绿洲-沙漠过渡带骆驼刺群落的防风阻沙作用

Effect of Alhagi sparsifolia community on wind block and drift sand control in the oasis-desert ecotone

以塔克拉玛干沙漠南缘的策勒绿洲——沙漠过渡带为研究区,从防风阻沙的角度研究该区域主要植物群落-骆驼刺群落的生态学特性,并分别对骆驼刺样地和裸沙样地进行梯度风速和多向输沙的同步对比观测,结合输沙势的季节和方向分布,确定骆驼刺群落的防风阻沙作用。结果表明,多年生木质化草本植物骆驼刺在4月上旬萌发,5～7月为生长旺季,8月以后生长缓慢,以木质化过程为主。4～6月为该区域的强风盛行期,活体骆驼刺植被的盖度并不能有效防止风蚀,但头年生长的骆驼刺地上部分干枯死亡后仍处于直立状态,在翌年风季来临时有效发挥防风阻沙作用。与裸沙地相比,覆盖度在30%左右的骆驼刺样地风速可降低26%～67%,对应的地表输沙通量也仅为裸沙地表的15%。根据实测输沙量与风能的关系推断,如果没有骆驼刺植物的保护,每年从策勒绿洲西部风沙前沿进入绿洲内的单宽输沙量可达到170.24 t.km-1.a-1,而骆驼刺地表单宽输沙量仅为26.43 t.km-1.a-1,可见骆驼刺群落具有极好的阻沙效果。

The oasis-desert ecotone is a special area,the process of oasis desertification or its reversion is mainly depended on the vegetation state there.The Cele oasis-desert ecotone was chosen as the study area and various parameters of Alhagi sparsifoli community were surveyed from April to October of 2009,including phenolphase observation,plant height,crown diameter,coverage,and biomass etc.Gradient wind velocity and wind-blown sand transport were conducted on the bare sand surface and Alhagi sparsifolia community ground as well and the relationships between sand transport quantity and sand drift potential were determined under the two underlayer conditions.The results show that Alhagi sparsifolia plants sprout in early April and grow up rapidly from May to July,just as aeolian sand activities come to the strongest stage in the desert regions of south Xinjiang.From August to October the plants are in a slowly growth stage and mainly carry through their lignification process,which can make the plants keep standing in whole winter.When next spring coming the dead but standing plants still have a well effect on wind block and drift sand control.Compared with the bare sand surface,wind velocity below 60 cm height in the Alhagi sparsifolia ground is decreased by 26%-67%.Total sand transport quantity on bare sand surface is 6.7 times of that on Alhagi sparsifolia community ground.According to the relationship between sand transport quantity and sand drift potential,we conclude that there are about 170.24 tons sands intruding into the oasis from its west rim per kilometer for one year,while the existence of Alhagi sparsifolia community with a coverage of 30% can block about 85% of drift sands away from the oasis.