关键词: 樟子松, 灌木固沙, 造林技术, 效益评价

Abstract: The main techniques used i n establishing the successful sand holding demonstration model were described in detail in the paper: (1) For mobile dune's fixation: Based on spot distribution of the mobile dun es and a relatively higher precipitation and higher water table in Zhanggutai, which allows a easy natural revegetation, enclosure of hillsides was conducted with Artemisia halodendron, Salix gordejevii, Lespedeza bicolor Turz. and Caragana microphylla Lam.. Each of the above mentioned shrubs was planted at a different site for a certain purpose. Artemisia halodendron was usually plant ed on the windward slope of a dune during rainy season, Salix gordejevii pla nted in wet layer of a dune in spring, Lespedeza bicolor on the fringe of a sand holding forest, Amorpha frutieasa L. on windward of sandhill or in blo wouts. (2) For preliminary fixed dune's fixation: After repeated trials Pinus sylvestris var. mongolica was selected and introduced to Zhanggutai. Th e species demonstrated drought resistant and inferitility tolerant characteristics in sand dune area. The main planting techniques are as follows: ① The optimum root length and embeded depth of 2 year old seedlings are 25 cm and 25~35 cm in order; ② The planting time is from April 8 to 20, a little later than other species; ③ Before transportation, the seedlings should be dipped with muddy soil, wrapped with straw sacks; ④ While planting, the seedlings should be kept in jars or buckets to prevent them from withering, and unqualified ones should be picked out. Meantime, dry soil layer needed to be removed; ⑤ In late October, t he newly planted young trees should be covered with soil to survive through winter. The experimental results showed that the establishment of sand holding forest with trees in a large scale could cause water d eficit in the stands after about 20 years, for example, soil moisture content in a 25-year-old Pinus sylvestris var. mongolica stands was 1.08% lower than that in an unforested land. But this could be improved through forest management. It is suggested that the afforestation techniques on sand dune with Pi nus sylvestris var. mongolica can be extended in such semi arid regions w here precipitation is not less than 300~350 mm; soil moisture content not lower than 2.0%~2.5%; soil types are grasscovered sandy soil, chestnut sandy soil an d clay sandy soil with their pH values between 6.8~8.3. To keep water balance, the key technique is that forest pattern be constituded by tree shrub grass an d planted alternately with equal width belt. The efficiency of afforestation with Pinus sylvestris Var. mongolica was evaluated by taking two experimental spot s, Dayijian fang and Wangjia, as examples. The whole earnings of Dayijian fang and Wangjia during experimental period amounted to 5.69 and 2.83 million RMB Yu an, respectively. The efficiency indicators of investment have reached 7.44 and 5.84 in order, among which, the direct investiment indicators are 2.14 and 1.62, and indirect investiment idicators are 5.30 and 4.38 respectively.

Key words: Pinus sylvestris var. mongolica, Sand fixation with shrub, Afforestation technique Effect evaluation