关键词: 鲁西北平原, 沙质土地, 退化防治, 高效利用

Abstract: Large areas of sandy land are distributed in the northwest region of Shandong Province. According to the previous investigation, the area of sandy land in the northwest region of Shandong Province is 634 500 ha, accounting for 16 4% of the total area of the region. Among the four prefectures in the region, Liaocheng has the largest sandy area, which amounts to 252 100 ha, making up 39 7% of the sandy land in the northwest region of Shandong Province. There were five types of land use representing the manners of land use in different periods of the recent 50 years, including extensive forests, annual crops on shift sandy land, annual crops on fixed sandy land, thick forest belt agroforestry and high productivity agroforestry. In this paper, the five types of land use were compared in terms of the impacts on sandy land degradation and the output benefits. Cropping without the protection of forests will not sustain because of wind erosion, while the benefits from extensive forests are extremely low. It was found that sandy land in this region could be effectively used without the occurrence of wind erosion by establishing agroforestry systems. The benefits from the thick forest belt agroforestry system are 20 times of that from extensive forests. The benefits from the high productivity agroforestry system are 36～37 times of that from extensive forests, and 1 82～1 89 times of that from the thick forest belt agroforestry system. The characteristics of agroforestry systems were also analyzed in this paper. It was concluded that both mutual beneficial and mutual competitive characters would be intensified with the elapsing of time. The sustainability of land use in sandy areas is obtained because of the protection by trees. The system therefore has a tendency of decreasing output and increasing stability. Even in the last two years in the 6～years production cycle when there are the largest shading and underground competing effects, the per hectare output from the thick forest belt agroforestry system will be 17 times of that from the extensive forests, and the output from the high productivity agroforestry system will be 31～32 times of that from the extensive forests. In these two years, the output from the high productivity agroforestry system is about 1 91 times of that from the thick forest belt agroforestry system. It was also proved that the capability of protection of the thick forest belt agroforestry system and the high productivity agroforestry system is obviously increased. It was indicated in this paper that high productivity agroforestry system is the best way to use sandy land, while thick forest belt agroforestry system is the second best.

Key words: Northwestern Shandong Province, Sandy land, Prevention of land degradation, Effective use of sandy land