Spatial Patterns of Clays and Organic Carbon along Semiarid Hillslopes.
Tony Hartshorn1, Lesego Khomo2, and Oliver Chadwick1. (1) University of California Santa Barbara, 3611 Ellison Hall, Department of Geography, Santa Barbara, CA 93106-4060, (2) University of the Witwatersrand, 1 Jan Smuts Avenue, Johannesburg, South Africa
In semiarid parts of southern Africa, vegetation patterns are controlled by water availability. Along hillslopes in Kruger National Park, South Africa, sandier crests grade to duplex, midslope soils where sandier surface horizons overlie clayier subsurface horizons. Footslopes generally have higher clay contents. We hypothesized that the spatial distribution of soil carbon could be predicted based on a clearer understanding of the landscape distribution of clays. Clays influence carbon inputs through moisture availability to plants; clays also enhance soil carbon storage. We quantified soil clay, soil carbon, and soil water holding capacity across a hillslope. We then tested whether terrain attributes such as contributing area could predict soil clay and soil carbon. Soil organic carbon generally increased with increasing clay and water content, both of which increased from crests to footslopes. Using two digital elevation models, we show that soil clay content is useful for predicting carbon for this region, but these estimates are sensitive to the scale at which soil wetness is measured.