•Surfactant coating (SC) increases root zone water reserves.•SC technology may provide a direct solution to addressing water scarcity issues.•Surfactants can decrease the soil water repellency.•Soil ...cover and rainfall intensity have the strong effect on runoff and erosion.
Wildfires can increase soil erosion due to the destruction of the vegetation and changes in soil organic matter (SOM) quantity and quality. This fact is especially dramatic in the case of ...Mediterranean ecosystems. Therefore, the major goal of the present study was to achieve a better understanding of the short-term effects of wildfires on the quantity and quality of organic matter (OM) in the topsoil of burnt Mediterranean eucalyptus plantations in north-central Portugal.
Wildfire had a large impact on slope-scale sediment losses, as they were approximately 30 times higher at the burnt site than at the unburnt site over the first 25months after the fire. The pH and total nitrogen (TN) content of the burnt topsoil showed a noticeable increase immediately after the wildfire, whereas the total organic carbon (TOC) content revealed the opposite behavior. However, the TOC content showed a partial recovery during the subsequent two years after the fire. The sediments eroded after the fire were consistently more acidic and richer in TOC and TN than the burnt topsoil; they also revealed less pronounced changes with time-since-fire compared with the burnt topsoil.
Analytical pyrolysis analyses indicated that the fire resulted in an enrichment of aromatic compounds, nitrogen (N) constituents, lignin-derived compounds and polysaccharides. The latter is best explained with the input of partially charred OM, ash and decaying parts of plants killed by the fire. The thermal transformation of SOM caused the thermal breakdown and cracking of n-alkane compounds, as was revealed by the increase of the ratio of short-to-long chains and the alteration of the typical odd-over-even carbon predominance indexes. The relative abundance of specific biomarkers for vegetation and, in particular for Eucalyptus globulus, such as terpenoids eucalyptol and globulol decreased drastically or even disappeared from the pyrolysates of the burnt topsoil. These fire-induced changes in the quality of topsoil OM persisted during the whole post-fire period of 25months. In general, the Py–GC/MS results pointed out that during the first two years after the fire the recovery of the topsoil OM quality was practically negligible.
•Post-fire eroded sediments and topsoil organic matter were characterized, both quantitatively and qualitatively.•Slope-scale sediment losses at the burnt site had a pronounced impact than at unburnt site.•Analytical pyrolysis indicates that fire produced noticeable changes in SOM composition.•Py–GC/MS results suggested that the recovery of the topsoil SOM quality was slow during the two years.
•Wildfire runoffs induce physic-chemical changes in downhill river waters.•In-situ exposure to affected water inhibits the feeding rates of several species.•Wildfire effects are better discriminated ...by in-situ than laboratory bioassays.•Metals incoming with the runoff should play a role in noticed ecotoxic effects.
Among the various environmental disturbances caused by wildfires, their impacts within burnt areas and on the downhill aquatic ecosystems has been receiving increased attention. Post-fire rainfalls and subsequent runoffs play an important role in transporting ash and soil to aquatic systems within the burnt areas. These runoffs can be a diffuse source of toxic substances such as metals. The present work aims at assessing the effects of ash-loaded runoff on feeding rates of three representative aquatic invertebrates (Daphnia magna, Corbicula fluminea and Atyaephyra desmarestii) and the mosquitofish, Gambusia holbrooki, through post-exposure feeding inhibition bioassays carried out in-situ and in the laboratory using water collected from the experimental field sites. Four sites were selected in a partially burnt basin for bioassay deployment and sample collection: one site upstream of the burnt area (RUS); three sites receiving runoff directly from the burnt area, one immediately downstream of the burnt area (RDS) and two in permanent tributary streams within the burnt area (BS1 and BS2). The in-situ exposure lasted four days and began following the first post-fire major rain events. At sites affected by the wildfire, post-exposure feeding rates for D. magna, A. desmarestii and G. holbrooki were lower, which is consistent with the highest levels of metals found at these sites compared to the unaffected site, although the individual concentrations of each metal were generally below corresponding ecological safety benchmarks. Thus, interactions between metals and/or between metals and other environmental parameters certainly played a role in modulating the ecotoxic effects of the runoffs; this was further supported by a Toxic Units Summation exercise. Even if direct causal links between the ecotoxicological effects observed in D. magna, A. desmarestii and G. holbrooki and the physicochemical parameters of the water samples could not be established, the results suggest an important role of major and trace elements in explaining post-exposure feeding rate variation.
•The impacts of wildfires on the freshwater clam Corbicula fluminea were assessed.•Aqueous extracts of ash (AEA) were used to represent ash-loaded post-fire runoff.•The bio-concentration ability of ...the clam was assessed in a filtration experiment.•Post-fire loads (rich in metals and PAHs) can compromise clams survival.
Wildfires, increasingly frequent and severe in the Mediterranean countries, can cause serious impacts on ecosystems. As a diffuse source of contaminants – namely inorganic elements (metals, metalloids and non-metallic elements) and polycyclic aromatic hydrocarbons (PAHs) – post-fire runoff may cause toxic effects on the aquatic biota. Despite the recognition of these likely impacts, this issue has been still largely neglected. This study explores the impacts of ash from wildfires on the freshwater clam Corbicula fluminea and the ability of this filter feeder to concentrate the contaminants associated with ash in post-fire runoff. The bio-concentration potential of the clam was assessed in a 7-day filtration experiment, using aqueous extract of ashes (AEA) to represent post-fire runoff. Despite the noticeable mortality of the clams exposed to the AEA (∼30% higher in AEA than in control after 7 days of exposure), there was a clear reduction on the concentration of almost all pyrolytic substances in the water linked to bio-filtration and bio-concentration activity. Along 7 days the clams operated decreases of more than 70% for some chemicals (Cu, Mn and Zn) while others were no longer detected in the water at the end of the experiment (Cr, NAP and PHE). The removal from water was accompanied by contaminants’ accumulation in clams’ soft tissues and, less extensively, in shells. Lower pollutant loads of filtered AEA translated into decreased toxicity of the matrix towards standard aquatic species (microalgae, macrophytes and cladocerans) confirming an improvement as well in the biological quality of the water through bio-filtration. Although post-fire loads can compromise C. fluminea survival, this study evidenced the potential of this invasive species to contribute to water quality improvement.
This work relied on the use microcosms to evaluate the individual and the combined effects of different levels of copper sulfate (0.0, 0.013, 0.064 and 0.318mg Cu L−1) – a fungicide commonly ...exceeding allowable thresholds in agricultural areas – and a range of water temperature increase scenarios (15, 20 and 25°C) on freshwater species belonging to different functional groups. Hence, the growth inhibition of primary producers (the microalgae Raphidocelis subcapitata and the macrophyte Lemna minor), as well as the survival and feeding behavior of a shredder species (the Trichoptera Schizopelex sp.) were evaluated. The results revealed that copper was toxic to primary producers growth, as well as shredders growth and survival, being the growth of L. minor particularly affected. Higher water temperatures had generally enhanced the growth of primary producers under non-contaminated (microalgae and macrophytes) or low-contaminated (macrophytes) conditions. Despite the tendency for a more pronounced toxicity of copper under increasing water temperatures, a significant interaction between the two factors was only observed for microalgae. Since the test organisms represent relevant functional groups for sustaining freshwater systems functions, the present results may raise some concerns on the impacts caused by possible future climate change scenarios in aquatic habitats chronically exposed to the frequent or intensive use of the fungicide copper sulfate.
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•Copper impaired different biological responses of primary producers and shredders.•Schizopelex sp. feeding activity was enhanced by copper contamination.•Tendency for inhibitory effects under higher copper levels and water temperatures.
Mediterranean forests are highly susceptible to wildfires, which can cause several impacts not only within burnt areas but also on downstream aquatic ecosystems. The ashes’ washout from burnt areas ...by surface runoff can be a diffuse source of toxic substances, such as metals, when reaching the nearby aquatic systems, and can be noxious to aquatic organisms. The present work aimed at assessing the ecotoxicological effects of post-fire contamination on two aquatic producers (the microalgae Raphidocelis subcapitata and the macrophyte Lemna minor) through in-situ bioassays, validating the obtained results with the outcomes of laboratory bioassays with surface water collected simultaneously. Four distinct sites were selected in a basin partially burnt (Ceira river basin; Coimbra district, Portugal) for bioassay deployment: one site upstream the burnt area in the Ceira river (RUS); three sites located under the influence of the burnt area, one immediately downstream of the burnt area in the Ceira river (RDS) and the other two in tributary streams within the burnt area (BS1 and BS2). The in-situ bioassays lasted for 13 days and began following the first post-fire major rain events. Results showed that the microalgae growth rate was able to distinguish the three sites within and downstream of the burnt area (BS1, BS2, RDS) from the site upstream (RUS). By contrast, the macrophytes growth rate only allowed to differentiate between the sites within the burnt area (BS1 and BS2) and those up- and downstream of the burnt area (RUS and RDS). The in-situ results for both species were corroborated with the results of the laboratory experiments, supporting the use of laboratory surrogates for a screening assessment of wildfire impacts in aquatic ecosystems. Direct causal relationships between the observed ecotoxicological effects on R. subcapitata and L. minor and the physical-chemical parameters of the water samples were difficult to establish, although the results suggest (i) a role of differential major and trace metal load in explaining species growth variation; (ii) interaction between metals and/or between metals and other field parameters are likely to modulate the biological responses to the challenges deriving from wildfire runoff.
•The input of toxic compounds, as metals, in post-fire scenarios, can be harmful for freshwater primary producers.•The use of in-situ assays with freshwater producers allowed establishing broad causal relationships.•More research is needed to better understand the impacts of post-fire contamination in the freshwater ecosystem functioning.
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.
Soil water repellency can impact soil hydrology, overland flow generation and associated soil losses. However, current hydrological models do not take it into account, which creates a challenge in ...repellency‐prone regions. This work focused on the adaptation for soil water repellency of a daily water balance model. Repellency is estimated from soil moisture content using site‐specific empirical relations and used to limit maximum soil moisture. This model was developed and tested using approximately 2 years of data from one long‐unburned and two recently burned eucalypt plantations in northern Portugal, all of which showed strong seasonal soil water repellency cycles. Results indicated important improvements for the burned plantations, with the Nash–Sutcliffe efficiency increasing from −0.55 and −0.49 to 0.55 and 0.65. For the unburned site, model performance was already good without the modification and efficiency only improved slightly from 0.71 to 0.74, mostly due to the better simulation of delayed soil wetting after dry periods. Results suggested that even a simple approach to simulate soil water repellency can markedly improve the performance of hydrological models in eucalypt forests, especially after fire.
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