Soil scarification is a natural regeneration practice that has been developed as a low-cost birch reforestation technique on Hokkaido, the northernmost island of Japan. Scarification practices may play a significant role in the treatment of Abies sachalinensis plantation facing a final cutting period in Hokkaido. Scarification removes forest floor organic matter and surface soil, therefore it has been a concern that it will adversely affect the regenerated birch growth. To clarify the long-term effects of soil disturbance due to scarification on regenerated birch growth, we investigated the physicochemical properties of surface soils (depth: 0 – 5 cm) at 17 scarification-regenerated birch forests treated from the 1970s to the 1990s. Tree height growth of 20 – 44-year-old Betula ermanii were higher than in stands regenerated in other ways. In the strip-scarified stands examined in this study, some stands had regenerated along non-scarified lines. There was no significant difference in site index between stands regenerated along scarified lines and these along non-scarified lines. A generalized linear model indicated that site index in scarification-regenerated birch forests was larger in conditions with low CN ratios and lower slopes. Some soil physicochemical properties changed due to soil scarification, while CN ratios did not. The effect of the scarification for the regenerated birch growth was not clear whereas the soil physicochemical properties, except for CN ratios, were different. The results of this study show that soil disturbance due to scarification might not affect long-term birch tree growth in these stands.

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The aim of the present study was to determine which factors affect the natural regeneration of tree species such as birch Betula spp. after clear-cutting Abies sachalinensis plantations in Hokkaido, Japan. To achieve this, the relationships between sapling density and the factors such as the presence/absence of scarification, the height of the undergrowth, and, in the case of birch saplings, the distance from adult birch trees were analyzed at five study sites. Sapling density was positively correlated with scarification and negatively correlated with undergrowth height, and scarification suppressed the height of the undergrowth. In addition, the density of birch saplings was negatively correlated with the distance from the adult trees. However, the density of birch saplings at the study sites was lower than has previously been recorded in preceding studies, indicating that the natural regeneration of this species may not be successful. This will have been due to a lower density of dispersed seeds.

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To clarify the effect of cooking on ¹³⁷Cs mass, 10 species and 11 organ samples of edible wild plants were cooked: the spore stem of Equisetum arvense (Ea), petioles and flower buds of Petasites japonicus (Pj), and sprouts of Fallopia japonica (Fj), Aralia cordata (Ac), Parasenecio delphiniifolius (Pd), Senecio cannabifolius (Sc), Pteridium aquilinum (Pa), Osmunda japonica (Oj), Eleutherococcus sciadophylloides (Es), and Aralia elata (Ae). They grew up on the land exposed to the 2011 Fukushima Daiichi Nuclear Power Station accident. Soaking in hot water reduced the ¹³⁷Cs mass of Fj [¹³⁷Cs food-processing retention factor or ¹³⁷Cs Fr = (processed/unprocessed sample ¹³⁷Cs mass ratio) = 0.14 ± 0.11 (mean ± SD)], and boiling in hot water with salt also reduced the ¹³⁷Cs masses of Pj, Ac, Pd, Es, and Ae (range ¹³⁷Cs Fr = 0.41 ± 0.14 to 0.99 ± 0.09). Stringent removal using baking soda reduced the ¹³⁷Cs masses of Pa (¹³⁷Cs Fr = 0.089) and Oj (¹³⁷Cs Fr = 0.32 ± 0.04). Stringent removal using baking soda and drying for long-term preservation markedly reduced the ¹³⁷Cs mass of Oj (¹³⁷Cs Fr = 0.009 ± 0.012). Desalting after prolonged salting also markedly reduced the ¹³⁷Cs masses of Pa, Oj, and Es (range ¹³⁷Cs Fr = 0.016 ± 0.015 to 0.041 ± 0.012). However, the effect of this recipe on Sc was smaller (¹³⁷Cs Fr = 0.24 ± 0.15). Preparation by removing the less edible parts before processing the remainder and making tempura had no significant effect on the ¹³⁷Cs mass. Cooking using baking soda and drying markedly reduced the ¹³⁷Cs mass, as did desalting after prolonged salting. Both recipes are for long-term preservation.

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In 2017, the mass flowering of dwarf bamboo (suzutake, Sasamorpha borealis) occurred throughout the Chubu region of Japan after a non-flowering interval of 120 years. Concern is growing that an abundance of seeds produced by the mass flowering could cause an outbreak of rodents and, thereby, damage to the forests. To investigate whether the rodent population would increase from the mast seeding of suzutake, trapping surveys were conducted in the hinoki cypress (Chamaecyparis obtusa) plantation forest in the Dando National Forest (Aichi Prefecture), located in the center of the mass flowering. The estimated rodent density did not prominently increase in the fall after mast seeding. The next spring, the density of voles (Microtus montebelli or Eothenomys smithii), which cause gnawing damage to trees, remained relatively low (3.3–23.3 individuals/ha), whereas the density of two wood mouse species (Apodemus argenteus and A. speciosus) was greatly increased (53.3–80.0 individuals/ha). These results indicate that the possibility of a widespread vole outbreak caused by mast seeding is low. However, further attention should be paid to population fluctuations in voles because populations may increase in other areas suitable for vole growth and survival.

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We investigated the cause on the rapid mass mortality of Larix kaempferi containerized seedlings at Iwate Prefecture, northern Japan in 2014. In particular, seedlings transplanted in current year were dead massively. The result of isolation test showed the main causal agent was Fusarium oxysporum. Thus, we diagnosed the disease as Fusarium root rot caused by transplanting. The rapid mass mortality may be related to the root damage by transplanting and various factors such as water and soil conditions in production of seedlings.

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Meteorological observations have been carried out at Tohkamachi Experimental Station (37°08’ N, 138°46’ E), Niigata Prefecture, since 1918 in order to obtain data for use in disaster prevention and studies on earth science. Since 1939-40 winter season, snow pit observations have been carried out at about 10 days intervals. In this report, we present data such as daily weather, air temperature, precipitation, snowfall depth, snow depth, and snow–water equivalent, and snow pit observations during the recent five winter periods from 2014-15 to 2018-19.

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