Butt rot ofChamaecyparis obtusa (Sieb. et Zucc.) Endlicher trees caused byPerenniporia subacida in Shikoku district, Japan: Pathogen, distribution of damaged trees in the stand, and soil investigation

The rot ofChamaecyparis obtusa (hinoki) trees was studied in the northern part of Kagawa Prefecture, Japan. Among 158 hinoki examined, butt rot was found in 28.6, 58.3, and 100% of trees in the 29, 30, and 34-year-old stands, respectively. All trees with butt rot, and 11 trees without it had rotted roots. Thirteen hinoki were peeled byCervus nippon (sika deer) and all of them were infected with butt rot. The maximum height of rot in deer-damaged trees was 2.6 m from the ground level, but was 1.9 m in undamaged trees. About eighty-two percent of rotted trees showed rotted areas of less than 40 cm² on the cross section of stems at the ground level. White mycelia and black flecks sometimes appeared in the rotted wood. Basidiocarps of polyporaceous fungus were often found on felled logs and rotted stumps of hinoki and identified asPerenniporia subacida. Basidiomycetous fungus was isolated frequently from rotted wood of roots and stems, and determined to beP. subacida by comparative study on cultural characteristics. An inoculation experiment and wood-decay test proved that the fungus was the cause of the rot of hinoki. Few absorbing roots of living trees were found in the clayey subsurface soil of the high dry bulk density and the less soil aeration. Some absorbing roots had root rot and the rot spread from the base of the absorbing root to the central part of the woody root. This is the first report on the rot of hinoki caused byP. subacida in Japan.     

Stand structure and establishment process of an old-growth stand in the mixed deciduous broadleaf/conifer forest of Mt. Moiwa Forest Reserve, central Hokkaido, Northern Japan

Stand structure of an old-growth forest was studied by tree (≥4.0 cm in DBH) census in a main plot of 1.3 ha and 8 additional plots (0.525 ha in total) located in the Mt. Moiwa Forest Reserve, central Hokkaido, northern Japan. Major tree species with ≥1.0% of the relative basal area and of relative number of trees (Acer mono, A. mono var.mayrii, Kalopanax pictus, Magnolia kobus var.borealis, M. obovata, Prunus ssiori, Tilia japonica, andUlmus laciniata) have positive values of skewness in DBH, which shows the abundance of smaller-sized stems. All stems over 1.3 m high in the main plot were mapped to clarify the relationship between stem densities and canopy states. Although advances from sapling (>1.3 m tall and <4.0 cm DBH) to small tree (10.0 cm ≤ DBH <25 cm) for all major component species, exceptP. ssiori andU. laciniata, were independent of canopy states, those ofP. ssiori andU. laciniata depended on canopy gaps.Betula spp. was the most abundant gap makers, butT. japonica andA. mono (including var.mayrii) were dominant species in the main plot. This suggests the shift of dominant species in the forest of the study site. Historical records of disturbance demonstrated that selective cuttings of conifers during the late 19th century were responsible for the dominance ofBetula spp. and the subsequent shift of dominant species. This fact suggests that artificial disturbance plays an important role in the establishment ofTilia japonica-Acer mono forest considered to be a climax of the mixed deciduous broadleaf/conifer forests.