부산대학교 도서관

An allelopathic interaction of a cover grass, Pennisetum clandestinum called kikuyu grass, intercropped with Chinese fir (Cuuninghamia lanceolata) was evaluated by experiments in field, greenhouse and laboratory assays. After deforestation of the Chinese fir, a split-plot design of four treatments (litter removed, litter retained, litter removed and kikuyu grass planted, and litter retained and kikuyu grass planted) was imposed. Field experiments showed that fir litter left on the ground slightly suppresses the growth of weeds in the first four months after deforestation, while kikuyu grass significantly reduced the growth of weeds longer than four months. Neither fir litter nor kikuyu grass reduced growth of fir seedlings. Bioassay of aqueous extracts of fresh fir leaves, fir litter, and kikuyu grass showed that fresh leaves produced significant phytotoxicity while litter and kikuyu grass has less toxicity. Nine phytotoxic phenolics and many unidentified flavonoids were found in the plant materials. Additionally, a similar experiment of pasture-forest intercropping system was also evaluated by employing the kikuyu grass and three hardwood forest species, Alnus formosana, Cinnamomum camphora, and Zelkova formosana. Results showed that kikuyu grass retarded growth of weeds soon after it was established but had little effects on the seedling growth of these three hardwood plants. However, aqueous extracts of the three hardwood plants significantly retarded the root growth of kikuyu grass, indicating that the growth of kikuyu grass might be suppressed when the woody forest became reestablished. Of them, Zelkova formosana exhibited the highest amount of allelopathic compounds, which might be responbsible for the reduction of weed growth beneath Z. formosana forest. The aforementioned findings show that a good correlation between the degree of phytotoxicity and phytotoxin levels was established, indicating that allelopathic mechanisms may play a significant role in the interaction of forest-pasture intercropping systems, and thus potentially reduce the need of herbicides and alleviate the labor cost of weed control. The findings concluded that an allelopathic potential cover grass, such as kikuyu grass, could widely be planted in areas of deforestation and hillsides in Taiwan.