ABSTRACT Here, we aim to establish possible morphogenetic associations between periglacial phenomena (sorted circles and turf-/stone-banked lobes) by examining (a) rock surface weathering rinds by thin section microscopy and SEM-EDX analysis, and (b) alpine shrub growth patterns of Helichrysum trilineatum supported by AMS 14C age determination. The study area is the Mafadi–Njesuthi summit zone, one of the highest alpine regions of southern Africa. Rock weathering results indicate that clasts in large sorted circle centres experience high chemical weathering rates on both exposed (upper) and non-exposed (lower) surfaces, whereas clasts in lobes and very large apparently ‘relict’ sorted circles have been inactive for a prolonged period of time, based on strongly contrasting weathering rates on both exposed and non-exposed clast surfaces. Large sorted circles originating from a previous (possibly Last Glacial Maximum or late-glacial) colder period are still marginally or episodically active, thus restricting plant succession on these landforms. Even where very large sorted circles and turf-/stone-banked lobes are inactive, their legacy continues, as expressed in today’s surface morphology, and still influence ground abiotic conditions through the generation of microrelief and microclimate which in turn have impacts on ecosystem patterns including the distribution of H. trilineatum. Such shrub growth patterns are influenced by microscale site morphology, associated abiotic controls, and ongoing seasonal cryogenic activity. Both active and inactive periglacial landforms on highest summits of the Drakensberg represent microscale environments with distinct fine-scale abiotic and geomorphic settings, which in turn are manifested through differences in plant ecology and rock surface weathering, respectively.

中文翻译：

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南部非洲德拉肯斯堡高地的冰缘地貌：与岩石风化皮和灌木生长模式的形态发生关联

摘要 在这里，我们的目标是通过（a）通过薄片显微镜和 SEM-EDX 分析检查岩石表面风化外皮，以及（b）高山灌木，来建立冰缘现象（分类圆和草皮/石堤裂片）之间可能的形态发生关联。 AMS 14C 年龄测定支持的 Helichrysum trilineatum 生长模式。研究区域是南部非洲最高的高山地区之一的马法迪-奈苏提峰顶区。岩石风化结果表明，大分选圆中心的碎屑在暴露（上）和未暴露（下）表面都经历了高化学风化率，而裂片和非常大的明显“残留”分选圆中的碎屑长时间不活跃一段时间，基于暴露和未暴露碎屑表面上强烈对比的风化速率。源自先前（可能是末次盛冰期或晚冰期）较冷时期的大分类圆圈仍然边缘或偶尔活跃，因此限制了这些地貌上的植物演替。即使在非常大的分选圈和草皮/石堤叶不活动的地方，它们的遗产仍在继续，正如今天的地表形态所表达的那样，并且仍然通过产生微地貌和微气候影响地面非生物条件，这反过来又影响生态系统模式，包括H. trilineatum 的分布。这种灌木生长模式受微尺度场地形态、相关的非生物控制和持续的季节性低温活动的影响。