林分密度和种植点配置对梭梭人工林防风效应的影响

Effects of density and plant point distribution on shelter efficiency of artificial Haloxylon ammodendron forest

研究不同密度和种植点配置对梭梭人工林防风效应的影响,为优化干旱区防风固沙林结构提供科学依据。以梭梭为原型,利用仿真植物设计了3种密度、4种种植点配置的品字形林带,编号与对应植株的株行距分别为A:17 cm×17 cm,B_(1):34 cm×17 cm,B_(2):17 cm×34 cm,C:34 cm×34 cm,通过风洞模拟试验,对林带在密度和种植点位发生变化时的流场和防风效应进行了测定分析。结果表明:(1)A、B_(1)、B_(2)、C林带的风速减速区(U/U0<1)的面积分别占流场总面积的78.06%、70.41%、74.36%和82.80%;弱风区(U/U0<0.4)的面积分别占流场总面积的22.46%、0.73%、5.91%和0;(2)林分密度越大,冠下平均风速越小,但林带后近地层风速恢复越快,A、B_(1)、B_(2)、C林带的最小风速点分别在带后的11H、15H、15H和20H处(H为树高);(3)4个林带防风效应从大到小的排序为A>B_(2)>B_(1)>C,林带防风效应与林分密度间为非线性关系,林带在带后近地层风速降幅的比例关系为A:B:C≈6:3:2。具体造林时,应根据土壤水分承载力确定造林密度,在此基础上,优先选用“小株距,大行距”的种植点配置方式。

This study aimed to study the shelter efficiency of Haloxylon ammodendron windbreak with different density and plant point distribution to provide scientific basis for optimizing the structure of windbreak in arid areas.With the field Haloxylon ammodendron as the prototype,windbreaks with three stand densities and four plant point distributions were designed,and their flow field and shelter efficiency were measured and analyzed by wind tunnel experiments.The corresponding label and“plant spacing×row spacing”of the windbreaks were as follows:A:17 cm×17 cm,B_(1):34 cm×17 cm,B_(2):17 cm×34 cm,and C:34 cm×34 cm.Results showed that(1)the area of wind speed deceleration region(U/U0<1)accounted for 78.06%,70.41%,74.36%,and 82.80%of the whole flow field of A,B_(1),B_(2),and C windbreaks,respectively;the area of weak wind speed region(U/U0<0.4)accounted for 22.46%,0.73%,5.91%,and 0%.(2)The higher the stand density,the lower the average wind speed under the canopy,but the faster the wind speed recovered at the leeside of windbreaks.The minimum wind speed was located at 11H,15H,15H,and 20H behind the A,B_(1),B_(2),and C windbreaks,respectively(H was the tree height).(3)The order of shelter efficiencies of the four windbreaks from large to small was A>B_(2)>B_(1)>C.The relationship between shelter efficiency and stand density was nonlinear.The ratio of wind reduction at the near surface was A:B:C≈6:3:2 behind the windbreaks.The density of afforestation should be determined based on the soil water carrying capacity in the practice of forestation.On this basis,the plant point distribution mode of“small plant spacing,large row spacing”should be preferred.