FLAMMA, 5 (1), 56-59, 2014 ISSN 2171 - 665X CC Attribution-NonCommercial-ShareAlike 3.0 License 56 Organic carbon exports by overland flow from recently burnt eucalypt stands, north-central Portugal S.R. Faria (1*), I. Skulska (1), M.E. Varela (1), M. Martins (1), V.I. Esteves (2), J.J. Keizer (1) (1) Center for Environmental and Marine Studies (CESAM), Department of Environment and Planning. University of Aveiro,3810- 193 Aveiro, Portugal (2) Center for Environmental and Marine Studies (CESAM), Department of Chemistry. University of Aveiro. 3810-193 Aveiro, Portugal *Corresponding author: silviaregina@ua.pt Keywords Abstract Eucalypt stand Organic carbon export Overland flow Wildfire While it is well documented that wildfires can have major impacts on hydrological and erosion processes, the associated transport of organic matter has received considerably less research attention. The present study estimates post-fire carbon exports by overland flow from two eucalypt plantations during the first year following the wildfire at contrasting spatial scales, i.e. the micro-plot and slope scale. The temporal patterns of these carbon exports were also analyze. Total organic carbon content in runoff samples was measured with a Shimazdu TOC-analyser. Total Organic Carbon (TOC) losses were greater at micro-plot scale than slope scale reflecting a stronger hydrological response at the smaller scale. The TOC losses at both sites and at both scales were largely determined by the Particulate Organic Carbon (POC), accounting for at least 83% of the exported TOC. In consequence, the contribution of DOC fraction in the TOC export it was lower. TOC losses varied markedly through time but did not reveal a clear decline with time- since-fire. Received: 24 October 2012 | Accepted: 6 June 2013 1 INTRODUCTION It is now widely recognized that wildfires are a natural phenomenon in Mediterranean regions and that they have played a crucial role in the evolution of the ecosystems in the region (Naveh, 1990). In the past decades, however, fire regimes in Mediterranean Europe have markedly intensified due to human activities, including through land- use changes such widespread planting of highly flammable tree species (Shakesby, 2011). Wildfires now consume an average 500.000 ha per year in southern Europe (San Miguel & Cami, 2009), with Portugal standing out with some 100.000 ha (Pereira et al., 2005). It is now also generally accepted that the indirect effects of wildfires can include strong and sometimes extreme increases in runoff generation and the associated losses of sediments (Shakesby, 2011). Such increases have also been observed for eucalypt and Maritime Pine plantations, the two principal fire-prone forest types in north-central Portugal (Ferreira et al., 2005; Prats et al., 2012; Shakesby et al., 1996). Arguably, fire-induced losses of soil per se pose a lesser risk of land degradation to Mediterranean ecosystem than losses of soil organic matter/carbon (SOM/C) and nutrients (Shakesby, 2011). Post-fire nutrient and SOM/C exports, however, have received comparatively little research attention, including in Portugal (Ferreira et al., 2005; Malvar et al., 2011; Thomas et al., 1999). For north-central Portugal, this research gap is being addressed by the FCT-funded project FIRECNUTS (PTDC/AGR-CFL/104559/2008), with this paper focussing on the organic carbon losses by overland flow for two of the projeĐt’s study sites.