Satoshi Tatsuhara

Risk assessment of wind disturbance in Japanese mountain forests.

Abstract: Wind damage of coniferous plantation forests containing hinoki (Chamaecyparis obtusa) and natural broad-leaved forests was studied in the Japanese mountains. Wind conditions determined using an air flow simulation model and historical wind disturbance records were integrated within a Geographic Information System (GIS). Based on the data set, the relationships between wind disturbance, wind speed, and stand height in plantation and natural forests were analyzed. A logistic analysis technique was applied to assess the probability of wind disturbance in stands that remained intact or were damaged as a result of the Isewan Typhoon. The results indicate that higher wind speeds and greater stand heights increase the probability of wind disturbance in both plantation and natural forests. Cross tabulation of the observed disturbance percentages in relation to wind speed and stand height in coniferous plantation forests and natural broad-leaved forests revealed that the former are more likely to be disturbed by strong winds than the latter. The logistic regression model enabled us to predict the likelihood of wind disturbance at our study site. Our results confirmed that it is possible, using wind condition prediction software, to analyze wind disturbance in mountain forests with complex terrain and steep slopes. Nomenclature: Murata et al., 2004.

Cost-effectiveness analysis of subsidy schemes for industrial timber development and carbon sequestration in Japanese forest plantations

This study uses simulations to investigate the effects of implementing two different Japanese forestry subsidy systems on timber production and carbon stock, and examines the consequences for harvesting strategies. An existing Local Yield Table Construction System (LYCS), a wood conversion algorithm, and a harvesting cost model were used in the simulations to test the applicability of different subsidies to the thinning of stands. Using forest inventory data collected by local government staff, simulation output was used to calculate forestry profits, carbon stocks, subsidies, the amount of labor required, and the cost effectiveness of investing in subsidies. By comparing the output of simulations based on two scenarios, we found that both the clear-cutting area and the amount of harvested timber were larger under Scenario 2, in which the rules governing subsidy allocations are more relaxed, than under Scenario 1, in which the rules are more restrictive. Because the harvested timber under Scenario 1 was mainly produced by clear-cutting, the forestry profits and the subsidy predicted in the early period of the simulation, were larger under Scenario 1 than under Scenario 2. In contrast, the carbon stock was larger under Scenario 2 than under Scenario 1. The simulation model is likely to be useful for improving Plan-Do-Check-Act cycles implemented in Japanese forest management systems.

A Growth Prediction System for Local Stand Volume Derived from LIDAR Data

Recent advances in light detection and ranging (LIDAR) technology have enabled the estimation of valuable canopy parameters (e.g., crown diameter, leaf area, and canopy structure) that are difficult to obtain through in situ surveys. The objective of this study was to assess the utility of LIDAR-derived measurements of crown and growth parameters to model and predict the growth of sugi (Cryptomeria japonica) stands located in the University of Tokyo Forest, Chiba Prefecture, Japan. Initially, we confirmed that crown lengths and widths of trees in stands of various densities obtained from LIDAR data correlated with those measured in situ. Then, we developed a crown growth model from repeated LIDAR measurements of stands, suggesting that LIDAR data are adequate for this purpose, and indicating that crown surface area and tree volume growth were linearly related (R2 = 0.90; p < 0.01; RMSE tree volume < 0.02 m3). The model also provided robust predictions of the volume growth of local forests in 10 × 10 m plots based on LIDAR-derived estimates of crown surface areas. Future work should test the applicability of this growth model to facilitate practical forest management.

Predicting the spatial distribution of the abundance of Siebold’s beech in a montane cool-temperate region based on environmental factors

Using a geographic information system (GIS), our goal was to predict the potential distribution of Siebold’s beech (Fagus crenata Blume) in a montane cool-temperate region at a fine spatial resolution based on topographical features. The study was conducted in Akashibayama National Forest in the village of Kamikawa, Niigata Prefecture, central Japan. Species composition was investigated in 28 sample plots selected in the study area. A digital elevation model (DEM) was created, and topographical, hydrological, and light factors were calculated using the DEM. Then, the relationship between species composition and these environmental factors was examined using tree-based multivariate regression to derive regression trees. The species composition for the six major species selected, which included Siebold’s beech, was used as the response variable, and environmental factors were used as explanatory variables. For the derived tree-based regression model, the shaded relief, slope, specific catchment area, and curvature were selected as explanatory variables. The model classified natural vegetation into six forest types, and the result was consistent with the moisture preferences of these major species. The model was applied to the GIS to predict and map the species composition of the major species, especially the relative basal area of Siebold’s beech.

Predicting the spatial distribution of major species composition in secondary hardwood forests on Mt. Gozu, central Japan, based on environmental factors

Our goal was to predict the spatial distribution of canopy species composition in secondary deciduous hardwood forests at a fine spatial resolution, based on climatic and topographical factors using a geographic information system. We studied secondary forests on Mt. Gozu, Niigata Prefecture, central Japan. Canopy species composition was investigated in 100 sample plots within the study area. A digital elevation model (DEM) was created, and topographical, hydrological, and light factors were calculated using the DEM. Climatic factors were interpolated by kriging. The five major species used as response variables were Fagus crenata, Quercus serrata, Quercus crispula, Magnolia obovata, and Castanea crenata. We prepared three possible explanatory variable sets: climatic variables only, both climatic and topographic variables, and topographic variables only. Multivariate regression trees were derived, and the accuracy of predicting the major species composition was tested. The multivariate regression trees derived from the climatic variable set and from the climatic and topographic variable set had better accuracy than the regression tree derived from the topographic variable set. In the regression tree generated by the climatic and topographic variable set, the warmth index was the principal explanatory variable in classifying forest types, followed by topographic factors. This regression tree would be preferable to the other two regression trees for the prediction of canopy species composition.

Effects of harvest restraint periods and fluctuation tolerances of profits and harvests on sustainable timber supply levels from private forests in a district

ABSTRACT The current age class distribution of plantation forests in Japan is bell-shaped, with the peak at 50 years. This offers opportunities to increase domestic timber supplies, but confidence in the long-term stability of supplies must be established. For this, greater knowledge of sustainable harvest levels starting from current stocks is required. Thus, this study analyzed effects on harvest levels of varying harvest restraint periods and fluctuation tolerances of both harvest and profit levels, focusing on privately owned Cryptomeria japonica plantations in the Sampoku district of Murakami City, Niigata Prefecture, Japan. A 0-1 integer programming model was formulated to predict maximum sustainable harvest levels from the forests that could provide stable profits. Permutations of five harvest restraint period cases and three fluctuation tolerance cases were simulated to assess effects on the volume of total harvests. A 10-year harvest restraint period dramatically increased the sustainable harvest level, but extending it further had weaker effects. Varying the fluctuation tolerances substantially affected sustainable harvest levels in the absence of harvest restraints, but not in their presence. Thus, imposing a 10-year harvest restraint period enabled maximal sustainable timber production in the study area.

Silviculture guidelines for developing mixed forests in old coniferous plantations under long-rotation stand density control

This study presents guidelines for developing mixed broadleaf–conifer forests in old coniferous plantations under a long-rotation silviculture system. We established nine square sample plots in Chamaecyparis obtusa (hinoki) plantation forests of various stand ages (22–116 years) and densities (250–1650 trees ha−1). Tree height and diameter at breast height were recorded for all standing trees taller than 1.3 m. This step revealed the varying diameters of coniferous plantation trees and natural broadleaf trees and showed that the density of large trees increased with stand age. The older the plantation forest, the smaller its canopy openness. The standard deviation of canopy openness ranged from 20–30%, with the largest values observed in the middle-aged forests. We estimated the stand density index under which understory vegetation may be established; the maximum stand density index (1028) in the forest studied was considered to be the critical upper limit of stand density control for introducing understory vegetation. Finally, we reviewed previous studies to confirm the validity of our recommendations of long rotation and low stand density control for the development of mixed old plantation forests.