黑河中游绿洲防护林的防护效应分析

Protective effects of oasis protection forest in the middle reach of Heihe River.

沿绿洲至荒漠戈壁和绿洲至流动沙丘的防护林体系分别选择一条观测样线 ,每条样线分不同防护区布设 4个观测点同步观测风速和输沙率。 2年的观测数据表明 ,绿洲至荒漠戈壁的前缘阻沙林带能明显降低风速 ,是维护绿洲安全的第一道防线 ,但在树种选择上不仅要考虑防护效果 ,而且要考虑树木的速生性和耐旱性 ,本文认为杨树和柽柳的组合较为理想。而固沙区具有生态功能和经济效益的双重作用 ,该区乔、灌木配置较少 ,风速没有明显降低。对绿洲至流动沙丘的防护林体系来说 ,在相同的风速条件下 ,输沙率随地表覆盖度降低而显著增加 ,因此 ,增加地表覆盖度是降低输沙率的有效途径。

Two sampling lines from oasis to desert and to dune were chosen,each with four observation points,to observe wind velocity and silt discharge rate synchronously.The data of two years showed that fore-protective forest of oasis-desert played an important role in decreasing wind velocity.As for the species,taking their growth rate and drought resistance into account,the combination of Populus simonii and Tamarix ramosissima was the most ideal fore-protective forest.Without arbor and shrubbery,the grass sand-fixing area could not reduce the wind velocity further.In the protective forest from oasis to dune,the slit discharge rate increased significantly with the decrease of ground surface coverage,which meant that the increase of ground surface coverage is the key to decrease the silt discharge rate.