Treeless grasslands occur within landscapes that are predominantly wooded savannas in the central Kruger National Park, South Africa. As a first step in identifying soil properties potentially underpinning differences in vegetation structure in these landscapes, we analysed the soil chemistry of the pedoderm (0–2 cm) in a grassland and two adjacent savanna types (Senegalia savanna and Delagoa Lowveld). The grassland was significantly enriched in P, Ca, Mg and Cu relative to both the savannas (1.8- and 5.8-fold for the Senegalia and Delagoa Lowveld savannas, respectively, for P; 1.8- and 5.7-fold for Ca; 1.7- and 6.0-fold for Mg; and 1.3- and 9.4-fold for Cu). It was also richer in Na (4.7-fold), Mn (6.3-fold) and Zn (1.6-fold) than the Delagoa Lowveld savanna. The competitive strength and nutritive value of the herbaceous layer in the grassland is likely to be greater than in the savannas because of the relative nutrient richness of the grassland’s pedoderm. Herbivory pressure is also likely to be greater in the grassland because of the greater nutritive value of the herbaceous layer. These effects provide a plausible mechanism for the constraint of trees in the grassland.

南非克鲁格国家公园中部以树木繁茂的稀树草原为主的景观中出现了无树草原。作为识别可能支撑这些景观中植被结构差异的土壤特性的第一步，我们分析了草地和两个相邻的稀树草原类型（塞内加利亚稀树草原和德拉戈亚低草原）中的土壤化学成分（0-2 厘米）。相对于热带稀树草原，草原显着富含 P、Ca、Mg 和 Cu（塞内加利亚和 Delagoa Lowveld 稀树草原分别是 P 的 1.8 倍和 5.8 倍；Ca 的 1.8 倍和 5.7 倍；Ca 的 1.7 倍和 5.8 倍） Mg 的 6.0 倍；Cu 的 1.3 和 9.4 倍）。它也比 Delagoa Lowveld 稀树草原富含 Na（4.7 倍）、Mn（6.3 倍）和 Zn（1.6 倍）。草原草本层的竞争强度和营养价值可能比热带稀树草原更大，因为草原土壤的营养相对丰富。由于草本层的营养价值更高，草地的食草动物压力也可能更大。这些效应为草地树木的限制提供了一个似是而非的机制。