HR: 1340h
AN: B23C-1503    [Abstracts]
TI: Combining Eddy Covariance, Leaf Level Measurements and Modelling to Investigate Ecosystem Fluxes in Tropical Grasslands
AU: * Wohland, P
EM: geopnw@leeds.ac.uk
AF: School of Geography, University of Leeds, University Street, Leeds, LS6 9JT, United Kingdom
AU: * Wohland, P
EM: geopnw@leeds.ac.uk
AF: Max Plank Institute for Biogeochemistry, Hans Knoell Strasse 10, Jena, 07745, Germany
AU: Mantlana, B
AF: Max Plank Institute for Biogeochemistry, Hans Knoell Strasse 10, Jena, 07745, Germany
AU: Mantlana, B
AF: South African National Biodiversity Institute, Private Bag X7, Claremont, Cape Town, 7735, South Africa
AU: Kattge, J
AF: Max Plank Institute for Biogeochemistry, Hans Knoell Strasse 10, Jena, 07745, Germany
AB: Our project determined seasonal and spatial variations in ecosystem fluxes of tropical grassland ecosystems by investigating three prominent grassland types along a hydrological gradient in the Okavango Delta, Botswana.

To identify the environmental factors that control CO₂ and H₂O exchange in tropical grassland ecosystems, we successfully combined eddy covariance measurements, leaf level measurements and remotely sensed data.

Grassland ecosystems growing under the same climate showed profound differences in ecosystem fluxes as well as what regulated those fluxes on an ecosystem level. The analysis of the eddy covariance measurements revealed a pronounced seasonal and spatial variation with maximum net ecosystem exchange (N_E) varying between -25μ mol ^-2 s^-1 and -1μ mol ^-2 s^-1 across sites and seasons.

Without water limitation the main factor for the differences in N_E between ecosystems was nutrient content per vegetation unit. This importance of nutrient content was also confirmed by our leaf level measurements. Seasonal differences in N_E varied between sites and were driven by phenology or temperature and light limitation.

Eddy covariance measurements for this project were predominantly campaign measurements. To determine annual course and sum of N_E, we adapted the ecosystem model BETHY (Biosphere-Energy Transfer Hydrology Scheme) by parameter inversion in combination with remotely sensed fraction of absorbed photosynthetically active radiation for each site.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0428 Carbon cycling (4806)
DE: 0438 Diel, seasonal, and annual cycles (4227)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting