从生态学论“三北”防护林在宁夏的规划原则

Ningxia Hui Autonomous Region is situated in 30;14′–30;14′ and 30;33′–30;39′.Though its area. Is only 67000km2, it has many various ecosystem categories. The vegetation is the core of the ecosystem, so it is very important to research. The vegetation in Ningxia is the combination of many various vegetation types which have certain egularity of ecogeographical distribution. The zonal vegetation types in Ningxia arc the semi-desert, the steppe and the meadow-steppe from north to south. And there are the spectrums of the vertical belts of the vegetation in Helan mountain and Lupan mountain. There are also many intrazonal vegetation types—the saline-meadow, the grass-swamp, the salt vegetation, etc. Every vegetation type exists many various plant communities. And each vegetation type or plant community can reflect the comprehensive ecological factors. According to the regularity, we may put forward a principle of plan of the "Sanbei’(northeast, north and northwest China)shelter-forest in Ningxia:l. It is suitable to establish the scrub belts in Ningxia. In the semi-desert, the steppe, the meadow-steppe and the grass-tuft, the soil erosion on the slopes may be controled by the scrub belts following contour-line and the wind-sand-harm on the plateau plain may be prevented by the scrub networks; 2. To plant the shrubs, the semi-shrubs and the therophytes is suitable for fixing the sanddrift; 3. It isn’t difficult to plant the shelter-forest in the irrigation farmland. But it is very important to choose the tree species adapting various soil; 4. All of the forest and the scrub in the mountains must be closed and tended. The mixed-forest may be expanded on the meadow slope.