The dense cover of sasa (dwarf bamboo) often inhibits tree regeneration, and silvicultural operations to control sasa are essential so as to ensure natural regeneration of forests. Operations to control sasa are usually conducted following timber harvesting. Controlling sasa under the closed canopy before timber harvesting is expected to ensure the establishment of advanced seedlings and make tree regeneration more successful. However, the effects of operations to control sasa under the forest canopy before timber harvesting have not been previously examined in Japan. In this study, we conducted a field manipulation in stands hinoki (Chamaecyparis obtusa) natural stand, Kiso region, central Japan, to examine the sustainable suppressing effects of the dwarf bamboo, Sasa palmata, under the closed canopy. We conducted five treatments that combined weeding and herbicide application. Every year from 2013 to 2017, in a 1 m² quadrat per treatment, we collected the aboveground and belowground parts of sasa and measured their biomass, number of culms, and carbohydrate concentration belowground. Sasa lost its culm emergence ability immediately after the first weeding practice in the three treatments that included weeding, and in the next few years, its belowground biomass disappeared. In contrast, the herbicide treatment slightly decreased the aboveground biomass of sasa, but caused no effects in the belowground biomass, indicating that this treatment does not eliminate sasa. Weeding under the closed canopy was the most suitable method to control sasa, raising the natural regeneration potential of hinoki from advanced regeneration.

In the eradication of the pine sawyer beetle (Monochamus alternatus), two types of covering methods are used for the fumigation of infested pine logs: the top covering method, which is widely used in Japan; and the complete wrapping method, which has been adopted in limited areas. To elucidate the effectiveness of the two covering methods, we measured the temporal changes in the MITC gas concentration in the coverings and evaluated the mortality of the insect larvae in the treated logs at four study sites with different soil conditions. The MITC gas concentrations peaked from 2 h to 1 day following the initiation of treatment and gradually declined toward 15th day when we terminated the census, regardless of the covering method and/or study site. High levels of larval mortality were recorded in all of the treated logs. A few larvae were found to be alive in pupal chambers plugged with tightly stuffed wood fibers in the galleries. Such chambers were formed at relatively deep positions from the wood surface. From these results, we concluded that both fumigation methods have equivalent effectiveness for eradicating the pine sawyer beetle.

Eleutherococcus sciadophylloides is a popular edible wild plant among Japanese citizens, though its leaves are known to have relatively high ¹³⁷Cs concentrations among the edible wild plants. Studies to investigate detailed ¹³⁷Cs distributions of each tree part, such as leaves, stems, main roots and lateral roots, were scarce. In this study, we aim to investigate why the high ¹³⁷Cs concentrations are in the leaves of E. sciadophylloides by measurements of proportions of ¹³⁷Cs content of each tree part and statistical analyses. Small sized samples of E. sciadophylloides were collected in spring and autumn in 2016 and 2017 in Fukushima Prefecture. The proportions of ¹³⁷Cs content of each tree part were calculated by the ¹³⁷Cs concentrations and the weights. Approximately 50％ of the total ¹³⁷Cs content was located in the leaves in spring. The proportions of ¹³⁷Cs content in the roots were relatively high compared with that in the stems in both seasons. The linear regression models indicated high positive correlations between the ¹³⁷Cs concentrations in the lateral root and that in both inner bark of the stems and the main roots. It is suggested that ¹³⁷Cs was translocated to the stems or the main roots through the inner bark. It is possible that the phenomenon which is the high ¹³⁷Cs concentrations in the leaves of E. sciadophylloides is caused by translocations related to seasons through the inner bark from the roots in addition to its features of shallow roots suggested by previous studies.

Guidelines for the sustainable and effective use of plantation forests are important for national land planning and mountain village development in Japan. Therefore, we analyzed the value of plantation forests in view of forestry using Land Expectation Value (LEV) as an investment indicator. Cash flow from expenditure was defined as production costs (PC), consisting of harvesting and transport costs, and silvicultural costs (SC), while cash flow from income was calculated by multiplying the Mean Annual stem volume Increment per unit of land area (MAI) by the price of standing timber and the rotation age. Assuming an average MAI of 10 m³/ha/year for cedar plantations and assuming current PC (7,000/m³) and SC (1,500,000/ha), they were not eligible for investment management at a discount rate of 1％. If the present cost is accepted, in order to succeed as an investment the MAI needs to be more than 17 m³/ha/year over 91 years of rotation age. If the PC and SC could be made about 10％ less expensive, it would became an investment target at a rotation age of about 40 years. Therefore, it is important to use MAI as a basis for zoning of plantation forests and to make management decisions based on the rotation age derived from production and silvicultural costs.

Natural regeneration practices via selection cutting were examined in a Chamaecyparis obtusa forest with undergrowth that lacked dwarf bamboo. The work was performed in the Akasawa Experimental Forest, Kiso District, central Japan. The forest floor light conditions were improved after selection cutting and clearing of the undergrowth of deciduous shrubs. Subsequently, the light conditions worsened due to reduced canopy gaps and undergrowth recovery, with different delayed deterioration rates depending on the location. Thirty years after cutting, the total mean density of C. obtusa seedlings and saplings amounted to hundreds of thousands ha^-1. The sapling(＞1.3 m in height) density varied widely; the relative frequency at which the sapling density exceeded 3,000 ha^-1 was no more than 38％. This variation demonstrated a mixture of successfully regenerated sites with sapling banks and unsuccessfully regenerated sites that would have had little chance of achieving sapling banks in the future. The seedling density 3-5 years after cutting did not significantly correlate with sapling density 30 years after cutting. In contrast, the seedling density and light conditions 15 years after cutting, and topographic conditions, were closely related to sapling density and sapling bank success. This relationship suggested the continuation of improved light conditions resulted in regeneration success. The prediction of successful regeneration probability is likely possible not from the initial seedling density but the light and topographic conditions.

We developed and validated a logging detection methodology using ALOS-2/PALSAR-2 data in order to effectively utilize logging area information in the forest cloud, which is becoming widely used by local governments. In Ibaraki Prefecture, we adopted a method of segmenting the images and extracting the areas where the backscatter coefficient decreased between two images. Then, we validated the accuracy and improved the method by conducting a field survey and comparing the observations with optical sensor satellite image. As a result, it was found that screening procedure based on the local microwave incidence angle can reduce false detections, and that using images with different directions of microwave radiation together can reduce undetected loggings, in mountainous areas where PALSAR-2 is not well suited. The detection accuracy was sufficient, with 82％ user's accuracy and 76％ producer's accuracy, even in mountainous areas. Next, we conducted a demonstration experiment in which we loaded logging area information onto Ibaraki Prefecture's forest cloud system, and four regional governments tested and confirmed it in the field. The results showed that the user's accuracy was 83％, the information was particularly effective in identifying logging areas deep in the mountains, and also showed that 30％ of the logging areas were unreported. These results demonstrate the potential of PALSAR-2 data for efficient monitoring of logging areas.

There is the long-term forest environmental education that has been conducted by Kawana Satoyama Ranger, student-led a volunteer group working to conserve Kawana green space located in the southern part of Fujisawa, Kanagawa. This forest environmental education activity, called the “Yato (valley) expedition” allows a child to experience nature with their bodies. The contents are mainly walks in nature and crafts. The purpose of this study was to examine consideration mainly from a safety perspective in the viewpoints of college students as rangers (instructors) as the contents changed, based on records of expeditions over 15 years conducted by this ranger team. Text mining was used to analyze the implementation records of rangers. The results showed that students pay attention to the following points in the student-led forest environmental education activities: injuries to participants, time management of the program, health management of participants, speed of movement according to the participants. On the other hand, if it is student-led, members will be replaced every year. Therefore, it should be noted that the safety and health care considerations of the student perspective may not be carried over.

We compared the growth of containerized and bare-root Japanese cypress (Chamaecyparis obtusa) seedlings for four years after planting, and also investigated the competition between seedlings and their surrounding weeds to assess the possibility of reducing the number of weedings. The height and diameter growth of the containerized seedlings was equal to or higher than those of the bare-root seedlings, though the superiority of the formers' relative growth rate was not evident after the first year. With regular weeding, once a year over the four years, the weeds observable in the summer of the fifth year were Miscanthus sinensis and deciduous shrubs (roughly 150 cm in height). The average height of the containerized seedlings at this time was 284 cm, roughly 40 cm higher than that of the bare-root seedlings. We considered that this was owing to the fact that the containerized seedlings had been reared with slow-release fertilizer, eluted over longer periods than usual, as base fertilizer. Furthermore, the vertical competition between the seedlings and weeds abated one year earlier than in the case of the bare-root seedlings, and weeding could be omitted, in the summer of the fifth year, in the containerized seedling plot. Consequently, it was suggested that the number of weedings could be reduced by one year in the case of the containerized seedlings.

The Japanese populations of Platypus quercivorus, the oak ambrosia beetle, are classified into two groups, namely groups A and B. These are based on the molecular sequence of D1-D2 segments of 28S ribosomal DNA, and each group consists of several sequence types. The sequence types were determined for beetles collected from Izu (Hachijo, Mikura, and Miyake), Tsushima, Shodoshima, and Shikoku islands, where Japanese oak wilt disease has been reported recently. Beetle populations from Hachijo, Shodoshima, and Tokushima (Shikoku) belonged to types 4c-e of group B, whereas those from Mikura, Miyake, Tsushima, and Kochi (Shikoku) belonged to types 1a-d of group A. The sequence types newly recognized in this study are not considerably different from previously reported types, and the previously described sequence types from the Ryukyu islands were not detected. The distribution pattern observed in the present study was found to be consistent with the results of previous studies. Because of the recent expansion of the P. quercivorus population, further sequence type analyses as well as disease monitoring are necessary to understand their population structure and for effective disease control.

Tree planting is a way to reuse abandoned agricultural fields, but hard soil layers near the surface in such fields may adversely affect the survival and growth of planted trees. We investigated the relationships between topsoil penetration resistance and trunk death and sprouting in Prunus sargentii trees planted in plowed and unplowed (control) areas of an abandoned upland slope. Penetration resistance to a depth of 0.1 m was lower in the plowed area than in the control area, indicating that plowing likely alleviated soil compaction. We observed fewer trees with dead trunks in the plowed area as compared to the control area. Trees with dead trunks generally produced sprouts, and sprout growth decreased with increasing values of Nc (number of weight drops per penetration interval) to a depth of 0.1 m. We conclude that management practices for planting in abandoned agricultural fields should include topsoil plowing.