论文部分内容阅读
林业生产周期性长,其经济效益特别是生态效益,需要经历一定时间才能发挥出来。因此在造林设计上要有长期的考虑,对树种的选择更为重要。尤其是平原农区的防护林建设,不仅在造林规格、密度上需要精细设计,而且在树种配置上必须认真研究选择,真正作到适地适树。廊坊市,各县虽都属于永定河下游泛区,但地势和土壤质地不尽相同。自50年代初至今已营造了大面积农田防护林,为了了解本地区防护林现有树种生长状况,1987年进行过一次典型调查。现将调查结果总结分析于后,以便于今后开展树种更新的研究。一、壤土和粘土区包括本市北部三河、大厂二县和香河县一部,土壤类型为石渣土,但石渣土面积较小,大部为黄土。土壤质地为沙壤、轻壤粘和土。一般土地较肥沃,水源丰富,是农业高产区,适宜榆树、毛白杨等多种树木生长,见表1。
Long-term forestry production, its economic benefits, especially ecological benefits, take some time to play. Therefore, in afforestation design to have long-term consideration, the choice of species is more important. In particular, the construction of shelter belts in the agricultural areas of the plain not only requires careful design on the specifications and density of afforestation, but also requires careful study and selection on the allocation of tree species so as to truly suit the tree. Langfang City, although all counties belong to the lower reaches of Yongding River, but topography and soil texture vary. Large-scale farmland shelterbelts have been built since the early 1950s and a typical survey was conducted in 1987 in order to understand the current status of tree species in shelterbelts in the region. The survey results are summarized and analyzed later, in order to carry out the study of tree species update in the future. First, the loam and clay areas include the northern part of the city Sanhe, Dachang County and Xianghe County, a type of soil for the gravel soil, but the gravel soil area smaller, mostly loess. Soil texture is sandy soil, light soil sticky soil. The general land is more fertile, rich in water, is a high-yield area of agriculture, suitable for elm, poplar and other trees, see Table 1.