Abstract:

This study was carried out on the dry sandy land in the draught facing the sea in Chishan Forest Farm of Dongshan County,Fujian Province since May,2000.Through the experimental study for 3 years,3 clones of Hui 1^#,Yue 701^#and Dong 9801^#, whose preserving rate for the afforestation reached 61.9%～69.5%,were selected from 7 tested clones.Thus,the significant breakthrough has been achieved in the respect of selecting plant materials for the afforestation on sites with such special difficulty.By means of the comparative analysis of the planting effects of Casuarina equisetifolia clones on 2 types of micro-topography sites of the forward position of highland and the back-edge of low-lying land of the sandy land in the draught of bordering on the sea, the preserving rate of trees planted on the latter site for afforestation raised by 5%,and forest trees grew faster.The growth status of the root system of forest trees grown on both micro-topographies sites indicated that on the smooth highland in the draught,the distribution of the root system was deep,the numbers were large,the structure was concentrated,and the absorptive network was developed,which was conducive to evade the atmospheric aridity and soil aridity.It also revealed the tendency of a negative correlation between the distribution depth,quantity, concentrated degree and network structure of the root system and the moisture content of the soil.The study showed that the mechanism of the planting survival on the dry sandy land in the draught was the physiology and morphological characteristics of forest trees forming the enormous and developed root system network so as to be suitable for the dry habitat and to guarantee the planting survival.The experimental results of different planting modes showed that the planting modes of clump,mass,etc.may raise the preserving rate by about 10%,thus possess the extensive popularization and application value in the productive practice.

Key words: the draught in the coastal zone, Casuarina equisetifolia clone, root system growth, survival mechanism, group afforestation