Soil type more than precipitation determines fine-root abundance in savannas of Kruger National Park, South Africa
Our aim was to examine how soil type and precipitation affect fine-root abundance in savanna ecosystems across Kruger National Park (KNP), South Africa.
Fine-root distributions were measured in four sites that represent the natural factorial combination of soil types (basalt-derived clay or granite-derived sand) and precipitation regimes [wet (~750 mm mean annual precipitation) or dry (~500 mm mean annual precipitation)] that occur in KNP. Root area and biomass (at soil depths of 0–75 cm) were estimated from measurements of root number, length and width in images from minirhizotron tubes at each site. Measurements were made during one mid-season sampling during three subsequent years.
Fine-root area was more than twice as large in clay (2.3 ± 0.0 mm2 cm−2) than sand (0.8 ± 0.3 mm2 cm−2) sites but did not differ between wet and dry sites. Root number, length and width, used to derive area, showed similar patterns to fine-root area. Fine-root biomass estimated from these values was 5.5 ± 0.6 Mg ha−1 in clay sites and 2.2 ± 0.9 Mg ha−1 in sand sites.
Across the four sites, a change from sand to clay soils had a greater effect on fine-root abundance and distributions than a 50% increase in precipitation from dry to wet sites. Results highlight the importance of soil properties on root dynamics and carbon pools in the region.
KeywordsBelowground biomass Grass Minirhizotron Rainfall Root Savanna Tree
Mean annual precipitation
Kruger National Park
We thank the Andrew Mellon Foundation for financial support, South African National Parks for allowing us to do this research (project registration number 213896412). Field managers: S. Doucette-Riis, M. Cooper, M. Mazzacavallo, M. Keretetsi, S. Heath and L. Hierl. Field/laboratory assistants: W. Sibuye, R. Mashele, and V. Sibuye. Statistical advice: S. Durham and A. Tredennick. Experiments complied with the present laws of the Republic of South Africa. This research was supported by the Utah Agricultural Experiment Station, Utah State University, and approved as journal paper number 8958.
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