| 研究実績の概要 |
Effect of subsurface water level on gully headcut retreat in tropical highlands of Ethiopia: The headcut retreat rate and sediment yield were closely related over the three study seasons. Elevated subsurface water levels facilitated the slumping of gully banks and heads, causing high sediment yield. When the soil was saturated, bank collapse and headcut retreat were favored by the combination of elevated subsurface water and high rainfall. This study indicates that area exclosures are effective in controlling subsurface water level, thus reducing gully headcut retreat and associated soil loss.
Cropland expansion outweighs the monetary effect of declining natural vegetation on ecosystem services in sub-Saharan Africa: Cropland expansion accounted for about 60% of the increase in the total ESV (US$125billionyear－1),thereby outweighing the decrease in ESV due to the decline in natural vegetation. Land degradation hotspots covered about 5% of SSA, resulting in a total ESV loss of about US $56 billion year－1, of which nearly 65% was due to the degradation of forests and croplands.
Predicting gully densities at sub-continental scales: a case study for the Horn of Africa: Analyses of the feature importance of predictor variables showed that patterns of gully head density across the Horn of Africa strongly depend on NDVI and annual rainfall, but also on normalized steepness index (k(sn)) and distance to rivers. Overall, our work opens promising perspectives to assess gully densities at continental scales.
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