Wildland Fire Disturbance - Recovery Dynamics in Upland Forests at Acadia National Park, Maine

The overall goal of this study was to evaluate whether coastal Maine (USA) forests are resilient to changing climate and fire regimes. The occurrence of a catastrophic wildfire at Acadia National Park (ANP) in 1947 provided a unique opportunity to examine the impacts of wildfire on forest dynamics in upland communities of coastal spruce-fir and northern hardwood forests of the Maine coast. This study, conducted 68 years after the stand-replacing 1947 Bar Harbor Fire, builds on studies by W.A. Patterson conducted in 1980 and 1992-1994, 33 and 45-47 years after the fire. There were two lines of investigation in this study: vegetation change following a large-scale, stand-replacing wildfire; and an assessment of wildfire risk following a long period with no major disturbance. In 2016 I quantified and characterized stand and site characteristics including: basal area and stem density of woody species; aboveground biomass and necromass of trees, saplings, and shrubs; dead downed woody fuel loads; duff depth; fuel height; soil depth to bedrock, and canopy closure for 23 stands throughout ANP. To evaluate long-term trends in post-fire recovery, I compared 2016 forest composition, structure and fuel loading data with that in 1980 and 1992-94. I mapped current wildfire risk to aid managers in identifying where mitigation practices would be most effective in reducing fire risk. I used an ArcGIS model that extends field data of current fuel conditions and spatially portrays wildfire risk across the landscape. Mixed effects models were used to determine the best remotely sensed numeric biomass data as a predictor of biomass and necromass measured on the ground. Widespread regeneration of red spruce following the initial establishment of aspen and birch suggests that forests of ANP are resilient to wildfire. Stands that did not burn in 1947 remain as mature-to-overmature spruce and fir. Biomass and necromass is continuting to accumulate. Fuel loads are generally high to very high outside the 1947 fire boundary. Within the fire boundary, fuel loads are primarily low to moderate, with small areas of high to very high risk due to topography (e.g., steep versus shallow slopes, north versus south aspect) and unique species composition (e.g., maturing pitch pine/heath communities). After 70 years, replacement of aspen and birch by spruce and fir in many stands suggests potentially increasing wildfire risk within the 1947 fire boundary. Mount Desert Island has and will continue to experience a marked increase in human development and visitation, thereby increasing the likelihood of human-caused ignitions. This, coupled with increasing fuel loads, may significantly increase the likelihood of wildfire occurrence. An uncertain climate future may exacerbate potential wildfire risk. Should climate warm substantially, spruce-fir stands may break up prematurely – significantly increasing dead, downed fuel for a period of time. Fire management programs should plan to operate strategically and efficiently to meet this challenge

Decay resistance against Coriolus versicolor in Sessile oak ( Quercus petraea Liebl.): analysis of the between-tree variability and correlations with extractives, tree growth and other basic wood properties

Abstract : Weight loss due to fungus Coriolus versicolor has been measured on 614 samples according to the NF EN 113 norm. Up to eight samples were cut at breast height (two opposite radii×four radial positions in heartwood) from 82 mature sessile oaks ( Quercus petraea Liebl.) originating from contrasting regions, silvicultural schedules and site qualities in France. The following points are addressed in the paper: (i) contribution to the total variability for weight loss of the effects "tree”, "position in the tree”, as well as their interaction; (ii) percentage of wood samples and trees in each of the five classes of natural durability defined by the norm NF EN 350-2; (iii) test of the effects of region, silvicultural schedule and site quality on weight loss and evaluating their contribution to the total variation; and (iv) correlations at tree level between weight loss and several traits related to tree growth and basic wood properties (density, swelling, grain angle, multiseriate wood rays characteristics, extractives content). The results are discussed with a view to aid the forest manager as well as the log/wood user to take advantage of the high level of between-tree variability observed as natural durability against C. versicolo

Transit times and mean ages for nonautonomous and autonomous compartmental systems

We develop a theory for transit times and mean ages for nonautonomous compartmental systems. Using the McKendrick-von F\"orster equation, we show that the mean ages of mass in a compartmental system satisfy a linear nonautonomous ordinary differential equation that is exponentially stable. We then define a nonautonomous version of transit time as the mean age of mass leaving the compartmental system at a particular time and show that our nonautonomous theory generalises the autonomous case. We apply these results to study a nine-dimensional nonautonomous compartmental system modeling the terrestrial carbon cycle, which is a modification of the Carnegie-Ames-Stanford approach (CASA) model, and we demonstrate that the nonautonomous versions of transit time and mean age differ significantly from the autonomous quantities when calculated for that model

Distorted Copulas: Constructions and Tail Dependence

Given a copula C, we examine under which conditions on an order isomorphism ψ of [0, 1] the distortion C ψ: [0, 1]2 → [0, 1], C ψ(x, y) = ψ{C[ψ−1(x), ψ−1(y)]} is again a copula. In particular, when the copula C is totally positive of order 2, we give a sufficient condition on ψ that ensures that any distortion of C by means of ψ is again a copula. The presented results allow us to introduce in a more flexible way families of copulas exhibiting different behavior in the tails

Optimizing Hybrid Plate Fixation with a Locked, Oblique End Screw in Osteoporotic Fractures

Background The end screw in a fracture plate creates the greatest resistance to bending. For osteoporotic fractures treated with plates, there is some question as to the optimal screw insertion technique for the screw farthest from the fracture. A locked, oblique end screw was previously shown to increase resistance to periprosthetic fracture. It is unknown, however, how this end screw configuration would resist pullout when subjected to bending. Methods Narrow, low contact 3.5 mm locking compression plates with 6 and 12 holes were anchored to simulated bone material with material properties representing osteoporotic bone. Four configurations were evaluated for the end screw: perpendicular and angulated 30 degrees away from the fracture for both non-locked and locked screws (n=6 per group). The constructs were subjected to 3 point bending until the peak load and finally total construct failure was achieved. Results Peak force, stiffness, energy to peak load, and the failure mode of each construct were determined. All four 12-hole construct groups failed by gross plastic bending deformation of the plate at the fulcrum past a previously established clinically relevant limit for failure (15°). All 12-hole plate constructs failed at statistically higher loads and energy than any of the 6-hole plate constructs, with the exception of the 6-hole locked, oblique construct. Conclusion The locked, oblique end screw provides equivalent pull out strength for 3.5 mm low contact plates regardless of plate length. Combined with its resistance to periprosthetic fracture, this end screw configuration appears to be the best option for the construct integrity of hybrid plating for osteoporotic fractures. Clinical Relevance Osteoporotic fractures are challenging to treat. The current study and the existing literature show that resistance to both bending loads and refracture at the end of a plate are minimized with a locked screw angled away from the fracture

Méthode d'auto-fuzzyfication par analyse des typicalités sur des lots de données réduits

Cet article expose une méthode de fuzzyfication automatique pour un classificateur à base de règles linguistiques floues. Elle s'appuie sur l'analyse des scores de typicalité des attributs caractérisant les formes à classer. La méthode proposée est appliquée à la reconnaissance de couleur sur des avivés. L'utilisation d'un classificateur flou n'étant pas aisée pour des non experts, l'industrialisation d'une telle méthode nécessite une simplification des phases de réglages. En outre, le cadre applicatif spécifique de cette étude ne permet d'avoir à disposition qu'une quantité de données réduite pour réaliser la phase d'apprentissage. Les scores de typicalité des attributs présentent l'avantage de discriminer les plages de valeurs associées à chaque classe couleur de sortie. L'étude des corrélations de ces typicalités améliore la fuzzyfication des paramètres et les essais réalisés sur des lots de données « industrielles » montrent l'augmentation du taux de reconnaissance. Ces taux sont comparés à ceux obtenus à partir d'une fuzzyfication équirépartie. Par ailleurs, une diminution du nombre de règles floues générées dans le modèle est constatée. Les temps de traitements en généralisation sont ainsi réduits

Color sorting system by fuzzy sensor

This article presents a color recognition system formalized under the fuzzy sensor concept. The main objective is to improve the color classification of wooden boards. Our study relates the development of an industrial vision system allowing the recognition of gradual colors. This context imposes a strong reliability constraint, because the currently used sensors are not always enough robust. Then, we are interested in techniques which improve the taking into account of the physical measure imprecision and the uncertainty concerning the definition of the wood color by a Human, the color classes being always neither identified nor separated. Moreover, the different users can have different perceptions of them. Besides, the vision system must be easy to tune. To carry out such a system, we propose to base the fuzzy sensor on a classification method with fuzzy linguistic rules (Fuzzy Reasoning Classifier) which main advantages reside in its generalization capacity from small training data sets and in the interpretability of its rule set. The obtained results show the efficiency of our intelligent sensor.Cet article présente un système de reconnaissance couleur formalisé sous le concept de capteur flou. L’objectif principal est d’améliorer la classification couleur de planches de bois. Notre étude concerne le développement d’un système de vision industriel permettant la reconnaissance de couleurs graduelles. Ce contexte impose une contrainte forte de fiabilité, les capteurs utilisés aujourd’hui n’étant pas toujours suffisamment robustes. Ainsi, nous nous sommes intéressés à des techniques qui améliorent la prise en compte des imprécisions des mesures physiques et la subjectivité concernant la définition de la couleur du bois par l’Homme, les classes de couleur n’étant jamais bien identifiées ni séparées. De plus, les différents utilisateurs peuvent en avoir des perceptions différentes. Par ailleurs, et dans ce contexte particulier, un système de vision doit être simple à régler. Pour réaliser un tel système, nous proposons de baser le capteur flou sur une méthode de classification par règles linguistiques floues (Fuzzy Reasoning Classifier) dont les principaux avantages résident dans sa capacité de généralisation à partir de lot de données réduits en apprentissage et dans l’interprétabilité de sa base de règles. Les résultats que nous obtenons montrent l’efficacité de notre capteur intelligent

Appariement couleur de planches de bois par inférence floue

Cet article présente une méthode de classification de couleurs sur des planches de bois à partir d'un mécanisme à base de systèmes d'inférences floues implémenté à travers l'algorithme d'Ishibuchi-Nozaki-Tanaka. Le raisonnement flou permet de prendre en compte la subjectivité de la perception des couleurs au sein d'un produit « bois ». De plus, les informations extraites des images ne peuvent pas être considérées comme précises et certaines. L'utilisation de notre méthode améliore les taux de reconnaissance en apprentissage et en généralisation dans la classification des couleurs du bois, mais aussi sur le benchmark IRIS

Intermediate Tail Dependence: A Review and Some New Results

The concept of intermediate tail dependence is useful if one wants to quantify the degree of positive dependence in the tails when there is no strong evidence of presence of the usual tail dependence. We first review existing studies on intermediate tail dependence, and then we report new results to supplement the review. Intermediate tail dependence for elliptical, extreme value and Archimedean copulas are reviewed and further studied, respectively. For Archimedean copulas, we not only consider the frailty model but also the recently studied scale mixture model; for the latter, conditions leading to upper intermediate tail dependence are presented, and it provides a useful way to simulate copulas with desirable intermediate tail dependence structures.Comment: 25 pages, 1 figur