•Soil Water Repellency is high under eucalypts regardless wildfire or slope aspect.•Comparing to the unburnt site, wildfire reduced SWR in the first post-fire years.•SWR is higher and less spatially ...variable under unburnt eucalypts in dry periods.•Comparing to the unburnt site, slope aspect had minimum impact on SWR after burning.•Wildfire causes greater, or quicker, temporal changes in soil moisture content.
Wildfire can induce, enhance, or destroy natural soil water repellency (SWR) depending mostly on soil burnt severity, soil and vegetation types, soil organic matter (SOM) content and type, soil texture, peak soil temperature and remaining time and, antecedent soil moisture content (SMC). In Portugal, SWR in eucalypt stands has been shown to increase surface runoff under dry antecedent SMCs in both burnt and unburnt sites, thereby enhancing soil erosion. Despite the many hydrological implications of SWR, intensive field monitoring under a wide range of SMCs is still limited. This study aimed to improve our understanding of the role of slope aspect and wildfire on the temporal evolution of SWR in Mediterranean environments, which will be helpful for hydrological modelling and post-fire soil erosion risk assessment. In this sense, two burnt eucalypt plantations (wildfire of July 2010) were selected along a neighbouring, long-unburnt eucalypt stand, in north-central Portugal, in order to assess SWR and SMC’s in a high temporal resolution. During the first two post-fire years, at 1–2 week intervals, surface (2.5 cm depth) SWR and SMC were monitored using the “molarity of an ethanol droplet” (MED) test and a soil probe, respectively. The results showed that the observed annual SWR was very high to extreme (80% of measurements ≥ 6 ethanol class) for all three sites. Wildfire reduced the annual median SWR by one class (extreme to very high) for both post-fire years. During prolonged dry periods the unburnt site was significantly more repellent (P < 0.01) and less spatially variable (P < 0.01) than the recently burnt site, while in the wet periods there was no significant difference. After burning, slope aspect did not have a strong impact on the annual median SWR class. However, the north-west aspect site recorded significantly (p < 0.01) greater annual frequencies of extreme repellency than the south-east aspect site (70–73% vs. 51–55%).
Wildfires have increased in Portugal in the recent decades, raising concerns about the long-term negative effects of fire recurrence on the environment. We studied the impacts of recurrent fires on ...the nitrogen (N) and phosphorus (P) content of mineral soil in the first year after a fire. Total nitrogen (TN) and phosphorus (TP) losses by runoff were also evaluated within the two years after a fire. Nine sites in a maritime pine forest were selected following a large wildfire in September 2012 that affected roughly 3000ha of the Viseu municipality. Three sites had been burnt four times in the past 40years (4×), three sites had been burnt once in September 2012 (1×), and three control sites had not been burnt (0×). Runoff was collected in 9micro-plots (0.25m2) at each site after rain events from September 2012 to September 2014. Soil N and P content were significantly higher in both burnt sites relatively to the control sites. Nitrogen as well as phosphorus losses via runoff were significantly higher at the 4× burnt sites than at both the 1× burnt and unburnt sites. Nutrient loss was particularly high after heavy rains. Vegetation and litter cover played an important role in reducing runoff and the associated N and P transport at the 4× burnt sites, since a decrease in both variables was observed with the increase in vegetation cover after fire.
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•Recurrent fires are expected to induce marked changes on the N and P cycles.•Repeated wildfires strongly increased N and P losses by runoff.•N and P exports were highest after the first post-fire rainfall event.•N and P losses were dependent on litter and vegetation recovery after fire.
Wildfire is a natural phenomenon that is a common ecological factor in Mediterranean ecosystems. The increase in occurrence in recent decades has raised widespread concern about the impact of ...repeated wildfires on runoff and erosion, a topic that has not been widely studied. We addressed these concerns in an area of north-central Portugal by comparing runoff at the micro-plot scale and the associated transport of sediments and organic matter (OM) in unburnt, once burnt, and repeatedly burnt plantations of Maritime Pine. We selected nine sites following a large wildfire in September 2012 that affected roughly 3000ha of the Viseu municipality. Three of the sites had not been burnt since 1975 and acted as controls, with covers of pine trees, shrubs, and annual vegetation; three sites had burnt only in 2012 and contained burnt pines but no shrubs or annual vegetation; and three degraded sites had suffered from three wildfires prior to 2012 and contained no vegetation. We established nine micro-plots (0.25m2) at each site and collected runoff, eroded soil, and OM losses in tanks after each rain from October 2012 to September 2014. The repeated wildfires strongly increased the runoff coefficient and the risk of downstream flooding after heavy rains. OM losses were nearly half the volume of the eroded soil in the degraded sites due to the transport of ash in the runoff. Runoff and soil losses occurred not only after erosive rainstorms following a fire but also after a subsequent period of drought. Soil cover, rain intensity, and soil moisture were key factors in the amount of runoff and erosion. The insights provided by this study can contribute to pre- and post-fire activities and management in protect areas and can thus improve post-fire recovery.
•Runoff and erosion can be seen also after drought phases in later years after fire.•Repeated wildfires strongly increase the risk of spilling over in downstream regions.•OM loss was quite high by repeated fire due to the runoff related ash transport.•Cover and rainfall intensity have the strongest effect on runoff and erosion.
Models can be useful for predicting the hydrological impacts of natural phenomenon such as wildfires and to help implement effective post-fire land management options. In this research, the revised ...Morgan–Morgan–Finney (MMF) model was used to simulate runoff and soil erosion in recently burned maritime pine plantations with contrasting fire regimes, in a wet Mediterranean region of north-central Portugal. The MMF model was adapted for burnt areas by implementing seasonal changes in model parameters in order to accommodate seasonal patterns in runoff and soil erosion, attributed to changes in soil water repellency and vegetation recovery. The model was then evaluated by applying it for a total of 18 experimental micro-plots (0.25 m2) at 9 once burned and 9 four times burned slopes, using both previously published and newly calibrated parameters, with observed data used to evaluate the robustness and wider applicability of each parameterization. The prediction of erosion was more accurate than that of runoff, with an overall Nash-Sutcliffe efficiency of 0.54. Slope angle and the soils' effective hydrological depth (which depends on vegetation and/or crop cover) were found to be the main parameters improving model outcomes, and different parameters were needed to differentiate between the two contrasting fire regimes. This case study showed that most existing benchmark parameters can be used to apply MMF in burned pine forest areas with moderate severity fires to support post-fire management, but indicated that further efforts should focus on mapping soil depth and vegetation cover to improve these assessments.
•MMF model performed accurately for soil erosion predictions (NS > 0.5)•Slope angle and effective hydrological depth plays a main role I results.•MMF was not very accurate for predicting runoff.•Seasonal predictions were less accurate than annual predictions.
Agrarian terraces are surely recognized as a traditional soil and water conservation technique, however the use of these methods in forestry are poorly studied, especially the hydrological impacts of ...bench terracing for forest plantations. The employment of heavy machinery in forests have been described to increase soil bulk density and compaction which might reduce soil water infiltration capacity, and thus, increase runoff generation. However, in the case of terraces, the flattening of the terrain may increase the infiltration and re-infiltration of runoff due to consecutive slope discontinuity. The present study assesses the short to medium-term impacts of bench terrace construction on soil water repellency and soil water infiltration in eucalypt forest plantations. A chrono-sequence approach was used to analyse a time series of sites terraced at different periods with neighbouring mature long-undisturbed sites. Therefore, Methanol droplet test was employed in-situ in four different periods of time-since-terracing (0, 5, 10 and 17 years after terracing). Three pairs of nearby terraced and non-terraced eucalypt plantations were studied for each period, counting a total of 24 study sites. Our results revealed clear differences in SWR between terraced and non-terraced eucalypt plantations, with all non-terraced sites showing extreme SWR values while at the terraced sites highly variable values were found. In addition, the median SWR increase with time elapsed since terrace construction, i.e. from very wettable immediately and 5 years after terracing, and increase to strong and moderate water repellent at 10 and 17 years following terracing. The infiltration variables were observed inversely correlated with SWR following terrace construction and were watched to decrease with time-since-terracing. The litter and the Oh humified layer were found positively correlated to the SWR as well as the stone and bulk density variables, while the percentage of organic matter and the soil moisture content in the soil were poorly correlated.
•Terracing for eucalypt reforestation resulted in an immediate reduction of SWR.•The SWR increase with time elapsed since terrace construction.•At short-term terracing SWR increased with soil depth while at medium-term did not.•Steady state infiltration rate was inversely correlated with SWR after terracing.•Oh layer thickness and amount of litter were positively correlated to SWR.
Soil and water losses due to agricultural mismanagement are high and non-sustainable in many orchards. An experiment was set up with rainfall simulation at 78mmh-1 over 1hour on 20 paired plots of ...2m2 (bare and straw covered) in new persimmon plantations in Eastern Spain. Effects of straw cover on the control of soil and water losses were assessed. An addition of 60% straw cover (75gm-2) resulted in delayed ponding and runoff generation and consequently reduced water losses from 60% to 13% of total rainfall. The straw cover reduced raindrop impact and thus sediment detachment from 1014 to 47g plot-1h-1. The erosion rate was reduced from 5.1 to 0.2Mgha-1h-1. The straw mulch was found to be extremely efficient in reducing soil erosion rates.
In the Baixo Vouga region of north-central Portugal, forests occupy half of the territory, of which two thirds are Eucalypts plantations. The hydrological implications of this large-scale ...introduction of eucalypt are unknown and the aim of this exploratory study, realized in the Caramulo Mountains, was to describe overland flow (OLF), subsurface flow (SSF) and stream flow (Q) in a catchment dominated by Eucalyptus plantations. The main conclusions are that annual OLF rate is low, spatially heterogeneous between 0.1% and 6% and concentrated during the wet season as saturation excess, particularly as return flow. Infiltration-excess OLF due to the strong soil water repellence (SWR) is dominant during dry season, but produces residual runoff amount. SSF is the principal mechanism of runoff formation. It originates from matrix flow and pipe flow at the soil-bedrock interface, principally during the wet season. Matrix flow is correlated with soil moisture (SM) content, with a threshold of 25 %. Pipe flow starts with saturation of soil bottom but without saturation of the entire soil profile, due to a large network of macropores. Stream flow response is highly correlated with matrix flow behaviour in timing and intensity. SWR induces a very patchy moistening of the soil, concentrates the fluxes and accelerates them almost 100 times greater than normal percolation of the water in the matrix.
Pinus pinaster
(maritime pine) is widely planted in the Mediterranean Basin. Maritime pine forests’ carbon stocks are dynamic because of the effect of wildfires and timber activities. Management ...practices offer an opportunity to mitigate climate change via increasing carbon storage in various ecosystems. In this work, we quantified carbon pools in
P. pinaster
forests in relation to fire occurrence and different post-fire salvage logging techniques. For this, we studied an area in northern Portugal where different parts had burned zero, one and four times during the last three decades. Following the last fire in 2012, two salvage logging treatments were carried out: (1) typical logging where all logs and tree biomass were removed and (2) conservation logging where burned tree branches were left in piles and log extraction was restricted to specific extraction trails. We assessed the carbon stocks for the aboveground and belowground compartments, taking into account their different components (vegetation, litter, roots and soil organic carbon). Our main findings were, firstly, that recurrent fires can be catastrophic in terms of carbon sequestration if the overstory dominated by
P. pinaster
does not regenerate after fire (2.4 times less). Secondly, soil organic carbon constituted an important carbon pool, being the most important when pines are eliminated due to recurrent fires with short intervals (90–95 %). Finally, the conservation technique applied here, leaving piles of branches on the soil surface, would be a suitable measure to increase carbon storage, at least in the short term, but might interfere with the recruitment of the pine stand.
Vines are one of the most ancient crops, with great relevance worldwide but especially in wine-growing areas in Southern Europe. In the Bairrada wine region of north-central Portugal, vineyards have ...long been managed intensively, with frequent tillage and application of fertilizers and phytochemical products. During the last decade, however, these conventional practices are increasingly becoming substituted by more sustainable management practices, in particular integrated production (IP) and, to a lesser degree, no-tillage (NT) and biodynamic (BD). This study investigated differences in soil quality of 4 vineyards managed with each of these practices for at least 6 years. Twelve topsoil (0-15 cm) samples were collected in vineyard rows and inter-rows, during one sampling campaign, and analyzed for selected physical and chemical properties. These physical properties were texture, bulk density and penetration resistance, while the chemical properties included pH, electrical conductivity, and the contents of organic matter, nutrients, cations, and metals. Nearby forest soils were also sampled as a reference, since this was the prior land-use in the study sites. The obtained results demonstrated that conventional practices were associated with diminished soil quality, as indicated by lower contents of organic matter and nutrients, such as total nitrogen (TN) and phosphorus (TP), and exchangeable cations, as well as by a higher concentration of Cu and, in some samples, of Ni and Pb. Cu concentrations were also relatively high under NT, so that overall soil quality, particularly associated with fertility, was best under IP.
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