Mie Forestry Research Institute

地質条件が異なる3カ所のスギ・ヒノキ人工林に設けた試験地において土砂移動レートを3年間測定し，林床被覆と間伐木を利用した筋工が表土移動に及ぼす影響を検討した。試験地別，筋工有無別に林床被覆率と土砂移動レートの関係を指数式で近似したところ，いずれにおいても林床被覆率が高いほど土砂移動レートが低くなる傾向がみられた。筋工有区の土砂移動レートは筋工無区よりも低かったが，林床被覆率が低いほど両者の差は大きくなる傾向を示した。

Understanding variation in root and shoot growth phenology among species is crucial to understanding underlying mechanisms of temporal niche differentiation. However, little is known about the relationship between root and shoot phenology, or how this relationship varies among functional traits. We examined fine root and shoot phenology of 42 seedlings representing a variety of woody species that inhabit the cool temperate forests of northern Japan. Some aspects of phenology were common to the pool of species examined: we found positive relationships between root and shoot phenology for the end of growth, and for the duration of growth, but not for the start of growth. Further, seedlings that started root growth relatively early also ended root growth relatively late. Other aspects of phenology varied predictably with functional traits, i.e. leaf habit and successional status: first, root growth in evergreen species started significantly earlier and ended later than in deciduous species; second, early successional species had the longest duration of shoot growth among all successional types. Our results suggest that niche differentiation may be promoted by differences in phenology between root and shoots, likely contributing to the co‐existence of woody seedlings in temperate forests.

Abstract We grafted scions of Dahurian larch (Larix gmelinii var. japonica) onto Japanese larch (L. kaempferi) and F1 hybrid larch (L. gmeli­nii var. japonica × L. kaempferi) rootstocks and examined root­stock-scion compatibility by assessing the survival rate (SR) in two independent experiments. Scion overgrowth on the root­stock was not observed. SR was not significantly different among rootstocks due to large interquartile ranges (IQR) among clones within a rootstock type. Results suggested that the SR was more dependent on the clonal characteristics of the scion than on the growth vigor of the rootstock. Shoot elonga­tion of grafts on F1 hybrid rootstock was superior to that of grafts on Japanese larch rootstock. Selection of an appropriate combination of scion and rootstock may improve the SR of grafted Dahurian larch and shorten the cultivation period.

In conifer plantations, enhancement of species diversity has become an important management goal. Although thinning is a useful method to enhance diversity, determining optimum thinning intensities may be rather complicated because of potential trade-offs among a broad array of management goals (e.g., recovery of biodiversity, increasing individual tree sizes, increasing net primary production, saving management costs). To evaluate the optimum thinning intensity by analyzing these relationships, we conducted a thinning experiment with three different thinning intensities—unthinned, 33% thinned, and 67% thinned—in a Cryptomeria japonica plantation in 2003, and investigated the number, diameter at breast height (DBH), and diversity of hardwoods (height > 1.5 m) in 2008, and the growth of conifers over five years. In hardwoods, the number of individuals, number of species, mean DBH, and total basal area were greatest in the 67% thinned treatment, irrespective of successional status. However, Shannon's diversity index did not differ among the three treatments due to a disproportionate increase with thinning intensity in the abundance of a mid-successional species, Cornus controversa. Diameter growth of conifers was also highest in the 67% thinned and lowest in the unthinned treatment, whereas the reverse was true for stand volume increment. These results suggest that intensive thinning is a reliable method to convert conifer plantations into conifer–hardwood mixed forests at canopy level much more quickly and consistently than weak thinning, although primary production is to some extent reduced. If forest managers prefer sustainable timber production of conifers rather than full recovery of diversity, weak thinning may be suitable.

We analyzed the chemical composition of vestures of vessel elements and wood fibres of Eucalyptus camaldulensis and Eucalyptus globulus by ultraviolet (UV) microscopy, transmission electron microscopy (TEM) after staining with potassium permanganate (KMnO4) or the PATAg reaction, and field-emission scanning electron microscopy (FE-SEM). Samples were treated with dilute solutions of NaOH at various concentrations. Before treatment with alkali, the vestures on the secondary walls of vessel elements and wood fibres were visible on UV micrographs taken at 280 nm and were strongly stained by KMnO4. Vestures were strongly stained by the PATAg reaction in samples that had been treated with 0.1% NaOH. However, treatment with higher concentrations of NaOH dissolved the vestures. FE-SEM observations showed that the process of dissolution of vestures during alkali extraction differed between the two species. It appears that vestures in Eucalyptus woods consist mainly of alkali-soluble polyphenols and polysaccharides. In addition, the chemical composition of vestures may differ between the two species of Eucalyptus that we examined.

Analysis of proportion of cell types in native wood is important to understand the environmental stresses including an increasing atmospheric CO2 concentration on the structure of wood, especially for the management of plantation forest which will reduce our reliance on natural forests. The conventional method to determine the proportion of cell types is a quantitative microscopy, which is one of the image analyzing systems using a light microscope combined with a microcomputer. However, it is a lengthy multistep procedure. We have examined the feasibility of using FT-Raman spectroscopy for rapid determination of proportion of cell types (fiber, ray parenchyma, vessels and axial parenchyma) in native wood with using wood meals of two Eucalyptus species, including samples of various ages and colors, which are of importance as a plantation source [1].

Relations between various extracted basic densities and wood chemical components were investigated by their within-tree variations in Eucalyptus globulus for assistance in the prediction of the properties of wood or wood-derived products. Extraneous compounds affect the relations between various basic densities and wood chemical components such as holocellulose and the lignin syringyl/guaiacyl ratio. We also discuss the relation of various densities, the molar composition of neutral sugars constituting hemicellulose, and fiber morphology.

Relationship between various extracted basic densities and wood chemical components were investigated by their within-tree variations inEucalyptus camaldulensis for assistance in the prediction of the properties of wood or wood derived products. Within-tree variation was not observed for basic density because extraneous compounds masked it. However, extractives-free basic density, total extractives-free basic density and extraneous compounds-free basic density were high on the bark side and top parts in the trunk. These extracted basic densities were expected to have significant relationships to the fiber morphology causing the within-tree variations, and to be very important factors for wood industries. These relationships were sought by correlations between extracted basic densities and wood chemical components based on their within-tree variations. Furthermore, fair relationships between extracted basic densities and hemicellulose composition were observed and speculation made as to the relationship to the constituent ratio of cell wall layers.