关键词: 立地类型, 土壤类型, 合理开发

Abstract: The middle reaches region of the Yalutsangpo River, or the one river and two tributaries (the Lhase River and the Nianchu River) region, is a major developing and artificial afforestation region. According to our field survey, there are 75 296ha waste land in the region, including 29 911 ha (39.70% of the whole waste land) which are suitable to forests. On the basis of the locality, conditions, the gravel content and other factors, we divide the waste land into 4 locality types and 4 soil types. The largest locality type is the pebble beach, and next are the moving dunes and the sloping fields of drift sand. The major soil type is the sand land. The area of fertile soil is 15.24% of the whole waste land, and the annual increment of the forest on this kind of soil can reach more than 5.5m3/ha. In the same part of the region, the productive capacity of the forest change violently with the gravel content. By our measurement, the difference between the largest and the least growth increment of the volume of Beijing Populus at different gravel content localities can be as great as ninefold. Therefore, soil reclamation is one of the most important problem of afforestation in the region.According to the conditions of the region, the utilization of the waste land suitable to forest is primarily to plant fuel forests and windbreak forests in order to get the benefits of fuel and protection. The development of the waste land suitable to forest may be divided into three steps. During the Eighth Five Year Plan, first we should chiefly levelop the waste land suitable to forest in Aimagang and Jiangdang, grasp the construction of the 3357 projects, dredge the Nianchu River and contruct the forests and grassland zone successively, afforest the waste land and the sand in the Yalutsangpo River valley step by step, levote major efforts to make shelter forest network and make forestry to play a better role in developing the national economy.

Key words: soil type, ra ional exploitation., locality type