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

Reconstructing crown shape from stem diameter and tree position to supply light models. I. Algorithms and comparison of light simulations

Light models provide an interesting way to analyse the influence of the forest canopy on understory biological processes but need a detailed description of tree crowns, requiring many field measurements. This study proposes supplying light models with only stem diameter and tree position and reconstructing crowns using diameter- related allometric relations. First, the diameter-related relations for total height, crown base height and mean crown radius were established for each species. Second, two reconstruction methods were compared: a simple isotropic method and a more sophisticated method, the Crown Reconstruction by Overlap Minimisation method. The latter method gave better results than the simpler one, even if some small bias was not completely resolved in the darkest areas. However, using crown centre position instead of stem position resolved this bias

Un exemple de gestion des géo-ressources au Paléolithique supérieur en moyenne montagne : Le Badegoulien de la grotte du Rond-du-Barry (Sinzelles, Polignac, Haute-Loire) = An example of Upper Palaeolithic lithic raw material management in the Middle Mountain Region: The Badegoulian of Rond-du-Barry Cave (Sinzelles, Polignac, Haute-Loire)

Abstract in englis

SilviLaser

Abstract Forest inventory automation has become a major issue in forestry. The complexity of the segmentation of 3D point cloud is due to mutual occlusion between trees, other vegetation, or branches. That is why, the applications done until now are limited to the estimation of the DBH (Diameter at Breast Height), the tree height and density estimation. Furthermore other parameters could also be detected, such as volume or species of trees (Reulke and Haala) . . . This paper presents an effective approach for automatic detection, isolation of trees and DBH estimation. Tree isolation is achieved using an innovative approach based on a clustering methodology followed by a skeletonization step. The DBH of trees is then determined automatically. The efficiency of our algorithm is evaluated with comparison with ground data, measured by classical methods

The use of terrestrial LiDAR for enhance forest inventory

Terrestrial LiDAR (TLidar) is an emerging technology that has high potential for forestry applications. It provides a detailed three‐dimensional (3D) point cloud representation of forest structure at tree‐ and plot‐level from which a wide range of forest attributes could be extracted with appropriate methods. Consequently, TLidar potentially offers the opportunity to expand on the estimation of new attributes beyond what is currently measured with conventional forest inventory. The presentation will describe how the use of TLiDAR data can enhance forest inventory. More specifically it will describe three novel sets of algorithms involving the use of TLiDAR data. The first set of algorithms provides information on forest plots that can routinely be extracted from TLiDAR using existing algorithms currently available as open source. The set of attributes includes stem diameter at breast height, tree height, map of tree position, digital terrain model and canopy height model. The second set includes four new algorithms developed in our group to estimate structural attributes from the point cloud collected in field plots, namely (1) the automatic estimation of stem taper of all trees in a plot, (2) the automatic segmentation of all the tree crowns, (3) tools to allow spatial analysis of tree growth/competition and (4) tools to quantify tree branchiness for wood quality assessment. Algorithms 1 and 2 are innovative adaptations of specific mathematical principles to take advantage of the spatially‐explicit information provided by the TLiDAR data. Our validation tests provided an average error on stem taper generally within 1.2 cm for the lower part of the stem (up to 5 to 10 m depending on the stand/tree configuration) and increasing rapidly in the upper part of the stem where signal occlusion becomes important. The crown segmentation method was capable to extract with success 90% of the tree crowns in a coniferous stand and 85% in a deciduous stand. Algorithms 3 and 4 were designed as interactive tools to manipulate the TLiDAR point cloud data for specialized analysis such as branchiness as well as crown mensuration in the context of tree growth and competition. The third set of new algorithms relates to the explicit 3D representation of tree components and dealing with LiDAR data limitations. More specifically, the main limitations that are intrinsic to TLiDAR acquisition systems include signal occlusion, over‐ and under‐sampling and noise. The proposed procedure, called L‐Vox, uses a voxel representation of the TLiDAR point cloud. Spatial distribution of canopy components is described through a new structural index called the Relative Density Index (RDI). Calculating the RDI from a point cloud by using the acquisition configuration allows dealing with the LiDAR data limitation while allowing a true 3D representation of the spatial distribution of canopy components. We demonstrate the capabilities brought by the L‐Vox algorithms through a test case where RDI values are used to assess the spruce budworm damage on white spruce stands using a three‐years monitoring TLiDAR scanning. All the new algorithms developed by our group are currently being further validated in preparation for their final implementation on an Open Source platform called CompuTree, specifically designed for the analysis of LiDAR data

“Undatable, unattractive, redundant”? The Rapavi silcrete source, Saint-Pierre-Eynac (Haute-Loire, France): Challenges studying a prehistoric quarry-workshop in the Massif Central mountains

International audienceSilcretes are not widely discussed archaeologically as a prehistoric lithic resource in Europe, despite there being many years of geological research into their formation, and in some regions, a long record of their use in prehistory. In the Massif Central, south eastern France, various silcrete sources represent some of the largest and best quality siliceous stone sources within this otherwise volcanic area. Field research within a wider programme of landscape archaeology and lithic sourcing identified a quarry-workshop for one of these silcrete sources, at Rapavi, Saint-Pierre-Eynac (Haute-Loire). Archaeological and geological results are reported, discussing the technological behaviour uncovered at this locale and its wider regional connections, including the presence of imported flint artefacts. Additionally, the Rapavi silcrete provides an example of the challenges encountered when analysing raw materials with idio-syncratic fracture properties, and attempting to disentangle quarry-workshop palimpsests

The use of terrestrial LiDAR for enhance forest inventory

International audienc

Les différentes phases d'occupation de la cavité : fonction(s) du site

Les différentes phases d'occupation de la cavité : fonction(s) du sit