Isotope composition and anion chemistry of soil profiles along the Kalahari Transect

• Published in: Journal of arid environments Vol. 73; no. 4; pp. 480 - 486
• Main Authors: Wang, L., D'Odorico, P., Okin, G.S., Macko, S.A.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.04.2009
• Subjects: 15N; Belowground; canopy; Chloride; dry season; Kalahari; Nitrate; Phosphate; savanna soils; seasonal variation; soil chemistry; soil nutrients; spatial distribution; stable isotopes; Sulfate; wet season; Botswana; Zambia; Chloride; Nitrate; Phosphate; 15N; Sulfate; Belowground; Kalahari
• ISSN: 0140-1963; 1095-922X
• DOI: 10.1016/j.jaridenv.2008.11.010

Savannas cover about 20% of the Earth's land area across a wide range of climatic conditions. As an important and distinct biome, savannas produce approximately 29% of global terrestrial net primary productivity. In these ecosystems the distribution of belowground resources remains poorly investigated and the relationship to the climatic conditions remains unclear. In the present study, vertical profiles of soil nutrients (chloride, nitrate, phosphate and sulfate) and nitrogen stable isotopes were analyzed at four sites along the Kalahari mega-transect, where a distinct rainfall gradient exists on a homogeneous soil substrate. The results show clear differences in nutrients and δ 15N vertical distributions between wet and dry seasons. The results also show how the formation of “fertility islands” (i.e., the concentration of soil nutrients in the soils beneath tree canopies) is not necessarily coupled with belowground processes in that the distribution of soil nutrients at the surface does not match belowground patterns. The results also indicate that phosphorus may be a limiting nutrient in these savanna ecosystems with seasonal dynamics in its cycling.