chapter  4
20 Pages

Functional Convergence in Ecosystem Carbon Exchange in Adjacent Savanna Vegetation Types of the Kruger National Park, South Africa

ByNiall P. Hanan, Nicolas Boulain, Christopher A. Williams, Robert J. Scholes, Sally Archibald

Approximately one-eighth of the global land surface is covered by savannas and open tropical woodlands. Of that total, about 60% is in Africa, where savannas are the dominant land cover south of the Sahara (Scholes and Hall, 1996). Savannas are characterized by the coexistence of a tree or shrub canopy of varying density with a lower canopy of annual or perennial herbs, often composed primarily of grasses, with variable contribution by forbs (Sankaran et al., 2004). In Africa, the savanna regions are of great economic and ecological importance to the human populations of the region, being the home and primary subsistence resource of the majority of the population. Future changes in land use and management practices (agricultural and grazing systems, fire frequency, and wood harvest) may result in the partial or complete modification of extensive areas of the remaining seasonal savannas,

CONTENTS

Introduction ...........................................................................................................77 The Skukuza Flux Tower...................................................................................... 78 Eddy Covariance and Environmental Measurements .....................................80 Summary of Earlier Studies at the Skukuza Flux Tower .................................84 Carbon Flux Characterization at Monthly Time Scales ...................................85 Results .....................................................................................................................86 Discussion .............................................................................................................. 92 Acknowledgments ................................................................................................ 93 References ............................................................................................................... 94

with direct impact on ecosystem functioning, water, and energy balance. Changes in weather patterns or increased variability associated with global climate change may also impact the productivity and sustainability of the savanna areas. Climate change could also modify tree-grass interactions sufficient to induce changes in community structure and the associated carbon, water, and energy relations of the vegetation (Bond, 2008).