TY - JOUR
T1 - Roads increase woody cover under varying geological, rainfall and fire regimes in African savanna
AU - Smit, I. P.J.
AU - Asner, G. P.
N1 - Funding Information:
We thank South African National Parks (SANParks) for permission to conduct this study within the Kruger National Park. The team that maintained the experiment for many decades deserves special mention, especially Andre Potgieter. We thank Ty Kennedy-Bowdoin, James Jacobson, David Knapp, and the CAO team for data collection, processing and analysis. We thank Kate Parr for sparking initial interest in this topic. Shaun Levick, Renaud Mathieu, Konrad Wessels, Jan van Aardt, Barend Erasmus and Moses Cho are thanked for support and advice during the CAO campaign. Eddie Riddell, Navashni Govender, Rina Grant and two anonymous reviewers are thanked for comments and ideas that have improved the manuscript. IPJS thanks the Andrew Mellon Foundation for funding a trip to the Department of Global Ecology that contributed towards this manuscript. Airborne mapping and analysis of the KNP was funded by the Andrew Mellon Foundation . The Carnegie Airborne Observatory is made possible by the W.M. Keck Foundation and William Hearst III.
PY - 2012/5
Y1 - 2012/5
N2 - Roads extend throughout savannas, yet few studies have quantified their effects on adjoining woody vegetation structure. Airborne LiDAR imagery collected over 168 experimental fire plots in the Kruger National Park, all bounded by graded firebreak roads, provided an opportunity to study if, and to what extent, roads influence woody vegetation structure under different rainfall, geologic and fire conditions. In 91.7% of the plots, woody canopy cover was higher on the edges of roads compared to areas farther away. The increase was most pronounced within 5 m of the road edge, but was detectable 10-15 m from the edge. On average, the area within 15 m from the road had approximately 6% and 2% higher woody vegetation cover than areas further than 15 m from the edge on wetter granitic and drier basaltic savanna landscapes, respectively. Increased edge effects on woody cover were observed even in fire exclusion plots, suggesting that non-fire processes, likely altered hydrological regimes, may be the underlying reason for woody encroachment. This study illustrates that roads cause selective woody plant thickening in savannas, even in areas without road edge management, and therefore careful consideration should be paid on how road edges are managed and when roads are planned.
AB - Roads extend throughout savannas, yet few studies have quantified their effects on adjoining woody vegetation structure. Airborne LiDAR imagery collected over 168 experimental fire plots in the Kruger National Park, all bounded by graded firebreak roads, provided an opportunity to study if, and to what extent, roads influence woody vegetation structure under different rainfall, geologic and fire conditions. In 91.7% of the plots, woody canopy cover was higher on the edges of roads compared to areas farther away. The increase was most pronounced within 5 m of the road edge, but was detectable 10-15 m from the edge. On average, the area within 15 m from the road had approximately 6% and 2% higher woody vegetation cover than areas further than 15 m from the edge on wetter granitic and drier basaltic savanna landscapes, respectively. Increased edge effects on woody cover were observed even in fire exclusion plots, suggesting that non-fire processes, likely altered hydrological regimes, may be the underlying reason for woody encroachment. This study illustrates that roads cause selective woody plant thickening in savannas, even in areas without road edge management, and therefore careful consideration should be paid on how road edges are managed and when roads are planned.
KW - Bush thickening
KW - Hydrology
KW - Kruger National Park
KW - LiDAR
KW - Road edges
KW - Woody encroachment
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U2 - 10.1016/j.jaridenv.2011.11.026
DO - 10.1016/j.jaridenv.2011.11.026
M3 - Article
AN - SCOPUS:84857366174
SN - 0140-1963
VL - 80
SP - 74
EP - 80
JO - Journal of Arid Environments
JF - Journal of Arid Environments
ER -