Impacts of climate change on savannah woodland biomass C density and water-use: a modelling study of the Sudanese gum belt region

Tutkimustuotos: Artikkeli kirjassa/raportissa/konferenssijulkaisussaKirjan luku tai artikkeliTieteellinenvertaisarvioitu


The Sudan drylands, including savannah woodlands, cover 1.9 million km2 and much of it lies within an area commonly known as the gum belt (10-16° N), where the bulk of gum producing Acacias grow. Mean annual precipitation (MAP) ranges from 300–800 mm, increasing from north to south. Water availability is the main factor limiting plant growth and distribution, and is strongly related to the amount of rainfall and evapotranspiration. Actual evapotranspiration (AET), which combines the evaporative energy and the availability of water as rainfall and storage in the soil, is directly related to biomass production. The relationship between biomass production and water-use is critical to understanding how dryland ecosystems function and how they may respond to climate change. In our study, we modelled the impact of various climate change and emission scenarios for the 2080s on biomass C densities and water-use of savannah woodlands across the Sudanese gum belt region.

Eight study grids (1:250,000; 1.0º lat. x 1.5º long.) covering semi-arid grassland and savannah woodland were selected from the Sudanese gum belt region. Modelled monthly mean scenarios of climate variables (temperature, precipitation and cloud cover) for the selected study grids were derived from the TYN SC 2.0 (0.5° global spatial resolution) under 10 possible scenarios (5 GCMs x A1FI and B1 emission scenarios) for the period of 2070-2099 using TETYN software. Baseline (1961-1990) observed monthly mean values of same climate parameters were extracted from the CRU TS 2.1 having same spatial resolution. The climate data for our study grids were calculated as the average of resulting six TYN/CRU grids per study grid. Sudanese National Forest Inventory data was used to calculate above-ground tree biomass C densities (g C m-2). Using an exponential relationship between biomass C density and rainfall (y = 6.7980.0054x, R2 = 70%), climate change scenario based biomass C densities were estimated. A water balance model, WATBAL, was parameterized for woodland vegetation and two soil types, arenosols (AR) and vertisols (VR) using HWSD soil data, to give monthly water-use (AET, mm) values for the baseline data and each climate change scenario dataset.

Grid baseline MAP ranged from 140 to 654 mm and mean annual temperature (MAT) from 23.3 to 29.1 °C. MAT increased under all climate change scenarios and for all eight grids (+1.2 to +8.3 °C), while MAP either increased (+112 to +221 mm) or decreased (-13 to -188 mm), depending on climate change scenario and study grid. Grid baseline mean biomass C densities varied between 14 and 232 g C m-2. Because of the explicit dependence of biomass on rainfall, biomass C densities under the climate change scenarios either increased (from +14 to +241 g C m-2) or decreased (from -1 to -148 g C m-2) with scenario/baseline ratios ranging from 0.36 to 3.30. Grid baseline mean annual AET varied from 140 to 595 mm for VR soils and from 140 to 464 mm for AR soils. Compared to baseline values, AET also either increased or decreased depending on map sheet and climate change scenario. For VR soils, the increases in AET varied from +100 to +145 mm and the decreases varied from -12 to -178 mm. For AR soils, the increases in AET varied from +82 to +197 mm and the decreases varied from -12 to -132 mm. Averaged over the climate change scenarios, VR soils would have equal or greater AET than AR soils. Our results indicate that future C sequestration and water-use of savannah woodlands in the Sudanese gum belt region will strongly depend on the degree and nature of climate change.
OtsikkoBIOGEOMON 2012-7th International Symposium on Ecosystem Behavior
ToimittajatIvan J. Fernandez, Stephen A. Norton, Tiffany A. Wilson
KustantajaThe University of Maine and Villanova University
ISBN (painettu)978-0-87723-108-0
TilaJulkaistu - 2012
OKM-julkaisutyyppiA3 Kirjan tai muun kokoomateoksen osa

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