The purpose of this research was to develop high resolution digital aerial photography to estimate fundamental stand parameters (number of standing trees, mean tree height, stem volume) in a Larix kaempferi stand. In order to identify tree species, a five-class (Japanese larch, Japanese red pine, broad-leaved trees, no vegetation, shadow) vegetation map was created with 90% accuracy from a multispectral digital orthophotograph. We extracted individual tree crowns by using a digital surface model (DSM) made from a stereo pair of panchromatic images and a digital terrain model (DTM) made from LiDAR data and, by overlaying the vegetation map, we were also able to determine the species of the crowns. Stand parameters were estimated for every tree crown. When we verified the accuracy of the stand parameter estimates with complete enumeration, we found that the accuracy rate for the number of standing trees was 85.6%, the difference in mean tree height was 0.4 m, and the accuracy rate for stem volume was 84.9%. Because of the difference in crown form, our estimates were more accurate for the conifers than for broad-leaved trees.

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The occurrence of boring by Sipalinus gigas in sawed timber of the Japanese red pine, Pinus densiflora, set in P. densiflora stands at Shiojiri, Nagano Prefecture and Morioka, Iwate Prefecture was examined. While most S. gigas larvae bored at the unbarked part of the timber, the others bored at the sawed side. Some of the insects boring at the sawed side grew into adults before the winter following the season when they were laid as eggs. The water content of sapwood of the timber used was 84∼96% in average at the end of the test period, meaning that the sapwood had kept being moist. These results suggest that S. gigas can oviposit and grow in sawed timber without bark if it is wet enough.

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Seedling banks in a beech forest were scarcely found around stems in snowy regions. Since snow cover prevents feeding activity of rodents, we considered that the seed predation might occur intensively around stems where snow pack tends to disappear earlier in spring. In order to verify this hypothesis, emergence of current seedlings derive from seeds dispersed in a previous good crop year were investigated. Although the number of dispersed seeds did not depend on distance from the mother tree, few seedlings occurred around stems and seedling banks tend to establish 2∼3 m apart from mother trees. Germination failure due to fungi attack or desiccation was negligible and irrespective of the distance from mother trees. These results suggested that snow cover prevents rodents from seeds feeding and played an important role to determine the distribution pattern of seedling banks in beech forests.

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The Ohdaigahara subalpine plateau has recently suffered deforestation caused by an increasing population of sika deer (Cervus nippon), which stripe the bark of many coniferous trees and browse seedlings. Deforested area has been transformed to forest with the floor dominated by Sasa nipponica and grassland densely covered by S. nipponica, which has a tolerance to heavy browsing by sika deer. Hence, deforestation involves an increase in dung supply because S. nipponica contains rich protain and is a major forage of sika deer. To examine the effects of deforestation on the dung-beetle community in the plateau, we compared the diversity of dung-beetle assemblages in the primary forest, transition forest, and S. nipponica grassland using dung-baited pitfall traps. The primary forest had the highest species richness, evenness (Smith-Wilson index, E_var) and species diversity (Shannon-Wiener index, H′) of dung beetles. The transition forest showed the greatest abundance but lowest evenness of dung beetles. The S. nipponica grassland had the lowest species richness and species diversity. These results suggest that loss of primary forest resulting from an increasing deer population decreases the diversity of the dung-beetle community. Deforestation in the Ohdaigahara subalpine plateau, therefore, is unfavorable from the viewpoint of biodiversity conservation even though it would increase the abundance of dung beetles.

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Spiders are common generalist predators in terrestrial ecosystems, half of which are web-builders living among vegetations and on the ground. Web spiders have diverse foraging mode and microhabitat requirement, and their ecological parameters can be easily obtained. Owing to these characteristics, they are ideal subject for studying impact by deer on ecosystems. We examined the underlying mechanisms of the effects of deer on forest-dwelling web spiders, as well as its further effect on insects. Spiders living on vegetations decreased with increasing deer density, which was caused by the reduction of vegetations as web support, not by the decrease in prey abundance. The rate of decrease in the kleptoparasitic spider Argyrodes that parasitize web spiders was greater than that of its host. In contrast, web spiders on the ground increased with deer density, probably because the reduction of ground vegetation cover favored these spiders. Furthermore, aerial insects derived from the soil increased by decreasing web spiders on vegetations. The work for theoretical generalization of these interaction chains is required in the future.

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Mammal herbivores have different indirect effects on structure and functioning of soil ecosystem. Mammal herbivores alter the quantity and quality of organic matter entering soil through transforming plant tissue to excreta and altering the amount of root exudates, the content of secondary metabolites and nitrogen in plant tissue, and vegetation. The effects of mammal herbivores on nitrogen cycling are largely determined by productivity and herbivory intensity. The modification of soil physical environment by mammal herbivores is thought to have less impact on decomposer system than the alteration of organic matter input. The change of organic matter input and physical environment in soil induced by mammal herbivores also affect the abundance and community structure of soil nematode. Although there are few studies on the effects of sika deer on soil decomposer system, the experimental defoliation of dwarf bamboo and the experimental introduction of deer showed that effects of deer on decomposer system vary with browsing intensity and population density and that deer has both positive and negative effects on nitrogen mineralization. The overall effects of sika deer on nutrient cycling in ecosystems should be understood by determining the quantitative relationships among amounts of browsing, primary production, litter supply and nitrogen mineralization and integrating them with well-studied patterns of deer-caused vegetational change as the further study.

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At Mt. Ôdaigahara, in west-central Japan, we compared the survivorship of an unidentified gall midge (Cecidomyiidae: tribe Oligotrophini) that forms galls on the culms of dwarf bamboo (Sasa nipponica), the major forage for sika deer (Cervus nippon), between in- and outside deer exclosures. We also compared the parasitism rates by two parasitoid wasps, Pediobius sasae (Eulophidae) and Torymus sp. (Torymidae), on the gall midge between in- and outside deer exclosures. Deer browsing reduced the gall width indirectly. Both the survivorship of the gall midge and the parasitism rate by Torymus sp. was higher inside deer exclosures than outside deer exclosures, but the parasitism rate by P. sasae was higher outside deer exclosures than inside deer exclosures. The parasitism of P. sasae concentrated on the galls with smaller width inside deer exclosures but it occurred irrespectively of the gall width outside deer exclosures. Torymus sp. has a longer ovipositor and finishes its emergence period earlier than P. sasae. These results suggested that both the gall midge and Torymus sp. was able to survive in larger galls that P. sasae could not penetrate with its shorter ovipositor, making the different survivorship and parasitism between in- and outside deer exclosures. Thus, deer browsing on the dwarf bamboo indirectly reduces the gall width, and this favors P. sasae by improving access to host and disturbs both the survival of the gall midge and the parasitism of Torymus sp.

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Mammalian herbivores can directly and/or indirectly affect ecosystems. Here, we review an indirect effect of mammalian herbivores, which affects plant reproduction by changing the relationships between plants and animals. As an example of this feed back indirect effect, we introduced a case study which detected the effect of Cervus nippon on the reproduction of Aucuba japonica Thunb. The success of seed production of A. japonica largely depends on the degree of pollination and seed parasitism. In the wild population of A. japonica, C. nippon decreased the density of A. japonica individuals causing the decrease in parasitism, but not in pollination. These result indicated that the effects of C. nippon on the plant animal interaction such as pollination and parasitism to seeds depended on the degree of decrease of A. japonica density. Such density dependent interactions can determine the degree of feed back indirect effect of mammalian herbivores on plants.

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In Nara Park, population density of conserved sika deer has been very high for several hundreds of years. This caused vegetation simplification to toxic and unpalatable plants. The andromeda lace bug, Stephanitis takeyai, usually alternates its host plants seasonally. However, in Nara Park, one of the host plants, Lyonia ovalifolia is very scarce so that S. takeyai lives on the other host, Pieris japonica throughout the year. I investigated the long-term genetic change in life history characteristics caused by the loss of seasonal host alternation in the Park. Reared at same condition, individuals from Kyoto population, where the bug alternates the hosts, preferred L. ovalifolia more than Nara individuals did. The former attained lower fecundity and larger relative wing length. Lower fecundity was considered as the cost of migration apparatus.

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