To clarify the size distribution characteristics of trees in old-growth Japanese cedar plantations, we conducted a multi-po int survey in Gujo City, Gifu Prefecture, Japan. The old-growth stands (≥ 80 years) comprised around 1000 m³ stand volume. The relationships between tree crowding indices (relative yield index), indices of size heterogeneity (coefficient of variation), and size asymmetry (skewness) revealed that the size heterogeneity of diameter and stem volume was significantly higher in old-growth stands than in mature stands (40–80 years) under identical crowding conditions. In most of the old-growth stands, the skewness of diameter did not significantly differ from zero indicating a normal distribution, whereas the skewness of stem volume was significantly positive, indicating a positively skewed distribution with its tail on the right side. These results suggest that the old-growth Japanese cedar plantations in Gujo City are characterized by relatively high stand volumes, high size heterogeneity and high size asymmetry. The results also suggest that individual tree management is important in old-growth stands with lower tree density and large disparity in tree size.

Bark-stripping by sika deer has often been reported to lead to high tree mortality. Only few species were reported to survive heavy bark-stripping. Here I report on bark recovery in Egonoki (Styrax japonicus), and discuss anatomical features related to successful bark recovery. The regenerated outer layer of a stem after bark-stripping in the previous year was investigated. The regenerated bark consisted of an inner bark and an outer bark segmented by a periderm. The innermost surface on the separated bark-side sample was a rather wider layer of thin-walled cells, presumably composed of cambial zone and developing phloem. The outermost layer on the separated xylem side was a developing-xylem-tissue with a wider primary-wall-zone but no apparent cambium remaining. Traumatic tissue was observed only as small traces in the previous-year’s growth ring. In contrast, primary-wall-developing xylem elements were only in 1 to 2-cell-layers remaining on the outermost surface of the stem soon after bark stripping, and was covered with a translucent substance. Interestingly, wood anatomical features common to tree species that can survive heavy bark-stripping by deer are “apotracheal axial parenchyma in tangential to oblique lines or in narrow bands” and “diffuse-porosity with narrow-diameter vessels”. Cambium can be regenerated within a surface callus formed over the entire wound area for some species. Although traumatic parenchyma zone was not formed in Egonoki, wound cambium may regenerate similarly. The fact that axial parenchyma cells can form a more-or-less continuous tangential plane just like a cambium leads to the speculation that cells differentiating into axial parenchyma cells under the covering substance can be reprogrammed (dedifferentiated) into meristematic cells, comparable to cambial initials, by the stimulation of bark-stripping.

A large-scale artificial crossing utilizing a large number of lines is conducted for forest tree breeding. It is essential to efficiently perform all procedures in artificial crossing including bagging, pollen collection, and injection of pollen during flowering in the target tree species. A pollen gun is an instrument utilized for artificial crossing. However, the discontinuation of production by manufacturers has made it difficult to obtain the pollen gun in recent years. Thus, a pollen gun was constructed using commercially available materials in this study. To improve work efficiency, the new pollen gun was constructed using a plastic centrifuge tube for pollen storage that could be directly attached to the gun. It was 0.6–7.7 g heavier than the conventional gun, but the amount of pollen that could be stored was 1.9–2.8 times greater; moreover, the amount of pollen ejected was 1.4–2.7 times more than the conventional gun. The results suggest that this pollen gun is effective for usage in artificial crossing. The newly developed pollen gun is expected to improve work efficiency as it is easy to fill and refill it with pollen.

We installed infrared automatic cameras in a Japanese cedar plantation of six-year-old and obtained the photographs of Japanese scops-owls Otus semitorques and a grey-faced buzzard Butastur indicus. Photographs were taken during April to June and individuals seemed to visit this site for foraging. Plantations at an establishment stage are likely to serve hunting areas not only for diurnal raptors but also for nocturnal raptors.