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This study quantified the effect of weeding frequency and weeding schedules on weeding operation time in a sugi (Cryptomeria japonica) plantation stand. A weeding operation time estimation model was developed; then the cumulative weeding operation time after six growing seasons was simulated using the developed model. The developed model included weed height, relative height of weeds to sugi, and initial planting density. The simulated cumulative weeding operation time decreased approximately 6% for each one-treatment decrease in weeding frequency. Under a three-treatment weeding frequency scenario, the simulated cumulative operation time when weeding was conducted during non-consecutive years was longer than that when weeding was conducted during three consecutive years. The results suggest that carrying out weeding treatment during consecutive years is the more effective for reduction of weeding costs. We conclude that weeding schedule as well as weeding frequency must be considered for reduction of weeding operation time.

This study investigated the effect of weeding on the height growth of planted sugi (Cryptomeria japonica) saplings in southwestern Japan. First, we developed stand-level sugi and weed annual height growth models that accounted for tree spacing, slope aspect, and mean sugi height at the end of prior growing season and mean weed height just after weeding. Then, we simulated sugi heights after the sixth growing season under 64 different weeding schedules, using the developed model to examine the effects of the weeding frequency and the timing of weeding. The selected model for sugi height growth was expressed in terms of mean sugi height, mean weed height, slope aspect, and the relative height of weeds to sugi. In the case of weeds, the selected model was expressed in terms of mean sugi height, slope aspect, and the relative height of weeds to sugi. The simulation showed that sugi height decreased approximately 20% for every one-time reduction in the number of weeding. The simulation also showed that...

木質系バイオマスのうち利用の進んでいない林地残材の有効活用に期待が集まっている。林地残材の一部である枝条に注目し, 野外乾燥時期の違いとビニルシート被覆によるスギ枝条の含水率 (乾量基準) の変化を明らかにし, 林地残材の野外での乾燥過程について検討した。スギ枝条を100 cm×90 cm×20 cmの金網でパックし, 三層に重ねて一つの堆積枝条とした。鹿児島大学高隈演習林において, 平成16年7月31日∼10月4日の66日間の枝条パックの重量測定から, 含水率の変化を実験１として明らかにした。次に実験2として, 平成16年11月9日∼12月14日の35日間の含水率変化を実験した。さらに実験3として, 実験2と同時期にビニルシート被覆した堆積枝条としないものを比較した。その結果, 実験1では146%から40%にまで含水率が低下し,実験2では120%から51%へと低下した。ビニルシート被覆があると含水率は115%から35%にまで低下し, シート被覆の効果があった。以上より, 野外乾燥によりスギ枝条の含水率を低下させることが可能であり,燃料としての低位発熱量に大幅な向上が認められた。

A room-cooling system of 2 kW capacity fueled by wood pellets was designed, built and tested. The system was demonstrated during summer at the Yakushima Field Station of Kagoshima University, Japan. It contained a pellet feeder, a pellet burner, a heat exchanger, a lithium bromide–water absorption heat pump and a control unit. The volume of the test room was 36.9 m3 and ambient temperature 30 °C. The airflow temperature from the room unit was decreased to 16 °C by the system, and the room temperature could be successfully controlled to 24 °C steady state. Room heating in winter was also demonstrated. Since the air was heat exchanged, the overall energy efficiency of the cooling system was low at about 19%. However, the calculation based on the heat flow showed that the efficiency could be enhanced to about 75% by direct heating of the regenerator by the flue gas.

We studied the effect of genotypes of planting stocks regarding the variation of the modulus of elasticity of tree trunks on standing trees (trunk-MOE), tree height (TH), and diameter at breast height (DBH) in a 19-year-old Japanese cedar plantation made with root cuttings. Trunk-MOE was assessed nondestructively using a tree-bending method. Genotypes of individual trees were detected using the random amplified polymorphic DNA (RAPD) technique. RAPD analysis revealed that the sampled plantation consisted of 14 genotypes. Genotypic effects on DBH and TH were unclear, and there was no significant difference among genotypes. This result indicated that an acquired variation should have more influence than an inherited variation on DBH and TH. For trunk-MOE, there were significant differences among the four largest genotypes at the 5% level. However the coefficient of variation in trunk-MOE of each genotype ranged from 7.5% to 26.8%. It seems reasonable to assume that the wide variation in trunk-MOE in a sampled plantation may depend on the environmental effect within a clone as well as on the genetic origin of clones. We therefore conclude that the use of multiple planting stocks from different cuttings for which the wood quality is unknown contributed strongly to the wide variation in trunk-MOE in the plantation of Japanese cedar.

A spacing experiment for Japanese oak (Quercus mongolica var.grosseserrata) with Nelder's design have been studied at the Kyushu University Forest in Hokkaido, since 1975. The oak seedlings were planted according to systematic spacings which were 20 levels varying gradually from 40,816 to 1,086 seedlings per hectare with concentric circular arcs (22 in number) and spokes (41 in number). In 1992 when the planted oak seedlings were 18-year-old, DBH, crown diameter, total height and clear length of the survival trees were measured. Based on the results obtained from analyzing the relationships between planting density and the mean values of each block, the optimum planting density should be 7,241 seedlings per hectare.