To discuss failure phenomena, rainfall and saturation conditions within the soil and soil-surface movement were observed on a steep weathered granite slope containing fragile layers with characteristics of collapse settlement . Although a failure did not initiate during the observation period, slight slope displacements were measured and a small crack was generated. The movement occurred from the top to central part of the slope, and then the bottom part. The tensile strain occurred at the top; the central part was almost translational, and compressive strain occurred at the bottom part of the slope. A saturated zone occurred non-uniformly during the slope movement. Many exposed rocks with the same strike were distributed on this slope, and these rocks differentiated the locations of fifteen old landslide scars. These rocks interrupted subsurface flow contributing to the heterogeneous saturated zone. The results of the investigation and observation were used to analyze the stability of the critical slip surface and estimate the shape of the failure. The calculations showed that a slip surface formed at the bottom boundary of the fragile layer and the initiation point of the slip surface was where a crack actually appeared under the exposed rock. The existence of the fragile layer was believed to dictate the depth of the slip surface; the existence of the exposed rocks determined the longitudinal position of failure.

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It has been known that there is a relationship between wind-falls of trees and such defects as cavities or decays within their trunks. However, up to now, no such methods or devices have been developed that can estimate the defects within a trunk with a certain level of accuracy without damaging the trunk. With the suggested method, the defects within a trunk can be estimated by analyzing the diagnostic slapping sounds which are got when hitting the trunk with a wooden hammer. Those diagnostic slapping sounds are analyzed by the wavelet analysis and the obtained power spectrum are utilized to estimate the defects. First of all, the measure for estimating the defects within a trunk is got by utilizing the wavelet analysis results of 15 logs and 702 trees whose conditions have been known. Then, the suggested method based implementing the obtained measure is tested to the estimation of the defects of 23 trees. As a result, all the estimations “with defects” are coincided with those of a tree doctor and 17 of them actually have defects. Adding to this, in the application to 6 trees including a healthy tree, all the estimation results coincided with the actual cross section conditions.

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We analyzed long-term monitoring data on old-aged plantations of sugi (Cryptomeria japonica) in Akita District to examine age-related changes in stand volume growth. Mean annual net volume increment increased with increasing age, and then decreased after an age of 80∼90 years, or sustained a constant level. The culmination age of mean annual gross volume increment was greater than that of the mean annual net volume increment. Mean annual increment in dominant tree height peaked before the first recorded measurement (plantation age 27∼39 years), and decreased with increasing age. Mean annual net increment in stand basal area increased with increasing age, and then decreased after an age of 40∼80 years. Our results suggest that sugi stands in Akita District seldom reach the culmination of mean annual volume increment until an age of 60 years, regardless of site productivity and stand density management; a thinning regime may extend the culmination age by reducing mortality due to suppression and disturbance. Additionally, dominant tree height growth peaks early, followed by basal area growth and stand volume growth.

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To develop a method to estimate crop size of oak trees (Quercus crispula) with least labor and as quickly as possible, the method proposed by Koenig et al. (1994) was tested in temperate forests of Japan. In autumn 2007, thirteen oak trees with various degree of fruiting were selected. First, following Mizui (1991), the number of acorns at 50-cm ends of six branches at the upper position of a crown was averaged for each of selected trees (Mizui’s index), as the de facto standard of index for crop size of a tree. Second, following Koenig et al. (1994), the number of acorns was visually counted within 30 seconds using a binocular (Koenig’s index) by eight observers. Koenig’s index was measured with nine replications per an observer. It is shown that Mizui’s index (y) was well regressed by Koenig’s index (x) using a power function (y =ax^b); parameter a were estimated as 1.4∼1.8 and parameter b as 0.32∼0.37, with coefficients of determination of 0.44∼0.56 after adjustments for the degrees of freedom. Although variation among the observers and among real fields of view for binoculars were mostly insignificant, one of the observers significantly underestimate Mizui’s index compared with other observers, and another observer also tended to underestimate Mizui’s index when using binoculars of narrower field of view. For the application of Koenig’s method, 6 replication of observation per a tree will be enough, although cautions will be needed to calibrate counting ability between observers and to use the same binocular, if possible, for every observer.

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Water consumption patterns and leaf water relations obtained from P-V curves were compared to examine the suitability for afforestation among one-year-old seedlings of 4 tree species, Robinia pseudoacacia L., an introduced species native to north America, and 3 others indigenous to the Loess Plateau, Quercus liaotungensis Koidz., Pinus tabulaeformis Carr., and Platycladus orientalis (L.) Franco., under well-watered and drought treatments. The results showed that R. pseudoacacia consumed more water than indigenous species in both water conditions. In the condition of water deficiency, indigenous species decreased water consumption by stomatal closure, whereas R. pseudoacacia reduced water loss through leaf abscissions. Under well-watered conditions, values of ψ_w^tlp and ψ_s^sat for P. tabulaeformis and P. orientalis were lower than those for R. pseudoacacia and Q. liaotungensis. These results indicate that P. tabulaeformis and P. orientalis have higher capacity to maintain turgor under drought conditions. Differences in the bulk elastic modulus (ε) were found between two conditions in P. tabulaeformis and Q. liaotungensis. The values of ψ_w^tlp and ψ_s^sat decreased as water stress increased in R. pseudoacacia, Q. liaotungensis, and P. orientalis, indicating that these trees respond to water stress through osmotic adjustment. Q. liaotungensis and P. orientalis had a higher ability of osmotic adjustment than R. pseudoacacia. It is suggested that indigenous species has advantages over R. pseudoacacia in drought tolerance and can be applied to the afforestation practice in this region.

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To examine temperature and humidity conditions in pupal chambers of Monochamus alternatus endai, logs that artificial pupal chambers were made inside of were set at a bare-site under direct sunlight and in a forest in the shade, and temperature and humidity of the chambers and the air at each site were recorded using thermo-recorders. The daily mean and minimum temperature, as well as the daily maximum temperature on a cloudy day, didn’t show significant difference either between the sites or between inside and outside of the chamber. However the temperature of the chambers at a bare-site in the daytime on a fine day rose easily and reached to a maximum of 39.9ºC. Humidity in the chambers didn’t fluctuate diurnally. It decreased gradually with dryness of logs. Based on the results, effects of temperature and humidity conditions in the xylem on adult emergence of M. alternatus were discussed.

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We investigated the relationship between degeneration of tissues and death of potted 3-year-old seedlings of Japanese black pine, Pinus thunbergii, from 6 families with different resistance, inoculated with pine wood nematode (PWN), Bursaphelenchus xylophilus. Branch pieces treated with distilled water control showed a little browning, but PWN-inoculated pieces showed marked browning 3 to 8 days after inoculation. As all PWN-inoculated pieces eventually browned completely, no seedlings were perfectly resistant to PWN at the tissue level. Days to full browning of the branch pieces was significantly correlated with days to seedling death (r_s=0.607, p<0.01, Spearman’s rank test). As inoculated seedlings that showed less browning tended to live longer, tissue resistance to PWN might be related to whole-plant resistance.

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Flume experiments with permeable rubber sponge attached to the base were conducted to determine the sediment filtering function of simulated forested hillslopes by placing litter on the sponge and collecting runout and subsurface drainage. The efficiency of the sediment filtering function of all litter treatments degreased linearly as the amount of cumulated sediment increased. When thinking that sediment filtering occurs respectively in surface runoff and in the sponge, the suspended sediment in surface runoff was not affected by turbid water flowing into the sponge base or the initial permeability of the sponge, but rather the presence of litter and gradient. The filtering function of the sponge was not affected by the experimental surface conditions (e.g. litter amount), and was influenced only by the initial conditions within the sponge. Therefore the filtering function of forested hillslopes involve not only the soil, but also litter because litter trapped at least two times the sediment compared to no litter cover.

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A review of the literature in terms of forest tourism and recreation after World War II was done using the FOLIS database. This result shows that studies were sporadically done from the 1940’s to 1960’s. It was also found that the National Recreational Forest designated in the late 1960’s became the first research topic which were intensively investigated. After this research, forest recreation became one of the most popular research topics in Japan. It is found that there are nine kinds of research topics which are started during late 1940’s to 1970’s. In this study these nine topics were reviewed and discussed.

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The forest resource database, called Shinrinbo, provides complete statistics about Japanese forests and forest resources. In 1999, a collaboration between the Japanese Forest Agency and the forest departments of individual prefectures resulted in the development of a new nation-wide forest inventory, which met the standards and rules of the Montral Process and the Santiago Declaration. This inventory involves systematic sampling covering the entire forest area of Japan. This paper highlights the forest inventory systems used in Japan after World War II.

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