绿洲-沙漠过渡带柽柳灌丛沙堆形态特征及空间分布格局

Morphological Features and Spatial Distribution Pattern of Tamarix ramosissima Nebkhas in an Oasis-desert Ecotone

以策勒绿洲-沙漠过渡带为研究区域,分析位于过渡带内侧、中部及外围的柽柳灌丛沙堆的形态特征、形态参数间关系、大尺度内空间分布格局以及相应的变化规律。结果表明：①柽柳沙堆的典型形态呈凸起半椭球状,上部被柽柳灌丛覆盖,沙堆高0.27～3.21 m,体积0.30～291.63 m3,树冠面积2.39～128.76 m2。过渡带由内向外单体沙堆及灌丛尺度显著增加,且沙堆外形向着沿风向拉长的不对称蝌蚪状发展。②柽柳灌丛沙堆各形态参数间存在良好的相关性,其中沙堆长度与宽度、底面积与高度间的显著回归关系会随过渡带由内向外逐渐由线性关系变为二次函数;柽柳树冠面积与沙堆体积间呈显著线性关系,其斜率会随过渡带由内向外逐渐增加。③柽柳沙堆分布密度沿过渡带由内向外逐渐降低,且空间格局类型会在100～250 m较大尺度范围上从聚集转向随机,整体聚集强度增加,而聚集强度峰值所在尺度和聚集规模则逐渐缩小。目前,该区域柽柳沙堆整体处于增长阶段,且可判定沙堆的产生是由土地退化引起的,其中过渡带外侧现处于快速退化时期。

The morphological features of Tamarix ramosissima nebkhas in three different sample plots in the inter- nal, central and peripheral areas of the oasis-desert ecotone in Qira, Xinjiang were investigated. The relationships among the morphological parameters, spatial distribution pattern and corresponding variation were quantitatively an- alyzed. The results are as follows： （~） The Tamarix ramosissima nebkhases were convex- and semielliptical-shaped, and they were covered with thickets. The values of nebkhas height and volume and crown area of T. ramosissima varied in ranges of 0.27 - 3.21 m, 0.30 - 291.63 m3 and 2.39 - 128.76 m2 respectively. From the internal area to the peripheral area of the oasis-desert ecotone, the scale of nebkhas became larger, and the thickets grew luxuri- antly;（~） There were the significant correlations among the morphological parameters of nebkhas. Among them the significant regression relationships between nebkhas length and width, nebkhas area and height changed gradually from linear relation to quadratic function for the nebkhases from the internal area to the peripheral area of the eco- tone. There was a significant linear relationship between the crown area of T. ramosissima and the nebkhas; （3） From the internal area to the peripheral area of the oasis-desert ecotone, the nebkhas density reduced, the spatial distribution pattern of nebkhas changed from aggregation to random pattern at spatial scale of 100 -250 m, and the aggregation degree decreased. The nebkhases are currently still at growing stage, and it was considered that the for- mation and development of nebkhas is caused by land degradation.