Simulation of the impacts of restoration techniques on soil organic
carbon content and structure in West Africa
Abstract
The main objective of this study was to evaluate two restoration
techniques, “stone rows” and “stone rows + tree planting” on soil
organic carbon (SOC) sequestration and structure in terms of water
stable aggregates as well as the time required to restore soil
fertility. The Carbon, Aggregate and Structure Turnover (CAST) model was
used to model the changes of SOC content and water stable aggregate
formation under the two restoration techniques. Field experiments used
for calibration of the model were conducted using a randomized block
design. Soil samples were class fractionated followed by a
micro-aggregate isolation procedure. The two restoration techniques
contributed significantly to improving soil total carbon content. By
running five year simulation of the “stone rows”, the estimated total
carbon input was 27 Mg ha-1 of which 6.1 Mg ha-1 were sequestered in the
soil and 20.7 Mg ha-1 were released as CO2. In “stone rows +
planting”, the total SOC content after five years was estimated to be
22.96 Mg ha-1, which was broken down to 15.43 Mg ha-1 aggregated carbon
and 26.60 Mg ha-1 CO2. Fifty-year simulations showed a SOC increase to
54.8 Mg ha-1 in “stone rows”, and to 86.0 Mg ha-1 in “stone rows +
planting”. This means that natural grassland vegetation slowly improves
soil carbon content and soil quality, but with trees behind stone rows,
the result will be about 50% higher.