PARENT SESSION
Oral Session #100: Landscape Ecology.
Presiding: T. Crist
Friday, August 9. 9:00 AM to 12:00 PM. Gila Meeting Room, TCC.
Origin of riparian-upland boundary sodic patches in Kruger National Park, South Africa .
Khomo, Lesego*,1, Rogers, Kevin1, 1 University of the Witwatersrand, Johannesburg, South Africa
ABSTRACT- The accumulation of sodium on the footslopes of granitic catenas in semi-arid southern Africa leads to the formation patches of sodic soil. Sodic patches are ecologically important for nutrient accumulation, predator evasion and wallowing, but they are often perceived as derelict lands due to vegetation denudation and low aesthetic quality. This negative perception, by both ecologists and tourists, often leads to ill-advised management and "rehabilitation" measures. In Kruger National Park, sodic patches occur at the riparian-upland boundary and hence the processes originating in both systems may contribute to their origin. The upland-based catena and riparian-based evapotranspiration models were used to explore the hypothesis that these soils originate from both catenal and evapotranspiration-driven hydraulic processes. The models predict vegetation zonation dictated by a salt tolerance gradient and an increase in sodic patch area over time as a result of progressive salt accumulation. Vegetation structure and hillslope morphology across the riparian-upland boundary and analysis of change in patch configuration over a 50-year aerial photographic record were used to test the hypothesis. Sodic patches have unique vegetation, occur on the intermediate positions of hillslopes, have increased in area three-fold over 50 years and are encroaching into the riparian zone. This behaviour is consistent with the assertion that these patches originate from both catenal and evapotranspiration processes. Results imply a dynamic aspect of sodic patches, which have been previously viewed as static landscape features in pedogenic time scales. However, we show that they change over relatively smaller time scales meaning that their management should be commensurate with this dynamic nature. Therefore, sodic patches should be managed under a scheme that incorporates their small-scale expansion, recognizes their ecological importance and challenges their current negative perception.
KEY WORDS: Sodic, Boundaries, Savanna, South Africa