Conifer crown profile models from terrestrial laser scanning

Abstract

• Crown models are derived from terrestrial laser data for 3 NW USA conifer species.• Crown models require only crown length for implementation.• Beta and Weibull curves fit to 95th percentile widths describe crown extent.• Crown profile curves are species-specific and not interchangeable.• Crown shape is not strongly conditioned by tree size or site. AbstractRegional crown profile models were derived for three conifer species of the interior northwestern USA from terrestrial laser scans of eighty-six trees across a range of sizes and growing conditions. Equations were developed to predict crown shape from crown length for Pseudotsuga menziesii, Pinus ponderosa, and Abies lasiocarpa from parametric curves applied to crown-length normalized laser point clouds. The 95th width percentile adequately described each crown's outer limit; alternate width percentiles produced little profile shape variation. For P. menziesii and P. ponderosa, a scaling parameter-modified beta curve gave the most accurate fit (using cross-validated Mean Absolute Error) to aggregated 95th width percentile points. For A. lasiocarpa, beta and Weibull curves (equivalently modified) produced similar results. For all species, modified beta and Weibull curves fit crown points with less error than conic or cylindrical profiles. Crown profile curves were species-specific; interchanging among species increased error significantly. Laser-derived crown base metrics provided objectivity and consistency, but underestimated field-derived base heights through inclusion of dead branches. Profile curve parameters were not correlated with tree or stand characteristics suggesting that crown shape is not strongly conditioned by size and site factors. However, laser sampling necessarily favored more open growing conditions, potentially under-representing variations in crown shape associated with social position. Overall, Terrestrial Laser Scanning (TLS) lends itself to detailed measurements of external crown architecture with occlusion-imposed limits to characterization of internal features. Yet, the time and cost of collecting and processing individual tree data precludes use of TLS as a common field sampling tool.

Modeling Variation in Crown Profile with Tree Status and Cardinal Directions for Planted Larix olgensis Henry Trees in Northeast China

“…Ferrarese et al [13] modified the Weibull equation to model the outer crown profile. We used this equation and modified it in Equation (1).…”

“…The first approach divides the entire crown into two sections: the "light crown" and the "shade crown", with models developed separately for each of the two parts [11]. The second method uses a single equation without a break point to model the entire crown [9,12,13]. The disadvantage of the first approach is that the continuity of the entire crown is not considered; thus, the second approach has become increasingly popular.…”

Comparison of Mature Douglas-Firs’ Crown Structures Developed with Two Quantitative Structural Models Using TLS Point Clouds for Neighboring Trees in a Natural Regime Stand

“…Therefore, the application of QSM to coniferous species is challenged by the small leaves on branches. For coniferous trees, TLS-based crown structure studies focus on depicting the general crown profile [50,51], rather than describing the inside canopy details, particularly the branch arrangements and dimensions. To date, few studies have characterized the Douglas-fir branch architecture of average trees from stands that experienced limited management [8,20,27].…”

Competencia, productividad y cambios a nivel de copas en bosques mixtos de pinos mediterráneos: señales a nivel del árbol individual

“…En la actualidad, el escáner laser terrestre (TLS, acrónimo en inglés de Terrestrial Laser Scanner) emerge como una herramienta de muestreo no destructivo innovadora, capaz de obtener datos tridimensionales de los árboles de manera efectiva, rápida, a escala milimétrica y sobre grades espacios (Dassot et al 2011;Liang et al 2016b). La investigación y el desarrollo de la tecnología TLS en el ámbito forestal se encuentra en una fase incipiente y de crecimiento sostenido, y existen experiencias exitosas tanto de su uso en la estimación de parámetros dendrométricos estándar (Bienert et al 2007), como en la caracterización de la estructura del dosel (Hardiman et al 2011;Seidel et al 2015a), la cuantificación de la geometría externa (Fleck et al 2011;Seidel et al 2011;Fernández-Sarría et al 2013;Metz et al 2013;Ferrarese et al 2015) e interna de las copas (Bayer et al 2013;Seidel et al 2015b), así como esfuerzos recientes orientados a la cuantificación de los diferentes componentes (fotosintéticos y no fotosintéticos) de las copas (Wang et al 2018). Dada la capacidad de la tecnología TLS para describir adecuadamente la estructura de copas, recientemente ha comenzado a utilizarse para estudiar los cambios a nivel de copas involucrados en la dinámica de los bosques mixtos, orientados principalmente en el análisis de las causas subyacentes a los incrementos en la productividad (Hardiman et al 2011;Bayer et al 2013;Martin-Ducup et al 2016;Barbeito et al 2017).…”

“…Es importante señalar que el patrón de distribución vertical de las copas, descrito en este estudio por las distribuciones , debe entenderse más como la probabilidad de encontrar ramas de una determinada longitud a una altura determinada, que como una descripción de la "forma real" de las copas. La forma de un sólido de revolución generado a partir de estas distribuciones puede desviarse considerablemente de la forma real de la copa, sobre todo cuando la rotundidad de la copa a diferentes alturas varía considerablemente (ver por ejemplo, Fleck et al 2011;Metz et al 2013;Ferrarese et al 2015;Hajek et al 2015;Martin-Ducup et al 2016, y la Figura 10). A partir del análisis del perfil vertical descripto por las distribuciones pueden hacerse varias observaciones relativas a cada especie.…”