Power generation using wood biomass has become popular as a renewable source of energy; however, the disposal of large amounts of combustion ash generated on account of it has become problematic, especially with the increasing operation of large power plants. Wood biomass ash contains nutrients, such as potassium and calcium; therefore, it may be used as a fertilizer in the growth medium of containerized seedlings. This may allow us to effectively utilize wood ash and also reduce the cost of growing seedlings. Hence, the influence of wood ash containing media on the growth of seedlings should be clarified not only in the container but also after planting. After outplanting containerized seedlings of sugi (Cryptomeria japonica) and hinoki (Chamaecyparis obtusa) in wood ash containing media with different wood ash mixing rates into the nursery, the growth of sugi seedlings in 5% and 10% mixing rates was observed to be similar to that in 0% mixing rate. The development of sugi seedlings in 25% mixing rate was significantly lower than that in 0%, 5%, and 10% mixing rates; however, it caught up with that of the other ones after three years. The growth of hinoki seedlings in 5% mixing rate was similar to that in 0% mixing rate. The mortality of hinoki seedlings in 10% and 25% mixing rates was high, whereas the growth of a few seedlings was the same as that in 0% mixing rate. Although the limit of wood ash mixing rate in the containerized seedling medium differed between sugi and hinoki, the growth of seedlings after outplanting could be ensured if the mixing rate was within the limit.

Wood decay in Abies mariessi and Abies veitchii growing in a subalpine evergreen coniferous forest was diagnosed using stress-wave velocity and drilling resistance. Factors affecting the outbreak of wood decay in subalpine forest was discussed. Stress-wave velocity was low in decayed trees and trees exhibiting frost-crack. Furthermore, stress-wave velocity decreased with increasing degrees of decay along trunk diameters in trees without frost-crack. The frequency distribution of stress-wave velocities was either normal or skewed to lower stress-wave velocity classes. Stem densities of individual Abies mariessi and Abies veitchii in the low stress-wave velocity class increased with increasing elevation. These results indicate that the stem density of decayed trees and trees exhibiting frost-crack increase with increasing elevation. Sapwood decay was observed in many frost-crack trees and, therefore, lacerations on the trunk made by frost cracking may be an infection route for wood-decay fungi. Since the stem densities of the frost-crack and the sapwood decayed trees was high at higher elevation, it was concluded that frost-crack may accelerate occurrence of wood decay at higher elevations in the subalpine evergreen coniferous forest.