Hideyuki Ida

Gnawing damage by rodents to the seedlings ofFagus crenata andQuercus mongolica var.grosseserrata in a temperateSasa grassland-deciduous forest series in southwestern Japan

The effects of dwarf bamboo,Sasa, cover on the initial morrality of hardwood seedlings were investigated by transplanting 1-year-old beech (Fagus crenata) and current-year oak (Quercus mongolica var.grosseserrata) seedling to three different stands; old-growth beech and secondary oak forests withSasa undergrowth, and aSasa grassland in a grassland-forest series near the top of Mt Jippo, southwestern Japan. The most frequent cause of seedling morrality was gnawing of the stems by rodents. In the beech forest, the gnawing was more likely to occur underSasa cover, suggesting that it provides a good habitat for rodents on the beech forest floor. TheSasa under growth may thus play an imporrant role in regeneration of beech forest. In the oak floor, mortality of both species was low and only a little gnawing occurred during a year. However, no natural oak seedling were found in the forest even after a mast year. This may be because most of the acorns disappeated before establishment. The early-stage demography of hardwood seedling as oak may thus play an imporrant role in regeneration of oak forest. In theSasa grassland where the seed supply is small, almost all of the seedlings died fromo gnawing regardless of the presence ofSasa cover. These factors prevent the recruitment of a sizable seedling bank. Rodents may thus play an imporrant role in maintenance of theSasa grassland.

Treefall gap disturbance in an old‐growth beech forest in southwestern Japan by a catastrophic typhoon

. In 1991, the catastrophic Typhoon 9119 created many treefall gaps in an old-growth beech (Fagus crenata) forest on Mt. Garyu, southwestern Japan. In a 3.3-ha plot, the density and basal area of fatally damaged trunks (DBH ≥ 20 cm) were 29.1 trunks/ha (16.9% of all pre-typhoon trunks) and 9.1 m2/ha (24.4% of total pre-typhoon basal area), respectively. Many of the dominant beech were lost and larger trunks were damaged. The pre- and post-typhoon DBH distribution both had an inverse J-shape. Spatial distribution of living trunks was not random but clustered irrespective of typhoon damage or DBH size, suggesting that the stand structure of the study plot would be an unusual one as compared with the previous study stands in Japanese beech forests. The death of pre-typhoon trunks, seemed to die standing or to be killed by snap-off, occurred singly; however, the typhoon fatally damaged many clustered trunks at the same time. Uprooting was the most frequent cause of gaps created by the typhoon. The intermediate DBH size class (40–70 cm) would be more likely to be uprooted than snapped-off. The DBH distribution of snap-off may reflect the total pre-typhoon trunk distribution. Branch-fall had a flat DBH distribution. Uprooting might have a clustered distribution, while snap-off and branch-fall both had random distributions. The smaller trunks of snap-off and branch-fall seemed to result from injuries caused by the fall of larger trunks.

Sustainability of an isolated beech-dwarf bamboo stand : analysis of forest dynamics with individual based model

The beech Fagus crenata forest on Mt. Jippo in southwestern Japan has been reduced to small fragments by past human activity. The forest floor is covered by dense dwarf-bamboo, Sasa, which is an inhibitor of beech regeneration. One of the ecological features of Sasa is that it withers synchronously over a large area once every several decades. An individual based model (IBM) was developed to evaluate the sustainability of such a fragmented beech stand considering the dynamics of Sasa. The model has three submodels for beech individuals: growth, mortality and seed production. The parameters of these submodels are estimated from field measurements. By using this model together with Sasa dynamics, we can evaluate the adverse effect of Sasa on enhancing the risk of extinction of a single fragmented beech stand over 500 years. The results obtained by Monte Carlo simulations are: (1) Sasa has a strong impact on the sustainability of a isolated beech stand; (2) the effects of two parameters for Sasa life history, the longevity and the recovery time, can be statistically separated from each other; and (3) the probability of extinction of a beech stand depends much more strongly on the parameters of beech mortality than those of growth rate.

Predispersal predation by rodents to beechnuts (Fagus crenata Blume)

The rodents’ predation intensity and discrimination ability toward the predispersal beechnuts (Fagus crenata) were investigated using a tree tower in a beech forest, central Japan in 1999 and 2000. In this stand, using seed traps, the densities of fallen viable nuts were 35.1 m−2 in 1999 and 8.4 m−2 in 2000. The vertebrate-damaged nuts had fallen 5.6 and 2.2 m−2 in 1999 and 2000, respectively. Yet, the crop of viable nuts in 1999 was not so rich as that in a mast year. In 1999, predispersal predation by rodents was recognized at 16–19 m above ground through the bagging experiment. In 2000, there were no predispersal predation and yet we captured Apodemus argenteus three times and Glirulus japonicus frequently on the tree. Judging from the facts of their feeding behaviors and the tooth scars left on the cupules and nuts, Apodemus argenteus might have been more responsible for predation to the predispersal beechnuts rather than Glirulus japonicus. Apodemus argenteus population seemed to be abundant on the ground in both years. If the main agent of predispersal predator were Apodemus argenteus, their number shifted to the canopy would be much larger in 1999 than in 2000 according as the crop of viable nuts. In an additional experiment, rodents preferred intact cupules to insect-damaged cupules on the tree, suggesting that they discriminated the quality of the predispersal nuts, even in the cupule stage, through olfactory and/or visual senses. Thus, predispersal nut predation by rodents was prevalent during the limited period in autumn.

Nation-wide litter fall data from 21 forests of the Monitoring Sites 1000 Project in Japan

This data paper reports litter fall data collected in a network of 21 forest sites in Japan. This is the largest litter fall data set freely available in Japan to date. The network is a part of the Monitoring Sites 1000 Project launched by the Ministry of the Environment, Japan. It covers subarctic to subtropical climate zones and the four major forest types in Japan. Twenty-three permanent plots in which usually 25 litter traps were installed were established in old-growth or secondary natural forests. Litter falls were collected monthly from 2004, and sorted into leaves, branches, reproductive structures and miscellaneous. The data provide seasonal patterns and inter-annual dynamics of litter falls, and their geographical patterns, and offer good opportunities for meta-analyses and comparative studies among forests.

Traditional Ecological Knowledge Determined Tree Species Choice in the Construction of Traditional Folk Houses in a Snowy Rural Landscape in Central Japan

To elucidate the selection of tree species for timber in traditional folk house construction, I examined the species used in seven houses in four rural villages in central Honshu, Japan, a region subject to heavy snowfall. All houses were mainly constructed of beech (Fagus crenata), cedar ( Cryptomeria japonica ), and oak (Quercus crispula and/or Quercus serrata). The species composition was similar to that of the current surrounding woodlands, suggesting that these species grew in the region when the houses were built, although the vegetation structure changed in the interim. Beech, cedar, and oak trees grow and maintain their upright structure even in environments that experience heavy snowfall; therefore, these species may have appeared to be the best choices for construction timber in this region. Beech was mainly used for its bending strength, in slanting or horizontal structural elements; cedar in elements used as structural reinforcement; and oak in various elements, complementing the selection of beech or cedar. Important structural beams are typically made of beech timber. Its high bending strength was considered to reflect the nature of living beech trees, which form dominant stands in regions with heavy snow in Japan, due to their sturdiness and ability to stand upright under heavy snow loads. Although beech timber is currently considered to be unsuitable for construction due to its trait such as easy to twist or easy to rot, the results of this study suggest that selecting beech timber for structural elements that bear heavy snow loads was feasible for indigenous builders when the traditional houses were constructed. Consequently, beech-dominated forests may have influenced the architectural style of houses with large-beamed structures and may have been a factor contributing to the settlement of this region. Understanding traditional ecological knowledge may contribute to the promotion of sustainable wood resource use in the future.