Usefulness of the spectral age, which was estimated using Landsat TM imagery based onsuccessional spectral change curves of spruce (Picea jezoensis Carr., Picea glehnii Mast.) stands in Tomakomai, Hokkaido, Japan, was evaluated by analysing stand condition and annual changes. Bigger and smaller spectral age than stand age showed denser spruce dominant stands and sparser spruce stands with broadleaved trees much more than standard stands of the successional spectral change curves respectively. Thus the spectral age showed standard spruce stand condition in each stand age rather than the stand age itself. The difference of spectral age images, which were estimated using winter and summer TM images in 1985, showed differences of spruce crown coverage in stands well. Removing of broadleaved trees or thinning of spruce trees were detected, when the spectral age images of two summer TM images in 1985 and 1993 were compared. Since the spectral age changes linearly against time coursing in any growth stages, it would be an excellent index, with which we can intuitively understand changes in stands during their growth.

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This paper analyzes the energy consumption of a remodeled excava-tor introduced in the previous report on the assumption that the minimum operational stability required of the remodeled excavator is secured with consideration for the running resistance and driving force working on undercar-riage wheels. By re-examining formulas for the static model of the previous report, we proved that if the moment at each arm joint is intensified so that the arms press the ground, the operational stability of the excavator chassis is enhanced enough to prevent the excavator from tumbling over. Next, the energy consumption of the remodeled excavator for hoisting a load was calculated. In the calculation, the reference value of the resistance force of the undercarriage and the running resistance and driving force working on the undercarriage wheels were varied and the moment at each small arm was adjusted to secure the minimum stability. As a result, it has been clarified that the running resistance of wheels has little effect on the energy consumption of the remodeled excavator, that when a driving force is applied to undercarriage wheels the energy consumption rather increases, and that as the resistance force of the ground undercarriage increases, the energy consumption is reduced.

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The effects of pruning on growth were investigated on 19 years old stand of Picea glehnii M. during 14 growing seasons to examine the validity of intense pruning in early stage. The stand contained plots of four different degrees of prunings, i.e. non-pruning as control, light, middle and intense pruning, which were estimated that approximately 0, 30, 55, and 80% of total amount of leave were removed for every individuals in each plot, respectively. Pruning had little effect on height growth. On the other hand, the reductions of increment in diameter correlated with the degree of pruning intensity. However, these reductions were occurred only during two years after pruning and there were no significant differences among plots in diameter increment during the last 10 years. In addition, the largest 1/3 individuals in diameter from each plots did not show significant differences in diameter increment among plots. These results suggest that intense pruning on young aged stand is effective when prunings are applied to dominant individuals.

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To clarify the relations of nitrogen mineralization and water-soluble ions of forest soils, in situ incubation method of core soil was used to measure nitrogen mineralization and the changes of water-soluble ions of forent soils in Japanese cedar (Cryptomeria japonica) and cypress (Chamecyparis obtuse) stands. Nitrogen contents in both cedar and cypress soils changed a little with the seasons. Rates of nitrogen mineralization were closely related with the soil temperature, but not with the soil moisture. Annual amounts of mineralized nitrogen in 020 cm soil were estimated to be 67 kg/ha and 77 kg/ha in the cypress and cedar, respectively, and were mainly NO₃-N form. Soil EC and water-soluble H⁺ concentrations increased with nitrogen mineralization rates. Al³⁺ increased much more in cypress soil than in cedar soil, but Ca²⁺ and Mg²⁺ increased much more in cedar soil than in cypress soil. Both in cedar and cypress soil, water-soluble NO₃-increased significantly with nitrogen mineralization rates, Cl^-changed little, and SO₄^2-obviously decreased. All of these changes in soil water chemistry may be attributed to the differences in soil pH and base cation contents of the two stands.

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Vegetation recovery process and amount of eroded soil were surveyed at the reforested stands in comparison with abandoned stands after forest fire. Reforestation works, especially terrace planting works, affected the successional pattern and species composition of postfire vegetation. Recovery of woody plant biomass at the reforested stands were more rapid than at the abandoned stands. In the early terms after reforestation, woody biomass was slightly larger at the terrace-planted stands than the natural-slope-planted stands. But, 12 years after reforestation, the woody biomass in natural-slope-planted stands were larger than that of the terrace-planted stands. Because vegetation recovery at the natural-slope-planted stands were progressed by both planted species and naturally recovered species; but the recovery at the terrace-planted stands were mainly progressed by the planted species. Amount of eroded soil at the natural-slope-planted stands were less than the terrace-planted stands and the abandoned stands. There was not significant difference of amount of eroded soil between at the terrace-planted stands and the abandoned stands.

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