Natural Resource Ecology Laboratory

Kruger Park Eddy Covariance Study

Net carbon and energy balance of savanna ecosystems in southern Africa

PI: Niall Hanan, NREL (niall@nrel.colostate.edu)

Co-I: Robert Scholes, CSIR, South Africa, and Mike Coughenour, NREL

This is a joint project between researchers at the Natural Resource Ecology Laboratory at Colorado State University and collaborators at CSIR in Pretoria, South Africa. Site instrumentation and initial operation was provided by the NASA-Terrestrial Ecology Program.

An eddy covariance system was built at a site near Skukuza Camp in Kruger National Park, South Africa, with meteorological measurements starting in February 2000, and first flux measurements in April 2000 (photo 1). The site is unique in that the micrometeorological instruments are positioned on a tower located between two distinct savanna types, a broad-leafed Combretum savanna and fine-leafed Acacia savanna. These contrasting savanna types are found on soils of differing texture, water holding capacity and nutrient status, and are characterized by different physical structure, physiology and phenology. Wind directions are such that we expect to obtain a good sample of net ecosystem fluxes from both ecosystems.

Measurements on the main eddy covariance tower include net ecosystem exchange of CO2, water and energy, and measurements of a range of meteorological variables with 30 minute averaging period. Additional continuous measurements in both adjacent savanna systems include soil heat flux, soil moisture and temperature profiles (from the soil surface to bedrock - photos 2, 3), and canopy profiles of CO2 concentration, humidity and air temperature (photo 4). Intermittent measurements include soil surface CO2 flux, and additional, spatially distributed, soil moisture and soil temperature measurements.

The Skukuza research site is the focus of several complementary studies by colleagues from South Africa and elsewhere into savanna biophysics, radiative transfer and biogeochemistry. Among others, these include the EOS validation activities of the SAVE project, which includes measurement of canopy radiative transfer, bidirectional reflectance, leaf area index and primary production. Other studies include measurements of nitrogen oxide and methane sources and sinks (Luanne Otter), and measurements of volatile organic compound emissions at both leaf and canopy scale (Otter and Alex Guenther).

The Skukuza flux measurements also form an important site-based component of the regional Southern Africa Research Initiative (SAFARI-2000). This international study is designed to investigate the bi-directional interactions in southern African savanna ecosystems between land surface biogeochemistry, fire, land use, management and atmospheric chemistry and dynamics.

Further information on the savanna vegetation communities in the vicinity of the Skukuza eddy flux tower will be posted soon. General information is already available on the SAVE home page and the Kruger Park home page.