Studies on the Zoysia Type Grassland : I. The numbers of seed grains and their germination characteristics of Zoysia japonica in cattle dung deposited on the grassland

Abstract

Autecological studies were carried out on seed population and germination characteristics of Zoysia japonica seed in cattle dung deposited on the Zoysia type grassland. The cattle dung were collected from the grassland at Sugadaira, Nagano prefercture in early spring of the following year of dung deposition. The number of species and the total number of seed grains contained in the dung sampled were 13 species and 6648 seed grains per 100 DM. g dung. The number of seed grains of Zoysia japonica, Veronica Onoei, Carex nervata and Potentilla Freyniana were 6229, 232, 86 and 27 per 100 DM. g dung, respectively. Subsequently, some germination experiments were performed to compare germina haracteristic of Zoysia japonica seeds hand-collected to that contained in the dung. The results are as follows. 1. Neither hand-collected seeds nor seeds contained in fresh dung showed any germination in late August. 2. After chilling at 1-5℃ for 120 days, the per・cent of germiation after 10 days of the seeds in dung was 35%, while that of hand-collected seeds was only 14%. 3. In natural condition, the seeds remained in the dung seemed to have been exposed to natural chilling during winter. When the seeds taken out from the dung were exposed to chilling in the laboratory during the corresponding period, the per・cent of germination of seeds was almost similar to that of naturally chilling seeds. 4. The per・cent of germination of the hand-collected seeds buried in the dung and chilled was similar to that of the seeds supplied with water and chilled in the Pe・tri dishes. 5. The seeds from two sources were collected in early spring, one was the seeds contained in the dung and another was collected from the ear in the preceding year. Both seeds were exposed under natural chilling by passing the winter on the grassland. The per・cent of germination of the seeds in the dung was 84% at 30/10℃ (day/night temperature regime) and 34% at 20/10℃. On the other hand, that of the seeds from the ear were 34% at 30/10℃ and only 4% at 20/10℃. From these results, we can recognize that morphological structures and physiological character such as fruit ripening and seed dormancy, of Zoysia japonica seed are considered to relate with grazing of livestock. The results also suggest that we can improve undesirable vegetation to Zoysia japonica vegetation by spreading the cattle dung contained seeds.