CROWN DELINEATION INFLUENCE ON STANDING VOLUME CALCULATIONS IN PROTECTED AREA

Abstract

The aim of this study was to evaluate the automatically determined parameters of tree crowns, which are then used in two-phase inventory method of growing stock. Research was performed in forest stands of different age, located in the Stolowe Mountains National Park (south-western Poland) where the dominant species was Norway spruce (Picea abies L.). On the test area of approximately 500 hectares, 35 sample plots were measured. On LIDAR-based Crow Height Model (CHM), in the places corresponding to the position of 500 m2 circular ground samples, automatic segmentation was carried out. The extent of the crown was associated with the height of the tree. Two variants of the assigning separate crowns in the sample were used: (1) according to the centroid position, (2) according to the location of any fragment of the crown inside the sample plot boundary. In each of the variants five series of measurements with different relative height of the range 0.65–0.8 (with a gap of 0.05) were carried out. Relationship between the volume of living trees measured on the ground and LIDAR parameters (average height of trees and tree canopy projection area) automatically measured based on CHM was determined. Multiple correlation coefficient differed depending on the location to extract coverage crowns and ranged from 0.687 to 0.788. The variant of counting of all trees with crowns or pieces inside the sample appeared to perform better. The relationship between the above-indicated characteristics was stronger after elimination of dead trees (about 0.1 for each of cases). This means that for measurements of the growing stock in forests under protection, it is necessary to improve the process of automatic segmentation of the crown, by identification and elimination of dead trees – usually present at sample plot.