Andrew Robinson

We propose a new modeling approach for inspection data that provides a more useful interpretation of the patterns of detections of invasive pests, using cargo inspection as a motivating example. Methods that are currently in use generally classify shipments according to their likelihood of carrying biosecurity risk material, given available historical and contextual data. Ideally, decisions regarding which cargo containers to inspect should be made in real time, and the models used should be able to focus efforts when the risk is higher. In this study, we propose a dynamic approach that treats the data as a time series in order to detect periods of high risk. A regulatory organization will respond differently to evidence of systematic problems than evidence of random problems, so testing for serial correlation is of major interest. We compare three models that account for various degrees of serial dependence within the data. First is the independence model where the prediction of the arrival of a risky shipment is made solely on the basis of contextual information. We also consider a Markov chain that allows dependence between successive observations, and a hidden Markov model that allows further dependence on past data. The predictive performance of the models is then evaluated using ROC and leakage curves. We illustrate this methodology on two sets of real inspection data.

ABSTRACT We introduce a novel methodology for measuring stand sapwood area (SA), which provides a useful indicator of evapotranspiration from forest stands. The method is demonstrated in a 73-year-old Eucalyptus regnans forest comprising 784 stems over a 5 ha area. We used photos of stump cross-sections to differentiate sapwood from heartwood, and found 90% of stump segments to have a visible transition boundary. The digital images were corrected for lens distortion and scaled to an actual cross-sectional area, with resulting stump perimeters corresponding well with field-measured perimeters traced using string (RMSE = 4 cm, R2 = 0.99). Calculated SA and basal area (BA) at stump height were coupled with tree and sapwood taper data to predict the SA:BA ratio at 1.3 m height (). Tree taper data was coupled with stump dimensions data in a mixed-effects model to predict each stump's BA at 1.3 m, and sapwood taper data from buttress logs was used to improve each stems . Using this procedure, we found our study site to have of 0.21 and total stand SA at 1.3 m height of 9.3 m2 ha-1.We quantified the bias in traditional estimates that use cores to measure sapwood thickness and diameter tape to calculate SA. We show traditional methods underestimate which increases with tree diameter and decreases with stem circularity, whereas our methodology gave more accurate measures of SA in large buttressing trees. Our methodology also provides a more efficient way of generating maps of SA variation across large forested catchments. This article is protected by copyright. All rights reserved.

ABSTRACT Site occupancy, as estimated by the probability of presence, is used for monitoring species populations. However, the detection of species at individual sites is often subject to errors. In order to accurately estimate occupancy we must simultaneously account for imperfect detectability by estimating the probability of detection. The problem with estimating occupancy arises from not knowing whether a nondetection occurred at an occupied site due to imperfect detectability (sampling zeros), or the nondetection resulting from an unoccupied site (fixed zeros). We evaluated the performance of the basic, normal approximation, studentised and percentile methods for approximating confidence limits for occupancy and detection of species. Using coverage and average interval width, we demonstrated that the studentised estimator was generally superior to the others, except when a small sample of sites are selected. Under this circumstance and when calculating limits for detection, no estimator produced reliable results. The experimental factors we considered include: (i) number of sites; (ii) number of survey occasions; (iii) probabilities of presence (occupancy) and detection; and (iv) overdispersion in the capture matrix. Similar conclusions were reached both for the simulated studies and a case study. Overall, estimation near the boundaries of the probability of occupancy and detectability was difficult.

ABSTRACT Aim: Effective decisions for managing invasive species depend on feedback about the progress of eradication efforts. Panetta & Lawes (2007) developed the eradograph, an intuitive graphical tool that summarizes the temporal trajectories of delimitation and extirpation to support decision-making. We correct and extend the tool, which was affected by incompatibilities in the units used to measure these features that made the axes impossible to interpret biologically. Location: Victoria, New South Wales and Queensland, Australia. Methods: Panetta and Lawes' approach represented delimitation with estimates of the changes in the area known to be infested and extirpation with changes in the mean time since the last detection. We retain the original structure but propose different metrics that improve biological interpretability. We illustrate the methods with a hypothetical example and real examples of invasion and treatment of branched broomrape (Orobanche ramosa L.) and the guava rust complex (Puccinia psidii (Winter 1884)) in Australia. Results: These examples illustrate the potential of the tool to guide decisions about the effectiveness of search and control activities. Main conclusions: The eradograph is a graphical data summary tool that provides insight into the progress of eradication. Our correction and extension of the tool make it easier to interpret and provide managers with better decision support.

... The equivalence test is a more appropri-ate tool for model validation (Robinson and Froese 2004). ... 46 38 Platymiscium sp. 83 50 Cordia alliodora (Ruiz & Pav.) Oken 79 43 Populus alba L. 52 20 Dalbergia cf nigra (Vell.) 67 34 Pseudotsuga menziesii 72 52 var. ...

Since its detection in 1998, the exotic aphid pest, Essigella californica Essig (Hemiptera: Aphididae) has caused extensive defoliation in commercial Pinus radiata plantations throughout Australia. A total of one hundred and twenty plots encompassing thirty tree ...

Allocating resources to detect invasive pests, diseases, and pathogens on exposure pathways requires a trade-off between the need to detect as many contaminated items as possible and the need to acquire knowledge about contamination rates. We develop a model and an algorithm that provide guidance for the allocation of inspection resources across multiple dynamic pathways in cases where not every item can be inspected. The model uses a null hypothesis that the contamination rate of a pathway is above a specified level: a risk cutoff. Pathways with a risk above the cutoff are fully inspected, and those with a risk below the cutoff level are monitored at a rate that would detect a change of the risk to being above the cutoff level with high probability. We base our decision on the 95% upper confidence limit for the contamination rate. We demonstrate via simulations and a data set that focusing inspection resources on specific pathways can result in substantially more effective intervention, and that the reduction in overall effectiveness of monitoring low-risk pathways need not be substantial. Use of the model demands the selection of the risk cutoff, and this limit can be set according to projected consequences.

... Dickinson, Robinson, Harrod, Gessler, and Smith argument that relates only the critical quantity of fuel consumed per unit time required for flame maintenance, divided by the available fuel quantity (equation 1). The result of this equation is the critical rate of spread (cROS, ...