Laser-scanned tree stem filtering for forest inventories measurements

International audienceWith specific flora and fauna, regional landscapes and forests constitute an important part of the cultural heritage. Several natural environments have already been classified as national or regional parks. The UNESCO World Heritage covers 13% of the protected forests in the world. Thus, preserving those sites represents a crucial issue. Such a safeguarding involves a detailed knowledge of the sites and forestry management plans. The management of a natural forest is traditionally based on forest plot inventories in which several features of the trees are measured. The set of data collected during these inventories represents the starting point of forest monitoring, flora preservation and risks prevention. Traditionally, measurements are made manually by operators. However, during the last decade, terrestrial laser scanning has become a new and promising way of measuring such attributes. This instrument provides a fine three dimensional point cloud virtual representation of the scanned scene. Trees location, stem diameter, and stem taper can be extracted from these point clouds using pattern recognition algorithms. In this paper we present a novel two steps way to improve the quality of tree branching detection in a three dimensional point cloud acquired by terrestrial laser scanner. This method was developed in order to enhance the results of a previous study. Our approach is based on the combination of a simplification step (using particle simulation), followed by a shape detection (discrete arcs of circle detection). It identifies the lack of accuracy in tree stem diameter measurements at branching junctions for further more detailed analysis

A method addressing signal occlusion by scene objects to quantify the 3D distribution of forest components from terrestrial lidar

SilviLaser 2015, La Grande Motte, FRA, 28-/09/2015 - 30/09/2015International audienceEstimating exact 3D distribution of canopy components using terrestrial lidar in forest is limited by signal occlusion. We propose a method to address this limitation: it uses voxels, beam returns and beam propagation through the scene. The proposed method was validated using simulated forest scenes and a lidar simulator

Managing understory light conditions in boreal mixedwoods through variation in the intensity and spatial pattern of harvest: A modelling approach

In the context of partial harvesting, adequately managing post-harvest light conditions are essential to obtain a desired composition of tree species regeneration. The objective of this study was to determine how varying the intensity and spatial pattern of harvest would affect understory light conditions in boreal mixedwood stands of northwestern Quebec using the spatially explicit SORTIE-ND light model. The model was evaluated based on comparisons of observed and predicted light levels in both mapped and un-mapped plots. In mapped plots, reasonably accurate predictions of the overall variation in light levels were obtained, but predictions tended to lack spatial precision. In un-mapped plots, SORTIE-ND accurately predicted stand-level mean GLI (Gap Light Index) under a range of harvest intensities. The model was then used to simulate nine silvicultural treatments based on combinations of three intensities of overstory removal (30%, 45% and 60% of basal area) and three harvest patterns (uniform, narrow strips, large gaps). Simulations showed that increasing overstory removal had less impact on light conditions with uniform harvests, and a more marked effect with more aggregated harvest patterns. Whatever the harvest intensity, uniform cuts almost never created high light conditions (GLI > 50%). Gap cuts, on the other hand, resulted in up to 40% of microsites receiving GLI > 50%. Our results suggest that either a 30% strip or gap cut or a 45–60% uniform partial harvest could be used to accelerate the transition from an aspen dominated composition to a mixedwood stand because both types of cut generate the greatest proportion of moderately low light levels (e.g., 15–40% GLI). These light levels tend to favour an accelerated growth response among shade-tolerant conifers, while preventing excessive recruitment of shade-intolerant species. A better understanding of how spatial patterns of harvest interact with tree removal intensity to affect understory light conditions can provide opportunities for designing silvicultural prescriptions that are tailored to species’ traits and better suited to meet a variety of management objectives

L’espace minéral au Paléolithique moyen dans les départements du Cantal, de la Haute-Loire et du Puy-de-Dôme

Date de l'opération : 2006 (PT) Les travaux se sont déroulés de juillet à la fin novembre 2006 dans les départements de la Haute-Loire, du Cantal et du Puy-de-Dôme et ont été complétés par des travaux dans l’Allier, suite aux prospections antérieures de l’un d’entre nous (Maurice Piboule). Notre démarche n’est pas un simple complément aux nombreuses études régionales consacrées au silex depuis Vinay en 1867 : aucune démarche antérieure n’a en effet utilisé une méthodologie minéralogique et pé..

Was sind Territorien in der Urgeschichte? Netzwerkanalysen als Annäherung an den Begriff des Raumes im Jungpaläolithikum

Addressed from the perspective of where they were obtained, lithic raw materials found in archaeological sites carry and contain data of geographical value. Thus, they are privileged witnesses to human movements in prehistoric times. By coupling the results of technological analyses with multi-scale diagnostic methodologies based on the principle of an evolutionary chain set up by some of us and recently optimised, today it is possible to evaluate the acquisition modes for raw materials, the manner of their introduction into sites, and better understand the prehistoric management of mineralogical resources. This techno-economic approach, becoming ever more precise, is being facilitated thanks to the results from a consortium of researchers interconnected in the ‘Réseau de lithothèques’ and ‘Silex’ projects.Detailed petro-archaeological studies of an archaeological series make it possible to identify litho-spaces that are not images of territories. Indeed, territories are not only shaped by economic constraints (where space is the basis of a society), but they are the way in which collectives build themselves by conferring meaning on places of singular use linked to each other by a complex network of values. Yet, the symbolic dimension of spaces is a central element in the cultural representations that societies have of it. Rather than limiting the analysis of the territories to the scale of a site, which in the context of nomadic societies is contradictory, it seems more efficient to analyse the relationships between places (i.e. networks of places). Taking as an example current or recently nomadic peoples – for whom networks in which materials circulate correspond to networks of places – we propose a method based on a concept of network analysis in order to escape the point of view based on single sites, and offer an approach to determining prehistoric territories. This side-step not only questions the spatial extent of archaeological records, but also their coherence as chrono-anthropological entities

Principales matières premières lithiques disponibles au Paléolithique entre le Bassin parisien et l'Auvergne: partie 2 - Loir-et-Cher, Indre-et-Loire. Le cas du Turonien inférieur et supérieur.

Dans le sud du Bass in parisien, les silex du Turonien inférieur - dits silex blonds - et supérieur - dits silex du Grand-Pressigny - constituent des ressources de première importance au Paléolithique supérieur. Leur exploitation préhistorique est reconnue dans tout le Berry, la Touraine, le Poitou et l'Auvergne. Ils se retrouvent également en petite quantité dans les séries lithiques du Paléolithique supérieur du Bassin parisien, de la vallée du Rhône, de l' Aquitaine et des Charentes. Ces ressources, malgré leur importance, n'avaient jusqu'alors pas fait l'objet d'une description pétrographique détaillée et ont été parfois confondues avec des silicifications cénozoïques localisées dans l'est et le sud du Massif central. Nous présentons une synthèse de nos observations sur plus de 700 échantillons issus de 104 gîtes différents et sur plusieurs milliers d'artefacts lithiques, étayée par une revue bibliographique des publications, cartes géologiques et mémoires universitaires ayant trait au sujet. En conclusion, rapport massif de silex du Turonien et notamment du Turonien inférieur comme élément structurant des assemblages lithiques du Paléolithique supérieur se cantonne pour l'essentiel dans un espace contraint au sud par le seuil du Poitou et les Combrailles creusoises au nord et à l'est par la Loire. Leur circulation sur plusieurs centaines de kilomètres n'est plus un rait anecdotique mais un élément structurant du fonctionnement des sociétés préhistoriques.info:eu-repo/semantics/publishedVersio

Flint in its diverse natural occurrences: geo-­‐tools for a better definition of the sourcing of secondary outcrops

International audiencePrecise identification of siliceous geo-resources used during prehistory still poses many problems, and archaeologists make ever-increasing demands for this data. The purpose is to provide a database containing an exact and descriptive identity for each different type of geological flint found within a region. The parameters we have chosen to characterize are the mineralogical composition (by optical microscopy, SEM, microprobe, cathodo-luminescence), microfacies characteristics (identified during microscopy and SEM image analysis), porosity measurements (by image analysis and porosimeter), and the presence and distribution of major and trace elements (using ICP, LA-ICP-MS, XRF, PIXE, Raman and SEM-EDS) at the surface or in the cracks in the matrix

Crown Plasticity and Competition for Canopy Space: A New Spatially Implicit Model Parameterized for 250 North American Tree Species

BACKGROUND: Canopy structure, which can be defined as the sum of the sizes, shapes and relative placements of the tree crowns in a forest stand, is central to all aspects of forest ecology. But there is no accepted method for deriving canopy structure from the sizes, species and biomechanical properties of the individual trees in a stand. Any such method must capture the fact that trees are highly plastic in their growth, forming tessellating crown shapes that fill all or most of the canopy space. METHODOLOGY/PRINCIPAL FINDINGS: We introduce a new, simple and rapidly-implemented model--the Ideal Tree Distribution, ITD--with tree form (height allometry and crown shape), growth plasticity, and space-filling, at its core. The ITD predicts the canopy status (in or out of canopy), crown depth, and total and exposed crown area of the trees in a stand, given their species, sizes and potential crown shapes. We use maximum likelihood methods, in conjunction with data from over 100,000 trees taken from forests across the coterminous US, to estimate ITD model parameters for 250 North American tree species. With only two free parameters per species--one aggregate parameter to describe crown shape, and one parameter to set the so-called depth bias--the model captures between-species patterns in average canopy status, crown radius, and crown depth, and within-species means of these metrics vs stem diameter. The model also predicts much of the variation in these metrics for a tree of a given species and size, resulting solely from deterministic responses to variation in stand structure. CONCLUSIONS/SIGNIFICANCE: This new model, with parameters for US tree species, opens up new possibilities for understanding and modeling forest dynamics at local and regional scales, and may provide a new way to interpret remote sensing data of forest canopies, including LIDAR and aerial photography

A map and a database for flint-bearing formations in Southern France: A tool for Petroarchaeology

Une carte des principales formations à silex du sud de la France est en cours de réalisation. Elle propose, à tous les préhistoriens, une base nécessaire au développement d’études interrégionales sur la circulation des silex. Elle est le fruit d’une collaboration entre des acteurs impliqués dans la problématique de caractérisation de la provenance des silex. Elle regroupe les résultats de leurs prospections systématiques ou ciblées dans six régions (Aquitaine, Auvergne, Languedoc-Roussillon, Midi-Pyrénées, Provence-Alpes-Côte-d’Azur, Rhône-Alpes). Elle intègre, en plus, le dépouillement d’un grand nombre de documents : i) les principaux articles et thèses traitant des formations à silex du sud de la France ; ii) plus de 200 fiches issues de la base de données du sous-sol BSS du BRGM, qui permettent de visualiser des logs ou des documents scannés ; iii) 529 cartes géologiques à 1/50 000 et leurs notices. La carte est organisée en trois couches de données superposables : une carte des affleurements ou gîtes primaires, une carte des altérites et des formations superficielles remaniées et une carte des formations alluviales. La carte existera dans deux versions numériques aisément actualisables : une version dans un format PDF et une version sous la forme d’un SIG. C’est l’ensemble de la formation contenant le ou les même(s) type(s) de silex qui est prise en compte, le terme de formation désignant un terrain possédant des caractères communs et qui constitue un ensemble cartographiable. Chacune des formations recensées fait l’objet d’une notice simplifiée qui décrit l’encaissant et - le ou les - type(s) de silex présent(s). Ces notices descriptives et explicatives contiennent des photos à toutes les échelles (de la formation à l’échelle microscopique). Des références bibliographiques géologiques et archéologiques complèteront chaque notice. La version définitive de ces notices constituera un atlas. Les archéologues et géologues disposeront ainsi de fiches descriptives pour chaque type de silex et son encaissant. Elles serviront aux diagnoses analytiques (structures, textures et compositions minéralogiques).A map of the main flint bearing formations in the South of France is under construction. It will provide an essential basis to develop interregional studies about flint procurements and travels. It results from collaboration between actors involved in topic flint sourcing. It includes results of their systematic surveys and studies in six regions (Aquitaine, Auvergne, Languedoc-Roussillon, Midi-Pyrenees, Provence-Alpes - Côte d’Azur, Rhône-Alpes). Moreover, it includes a large number of associated data : i) The main papers and those dealing with flint bearing formations of southern France, ii) more than 200 records from the under-soil database BSS BRGM, which give access to logs or scanned documents iii) 529 geological maps at 1/50 000 and their leaflets. The map is organized in three superimposed layers : a map of outcrops or primary deposits, a map of surficial weathered formation and a revised map of alluvial formations. The map is available in two versions which are easily updatable : a PDF version and an interactive GIS version. In this document, every formation containing the same type (s) (s) of flint is taken into account and forms a mappable entity. Every listed formation is linked to a text which describes the parent rock and/or the type(s) of flint(s). These records contain descriptive and explanatory pictures at different scale (naked eye to microscopic scale). Geological and archaeological references complement every record. The final version will constitute an atlas. Archaeologists and geologists will find description sheets of every type of flint and bearing rock. They will help for analytical diagnoses (structure, texture and mineralogical composition)