Dielectric soil moisture sensors are commercially available and widely used in soil science. In this study a type of soil moisture sensor was applied to the moisture measurement of living and standing conifer tree stems. Some noticeable seasonal and diurnal changes of volumetric water content (VWC) of stem were observed during a long-term continuous measurement with high time-resolution. A detailed analysis revealed the following four kinds of factors influencing the changes of the measured VWC of tree stems. (1) Gradual decrease of measured VWC for one to two months starting at sensor installation due to dehydration from xylem surrounding the sensor probes. (2) Rapid decrease of measured VWC due to winter stem freezing. (3) Rapid increase or decrease of measured VWC after rainfall due to electric noises in the measurement system. (4) Temperature dependency of measured VWC on stem temperature, which arose from the dependency of water permittivity on temperature. Factors (1) to (3) above are unavoidable in the field measurement and uncontrollable by operation; the solution is data omission in the analyses of stem moisture fluctuation under conditions when such factors arise. The factor (4) can be compensated with the simultaneous temperature measurement of stems, by a theoretical correction from the relationship between temperature and water permittivity, and by an empirical correction developed by data analyses of the observed relationship between stem temperature and measured VWC. Corrected data showed that the seasonal fluctuation of stem VWC was small in general, in agreement with the results from former destructive and non-destructive methods, but sometimes the VWC was apparently increases or decreases and that the fluctuating patterns differed between species, between individuals and even between positions within a tree.

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The current stand density control diagram (SDCD) for private and public Sugi (Cryptomeria japonica) man-made forests were created between FY1978 and 1980. Several studies have suggested need for revising the current SDCD due to existence of high-density stands with the relative yield index (Ry) exceeding 1.0 and the tendency for total stem volume to be underestimated. In this study, SDCD for seven regions was revised using new data collected since 2003. First, a new maximum density curve, common to private and public Sugi forests across Japan was developed, resulting in a gentler slope than the current version, closer to -3/2. The current SDCD underestimates both the stand volume and mean diameter at breast height (DBH), but the revised version is able to estimate these values without bias. However, variability was high, with only 50–70% of the data achieving an estimate of stand volume with an error margin of less than 20%, depending on the region. This is likely due to the increasing diversification of management history and stand structure resulting from the thinning age, thinning rate and the aging of the stands. In order to improve estimation accuracy, it is necessary to produce more detailed regional classifications, such as at the prefectural level. Unlike the current SDCD, Ry calculated in the revised version can be approximated by a nearly single curve for each region in relation to relative spacing (Sr), making it easier to interpret the relationship between Ry and Sr. In conclusion, the revised SDCD could estimate total stem volume more accurately than current version, based on the top height and stand density. This improved reliability of using the SDCD as the basis for creating the yield table.

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We propose a portable gas analyzer (PGA)-based system for analyzing stored methane (CH₄) and carbon dioxide (CO₂) samples more rapidly compared to gas chromatography (GC) for application in the closed chamber technique. A gas analysis system was established using an ABB LGR-ICOS gas analyzer, which was connected to a carrier gas flow line with nitrogen as the carrier gas and to a gas injector equipped with a septum. This new system enabled more rapid analysis of CH₄ and CO₂, within 2 minutes, which was more than three times faster than GC. The linearity of gas measurements using the PGA-based system was evaluated by measuring the peak heights of known concentrations of CH₄ and CO₂ gases introduced into the system. The results demonstrated excellent linearity, with R² values exceeding 0.998. The repeatability of the gas measurements was high, as indicated by the low coefficient of variation (CV), with all CVs remaining below 3%. To validate the PGA-based system, we compared its results with those obtained from GC. The results from the system showed a high correspondence with the GC measurements, with R² values exceeding 0.995 and the ratio of CH₄ and CO₂ concentrations measured by the PGA-based system relative to those measured by GC being nearly 100%. Overall, we concluded that the PGA-based system is a robust method for measuring CH₄ and CO₂ concentrations of stored samples in sealed containers more rapidly compared to GC.

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We surveyed the flora of wild vascular plants in Tohoku Research Center, Forestry and Forest Products Research Institute (Morioka, 39°46′04″N, 141°07′56″E, 191 m above sea level). As a result, 492 species of vascular plants in 320 genera, 112 families (29 of ferns, 10 of gymnosperms and 453 of angiosperms) are recorded. As compared with the previous flora list recorded approximate 40 years ago, 189 species are newly added while 91 species unfound. Newly added species are composed of many forest floor plants, while unfound species includes grassland plants. This reflects well the environmental changes over the past 40 years in Tohoku Research Center, where forestation is progressing.

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Morphology of Epinotia piceae (Lepidoptera: Tortricidae), a defoliator causing mass mortality in Abies mariesii, a native fir in the Zao mountains, northern Japan was comprehensively reviewed. Specific morphologies such as thefore wing markings, the tegumen, uncus, socius, henion and valva of male genitalia, and the sterigma and signum of female genitalia characterized adult E. piceae. The larvae were distinguished by a combination of morphological characters on the pinaculum, crochet, anal fork, and subventral setae. Unique larval features in the area include an anal fork and uniordinal crochets on prolegs, which differed from the previous description. The diagnostic characters of the bark beetle, Polygraphus proximus (Coleoptera: Curculionidae), which caused additional tree mortality, were presented in photographs. This review will aid non-specialist researchers in determining whether fir and spruce pests belong to these species.

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Focusing on microtopography units, we investigated the thickness of colluvium soil and saprolite, as well as physical properties of soils at a small watershed (Kahoku Experimental Watershed No. 3) in the northern part of Kumamoto Prefecture, located in the warm temperate zone. Both the surface soil thickness and the weathered layer thickness were thicker above the knick line. The colluvium soil thickness and saprolite thickness were particularly notable in the head hollows with a gentle slope in the middle of the slope. Regarding the general physical properties of the soil, the bulk density was large, the total porosity was low, and the liquid phase ratio was high, especially in the B horizon. Meanwhile, the saturated hydraulic conductivity showed a good value. The effective porosity, which contributes to the soil's water storage function, was generally low except for the upper side slopes, which occupies the widest area in the watershed.

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Leaf beetles, which are almost exclusively phytophagous insects, were collected using Malaise traps in ten regenerated broad-leaved stand plots (1–178 years old) and eight Cryptomeria japonica conifer plantation plots (3–76 years old) every two weeks from April to November in the north of Ibaraki Prefecture, Japan. We provide collection data showing the biweekly catch at each plot. A total of 129 species (22,172 individuals) and 102 species (10,324 individuals) were collected in the broad-leaved plots in 2002 and conifer plantation plots in 2003, respectively. In both groups of plots, species richness was higher in younger stands than older stands. Beetle abundance (the number of individuals) was highest in spring, while species richness peaked in July.

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As a preliminary investigation to elucidate the impact of Pallas's squirrel on insect populations, we conducted an insect capture survey using traps in the forests of a small island (Takashima, Oita City, Kyushu, Japan) before squirrel eradication, as well as on the squirrel-free peninsula (Saganoseki) on the opposite shore. Three types of baited traps were employed: flight intercept traps, pitfall traps, and hornet traps. At the insect group level, species richness and abundances for longhorn beetles and hornets were significantly higher on the peninsula, likely due to negative effects of squirrel predation. In contrast, the abundance of necrophagous silphid and dung beetles was significantly higher on the island, presumably reflecting the high availability of squirrel carcasses. No significant differences were observed in ground beetles, suggesting they were unaffected by squirrel presence. The findings of this study can be utilized in post-eradication comparative research to assess the impact of the squirrel.

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We conducted questionnaire and field surveys for the land leech (Haemadipsa japonica) on Shikoku Island, where the leech has been reported from a small area. A questionnaire survey was distributed to the staff of the Forestry Agency in Shikoku in October 2024. Further, a field survey was conducted at 24 sites in Naka town, Tokushima Prefecture, and the surrounding areas at the beginning of the month. Blood-sucking injuries surely by the leech in Naka and Kaiyo towns were reported in the questionnaire survey. The land leeches were found at 10 sites stretching in an area 19 km by 14 km during the field survey, which covered the western part of Naka town and the northern tip of Kaiyo town. The land leech expansion accompanied by over-abundant sika deer was expected, however, land leech distribution in Shikoku remained restricted in the area centering on the western part of Naka town.

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