Abstract

Laikipia rangelands in Kenya are among the most productive ecosystems but there is concern that the traditional free grazing regimes may accelerate soil and vegetation deterioration. We investigated the distribution of soil properties in the rangelands of Ilmotiok ranch in Laikipia County where grazing is predominantly open or free and examined selected soil chemical properties and particle size distribution in three types of habitats (tree, grass and bare ground) along four transects, placed diagonally across hillslope positions. We focused our study on the hypotheses that habitat types and hillslope position had an effect on soil properties distribution along the profile. Along each identified transect, soil samples were collected at four depths 0–10, 10–20, 20–30 and 30–40 cm. Distribution of soil properties mainly carbon, total nitrogen and phosphorus were influenced by hillslope position and habitat type and their contents decreased gradually with soil depth. Soil organic carbon content was high in tree habitats while in grass habitats average total phosphorus content in the profiles was slightly lower than in tree habitats. Total soil nitrogen was highest in the footslope in the tree and grass habitat and ranged between 0.81−2.17 g/kg and 1.26−2.50 g/kg, respectively. Sand was the dominant grain size fraction which accounted for 50−88%. This study demonstrated that there are soil fertility differences in the rangelands caused by vegetation cover and hillslope positions which are particularly important for future agro-pastoral use decisions.

摘要

肯尼亚的莱基皮亚牧场是生产力最高的生态系统之一，但人们担心传统的自由放牧制度可能会加速土壤和植被的退化。我们调查了莱基皮亚县 Ilmotiok 牧场牧场的土壤特性分布，该牧场主要是开放或自由放牧，并沿四个样带检查了三种栖息地（树木、草地和裸地）的选定土壤化学特性和粒度分布，斜跨山坡位置。我们将研究重点放在栖息地类型和山坡位置对沿剖面的土壤性质分布有影响的假设上。沿着每个确定的样带，在 0-10、10-20、20-30 和 30-40 厘米的四个深度收集土壤样本。土壤性质的分布主要是碳，总氮、磷受山坡位置和生境类型的影响，其含量随土壤深度逐渐降低。树木生境的土壤有机碳含量较高，而草生境的平均总磷含量略低于树木生境。树木和草地栖息地的山脚坡土壤总氮含量最高，分别介于 0.81-2.17 g/kg 和 1.26-2.50 g/kg 之间。沙子是主要的粒度部分，占 50-88%。该研究表明，植被覆盖和山坡位置导致牧场土壤肥力差异，这对未来的农牧利用决策尤为重要。树木生境的土壤有机碳含量较高，而草生境的平均总磷含量略低于树木生境。树木和草地栖息地的山脚坡土壤总氮含量最高，分别介于 0.81-2.17 g/kg 和 1.26-2.50 g/kg 之间。沙子是主要的粒度部分，占 50-88%。该研究表明，植被覆盖和山坡位置导致牧场土壤肥力差异，这对未来的农牧利用决策尤为重要。树木生境的土壤有机碳含量较高，而草生境的平均总磷含量略低于树木生境。树木和草地栖息地的山脚坡土壤总氮含量最高，分别介于 0.81-2.17 g/kg 和 1.26-2.50 g/kg 之间。沙子是主要的粒度部分，占 50-88%。该研究表明，植被覆盖和山坡位置导致牧场土壤肥力差异，这对未来的农牧利用决策尤为重要。分别为 81-2.17 g/kg 和 1.26-2.50 g/kg。沙子是主要的粒度部分，占 50-88%。该研究表明，植被覆盖和山坡位置导致牧场土壤肥力差异，这对未来的农牧利用决策尤为重要。分别为 81-2.17 g/kg 和 1.26-2.50 g/kg。沙子是主要的粒度部分，占 50-88%。该研究表明，植被覆盖和山坡位置导致牧场土壤肥力差异，这对未来的农牧利用决策尤为重要。