Combining state and transition models with dynamic Bayesian networks

Bashari et al. (2009) propose combining state and transition models (STMs) with Bayesian networks for decision support tools where the focus is on modelling the system dynamics. There is already an extension of Bayesian networks - so-called dynamic Bayesian networks (DBNs) - for explicitly modelling systems that change over time, that has also been applied in ecological modelling. In this paper we propose a combination of STMs and DBNs that overcome some of the limitations of Bashari et al.’s approach including providing an explicit representation of the next state, while retaining its advantages, such an the explicit representation of transitions. We then show that the new model can be applied iteratively to predict into the future consistently with different time frames. We use Bashari et al.’s rangeland management problem as an illustrative case study. We present a comparative complexity analysis of the different approaches, based on the structure inherent in the problem being modelled. This analysis showed that any models that explicitly represent all the transitions only remain tractable when there are natural constraints in the domain. Thus we recommend modellers should analyse these aspects of their problem before deciding whether to use the framework.     

Integrated real-time monitoring system to investigate the hypoxia in a shallow wind-driven bay

Corpus Christi Bay (Texas, USA) is a shallow wind-driven bay which experiences hypoxia (dissolved oxygen < 2 mg/L) during the summer. Since this bay is a very dynamic system, the processes that control the hypoxia can last on the order of hours to days. Monitoring systems installed on a single type of platform cannot fully capture these processes at the spatial and temporal scales of interest. Therefore, we have integrated monitoring systems installed on three different platform types: (1) fixed robotic, (2) mobile, and (3) remote. On the fixed robotic platform, an automated profiler system vertically moves a suite of water quality measuring sensors within the water column for continuous measurements. An integrated data acquisition, communication and control system has been configured on our mobile platform (research vessel) for synchronized measurements of hydrodynamic and water quality parameters at greater spatial resolution. In addition, a high-frequency radar system has been installed on remote platforms to generate surface current maps for the bay. With our integrated system, we were able to capture evidence of a hypoxic event in summer 2007; moreover, we detected low dissolved oxygen conditions in a part of the bay with no previously reported history of hypoxia.     

Effects of life history and reproduction on recruitment time lags in reintroductions of rare plants

Reintroductions are important components of conservation and recovery programs for rare plant species, but their long-term success rates are poorly understood. Previous reviews of plant reintroductions focused on short-term (e.g., ≤3 years) survival and flowering of founder individuals rather than on benchmarks of intergenerational persistence, such as seedling recruitment. However, short-term metrics may obscure outcomes because the unique demographic properties of reintroductions, including small size and unstable stage structure, could create lags in population growth. We used time-to-event analysis on a database of unusually well-monitored and long-term (4–28 years) reintroductions of 27 rare plant species to test whether life-history traits and population characteristics of reintroductions create time-lagged responses in seedling recruitment (i.e., recruitment time lags [RTLs]), an important benchmark of success and indicator of persistence in reintroduced populations. Recruitment time lags were highly variable among reintroductions, ranging from <1 to 17 years after installation. Recruitment patterns matched predictions from life-history theory with short-lived species (fast species) exhibiting consistently shorter and less variable RTLs than long-lived species (slow species). Long RTLs occurred in long-lived herbs, especially in grasslands, whereas short RTLs occurred in short-lived subtropical woody plants and annual herbs. Across plant life histories, as reproductive adult abundance increased, RTLs decreased. Highly variable RTLs were observed in species with multiple reintroduction events, suggesting local processes are just as important as life-history strategy in determining reintroduction outcomes. Time lags in restoration outcomes highlight the need to scale success benchmarks in reintroduction monitoring programs with plant life-history strategies and the unique demographic properties of restored populations. Drawing conclusions on the long-term success of plant reintroduction programs is premature given that demographic processes in species with slow life-histories take decades to unfold.     

Transport and survival of viruses in the subsurface—processes,experiments, and simulation models

The remediation of groundwater contaminated with waterborne pathogens, in particular with viruses, is based on their probable or actual ability to be transported from the source of origin to a point of withdrawal while maintaining the capacity to cause infections. The transport is often associated with both the unsaturated and saturated subsurface composed of varying geological settings with commensurate hydrogeological variability. Included among the most important hydrogeological factors that can be used to evaluate viral transport are the flux of moisture in the unsaturated zone, the media through which the particles travel, the length of the flow path, and the time of travel. With respect to the movement and inactivation of viruses in the subsurface, the vadose zone can provide an effective barrier for movement into groundwater and for the protection of downgradient points of withdrawal and use. Models developed to predicate viral transport in soil and groundwater are introduced, including screening models and more sophisticated predictive numerical models. As evidenced by the exponential growth of virus transport research in the literature, as well as a continuing interest in human health, the subject will continue to be one of critical importance to professionals active in the development, treatment, and conveyance of groundwater in the future. © 2005 Wiley Periodicals, Inc.     

In their words: How Detroit residents perceive the effects of their physical environment

This article examines results from in-depth interviews conducted with parents of children with asthma living in an urban environment. We examine themes from the in-depth interviews related to participants' perceptions of the influence of their physical environment on their mental and physical health, and the actions that they take in an effort to protect their health within this context. The findings from this study suggest several implications for understanding the interface between the physical environment of urban communities and residents' health, as well as for the policy and practice of risk assessment strategies.     

Which comes first,organizational culture or performance? A longitudinal study of causal priority with automobile dealerships

Prior research supports a link between organizational culture and performance but generally falls short of establishing causality or determining the direction of a culture–performance (C‐P) relationship. Using data collected from 95 franchise automobile dealerships over 6 years, we studied longitudinal culture–performance relationships to determine whether culture or performance has causal priority, or alternatively, whether a reciprocal relationship exists. Results from cross‐lagged panel analyses indicate that culture “comes first,” consistently predicting subsequent ratings of customer satisfaction and vehicle sales. Furthermore, the positive effect of culture on vehicle sales is fully mediated by customer satisfaction ratings. Copyright © 2015 John Wiley & Sons, Ltd.     

Population genetic variation in the New Zealand greenshell mussel: locus-dependent conflicting signals of weak structure and high gene flow balanced against pronounced structure and high self-recruitment

A pronounced north–south multitaxon genetic discontinuity occurs in central New Zealand (NZ). Polymorphic microsatellite markers have been used to test the location and structure of this discontinuity in the endemic greenshell mussel, Perna canaliculus. Nine neutral loci revealed limited evidence of genetic structure, but one outlier locus (Pcan1-27) which may be under selection provided evidence of the discontinuity in central NZ. Whilst the limited multilocus evidence of structure is assumed to result from high levels of gene flow among populations of this continuously distributed species, assignment tests indicated high to very high mean levels of self-recruitment within the 14 populations and the north and south regions. The nine neutral loci were unable to provide further clarification as to the geographic location of the discontinuity, whereas the Pcan1-27 locus was particularly informative. These results highlight a tension between limited evidence of genetic structure and presumptive high gene flow among populations versus high levels of self-recruitment and pronounced structure depending on microsatellite loci and analyses in question. Evidence from all 10 loci indicates that the genetic discontinuity is maintained by high levels of self-recruitment, and evidence from Pcan1-27 suggests that selection may also be important in explaining the existence of the discontinuity.