Abstract
Carbon dioxide (CO_2) is well known to be a "greenhouse gas" capable of causing significant climatic change. The optimum ranges of grass species are likely to shift as a result of climatic change. Accordingly, the optimum range for each species must be determined in order to select grass species that will grow in the new vegetation zones expected to result from climatic change. Changes in the cultivation limit and productivity of bahiagrass (Paspalum notatum Flugge) were estimated. The monthly dry matter productivity for each secondary grid square (approximately 10×10km) at the present time, 30 years and 100 years in the future was simulated by applying grid climatic data to the neural network model. The data were adjusted using the relationship between CO_2 concentration and net photosynthesis in order to evaluate the effects of rising temperature and increasing CO_2 concentration simultaneously. Then maps of suitable cultivation zone and productivity were drawn. These maps show that under present climatic conditions the cultivation zone of bahiagrass is limited to the south-western part of Japan, and dry matter productivity is about 0-3,000 g・m^<-2>・year^<-1>. In 100 years, the cultivation zone will extend northwards, and the dry matter productivity is predicted to increase to more than 3,000 g・m^<-2>・year^<-1> in most parts of the cultivation zone.
