[in Japanese]

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Cerasus jamasakura and Padus grayana are wild cherry species indigenous to Japan. These wild cherries have high values in secondary forests. However, their population declines due to forest degradation are concerned recently in sub-urban areas. To collect fundamental information on forest ecology, we conducted an assessment on all woody stems in a 2.21 ha research plot in a secondary forest of the sub-urban area of Nara, Central Japan in 2006 and 2011. Basal area increment (ΔBA) during 2006-2011, was calculated for each wild cherry species, based on the measurement of stem diameter at breast height in 2006 and 2011. Through the development of growth prediction models using ΔBA and its natural logarithm as objective variables, we examined the growth of the wild cherries as affected by environmental factors such as indices of neighborhood competition and topography (index of convexity, slope position and slope azimuth) .The decrease in stem density and sum of basal area of C. jamasakura and P. grayana decreased from 2006 until 2011 and the highest frequency of both species in the smallest ΔBA class suggest that the population decline of these species in this site. Our results indicate that a model with a competition index used as an explanatory variable predicted the C. jamasakura growth well (R²＝0.54) and that their growth are significantly affected by the neighboring competitive trees. In contrast, a model developed for P. grayana didn't perform well (R²＝0.17) , while suggests that there are other factors that affect the P. grayana growth.

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In previous studies, seeds of Weigela hortensis K. Koch had high germination rates in light but did not germinate or only germinated less than a few percent in darkness, even after cold stratification. However, those studies were conducted under experimental conditions in relatively narrow range. If we can work out how to germinate seeds of W. hortensis in darkness, we can germinate them in soil and thus improve the rate of germination in seedling works to cover slopes. Therefore, we tested a broader range of temperatures and stratification treatments in this study than in previous studies and confirmed the results of those studies. We also tested the effects of temperature, stratification, light irradiation in detail, and GA₃ on germination in darkness, which have not hitherto been reported. Germination in darkness was optimized by cold stratification at 5 to 10℃ for ≥15 days and then irradiation at ≥7 μmol • m^-2 • s^-1 for 1 to 2 days at 25 to 30℃. With this treatment, even seeds stored at room temperature without desiccant for 401 days had an 80% germination rate at 20 to 30℃ in darkness. However, seeds cold-stratified, irradiated by such methods, and then stored moist at 5℃ in darkness for ≥ 3 days decreased subsequent germination at 25℃ in darkness.

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[in Japanese]

View full abstract

[in Japanese]

View full abstract