Estimation of diameter and height of individual trees for Pinus sylvestris L. in Álava based on the individualising of crowns using airborne LIDAR and the 4th National Forestry Inventory data.

Aim of study: The objective of this study is to test the validity of the DBH and total height allometric models fitted to the crown polygon data obtained by the application of a crown delineation and individualisation algorithm which uses the geometrical relationships between the points in the original LiDAR point clouds in the Pinus sylvestris L. stands.Area of study: The study area is located in the province of Álava in the Autonomous Community of the Basque Country.Material and Methods: The crowns are delineated using data from airborne LiDAR point clouds obtained in the 2008 overflight of the Basque Autonomous Community. The DBH and total height data for field trees are obtained from the plots in the 4th National forest inventory.Main Results: For the adjusted total height and DBH models coefficients of determination of 0.87 and 0.74 respectively were obtained. The root mean squared errors were 10.67% and 18.97% respectively. The distributions of obtained DBH and total height fitted values and the distributions of the DBH and total height of the field trees are very similar except for the DBH below 15 cm.Research highlights: For stands of Pinus sylvestris L. in Álava, the geometrical relationships between the points that correspond to laser signal echoes obtained with airborne LiDAR sensors can be used directly to delineate approximations of the horizontal projections of the crowns of the trees. Although the procedure set out here was developed for stands of P. sylvestris L. in Álava, it can be applied to other conifers in regular stands by adjusting the working parameters of the function which delineates the crowns on the basis of the point cloud.Abbreviations used: IFN4: 4th National Forest Inventory; Ht: Field Tree Height; Hl: LiDAR Tree Height; DCL: LiDAR Crown Diameter.The possibility of generalising the use of airborne LIDAR data not only gives rise to cost reductions in acquisition and universal distribution, following their inclusion in the National Aerial Orthophotography Plan, but also enables automatic methods to be drawn up for inventorying and assessing forestry resources cheaply and very accurately.This paper describes a procedure developed for estimating the diameter at breast height (DBH) and total height of individual trees that can be applied to stands of Pinus sylvestris L. in Álava, based on data from the National Forestry Inventory [Inventario Forestal Nacional] (IFN4) and a crown individualisation algorithm that uses data from airborne LIDAR point clouds obtained in the 2008 overflight. The procedure was drawn up using free-license software at all stages. It represents an innovation on conventional methods which use digital models of crowns or height percentiles from point clouds. The DBH and total height data for trees are obtained from the plots in IFN4: these data are used to adjust the models for DBH and total height of trees located by the delineation of their crowns from the LIDAR point clouds corresponding to the plots in question. Obtaining data on each individual tree enables stand variable values to be calculated for both complete hillsides and for their silvicultural and management zoning divisions.