Runoff and inter-rill erosion in a maritime pine and a eucalypt plantation following wildfire and terracing in north-central portugal

Abstract

The purpose of this study was to assess how terracing affected overland\nflow and associated sediment losses, at the micro-plot scale (0.25\nm(2)), in recently burnt stands of the two principal forest types in\nnorth-central Portugal, i.e. mono-specific stands of Maritime Pine and\nEucalypt. Terracing is an increasingly common practice of slope\nengineering in the study region but its impacts on runoff and erosion\nare poorly studied. Non-terraced plots at the Eucalypt and the Pine site\nrevealed similar median runoff coefficients (rc: 20-30%) as well as\ncomparable median sediment losses (15-25 g m(-2)) during the first seven\nmonths following wildfire. During the ensuing, slightly wetter 18-month\nperiod, however, non-terraced plots at the Pine site lost noticeably\nmore sediments (in median, 90 vs. 18 g m(-2)), in spite the runoff\nresponse had remained basically the same (median rc: 33 vs. 28%). By\ncontrast, terraced plots at the same Pine site lost hugely more\nsediments (in median, 1,200 g m(-2)) during this 18-month period.\nTerraced plots at the Eucalypt site even lost three times more sediments\n(in median, 3,600 g m(-2)). Ground cover and resistance to shear stress\nseemed to be key factors in the observed/inferred impacts of terracing.