The effectiveness of tree-log check dams to reduce post-fire sediment yields from terraced and contour-ploughed swales planted with maritime pine

Intensifying wildfire regimes have increased concerns about extreme post-fire erosion responses. The mitigation of these responses has only been assessed beyond the slope scale by one prior study in the present study region of north-central Portugal, while their mitigation using check dams has merely been addressed by one prior study across the world. The present study quantified sediment yields from three pairs of adjacent swales during the first two post-fire years, of which two pairs were dominated by bench terraces and the other by contour-ploughed slopes. Two to four tree-log check dams were installed in the ephemeral channels of one swale of each pair. The eroded sediments were measured at the swale outlets at 12 occasions while the sediment retained by the check dams were only measured once, at the end of the first year. The annual sediment yields without treatment over the first year were lowest for the pair with undisturbed terraces (≤0.05 Mg ha −1 ), intermediate for the contour-ploughed pair (0.23 and 0.26 Mg ha −1 ) and highest for the pair with terraces disturbed by salvage logging following a previous wildfire (0.52 and 0.66 Mg ha −1 ). The underlying temporal patterns revealed contrasting erosion responses for the terraced and contour-ploughed swales, suggesting respectively transport- and supply-limited responses. The reduction in first-year yields by the tree-log check dams was apparently supply limited as well, as it increased with increasing yields without treatment (from 21 to 81%). The second-year yields were much smaller (≥88%) than the respective first-year yields, but the second-year effectiveness could not be determined unequivocally.