Ei'ichi Shibata

Seed dispersal and predation by Yakushima macaques, Macaca fuscata yakui, in a warm temperate forest of Yakushima Island, southern Japan.

The relationships between fruit morphology and the foraging behavior of the Yakushima macaque, Macaca fuscata yakui were studied during a 9-month field study and series of laboratory experiments on Yakushima Island, southern Japan. These relationships may affect seed germination traits through seed dispersal. The macaques’ foraging behavior was observed in order to obtain data concerning the treatment of pulp and seeds. Seeds in feces and spat seeds were collected and analyzed. A linear discriminant analysis of the data led to the following results: (i) an increase in the relative flesh volume of a fruit was one of the potential factors which increased the probability of seed dispersal by the macaques; and (ii) seed size was an important parameter in relation to the type of seed dispersal (by defecation or spitting out). The germination test was conducted in a laboratory, then the germination rates and delays of dispersed seeds were compared with those of seeds collected directly from trees. The germination of dispersed seeds of Ficus thunbergii, Eurya japonica, and Vaccinium bracteatum, was significantly enhanced by passage through the macaques’ gut. The enhanced germination behavior was not seen in larger seeds, such as those of Psychotria serpens, Myrsine seguinii, Diospyros morrisiana, and Neolitsea sericea. The germination enhancement in small-seeded plants could be due to a sorting effect from the passage through the gut, which selects seeds with a narrower range of germination traits.

Food Habits of Sika Deer as Assessed by Fecal Analysis in Mt. Ohdaigahara, Central Japan

Food habits of sika deer,Cervus nippon centralis temminck, in Mt. Ohdaigahara, central Japan, were investigated by the fecal analysis method from September, 1990, to June, 1991. The fecal analysis showed that the percentage ofSasa nipponica Makino et Shibata in the fecal composition was approximately 50% throughout the year, indicating that it was the main food plant. Bark and twigs were also found in the feces in all seasons, suggesting that the deer ate bark throughout the year. Even though the amount of the bark eaten per capita was small, the high density of deer may possibly cause serious bark damage. Barking can be one of the main causes of the mortality ofPicea jezoensis Sieb. et Zucc. var.hondoensis (Mayr) Rehder andAbies homolepis Sieb. et Zucc. in Mt. Ohdaigahara.

The effects of sika-deer browsing on the biomass and morphology of a dwarf bamboo, Sasa nipponica, in Mt. Ohdaigahara, central Japan

Abstract We investigated the browsing effect of sika deer (Cervus nippon Temminck) on the biomass and morphology of Sasa nipponica Makino et Shibata, a dwarf bamboo, in Mt. Ohdaigahara, central Japan. The investigation was performed through comparison of S. nipponica inside and outside a deer-proof fence. The S. nipponica outside the fence decreased in biomass (292.7 d.w.g./50×50 cm inside and 105.1 d.w.g. outside in August 1994), became miniaturized in culm height (49.1 cm inside and 15.6 cm outside), decreased in top leaf length (118.9 mm inside and 69.8 mm outside) and in culm diameter (2.0 mm inside and 1.2 mm outside) and densified in culm number (254/50×50 cm inside and 622 outside). After the destruction of the deer-proof fence, S. nipponica inside the fence underwent similar changes, that is, biomass decrease, miniaturization and densification in the next flush.

Population Density and Range Use of Sika Deer, Cervus nippon, on Mt. Ohdaigahara, Central Japan

We investigated the population density and range use of sika deer,Cervus nippon, on Mt. Ohdaigahara, central Japan, from July 1996 to July 1997. The deer population density estimated by the block count was high at 17.5–30.9 deer/km2. Although the deer remained this area from spring to fall, they moved out in winter, probably because of deep snow. A spotlight count showed that the deer prefer the eastern area as spring-summer range, where the forest consists of coniferous trees over a floor cover ofSasa nipponica, andS. nipponica grassland. The deer also use dense coniferous forest for cover, especially in summer and fall.

Characteristics of Sasa nipponica grassland as a summer forage resource for sika deer on Mt Ohdaigahara, central Japan

Recently, the sika deer, Cervus nippon Temminck, population has increased on Mt Ohdaigahara, central Japan. The dwarf bamboo, Sasa nipponica Makino et Shibata, is a primary forage plant for sika deer in this area. To demonstrate the characteristics of S. nipponica grassland, especially as summer forage for sika deer, the habitat use intensity of sika deer was estimated by fecal densities, and biomass, growth rate, removal by deer and crude protein content were examined. Sika deer utilized the S.␣nipponica grassland on Mt Ohdaigahara during summer when the biomass, growth rate and crude protein content of S. nipponica were high. The recent increase in the deer population seems to be partly due to S.␣nipponica grassland being a favorable summer habitat.

Diurnal changes in branch diameter as indicator of water status of Hinoki cypress Chamaecyparis obtusa

Abstract. We investigated use of strain gauges for monitoring the water status of trees by measuring changes in the diameter of the largest spreading branch of a 27-year-old Chamaecyparis obtusa tree. The change in xylem diameter in the branch is more closely related than the change in phloem diameter to the change in leaf water potential. Since the diurnal changes in diameter match the diurnal changes in water balance (sap flow velocity – transpiration), measuring the change in xylem diameter using a strain gauge is useful in evaluating the water status of C. obtusa.

Spatial distributions of the leafminer Ophiomyia maura (Diptera: Agromyzidae) in host plant Aster ageratoides

The seasonal occurrence and among‐plant and within‐plant spatial distribution of the multivoltine leafminer Ophiomyia maura Meigen (Diptera: Agromyzidae) on the herbaceous plant Aster ageratoides Turcz. subsp. ovatus (Asteraceae) were investigated in the field. O. maura has at least four generations a year and mines per leaf fluctuate with a mean of 0.007 throughout the occurrence period. Seasonal occurrence is associated with abundance of new host leaves, suggesting O. maura females prefer to oviposit in newly emerged leaves. The among‐plant distribution of O. maura is described by a Poisson distribution early in the season but tends to be weakly clumped later. The within‐plant vertical distribution of larval mines increased from middle to upper leaves during plant development, because mined leaves in the middle position early in the season move downward with the emergence of new leaves, shifting mined leaves from the position where O. maura oviposits eggs. Later in the season, mined leaves remain where they are deposited because few new leaves emerge. The spatial distribution of O. maura, resource utilization patterns, and host plant characteristics are discussed.

Water status of Hinoki cypress (Chamaecyparis obtusa) under reduced hydraulic conductance estimated from diurnal changes in trunk diameter

Abstract. To estimate the water status of Hinoki cypress (Chamaecyparis obtusa) under reduced hydraulic conductance, we measured diurnal changes in the trunk diameter of two 20-year-old trees during a hot dry summer. One tree showed a greatly reduced water-transport area in its trunk cross-section and leaf specific hydraulic conductivity. Diurnal changes in trunk diameter were measured at the xylem surface using a strain-gauge method. At the start of the experiment, the diurnal changes in trunk diameter were similar in both trees with shrinking during the day and swelling at night. However, in the trunk of the tree with reduced hydraulic conductance, the maxima and minima decreased rapidly as days passed. These differences in trunk diameter changes might be caused by the differences in the leaf-specific hydraulic conductance.

Bark borer Semanotus japonicus (Col., Cerambycidae) utilization of Japanese cedar Cryptomeria japonica: a delicate balance between a primary and secondary insect

Abstract: The bark borer, Semanotus japonicus (Col., Cerambycidae), attacks living Japanese cedar, Cryptomeria japonica, with newly hatched larvae mainly feeding within the inner bark of the trunk. To understand how S. japonicus is affected by host nutrition and resin flow, newly hatched larvae were introduced into stressed cedar trees. Stress was induced by either heavy pruning, stem cutting (i.e. removing the side branches and top of tree), or girdling. Larval mortality due to resin flow in the ‘heavy pruning treatment’ and the ‘stem cutting treatment’ tended to be lower than that in the untreated control cedar trees where all larvae were drowned by resin flow. Parasitism to the larval stage was observed in the stem‐cutting trees, not in living trees, suggesting that S. japonicus may avoid parasitism in living cedar trees because few volatiles are produced. In the ‘stem‐girdling treatment’, although more than 90% of the introduced larvae died due to poor nutrition below the girdle, 7.8% of the larvae above the girdle reached the adult stage. The live body weight of the adults collected from above the girdle was similar to those taken from naturally infested cedar trees. These results suggest that S. japonicus requires adequate host nutrition but that larvae are defenceless against high resin flow. Thus, S. japonicus seems to be in a transition state between being primary or secondary with respect to its attack behavior on living cedar trees.

Synchronization of Shoot Elongation in the Bamboo Phyllostachys heterocycla (Monocotyledoneae: Gramineae) and Emergence of the Gall Maker Aiolomorphus rhopaloides (Hymenoptera: Eurytomidae) and its Inquiline Diomorus aiolomorphi (Hymenoptera: Torymidae)

Abstract Adult emergence of the gall maker Aiolomorphus rhopaloides Walker and its inquiline, Diomorus aiolomorphi Kamijo, was examined in three stands of the bamboo, Phyllostachys heterocycla Matsumura. A. rhopaloides emerged from the galls from mid-April to early May, coinciding with the bamboo bud elongation period. This synchronization suggests that eggs laid in the new shoots have a nutritional advantage for resulting larvae, and that a slight advance or delay in emergence may reduce suitable oviposition sites, causing population fluctuations. D. aiolomorphi emerged from late April to early June during the bamboo shoot elongation period and females could lay eggs in elongated shoots providing relatively higher nutrition for larvae. The difference in the gall density on P. heterocycla and P. bambusoides Siebold and Zuccarini is explained on the basis of synchronization with host plant phenology.