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Mizutani M.,Fukui Nature Conservation Center | Nakajima H.,Forestry Research Institute | Kodani J.,Ishikawa Agricultural and Forestry Research Center | Nogami T.,Hakusan Nature Conservation Center | And 2 more authors.
Nihon Ringakkai Shi/Journal of the Japanese Forestry Society | Year: 2013

The relationship between the acorn crops of trees belonging to the Fagaceae family and the mass intrusion of Asiatic black bears (Ursus thibetanus) into the residential areas of the Hokuriku region were investigated based on an acorn crop monitoring survey conducted over a 7-year period, from 2005 to 2011, in the Toyama, Ishikawa, and Fukui Prefectures of Japan. Large fluctuations were observed in the annual acorn production of both Fagus crenata and Quercus crispula located in the high-altitude areas of all three prefectures. In particular, extremely poor yields of acorns were noted for 2006 and 2010, which coincided with the mass intrusion of bears into the residential areas. In contrast, little fluctuation was observed in the annual acorn production of Q. serrata distributed in low-altitude areas, and there were no incidents of years with extremely poor yields. These results infer that food shortages, due to simultaneous poor crops of F. crenata and Q. crispula in the mountainous areas of Hokuriku region, triggered the mass intrusions of bears into residential areas. Since the fluctuations in the annual acorn production of these key species were synchronized across a wide geographic area, a comparative analysis and coordinated survey of the acorn crop monitoring of each neighboring prefecture should result in an effective as well as accurate forecast of the acorn yields and therefore of bear intrusions.


Mizutani M.,Fukui Nature Conservation Center
Nihon Ringakkai Shi/Journal of the Japanese Forestry Society | Year: 2013

A simple method for evaluating the acorn yield of Quercus serrata was developed and tested. This simple method of evaluation, classified the yield qualitatively according to descriptive criteria assessed by direct observation of the tree canopy. A quantitative standard was also established to determine whether trees had fruited, and, if so, to estimate whether the crop yield would be above or below average. The fruiting of 392 Q. serrata trees were examined simultaneously in two ways: (A) by several unskilled observers using the simple evaluation method, and (B) by a forest researcher employing the established method based on the average number of acorns on the terminal 50 cm region of the branches. The results obtained using these two methods (which were summarized into 3 levels) were in agreement for 75% of the trees, when the data from individual observers using method (A) were compared with method (B), although the simple evaluation method (A) had a tendency for underestimation. However, when the largest value from the multiple observers was used, the concordance rate with (B) improved to 86% and the evaluation bias was also eliminated. The results of the study indicate that the newly developed, simple evaluation method, when used by several unskilled investigators simultaneously, produces a reliable assessment of the acorn yield and is suitable for monitoring acorn crops in practice.


Kuninaga T.,Kyoto Prefectural University | Kuninaga T.,Fukui Nature Conservation Center | Hirayama K.,Kyoto Prefectural University | Sakimoto M.,Kyoto University
Plant Ecology | Year: 2015

Negative density-dependence (NDD) is a major mechanism for shaping forest communities. However, its influence on species coexistence in conifer–hardwood mixed forests remains unclear. We aimed to determine whether NDD influences establishment of the seedling and/or sapling bank of Fagus crenata in an evergreen, coniferous Cryptomeria japonica-dominated stand, focusing on canopy structure (openness, distance from mature plants and species composition). For F. crenata trees, we analysed the spatial pattern using the pair-correlation function g(r) to test for NDD and spatial correspondence to canopy structure in two study plots established in a cool-temperate, old-growth conifer–hardwood mixed forest in western Japan. We also analysed the height growth of offspring and understorey light condition with respect to canopy structure. We detected evidence of NDD among neighbours during the transition of seedlings (age ≤ 4 years) to saplings (age > 4 years, stem length < 3 m). Although offspring densities at the seedling stage were highest under the conspecific canopy, those at the small sapling stage were significantly elevated under the C. japonica canopy in a zone extending 5 m beyond the drip lines of conspecifics. The height growth of saplings (age > 4 years) was elevated under the canopy of C. japonica, which was lighter than under that of F. crenata. Our results suggest that F. crenata recruitment was affected by NDD at the seedling-to-sapling transition under the conspecifics and allowed for the formation of the sapling bank under C. japonica canopies beyond the drip lines of conspecifics. © 2015, Springer Science+Business Media Dordrecht.

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