Using remote sensing to model carbon source/sink dynamics in the sahel

• Recent research has identified the grasslands of the Sahel as a potential carbon sink, but regional carbon stock accounting in such biomes is undermined by the poorly recognized role they play in the carbon cycle as well as lack of data. In this paper, we demonstrate the feasibility of coupling the satellite data-driven light use efficiency model (Lund University Light Use Efficiency Model - LULUE) with Roth-C, a dynamic model that estimates the turnover of carbon in non-waterlogged soils for a 10560 km2 test area in the Sahel. LULUE is used to estimate the rate and amount of carbon drawdown into the vegetative carbon pool while Roth-C is used to estimate soil respiration from a number of well-defined pools, ranging from labile to inert. Running the ensemble requires the parameterisation of Roth-C using NPP from LULUE, with the aid of a land cover/use map. The result is an estimate of NEP (Net Ecosystem Production). Our results show that total annual area-averaged NPP ranges from 1.8 tCha-1 in 1987, to 4.1 tCha-1 in 1992, and increases steadily throughout the period (r2 = 0.44). Total annual area averaged soil respiration ranges from 2.5 tCha-1 in 1986, to 5.0 tCha-1 in 1993, with no appreciable trend observed. Our NEP trend analysis (r2 = 0.14) suggests that this ecosystem became a carbon sink around 1994 with a total 5.14 tCha-1 sequestered throughout the period. This approach holds promise for quantifying carbon sink/source dynamics in a spatially explicit manner for grasslands, though a full sensitivity analysis should be implemented before geographically extending the method.

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Klimatforskning (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Climate Research (hsv//eng)

Nyckelord

Carbon dynamics

Carbon stocks

Light-use efficiency

Remote sensing

Roth-C

Sahel

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