We surveyed species composition in relation to substrates, and microsite characteristics of temperate conifer species in an old growth Chamaecyparis obtusa forest on Mt. Shiraga, Kochi, Japan. We established nine study quadrates on a gentle slope where masses of rock or dwarf bamboos are dominant on forest floor, and we measured the diameter at breast height of all trees that were more than 1.5 m in height and the height of all conifer seedlings (< 1.5 m in height) while recording their standing substrates: stump, fallen log, rock, mound, and ground. According to detrended correspondence analysis, the nine quadrates were roughly divided into a group dominated by Chamaecyparis obtusa and Tsuga sieboldii, and a group of mixed broad-leaved tree stands, implying that the former establish on a block slope and the later establish on the ground. Chamaecyparis obtusa seedlings significantly established on fallen logs and old stumps while larger trees (> 1.5 m in height) were found on stumps. Thirty percent of large Chamaecyparis obtuse trees were established at an elevated position above the ground, and half of them had stilt-like roots. Tsuga sieboldii seedlings were established on rocks and stumps, while the larger trees were found on stumps. Both seedlings and larger trees of Pinus parviflora established on stumps though there were few of these. Abies firma seedlings were more likely to be found on the ground, but intermediate-sized trees were missing, showing their limited regeneration. Thus the stumps and logs play an important role as microsites for establishing conifers, except Abies firma, in an environment in which masses of rock or dwarf bamboo are dominant on the forest floor.

Large animals such as sika deer are considered to have diverse impacts on the aboveground and belowground processes in terrestrial ecosystems. Previous studies on the ecological impacts of deer grazing have been mostly conducted in open ecosystems where the home ranges of the deer are not restricted; however, few studies have been conducted in closed ecosystems. The present study was carried out to investigate the impact of deer on soils and plants in Nakajima Island in Lake Toya, where sika deer populations are dense within the closed ecosystem. We used six deer fences on the island and examined the physical and chemical properties of soils along with the chemical properties of plants. The thickness of litter layer on the soil surface was smaller and the surface soil hardness was larger outside the fences than inside. In addition, the soil nitrogen characteristics inside and outside the fence varied with the locations, especially the grassland soil outside the fence had higher nitrate-N than the forests. Similarly, nitrogen concentrations in Japanese spurge leaves were significantly higher outside the fences in the grassland than inside. These results suggest that in Nakajima Island, increased density of deer variously changes the physical properties of the soils and the chemical properties of the soils and plants, and these changes vary based on deer abundance and vegetation type. Because ranges for the movement of deer are limited in Nakajima Island, the effects of high deer density could be observed over the island, and stabilized for long time.