The role of seeds in habitat expansion and the contribution of seed banks were examined for populations of Robinia pseudoacacia L. in the Akagawa river basin, Yamagata Prefecture, Japan. Vegetation map analysis determined that around one third of patches of R. pseudoacacia had emerged from seeds rather than from root suckers, and were distributed where root suckers could not invade, i.e. on a river holm or situated more than 60 m from the nearest conspecific patch. During a 5-year period between 1999 and 2004, 30 patches emerged, of which 12 were considered to be derived from seeds. Hard seeds of R. pseudoacacia tend to form soil seed banks, but in this area most hard seeds were found in soil under R. pseudoacacia stands. However, at sites of other types of vegetation, such as Salix and Juglans stands, and at denuded sites, dormant seeds were almost entirely absent. This study's findings indicate that there is self-replacement of the soil seed bank of R. pseudoacacia following destruction of existing stands due to disturbance, but that self-replacement scarcely contributes to the generation of new populations. This suggests that stands established at newly disturbed sites tend to result from seedling emergence from seeds without dormancy or where dormancy was removed during dispersal by water in streams. Hence, decreased regeneration from dispersed seeds should also be taken into consideration in the population control of R. pseudoacacia.

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We analyzed the streamwater from 33 forested watersheds in Nara Prefecture, Japan, in 2002 to clarify the influences of forest clearcut and subsequent afforestation on streamwater chemistry. Each watershed is covered with even-aged Japanese cedar (Cryptomeria japonica) stands with ages ranging from 1 to 87-years-old. The highest arithmetic mean of nitrate (NO₃⁻) concentrations in streamwater was observed in the watershed with 1-year-old stands. Mean NO₃⁻ concentrations declined sharply as the stand age increased, and reached the pre-cutting low level in the 13 year-old-stand watershed. The results of multiple regression analysis showed that NO₃⁻ concentrations were determined mostly by the stand age rather than the geographic factors (area, elevation, relief ratio, or aspect) of each watershed. The rainfall on the sampling day did not affect the relationships between NO₃⁻ concentrations and stand age. The effects of clearcut on streamwater NO₃⁻ agreed with the results from other studies in the U.S. and Europe. Among 1- to 9-year-old-stand watersheds, a positive correlation was found between NO₃⁻ and the sum of base cation concentrations, suggesting that nutrient losses caused by clearcut remain at least for 9 years after the afforestation. In contrast, there were no increases in H⁺ or total Al concentrations observed in this study. This finding indicates that all the watersheds have the acid-neutralizing capacity to buffer H⁺ produced in the soil due to the enhanced nitrification after clearcut.

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This study examined the environmental conditions that were required to maintain a threatened species, Salix hukaoana. Twenty-five plots were set up in the riparian zone along the Yubiso River, and forest structure, topography, and forest age were investigated. The riparian forest in the area was classified into the following five forest types by dominant species: Salix sachalinensis, Toisusu urbaniana, Salix hukaoana, Pterocarya rhoifolia, or Fagus crenata. The Salix sachalinensis type was found only in the lower floodplain. The Salix hukaoana type and Toisusu urbaniana type were found in both the lower and the higher floodplain. The Pterocarya rhoifolia type was found in the lower floodplain and on hillslopes in the higher floodplain. The Fagus crenata type was found on both terraces and hillslopes. All the stands of Salicaceae forest types were less than 45 years old. Among the five forest types, the stand age of Salix sachalinensis type was lower than the other types by 27 years, while those of Pterocarya rhoifolia and Fagus crenata types aged more than 88 years. The Salix hukaoana type was likely to become established on open areas in the floodplain after a fluvial disturbance and was maintained until its replacement by the Pterocarya rhoifolia type. In the Yubiso River valley, a mosaic structure consisting of various types of forest might be formed due to the diverse disturbance regime and environmental conditions that are peculiar to the wide valley floor. Therefore, it is crucial to maintain this variation in disturbance regime and site conditions for conserving the S. hukaoana population together with the riparian vegetation and along the Yubiso River.

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To investigate frugivory by Carnivora, literature on the Asiatic black bear (Ursus thibetanus), Japanese marten (Martes melampus), and Raccoon dog (Nyctereutes procyonoides) was analyzed in terms of fruit utilization. Species of frequently-eaten fruits were different among these three species; bears and raccoon dogs showed conspicuous use of fleshy fruits of tall trees and vines, whereas martens depended more on fleshy fruits of shrubs and vines. Bears fed also on dry fruits of tall trees such as acorns of Fagaceae species. These differences among animals probably reflect specific climbing ability. In addition, bears used lipid-rich fruits compared with other animals, probably due to hibernation during winter. All carnivores are considered dispersal agents of fleshy-fruited plants because they use some fleshy fruits.

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We used the paired-watershed method to analyze changes in the flow duration curve after forest clear-cutting in the Fukuroyamasawa Experimental Watershed (35°12′ N, 140°06′ E) in University Forest, Chiba, Japan. The watershed is located in a Tertiary formation area and is covered by a mixed plantation of sugi (Cryptomeria japonica) and hinoki (Chamaecyparis obtusa). The annual precipitation and annual mean temperature are 2,170 mm and 14.2°C, respectively. The control and treatment watersheds were both about 1 ha. Daily flow was higher on almost all days after cutting in the treatment watershed, and the increase was greater on the high-flow side than on the low-flow side. However, flow changes on the first through eleventh days after cutting were not obvious. We compared pre- and post-cutting regressions of daily flow in the treatment watershed against daily flow at the control watershed; the slope of the regression lines did not change, but the y-intercepts increased after cutting. The change in daily flow after cutting was smaller than the variation caused by geological differences in the daily flow of several forested watersheds in Japan. The flow duration curves in forested watersheds are influenced by vegetation but are more strongly influenced by geology.

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We investigated stand and multi-stem clump structure of nine stands of secondary lucidophyllous (warm-temperate natural evergreen) forests with different ages to clarify the effects of the dynamics of multi-stem clump structure on the change in stand structure along the secondary succession after felling. As a result, three major stages were detected in the developmental process of the secondary forest as follows. 1) Up to 18 years after felling, secondary forests consisted of both multi-stem canopy trees of sprout-origin and understory individuals of seedling origin of lucidophyllous species, whereas pioneer species which might have dominated the canopy at the stand initiation stage disappeared due to the suppression by evergreen multi-stem individuals of sprout origin. 2) The proportion of multi-stem individual and average number of stems of canopy trees decreased during 23-46 years after felling. This change indicated stem exclusion within the clump of multi-stem individuals. We suggest that the severe competition between stems within the clumps provided a dark environment on the forest floor, resulting in exclusion of the seedlings of lucidophyllous species. 3) Since 60 years after felling, the number of canopy trees of sprout origin decreased, indicating the change from death of stem level to individual level. This probably resulted in gap formation and heterogeneous canopy structure, which improved the light environment on the forest floor and promoted the reinitiation of understory individuals.

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The effects of thinning and litter removal treatments on the establishment of riparian vegetation were investigated in a Cryptomeria japonica plantation. The number of germinated seedlings and species richness were significantly greater in the plots that were thinned (30% and more) than in the control or girdling plots. Litter removal also encouraged the germination of many species, resulting in greater numbers of seedlings and species. Thinning increased the number of component species of natural riparian forests. However, the established understory vegetation was dominated by Euptelea polyandra, while Pterocarya rhoifolia and Fraxinus platypoda, the typical canopy trees of natural riparian forests, and several regional riparian perennial herbs were absent. These results suggest the possibility of natural regeneration of riparian species in managed forests, and the need for long-term monitoring to establish optimal management practices, including planting, for the restoration of semi-natural riparian forests.

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Techniques for rearing longhorn beetles were reviewed with focuses on collecting the insects, handling adults, eggs, larvae, and pupae, and a method for synchronizing development. Under rearing conditions, the larval diet can consist of natural food or an artificial diet. Two types of artificial diets are generally used: one consists mainly of dry host plant powder and the other mainly of defatted soy bean powder, starch, sucrose, and wheat germ, and host plant materials. Low-temperature treatment for terminating diapause and desirable day-length conditions for synchronizing pupation and eclosion were determined. To rear beetles successfully in the laboratory, the diet must be chosen after considering the purpose for which the insects are being reared, the labor involved, and the laboratory facilities. Then, a procedure for rearing insects from eggs to adults must be designed.

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