关键词: 城市周边区域, 人口时空格局, 北京, 城市化, 生态系统质量

Abstract: A L₁₆ (4⁵) orthogonal experiment was conducted to study the photosynthesis, yield, and quality of Pennisetum purpureum cv. Guimu-1 in a karst region of Southwest China under effects of different nitrogen fertilization rates and cutting times and intensities. Nitrogen fertilization increased the chlorophyll a and b and total chlorophyll contents, net photosynthetic rate, yield, and plant nutrient contents significantly, with the best effect of 1000 kg·hm^-2·a^-1. Cutting times had significant effects on the net photosynthetic rate, chlorophyll content, and plant nutrient contents. After 2 or 3 times cutting, the photosynthesis improved significantly; after cutting 3 or 4 times per year, the nutritional quality of Guimu-1 was the best. Cutting intensity had significant effects on the crude protein content, but minor effects on the other nutrient contents and yield. The best effects were obtained when the cutting intensity was at the distance 5 cm or 20 cm from the roots. Based on the comprehensive analysis of the indices, the optimum scheme for high yield and good quality of Guimu-1 in the karst region was proposed as nitrogen application rate 1000 kg·hm^-2·a^-1, 3 times cutting per year, and cutting at the distance 5 cm or 20 cm from the roots.

Key words: urbanization, urban surrounding region, population spatio-temporal pattern, Beijing., ecosystem quality