The invasion pattern of nine deciduous broad-leaved trees and shrubs in a snow-damaged Cryptomeria japonica plantation was studied. The highest dominant species invading was Cornus controversa followed by Prunus grayana. The nine species had invaded at the opportunity of a canopy gap formation, but they had different species-specific invasion patterns. Two major types were observed for the pattern; the C. controversa type (C. controversa, Magnolia obovata and Morus bombycis), which depended on the gap attribute and had invaded only a few years after the gap formation, and the P. grayana type (P. grayana, Helwingia japonica and Alangium platanifolium var. trilobum), which did not necessarily depend on canopy gaps and invaded continuously. The results indicate that the former type needs a sudden change in light conditions, and the latter type needs stable light conditions for invasion. The distribution pattern of these types, indicated that the C. controversa type takes advantage of a small gap and the P. grayana type invades under the canopy of Cr. japonica near the gap attribute. Consequently, it was considered that frequent formation of small canopy gaps was effective in order for these broad-leaved species to broadly and randomly invade the Cr. japonica plantation.

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This study was conducted to clarify the distribution and content of nutrients in plant tissue (foliage, branch, root), forest floor (Ao layer), and litterfall in four pioneer stands, i.e., aspen (Populus sieboldii M.), alder (Alnus maximowiczii C.), poplar (Populus maximowiczii H.), and black locust (Robinia pseudo-acacia L.) stands established on Mt. Showa-Shinzan. The content of N in foliage was higher in black locust and alder than them in aspen and poplar. Among the various tissues, nutrient concentrations were higher in foliage than in branch or root. The concentration of N on the forest floor was the highest in the alder stand. The contens of nutrient on the forest floor was in the order of Ca>N>Na>Mg>K>P. The dry matter of the understory biomass was most abundant in black locust stand, but dry weight of organic material on the forest floor did not show significant difference among the study stands. The production of litter were higher in the alder and black locust stands than in the poplar and aspen stands, and the content of N in litter was high in both alder and black locust which are N-fixing species. These results suggested that these early pioneer species would be well adapted to nutrient-poor sites after volcanic eruptions because the rapid growth and N fixation properties that increased nutrient availability in the forest ecosystem.

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The pH value and electric conductance (EC) of precipitation were measured in the Chichibu Mountains (Ootaki) and Kanto plain (Yorii) in Saitama Prefecture for 8 years from 1989 to 1996. These data were compared with those of an urban area (Urawa). The average pH values of Ootaki, Yorii and Urawa for 8 years were 5.08, 4.47 and 4.53, respectively. The average EC values were 10.3, 21.3 and 24.1μS/cm, respectively. The average concentration of Cl^- in precipitation from 1990 to 1991 were 0.32, 0.75, 0.73mg/L, NO^-_3 were 0.79, 1.74, 1.99mg/L, SO^<2->_4 0.80, 1.65, 2.34mg/L, respectively. The precipitation of Ootaki was cleaner than that of Yorii and Urawa. The fact that there was no difference in the pH and EC values of precipitation between Yorii and Urawa supported the assumption that air pollutants were transported from Tokyo Bay to Yorii by the air stream. On the other hand, there are no sources of air pollutants in Ootaki, but some air pollutants were transported from Tokyo Bay. As a result, Ootaki was a background area of precipitation with few pollutants.

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Wind direction and wind velocity data are necessary to analyze the behavior of forest fire and its propagation. It is possible to obtain prevailing wind data from weather stations but not the characteristics of fire whirlwind at the site of the forest fire unless we measure it at the time of the fire. This paper presents a procedure of estimation of wind direction and wind velocity from the stem-bark char remained at the forest fire damaged area. In this investigation, in order to clarify the relation among the factors affecting fire-scar of stem, wind tunnel experiments were carried out. It was observed that the height of stem-bark char registered at the windward face of a stem is smaller than that of the opposite face of a stem under all the experimental conditions. Therefore, an estimate of wind direction from the remaining stems in a burned field can easily be done. Further it was found that, the height of stem-bark char of windward face of a stem decreased as the wind velocity increased. The height of stem-bark char of a stem opposite the windward direction increased as the diameter of the stem increased. It was derived from these results that the magnitude of the difference (Hd) in height of stem-bark char of windward face and opposite face of a stem was an important factor for estimation of wind velocity. From a viewpoint of field application, stem-bark char ratio (Hr) of both faces of a stem tends to be significant as well as the difference in height of stem-bark char of both faces, because of the dissimilarity of scale in wind tunnel experiment and actual phenomena in the field. Dimensional analysis was carried out for the factors affecting the stem-bark char using the observations mentioned above. Based on the results of the study we propose the following equations for estimation of wind velocity when the stem partially burned. H/D=1.86×10^<-6>(U・D/v)^<1.64> in case of heading fire, H/D=7.24×10^<-5>(U・D/v)^<1.20> in case of backing fire, where, H is Hd×Hr, D is diameter of stem, U is wind velocity and v is coefficient of kinematic viscosity. We compared the wind velocity calculated by experimental equtions with wind velocity observed in two prescribed fire sites. It was observed that the wind velocity could be expressed with a high accuracy by the above proposed equations.

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In the previous investigation, the author proposed experimental equations for estimation of fire whirlwind velocity at the time of the fire from the fire-scar of a stem remained in the forest fire damaged area and observed applicability of these equations in the field experiments. This paper presents the results of analyzing the fire behavior in detail using these equations at two prescribed fire sites. One experimental site was at Akiyoshidai in Yamaguchi prefecture and the other was at Hiraodai in Fukuoka prefecture. In these experiments, Sugi (Cryptomeria japonica) logs were used as a substitute for stems. Factors affecting the fire-scar of stems were measured after burn in order to estimate wind velocity at the time of the fire using experimental equations. The direction and the velocity of prevailing wind were measured at selected points around the experimental sites. Further, scenes at both fires were recorded on videotape for making survey maps of fire behavior. At Akiyoshidai site, investigation of fire behavior was a bit complicated owing to the moisture of vegetation and soil. Wind directions estimated by fire-scar of stems in the experimental site did not show a fixed direction. However, it was found that general fire behavior was simplified into six groups by examining the fire behavior pattern with the prevailing wind data, fire whirlwind data estimated using experimental equations and the state of combustion analyzed from the recorded videotape. Relation between the fire whirlwind velocity and the spread rate of fire among these six parts was studied. In the case of heading fire, the spread rate of fire increased as the wind velocity increased, and was constant for backing fire. In the experiment at Hiraodai site, when the fire behavior was an upslope fire, the fire whirlwind directions estimated from the stem-bark char showed a fixed direction. Fire whirlwind direction agreed approximately with slope azimuth, in spite of a prevailing opposite wind direction. Further relationship between fire whirlwind velocity estimated by experimental equations and maximum slope gradient was investigated. However, it was not possible to recognize a relationship between them using individual data of slope angles and wind velocities estimated, which could be due to the differences in on-site condition of experimental logs. But, dividing the slope into ranges and taking mean values for gradient instead of individual values, it was observed that fire whirlwind velocity increased as maximum slope gradient increased.

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The surface conductance of a deciduous secondary forest in Kansai region was estimated during the foliate season. The value of estimated surface conductance rate varied widely in the low vapour pressure deficit condition and converged to a constant (6mm・s^<-1>) when the vapour pressure deficit became high. The cause of the convergence value of 6mm・s^<-1> is supposed due to the large evaporation from the forest floor. The algebraic form of the relative surface conductance for the influence from the solar radiation shows as a hyperbolic curve with a relatively small curvature with those in the other reports. It is thought that it was caused by the transpiration from the leaves located in the relatively low layer of the community and the large evaporation from the forest floor. The difference of these algebraic forms was judged to be effective both in the present forest and the pine forest in U.K.. When the algebraic form of the relative surface conductance for the influence from the air temperature is at the maximum value, the air temperature shows higher than that in the European forests and lower than that in the Amazonian forest. The algebraic form of the relative surface conductance from the vapour pressure deficit was evaluated to be most similar to one in the oak forest in Dutch.

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The leaf phenology of over-and understory trees was investigated in a deciduous broad-leaved forest in 1997. In the study area, the snow usually melts in late March or early April, and it does not prevent understory plants from using the light penetrated from the canopy. In the understory, the earliest leaf flushing was observed for Euonymus oxyphyllus and Prunus apetala in May, when the overstory trees were leafless. In the overstory, the earliest leaf flush was observed in late May for Betula platyphylla var. japonica and Prunus grayana. The latest was in early June for Castanea crenata. The leaf flushes of most of understory trees occurred earlier than overstory trees. Moreover, there is a tendency that smaller sized individuals wihin a tree species flush leaves earlier than those of large sized ones. Most of trees shed leaves in a short period at late October. From these, it is suggested that most of understory trees can utilize the favorable light in spring for photosynthetic activities before the leaf flushing of overstory trees.

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