Circular depressions are concave, shallow depressions found on planar landscape surfaces in the southern Namib Desert. They occur on gravelly substrates with nearly level to very slightly inclined surfaces. The depressions range from 6 to 10 m in diameter with centers typically depressed 10–20 cm below the level of the surrounding terrain. Locations of individual circular depressions were mapped at one site using ground-based measurements and at three additional sites using Google Earth imagery. At all sites, circular depressions are highly overdispersed with densities ranging from approximately 10–20/ha and corresponding nearest neighbor distances of 17–24 m. Large fragments of weathered calcrete and stones occur on soil surfaces surrounding circular depressions, but not within the depressions. Circular depressions at one site contained active burrow systems of Brants’ whistling rat ( Paratomys brantsii). Bioturbation by these rodents contributes to the non-cohesive nature of the sandy substrate, which promotes aeolian deflation and formation of the depressions. Excavations of the burrow systems by the honey badger ( Mellivora capensis) in search of rodent prey can transfer large stones and calcrete fragments from the subsurface to the surface and subsequently move those materials about the surface. Even if such sequential, horizontal displacements are in random directions, such movements can eventually yield a central, clast-free area surrounded by a peripheral zone where the clasts accumulate once they have been displaced beyond the margin of the area to which the predator is drawn in search of rodent prey. A conceptual model consisting of a two-dimensional random walk of large clasts about the surface until they are displaced from the focal “arena” of rodent occupation provides a novel explanation for origin of a spatially organized pattern that is initiated through the random displacement of those materials. Comparable microtopographic patterning associated with bioturbation in other arid and semi-arid environments may have similar origins.

中文翻译：

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纳米比亚 Tsau ၁Khaeb (Sperrgebiet) 国家公园纳米布沙漠南部无碎屑圆形洼地的出现和形成

圆形洼地是在纳米布沙漠南部的平坦景观表面上发现的凹形浅洼地。它们出现在砾石基质上，表面几乎水平到非常轻微倾斜。洼地的直径范围为 6 至 10 m，中心通常比周围地形低 10 至 20 cm。使用地面测量在一个地点绘制了单个圆形凹陷的位置，并使用谷歌地球图像在另外三个地点绘制了单个圆形凹陷的位置。在所有地点，圆形洼地都高度分散，密度约为 10-20 个/公顷，相应的最近邻距离为 17-24 m。风化钙质混凝土和石头的大碎片出现在圆形凹陷周围的土壤表面上，但不在凹陷内部。一处的圆形凹陷处含有布兰茨口哨鼠（Paratomys bantsii）活跃的洞穴系统。这些啮齿动物的生物扰动导致沙质基质的非粘性，从而促进风气紧缩和洼地的形成。蜜獾（Mellivora capensis）为了寻找啮齿动物猎物而挖掘洞穴系统，可以将大石头和钙质碎片从地下转移到地表，随后将这些物质移动到地表。即使这种连续的、水平的位移是随机方向的，这种运动最终也会产生一个中心的、无碎屑的区域，周围是一个外围区域，一旦碎屑移动到捕食者被吸引到的区域的边缘之外，碎屑就会在外围区域聚集。寻找啮齿动物猎物。一个概念模型由大型碎屑在表面上的二维随机行走组成，直到它们从啮齿动物占据的焦点“竞技场”中移出，这为空间组织模式的起源提供了新颖的解释，该模式是通过那些碎屑的随机位移而启动的。材料。其他干旱和半干旱环境中与生物扰动相关的类似微地形图案可能具有相似的起源。