The objective of this study was to clarify the regeneration process of a secondary Abies firma and Tsuga sieboldii forest after clear-cutting in Kirishima. The stand structure and individual tree height growth pattern were analyzed. Then, the regeneration process of such a forest was discussed based on the above results. The dominance of coniferous species such as Pinus densiflora, A. firma, and T. sieboldii was observed. The study stand was considered to be stratified into two strata from tree height distributions, but the degree of separation between the strata was low. However, analysis of the individual height growth pattern showed that this study stand was in a transition period to discontinuous tree height distribution in the Abies and Tsuga population. Therefore, we consider that the structure of this Abies and Tsuga stand will shift in the future to one observed in a nearby old-growth stand. Based on the age of P. densiflora, the approximate year of clear-cutting on this site was determined. P. densiflora trees colonized after clear-cutting, whereas some A. firma and T. sieboldii seedlings were established before clear-cutting. It is suggested that the advance growth of A. firma and T. sieboldii played an important role in the regeneration process of the secondary Abies and Tsuga forest after clear-cutting. Therefore, advance growth must be left on clear-cut areas in order to grow the forest as fast as possible after clear-cutting.

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The free (unobstructed) sight through the foliage layer of forest canopy is expected to depend on the density of the foliage, i.e. dense foliage shortens the free sight while sparse one extends it. Conversely, it is possible to estimate foliage density from the free sight. Furthermore, it is possible to estimate from the free sight the amount of leaves in terms of leaf area or leaf area index (LAI) as a product of estimated foliage density and the thickness of the foliage layer. This paper presents a simple theory of estimating LAI from the free sight along with its verification using a set of field data from boreal forest of Canada. Free sight through the canopy was measured using airborne laser altimetry (ALA). Laser beams emitted vertically from an aircraft are reflected from different layers of the canopy, ranging from the uppermost canopy surface to the ground. The distance that a laser beam travels unimpeded into the canopy was assumed to be the free sight or more aptly, the free path, and the mean of a number of penetrations within the canopy as a good measure of the amount of leaf area. We assembled a set of field leaf area and mean free path data for 13 boreal forest sites in central Alberta, Canada. We related leaf area density with mean free path and found an inverse relationship between them. Furthermore, we verified that LAI can be estimated as a product of mean free path-based leaf area density and an estimate of canopy depth (D) obtained based on the relationships we found between D and mean tree height (H) and between H and mean laser vegetation height.

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A semi-automatic image analysis system, CROCO, was developed for assessing tree crown condition objectively and at low cost in forest health monitoring. The system is composed of a Macintosh computer, a digital camera, the commercially available software Adobe Photoshop and the public domain software NIH Image. Most of the procedures are automated by the batch processing tool of Adobe Photoshop and a set of macro programs of NIH Image, which enable us to analyze large numbers of images rapidly and at low cost. After pre-processing, the macros automatically generate a silhouette from the color image based on the between-class variance method and calculate the index DSO as a measure of crown transparency based on two fractal dimensions. The precision of the system was examined in terms of weather conditions, camera angle (CA) and overlap rate of the target crown with other trees (OR). The results suggested that CROCO can provide a consistent measure of DSO irrespective of either cloudy or sunny conditions, if photographing conditions satisfy the criteria of CA less than about 45 degrees and OR less than about 50% of crown width. CROCO may be used as a control assessment to detect and correct observer bias.

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This paper describes the error in stem volume when estimated using standing tree height (h_s) measured with a wide-scale Spiegel Relascope and upper-stem diameters at i/10 of h_s from the ground level (d_<w0.ihs>, i=3, 5, 7) measured with a Wheeler Pentaprism Caliper. To measure tree height and upper-stem diameter, 15 sample trees in a 29-year-old stand of Japanese cypress (Chamaecyparis obtusa E_<ndl>.) were selected. The mean, standard deviation and range (minimum〜maximum) of error in h_s were -0.33m, 0.31m and -0.8〜0.5m, respectively. The means, standard deviations and ranges (minimum〜maximum) of error in d_<w0.ihs> (i=3, 5, 7) were 0.31cm, 0.57cm and -0.3〜1.3cm for d_<w0.3hs>, 0.37cm, 0.69cm and -0.9〜1.2cm for d_<w0.5hs>, -0.34cm, 0.79cm and -1.6〜1.1cm for d_<w0.7hs>, respectively. Such errors were common or slightly worse in both tree height and upper-stem diameter measurements. The mean, standard deviation and range (minimum〜maximum) of error in stem volume estimated using hs and d_<w0.ihs> (i=1, 3, 5, 7, 9) were 0.0023m^3, 0.0084m^3 and -0.0097〜0.0201m^3, respectively.

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