Development of Stem Density Analyzing System Combined X-ray Densitometry and Stem Analysis

摘要

The function of the forest as a carbon sink is now a growing concern worldwide and there is a need to accurately estimate the forest biomass. A method was developed for estimating the stem weight based on the volume-density of stem measured by soft X-ray densitometry and the stem volume estimated by morphological analysis. The volume of log segment at each height and in each year was calculated using a formula for cone trapezoid, and the dry weight was calculated by multiplying the volume by the volume-density. These calculations were made using the application program [Stem Density Analyzer (SDA)] operating on Microsoft Windows-XP. The sample tree for analysis was chosen from the sample trees in the secondary breech forest at Kaminagawa Experimental Forest, Yamagata University. The cross sectioned wood disks were obtained from the stem at 1-m intervals. After drying, they were photographed with the soft X-ray together with the standard absorber for calculating volume-density. This film was scannedwith a permeation-type image scanner, and the image data were analyzed with WinDENDRO. The annual growth in wood volume and dry weight increased year by year, but the growth in 1965 and 1995 was extremely poor. In the 82-year-old tree, the sum of each annual growth in dry weight was 441kg, and the amount of carbon estimated by multiplying a carbon ratio 0.5 was 220kg. The amount of carbon stored in the stems can be estimated precisely by calculating the weight of stems in each diameter class using thisnew method.