Abstract
Two types of plant succession have been known in native grassland under cattle grazing at Kawatabi farm. These are the changes from tall grassland dominated by Miscanthus sinensis to sod grassland dominated by Zoysia japonica and to shrub dominated by Weigela hortensis. The prediction of these succession types will be important because of getting an information of carrying capacity for grazing cattle in the future. In order to recognize the ground that these two types rise in under cattle grazing, we surveyed the depth of human layer and the coverage of dominant species in three native grasslands with a different grazing history at Kawatabi farm. Surveyed grasslands are named Ungrazed grassland, Grazed A (6 years grazed) and Grazed B (15 years grazed). Results are as follows. 1. There are close relationships between slope shape and the depth of humus layer. The depth of humus layer at the convex slope site was thin (25 cm-50 cm), and at the concave slope site was deep (50 cm-110 cm). 2. In the Ungrazed grasslands, Miscanthus sinensis dominated and partly Sasa palmata and W. hortensis. S. palmata distributed at the thin humus layer site and W. hortensis distributed at the deep humus layer site .3. The coverage of M. sinensis in Grazed A was lower than that in Ungrazed grassland. The plant community at the deep humus layer site of Grazed A was dominated by W. hortensis. Z. japonica distributed at some stands at the thin humus layer site. 4. Grazed B was dominated by Z. japonica and W. hortensis. The former only appeared at the thin humus layer site and the latter at the deep humus layer site. The native grassland under grazing shows a different types of plant succession between convex slope and concave slope. At the convex slope, tall grasslands dominated by S. palmata and M. sinensis changed to sod grassland dominated by Z. japonica. At the concave slope, M. sinensis community changed by grazing to shrub dominated by W. hortensis.
