The Gamka Karoo is a low-lying vegetation type in the semi-arid Nama Karoo in the south-western part of South Africa with extensive rangelands used for livestock ranching and wildlife. Although the Nama Karoo is generally resilient to grazing and most responsive to variable rainfall, chronic overstocking, particularly in the driest regions and around water points, could degrade vegetation and soils. The interactive effects of rainfall (MAP) and grazing (stocking rate, percentage overstocking, resting system) on plant species composition and soil chemical characteristics were examined on 36 farms across a regional rainfall gradient (120–300 mm y⁻¹) and around water points (n = 3) on farms. Multivariate direct gradient analyses revealed regional species compositional differences were related most strongly to MAP (r = 0.736), but not to grazing, with no MAP × grazing interaction. On a smaller scale, grazing intensity (1/distance from water point) had a weak negative impact on the vegetation (r = 0.36) and soil chemistry (r = 0.49) with nutrient enrichment around water points in paddocks. Our findings suggest that the Karoo is responsive to rainfall, but loosely coupled to grazing. Adaptive management with livestock numbers matched to rainfall and forage supply is recommended to sustain animal production, vegetation and soils.

Gamka Karoo 是南非西南部半干旱 Nama Karoo 的低洼植被类型，拥有广阔的牧场，用于放牧和野生动物。尽管 Nama Karoo 通常能够适应放牧并且对多变的降雨最敏感，但长期过度放牧，尤其是在最干旱地区和水源地附近，可能会导致植被和土壤退化。^{在区域降雨梯度 (120–300 mm y −1} ) 和水域周围的 36 个农场，研究了降雨 (MAP) 和放牧（载畜率、蓄积率、休眠系统）对植物物种组成和土壤化学特征的交互影响点 ( n= 3) 在农场。多变量直接梯度分析显示区域物种组成差异与 MAP ( r = 0.736) 最相关，但与放牧无关，没有 MAP × 放牧相互作用。在较小的范围内，放牧强度（1/与水点的距离）对植被（r = 0.36）和土壤化学（r = 0.49）具有微弱的负面影响，同时牧场水点周围的养分富集。我们的研究结果表明，卡鲁对降雨有反应，但与放牧松耦合。建议采用与降雨量和草料供应相匹配的牲畜数量进行适应性管理，以维持动物生产、植被和土壤。