The piezoelectric effect of wood is explained using practical examples. The mechanisms of piezoelectricity in wood, cellulose, and cellulose derivatives are analyzed based on observations of the relationship between piezoelectric temperature and dielectric and elastic properties. The piezoelectric temperature dispersions characteristics are different in various wood species. Liquid ammonia treatment, delignification treatment, and noncrystalline treatment causes variations in the piezoelectric behaviors. The relationship between the crystallinity and the components of wood chemical structure is analyzed using the two-phase model. The cellulose derivatives are explained in the outline about a highly utilization.
Finally, some recommendations are made, such as the development of device, the development of a nondestruction evaluation method, and the clarification of the piezoelectric behavior in a living tree.

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Terpenes are volatile compounds emitted from wood, and they have been suggested to be related to the comfort in a woody environment. Terpenes emission influences the concentration of total volatile organic compounds in the indoor air. Studies on the long-term emission of volatile compounds, including terpenes, from wooden interior finishing installed in buildings are few; therefore, in this study, wooden materials were finished on the floor and wall of a laboratory, and the volatile compounds in the room were analyzed for about two years from the day after finishing. 51 compounds such as hydrocarbons, alcohols and carbonyl compounds were quantified and unidentified compounds between hexane and hexadecane were semiquantitated. In addition, the air change rate in the room, temperature, and relative humidity were measured. Compared with all compounds measured in this study, the volume of emitted terpenes was the largest during almost the complete experimental period. And the concentration of terpenes in the air was higher at immediately after finishing and during summer. After two years, the concentration declined to 0.15 % as compared to the day after finishing. In addition, the eight substances with regard to which the guideline of the indoor air concentration values were defined were below the indoor concentration guideline values. The air change rate per hour in the room was 1.1 times/h. The temperature ranged from 6 ℃ to 32 ℃ , and the relative humidity ranged from 47 % to 63 %.

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Stand dynamics of 61 years since 1955 of a forest stand located on volcanic mudflows originating from the eruption of Mt. Tokachi in 1857 were examined. The forest stand had standing tree density of 358 trees・ha^-1, basal area of 57 m²・ha^-1, and stand volume of 658.8 m³・ha^-1 in 2015, 158 years after the volcanic mudflows occurred. Pisea jezoensis and Populus maximowiczii dominated the upper layer of the stand, and stem of ingrowth of broadleaved trees had increased. Stand volume increased until 148 years after the volcanic mudflows and then began to decrease. During the past 61 years, the number of trees has decreased by half. Based on the stand development stage after a stand-replacing disturbance, we considered that the forest stand is shifting from the stem exclusion stage to the understory reinitiation stage.

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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. In this report, we present data such as the air temperature, relative humidity, precipitation, wind speed, snowfall depth, snow depth, and snow–water equivalent obtained over a period of 100 years, i.e., from 1918 to 2017.

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An experiment plot (1 ha) was established in the Yamanashi prefectural forest of Hokuto City on the east slope of Mts. Yatsugatake to preserve the endangered species Picea koyamae. Comparative observations of trees in the plot were carried out in 2005 and 2017. During this period, the alive stem number greatly decreased from 2,755 to 1,248, the basal area at breast height (BA) increased from 30.0 m² to 31.4 m², and the number of confirmed taxa decreased from 37 to 29. We guessed that the decreases in number of stems and number of c onfirmed taxa were due to damage by Cervus nippon. The number of mother trees of P. koyamae larger than 20 cm in diameter at breast height (DBH) slightly decreased from 42 to 36 due to the positive influence of bark guards attached in 2005. However, it of younger trees smaller than 20 cm in DBH decreased significantly from eight to two. We propose that propagation of seedlings is necessary due to the lack of successful saplings for its in situ conservation.

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We compiled daily data of precipitation and runoff observed from 2006 through 2010 in the Minami-dani and the Kita-dani in the Tatsunokuchi-yama Experimental Watershed of the Kansai Research Center of the Forestry and Forest Products Research Institute. Each day was separated at 0:00 JST. Precipitation data were the sum of hourly mean values of three tipping bucket-type rain gauges arranged at a meteorological station in the Okayama Experimental Forest, which is located at the west-northwest foot of Mt. Tatsunokuchi. For the period from August 2 to December 10, 2006, the data of a storage-type rain gauge were employed because the three tipping bucket rain gauges failed to record data. Runoff data were the sum of water flows converted from water stages measured at 60°V-notch gauging weirs. Water stage fluctuations were recorded using a float-type pen recording water level gauges, and the analogue waveforms were digitized manually. At the Minami-dani, data missing because of mechanical malfunction of the gauge occurred during several hours on May 29 and September 26, 2008. Therefore, runoff data based partly on estimated water stages were employed for these days. For the mean annual precipitation of 1071.2 mm, the mean annual runoff was 315.2 mm in the Minami-dani and 349.9 mm in the Kita-dani during the reporting period. In early 2006, Hinoki （Chamaecyparis obtusa） was planted in the upper slope and four species of broadleaved tree were planted in the lower slope in a 0.48 ha tree windfall area that formed in 2004 because of typhoons. Subsequently, weeding in the planted area was conducted once each year in summer until 2010. However, overall, changes of vegetation cover were not conspicuous in both catchments.

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We have been monitoring rainwater and streamwater chemistry in forests located in the upper reaches of the Shimanto River within Yusuhara-cho, Takaoka-gun, Kochi Prefecture, since 2000. The rainwater was collected at one location, whereas streamwater was sampled at run-off points of seven forested catchment basins. In this study, we analyzed data collected from 2000 to 2015 to examine changes in rainwater and streamwater chemistry. In particular, we investigated the effects of the volume of rainfall on water chemistry and the long-term changes. During periods with lower total rainfall, electrical conductivity (EC) was higher and variation in the range of pH was greater. In addition, no long-term trend was observed for rainwater pH, EC (annual average), and annual input of various ions. Although streamwater EC decreased with the increase in cumulative rainfall for 14 days before the sampling day, only a little effect on pH was observed. No long-term change in streamwater pH was found. However, the concentration of dissolved ions such as Na⁺, Ca²⁺, and Mg²⁺ tended to decrease in all seven forest watersheds from 2007 to 2015; the decrease in Cl⁻ and SO₄²⁻ was distinct. We recommend continuous monitoring of these decreasing trends to determine how long they continue.

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Trap-nests are useful tools to monitor solitary bees and wasps that nest in tube-like cavities. We installed trapnests made from internode tubes of bamboos and reeds in ten secondary deciduous broad-leaved stands of different ages of one to over 100 years after clear-cutting. Thirty-two species (eight families of Hymenoptera and one of Diptera) were obtained with the trap-nests: 20 host species and 12 of their natural enemies. The species richness of most families of hosts and natural enemies, except for Pompilidae, was higher in younger to middle-aged stands than in older ones over 70 years old. On the contrary, the family Pompilidae (spider wasps) proliferated in both young and old stands, with its relative abundance becoming greater with the increase in stand age.

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