西藏雅鲁藏布江中游地区宜林荒地造林探讨

西藏雅鲁藏布江中游地区,或称“一江两河”地区是西藏的重点开发区和人工造林重点地区。据我们野外调查勾绘,本区河谷地区现有荒地资源 75 296ha,其中宜林荒地29 911ha,占荒地资源的39.70％。根据立地条件及砾沙含量等因子,我们将本区宜林荒地分成4种立地类型和4种土壤类型。在各立地类型中,以河谷卵石滩地为多,其次为流动沙丘及流沙坡地;宜林荒地的土壤类型则主要是沙地,土壤肥力较好的壤化粉砂土和壤土仅占 15.24％,其林木年生长量可达 5.5m³/ha 以上。本区同一地域上的林木生产力随砾石含量而变化很大,据我们测定,不同砾石量立地上的北京杨,其材积生长量差异达9倍之多。因此,土壤改良是本区造林工作中的重要问题之一。根据本区条件,宜林荒地的利用主要是营造以薪柴和防护效益为主的薪炭林和防风固沙林,因地区而异;宜林荒地的开发可分三期进行,“八五”期间主要开发艾马岗、江当宜林荒地,认真搞好“3357”工程建设,进一步搞好年楚河的整治和林草带建设,逐步绿化雅江荒地沙滩,大力做好防护林网的建设工作,使林业在国民经济发展中起到更大的作用。

A DISCUSSION ON THE AFFORESTATION ON THE WASTE LAND SUITABLE TO FORESTS IN THE MIDDLE REACHES REGION OF THE YALUTSANGPO RIVER, TIBET

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.