Kazuaki Naito

The reintroduction of threatened animals, such as the Oriental White Stork (Ciconia boyciana) in Toyooka Basin in 2005 and the Crested Ibis (Nipponia nippon) in Sado Island in 2008, is becoming increasingly popular in Japan. In this study, we assess the reintroduction of the Oriental White Stork from the preparatory stage to pilot release and discuss its biological and social aspects. The basic plan of reintroduction, in accordance with IUCN reintroduction guidelines, was agreed upon before the pilot release. In the preparatory stage, historical distribution, the foraging habitat of a wild individual, and diets of animals in foraging habitats were surveyed. Furthermore, restoration projects on paddy fields and rivers were simultaneously being carried out. The pilot release began in 2005, and reproduction in the wild began in 2007. As oriental white storks forage on various animals in various habitats, restoration of the regional community, which contributes to the maintenance of ecological services through biodiversity conservation, is necessary.

To examine the possibility of using cattle grazing to maintain the Swertia pseudochinensis Hara populations, we surveyed the small-scale population density of S. pseudochinensis and the vegetation structure in the grassland at the foot of Mount Sanbe, southwestern Japan, where grassland management practices have shifted from burning (mowing and burning) to cattle grazing. In the first year of grazing management (1996), the mean density of S. pseudochinensis was 5.8/m^2 in October, with a maximum of 41/m^2. After 9 years of grazing, only a few individuals of S. pseudochinensis occurred in October 2005, with a total of 2/50m^2. The number of species and coverage of ungrazed plants such as trees and scrubs tended to be more in the ninth year of grazing than in the first year, whereas those of herbaceous plants mostly decreased over the 9 years. With a closed canopy layer of dominant woody species, S. pseudochinensis could become extinct. This result suggests that when grazing cattle are used to conserve S. pseudochinensis, additional management practices such as burning and mowing might be required to control the spread of woody species in the pasture.

Six stands of secondary vegetation at different ages from abandonment, an in-using grassland and a climax forest in upland Southwest Honshu, Japan, were surveyed in summer 1998. The grasslands of 0-2 years old from abandonment had the least species composition and one layer. Shrublands (with age of 32 yr.) had two layers in structure and were dominated by Ilex crenata and Miscanthus sinensis or Arundinaria variegata, with tree saplings colonizing among the shrub layer. The young Pinus densiflora forests (with age of 20-30 yr.) formed 3-4 layers, co-dominated with Clethra barbinervis. Mature secondary forest (with age of 33 yr.) was constructed of four layers, dominated by Quercus serrata and Castanea crenata. Fagus crenata climax forest had four layers in structure. As the age increased, height of the vegetation (as 25 m in maximum) increased, together with its complexity (four layers in its vertical structure). Both dominance degree (DD) and basal area (BA) increased till the climax (as 7438 for DD and 6109cm2 100m^<-2> for BA), while coverage of herb layer decreased to 18.3%, thought total coverage kept constant from the very beginning. Peaks of species number per plot (as 40 species 100 m^<-2> in a 32-yr-old stand), trunk density (as 115±52 100 m^<-2> in the 30-yr-old stand) and mortality (as 11.8% for trunk density, or 6.5% for BA in a 33-yr-old stand) appeared at intermediate age of the secondary succession.

In grazing pastures, a mosaic or patch vegetation pattern resulting from selective grazing by livestock animals is often observed. This heterogeneous structure contributes to the maintenance of species richness in grassland communities. The patch pattern of a grazing grassland and the distribution of component species in the grassland community were surveyed in order to elucidate the effect of selective grazing of cattle on the maintenance of species diversity. By comparison of the fioristic composition among the plots in tall ungrazed patches with those in short grazed turf, plots in the patches were revealed to have higher diversity within and among plots than those in the turf. Most of the autumn-flowering species showed higher stem densities in the patches than in the turf. Based on these results, the ungrazed patches should be evaluated in terms of their positive effect on maintaining species diversity. The function of the patches was discussed from this viewpoint.