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The purpose of this study was to assess how terracing affected overland flow and associated sediment losses, at the micro-plot scale (0.25 m2), in recently burnt stands of the two principal forest types in north-central Portugal, i.e. mono-specific stands of Maritime Pine and Eucalypt. Terracing is an increasingly common practice of slope engineering in the study region but its impacts on runoff and erosion are poorly studied. Non-terraced plots at the Eucalypt and the Pine site revealed similar median runoff coefficients (rc: 20-30%) as well as comparable median sediment losses (15-25 g m-2) during the first seven months following wildfire. During the ensuing, slightly wetter 18-month period, however, non-terraced plots at the Pine site lost noticeably more sediments (in median, 90 vs. 18 g m-2), in spite the runoff response had remained basically the same (median rc: 33 vs. 28%). By contrast, terraced plots at the same Pine site lost hugely more sediments (in median, 1,200 g m-2) during this 18-month period. Terraced plots at the Eucalypt site even lost three times more sediments (in median, 3,600 g m-2). Ground cover and resistance to shear stress seemed to be key factors in the observed/inferred impacts of terracing.

Wildfires typically affect multiple forest ecosystem services, with carbon sequestration being affected both directly, through the combustion of vegetation, litter and soil organic matter, and indirectly, through perturbation of the energy and matter balances. Post-fire carbon fluxes continue poorly studied at the ecosystem scale, especially during the initial window-of-disturbance when changes in environmental conditions can be very pronounced due to the deposition and subsequent mobilization of a wildfire ash layer and the recovery of the vegetation. Therefore, an eddy-covariance system was installed in a burnt area as soon as possible after a wildfire that had occurred on 13 August 2017, and has been operating from the 43rd post-fire day onwards. The study site was specifically selected in a Mediterranean woodland area dominated by Maritime Pine stands with a low stature that had burnt at high severity. The carbon fluxes recorded during the first post-fire hydrological year tended to be very low, so that a specific procedure for the analysis and, in particular, gap filling of the eddy covariance data had to be developed. Still, the carbon fluxes varied noticeably during the first post-fire year, broadly revealing five consecutive periods. During the rainless period after the wildfire, fluxes were reduced but, somewhat surprisingly, indicated a net assimilation. With the onset of the autumn rainfall, fluxes increased and corresponded to a net emission, while they became insignificant with the start of the winter. From the mid winter onwards, net fluxes became negative, indicating a weak carbon update during spring followed by a strong uptake during summer. Over the first post-fire year as a whole, the cumulative net ecosystem exchange was −347 g C m−2, revealing a relatively fast recovery of the carbon sink function of the ecosystem. This recovery was mainly due to understory species, both resprouter and seeder species, since pine recruitment was reduced. Specific periods during the first post-fire year were analyzed in detail for improving process understanding. Perhaps most surprisingly, dew formation and, more specifically, its subsequent evaporation was found to play a role in carbon emissions during the rainless period immediately after fire, involving a mechanism distinct from de-gassing of the ash/soil pores by infiltrating water. The use of a special wavelet technique was fundamental for this inference. [ABSTRACT FROM AUTHOR]

Increases in post-fire runoff and erosion have been reported worldwide, but little is known about the combined effect of wildfires and pre-existent ploughing operations. A previous study using simulated rainfall found a similar runoff for an unploughed and a pre-fire ploughed site, but clearly showed lower erosion for the pre-fire ploughed site. This study measured post-fire runoff and erosion at the same two sites, with the same experimental design, but under natural rainfall conditions. Four micro-plots were installed on each of two eucalypt stands, one of which was rip-ploughed 20 years before the fire. The rainfall amount was 35% lower during the first post-fire year than during the second, but the runoff coefficient was approximately 20% for both years and sites. The sediment losses were significantly higher on the unploughed than on the pre-fire ploughed site during the first year (378 vs. 112 g m−2 y−1) and especially during the second year (552 vs. 67 g m−2 y−1). Half of the eroded sediments consisted of organic matter. On the unploughed site, both the natural and the extreme-intensity simulated rainfall produced specific sediment losses of 0·35 gm−2 mm−1 rain, whereas the high-intensity simulated rainfall produced approximately half (0·16 g m−2 mm−1 rain). At the pre-fire ploughed site, the natural, high, and extreme-intensity simulated rainfall produced similarly low-specific sediment losses (0·07 g m−2 mm−1 rain). These low rates and the absence of differences between methodologies and simulated intensities suggested a depletion of soil stocks 20 years after the rip-ploughing. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The carbon dioxide emission of a forest area of young Maritime Pines (Pinus pinaster Ait.) in Central Portugal was investigated after a wildfire on 13 August 2017 that was classified by EFFIS as of mostly moderate severity. Eddy-covariance measurements together with auxiliary measurements commenced about one month after the end of the fire, making this study one of the first investigations with carbon dioxide flux measurements starting almost immediately after a wildfire. For this study, about 15 months of post-fire data were analyzed. First results indicated that no emissions took place during the - dry - period that followed the installation of the instruments, except for short events after dew fall. During this same period, a small uptake was recorded during daytime. After the first days with significant rainfall in October 2017 the emission dominated, while no fluxes occurred during winter time. Stronger emissions were observed during the rainy season of spring 2018 but during the summer of 2018 the forest already acted a sink. Because fluxes were generally low, large efforts were required for data quality and footprint analysis. A big challenge was the gap filling because conditions differed dependent on the time after the forest fire. [ABSTRACT FROM AUTHOR]