1 than in F2 progeny, especially when the F2 was produced by self‐fertilization. The benefit of admixture also depended on the range of origin and the test environment.

Synthesis. Our findings indicate that increased performance of admixed F1 progeny is partly maintained in the F2 progeny. Admixture might thus significantly boost performance of an invasive plant across multiple generations.
Functional trait differences and trait plasticity mediate biotic resistance to potential plant invaders
Authors: Conti Luisa , Block Svenja , Parepa Madalin , Münkemüller Tamara , Thuiller Wilfried , Acosta Alicia T. R. , van Kleunen Mark , Dullinger Stefan , Essl Franz , Dullinger Iwona , Moser Dietmar , Klonner Günther , Bossdorf Oliver , Carboni Marta
Published: December 2017

Biotic resistance represents an important natural barrier to potential invaders throughout the world, yet the underlying mechanisms that drive such resistance are still debated. In theory, native communities should repel both functionally similar invaders which compete for the same resources, and invaders which possess less competitive traits. However, environmental stress, trade‐offs across vital rates and competition‐induced plastic trait shifts may modify expected competitive outcomes, thereby influencing invasion dynamics.

In order to test these theoretical links between trait distributions and biotic resistance, we performed a mesocosm experiment with 25 non‐native ornamental species invading native plant communities. Each non‐native species was grown with and without the native community under two watering treatments (regular and reduced). We measured biotic resistance as the difference in performance of non‐native individuals grown with and without the community in terms of their survival, growth and reproduction. We quantified overall functional dissimilarity between non‐native ornamental individuals and native communities based on the combination of plant height, specific leaf area and seed mass. Then, assuming each of these traits is also potentially linked to competitive ability, we measured the position of non‐natives on trait hierarchies. While height is positively correlated with competitive ability for light interception, conservative leaf and seed characteristics provide greater tolerance to competition for other resources. Finally, we quantified plastic trait shifts of non‐native individuals induced by competition.

Indeed, the native community repelled functionally similar individuals by lowering the invader's survival rate. Simultaneously, shorter ornamental individuals with larger specific leaf areas were less tolerant to biotic resistance from the community across vital rates, although the effect of trait hierarchies often depended on watering conditions. Finally, non‐natives responded to competition by shifting their traits. Most importantly, individuals with more competitive traits were able to overcome biotic resistance also through competition‐induced plastic trait shifts.

Synthesis. Our results highlight that both functional dissimilarity and trait hierarchies mediate biotic resistance to ornamental plant invaders. Nevertheless, environmental stress as well as opposing trends across vital rates are also influential. Furthermore, plastic trait shifts can reinforce potential invaders’ competitive superiority, determining a positive feedback.
Clinical acceptability of the sense_assess© kids: Children and youth perspectives
Authors: Taylor Susan , McLean Belinda , Blair Eve , Carey Leeanne Mary , Valentine Jane , Girdler Sonya , Elliott Catherine
Published: December 2017

Background

The sense_assess© kids is a standardised, norm‐referenced assessment designed to measure the functional somatosensation capacity of the upper limb of children with cerebral palsy. The objective of the current study was to determine if the sense_assess© kids was clinically acceptable to children and youth.

Methods

A questionnaire was completed by participants following administration of the sense_assess© kids by a trained occupational therapist. Twenty‐six children with spastic hemiplegic cerebral palsy (aged 6–15 years six months; mean 10 years eight months; 16 boys) were recruited. Participants responded to questions regarding the administration and level of difficulty of the sense_assess© kids using a Q‐Sort of ‘like’ and ‘dislike’, Likert scales and short answers. Content analysis was applied.

Results

Twenty‐one of twenty‐six children, indicated that they were ‘very happy’ or ‘happy’ with the administration process of the sense_assess© kids. Most participants indicated that they liked the sensation they felt in the hand when tested.

Conclusion

This study has demonstrated the acceptability of sense_assess© kids for the population for whom it is intended.