A light-weight CCD camera technique for estimating three-dimensional distribution of foliage density in tree crowns

Abstract

:A method was developed for non-destructively estimating spatial density of foliage mass and area in crowns of small individual trees. A light-weight CCD camera with a capability for wireless image transmission is mounted on top of a telescoping height measuring pole so that it views the zenith. A daisy flap, a thin 10-cm diameter plastic plate with 12 equally-spaced incisions along its radii, is placed horizontally 20 cm above the camera. Then, images are recorded while the CCD camera is lowered at 10-cm increments from the top of the crown. The number of contacts between the daisy flap and the foliated portions of shoot segments are counted while the CCD camera goes through each 10-cm segment. The number is evaluated (i) by simply counting the contacts regardless of the size of touching shoot or proportion of the daisy flap that makes a contact (referred to as simple CCD method), and (ii) by counting the number of flaplets (12 parts of the daisy flap that are separated by radial incisions) that touch the foliated shoots (weighted CCD method). The methods are repeated five times for the same column of 20 cm × 20 cm base area. Then the foliage density was calculated for each 20-cm cube from regression equations relating the mean contact number among the ten 10-cm segments searched within a 20-cm cube and the foliage density in dry mass or area. The foliage mass estimated by the weighted CCD method was comparable to direct measurement by harvesting, when the method was applied to estimation of total leaf mass of a tree. The calculated value of foliage mass density was also comparable to that estimated by the direct harvesting method of Sainome cutting when 40-cm or larger cubes are used as the unit volume. Advantages and disadvantages of the CCD camera technique are discussed in comparison to other methods available for estimation of foliage distribution in tree crowns and forest canopies.