424 research outputs found
Effectiveness of hydromulching to reduce runoff and erosion in a recently burnt pine plantation in central Portugal
Forest fires can greatly increase runoff and surface erosion rates. Postâfire soil erosion control measures are intended to minimize this response and facilitate ecosystem recovery. In a few recent cases, hydromulch has been applied, and this consists of a mixture of organic fibers, water and seeds. The objectives of this research were to (i) analyze the effectiveness of hydromulch in reducing postâfire runoff and sediment production and (ii) determine the underlying processes and mechanisms that control postâfire runoff and erosion. After a wildfire occurred in August 2008, 14 plots ranging in size from 0·25 to 10âm2 were installed on a 25 degree slope in a burnt pine plantation that had also been subjected to salvage logging. Half of the plots were randomly selected and treated with hydromulch. One of two slope strips adjacent to the plots was also hydromulched and used for monitoring some soil properties. Measurements made in each of the first 3âyears following the wildfire included (i) the plotâscale runoff volumes and sediment yields; (ii) soil shear strength, soil moisture, and soil water repellency; and (iii) surface cover. The hydromulch reduced overland flow volume by 70% and soil erosion by 83%. The decrease in runoff was attributed to the increase in soil water retention capacity and the decrease in soil water repellency, whereas the reduction in soil erosion was initially attributed to the protective cover provided by the hydromulch and lately to an enhanced vegetative regrowth in the third year after burning.publishe
Potential Impact of Climate Change on Suspended Sediment Yield in NW Spain: A Case Study on the Corbeira Catchment
[Abstract] Soil losses and the subsequent sediment delivery constitute significant environmental threats. Climate change is likely to have an impact on the availability of water and therefore on sediment yield in catchments. In this context, quantifying the sediment response to an increased atmospheric CO2 concentration and climate change is of utmost importance to the proper management of rural catchments. However, quantitative assessment of climate change impact remains a complex task. In this study, the potential medium (2031â2060) and long-term (2069â2098) impacts of projected changes of temperature, rainfall and CO2 concentration on sediment yield in a small rural catchment located in NW Spain were evaluated using the Soil and Water Assessment Tool (SWAT) model. Climate change scenarios were created using future climate data projected by regional climate models from the ENSEMBLES project and two CO2 concentration scenarios (550 and 660 ppm). The results showed that climate change would have a noticeable impact on suspended sediment if the forecast temperature, rainfall and CO2 concentration changes included in this study were met. Overall, suspended sediment is expected to decrease (2031â2060: â11%, 2069â2098: â8%) compared to the baseline period (1981â2010), mainly due to decreased streamflow. However, an increase in sediment transport in winter is predicted, possibly associated with increased erosion in cultivated areas (11%â17%), suggesting that, at this time of the year, the effect of soil detachment prevails over sediment transport capacity. Consequently, management practices aimed at reducing soil erosion in cultivated areas should be carried out, because these are the main source of sediment in the study area.Galicia. ConsellerĂa de EconomĂa e Industria; 10MDS103031Ministerio de EconomĂa y Competitividad; CGL2014-56907-
Wildfire impacts on freshwater detrital food webs depend on runoff load, exposure time and burnt forest type
In the last decades, land-use changes have made Mediterranean forests highly susceptible to wildfires, which can cause several impacts not only on burnt areas, but also on adjacent aquatic ecosystems. Post-fire runoff from burnt areas may transport toxic substances to streams by surface runoff, including polycyclic aromatic hydrocarbons (PAHs) and metals, which can be noxious to aquatic organisms. Impacts on aquatic ecosystems can be related to fire severity, forest type and the exposure period; however, these factors have not been investigated in tandem. Here, we used the stream detrital system to determine the impacts of post-fire runoffs and stream water from a burnt catchment on trophic interactions between stream microbial communities and invertebrate shredders involved in leaf litter decomposition. Three distinct types of samples were collected from a burnt catchment: post-fire runoffs from high severity wildfires in Pinus and Eucalyptus forests, and stream water. Microbial decomposer communities (fungi and bacteria) and the invertebrate shredder Allogamus ligonifer were exposed for 10 and 20âŻdays to increasing concentrations (0, 50, 75 and 100%) of runoff extracts. Our results showed that post-fire runoffs from high severity wildfires reduced microbially-driven leaf litter decomposition (up to 79%), invertebrate feeding (up to 75%), fungal biomass (up to 39%) and altered community composition; effects were more severe at the longer exposure time. The impacts varied with the runoff source and were related to the chemical composition in metals and total PAHs. This study emphasizes the importance of assessing the indirect effects of wildfires taking into account the effects of the runoff source, load and exposure time on freshwater biota and their ecological functions. Therefore, best forest management practices should be applied to minimize post-fire runoffs reaching aquatic ecosystems and to reduce the effects of these extreme events on freshwater biodiversity and ecosystem functioning.This work was supported by the strategic programmes UID/BIA/04050/2019 (POCI-01-0145-FEDER-007569), UID/AMB/50017 (POCI-01â0145-FEDER-007638) and (UID/AMB/50017/2019), funded by national funds through the Portuguese Foundation For Science and Technology (FCT) I.P. and by the ERDF through the COMPETE2020 - Programa Operacional Competitividade e Internacionalização (POCI). FEDER-POFC-POCI-COMPETE and FCT supported this work (PIDDAC - PEst-OE/BIA/UI4050/2014, PTDC/AAG-GLO/4176/2012, POCI-01-0145-FEDER-028936, SFRH/BD/119957/2016 and PTDC/CTA-AMB/28936/2017)
Modelling the Contribution of Land Use to Nitrate Yield from a Rural Catchment
The nutrient flow dynamics in rural landscapes are among the basic characteristics of landscape functioning. In this study, the ecohydrological model SWAT (Soil and Water Assessment Tool) was applied in a small rural catchment in northwest (NW) Spain to evaluate the contribution of land use on nitrate losses and to assess the relative importance of different pathways by which nitrate is delivered to the drainage network. The model was first calibrated and validated at a monthly time step. The SWAT model performance was satisfactory (R2 > 0.5; Nash-Sutcliffe efficiency (NSE) > 0.5 and percent bias (PBIAS) < 10%) during both the calibration and validation periods, indicating that SWAT predicted the nitrate discharge accurately. Using the calibrated SWAT model, this study showed that agricultural lands, even though they represent only 30% of the catchment, were main contributor to the nitrate losses accounting for about 77% of the total nitrate yield. The model results also indicated that, irrespective of the land use, groundwater flow is the main pathway for nitrate losses (63%); therefore, appropriate management practices aimed at decreasing nitrate leaching will be key factors in reducing nitrate yield in the study catchment
Water resources response to changes in temperature, rainfall and CO2 concentration: a first approach in NW Spain
Assessment of the diverse responses of water resources to climate change and
high concentrations of CO2 is crucial for the appropriate management of natural
ecosystems. Despite numerous studies on the impact of climate change on different
regions, it is still necessary to evaluate the impact of these changes at the local scale. In this
study, the Soil and Water Assessment Tool (SWAT) model was used to evaluate the
potential impact of changes in temperature, rainfall and CO2 concentration on water
resources in a rural catchment in NW Spain for the periods 2031â2060 and 2069â2098,
using 1981â2010 as a reference period. For the simulations we used compiled regional
climate models of the ENSEMBLES project for future climate input data and two CO2
concentration scenarios (550 and 660 ppm). The results showed that changes in the
concentration of CO2 and climate had a significant effect on water resources. Overall, the
results suggest a decrease in streamflow of 16% for the period 2031â2060 (intermediate
future) and 35% by the end of the 21st century as a consequence of decreasing rainfall
(2031â2060: â6%; 2069â2098: â15%) and increasing temperature (2031â2060: 1.1 °C;
2069â2098: 2.2 °C)
Impacts of climate and land use changes on the hydrological and erosive response of a humid and dry Mediterranean catchment
The impacts of climate and land use changes on streamflow and sediment export were evaluated for a humid (SĂŁo
Lourenço) and a dry (Guadalupe) Mediterranean catchment, using the Soil and Water Assessment Tool (SWAT)
model. SWAT was able to produce viable streamflow and sediment export simulations for both catchments, which
provided a baseline for investigating climate and land use changes under the A1B and B1 emission scenarios
for the period between 2071 and 2100. Compared to the baseline period (1971-2000), climate change scenarios
forecasted a decrease in annual precipitation in both catchments (humid, both scenarios: -12%; dry, both scenarios:
-8%), but with strong increases during winter. Land use changes followed a socio-economic storyline in which
traditional agriculture was replaced by more profitable land uses, i.e. corn and commercial forestry at the humid
site and sunflower at the dry site. Climate changes led to a decrease of streamflow in both catchments (humid, both
scenarios: -13%; dry, A1B: -14%; B1: -18%), mostly as a consequence of the projected decrease in rainfall. Land
use changes led to small increases in flow discharge, but a higher increase was observed for the dry site under
scenario A1B (humid, A1B: +0.3%; B1: +1%; dry, A1B: +6%; B1: +0.3%). The combination of climate and land
use scenarios was mostly dominated by the climatic response, since a decrease in streamflow was observed for
both catchments (humid, A1B: -13%; B1: -12%; dry, A1B: -8%; B1: -18%). Regarding the erosive response, clear
differences were observed between catchments mostly due to differences in both the present-day and forecasted
vegetation types. Climate scenarios led to a decrease in sediment export at the humid catchment (A1B: -11%;
B1: -9%) and to an increase at the dry catchment (A1B: +24%; B1: +22%) in the first case due to the predominant
vegetation type (vineyards and maritime pine) providing year-round cover, while in the second, due to annual crops
(wheat and pasture) exposing soils during winter. For land use scenarios, the same contrast occurred between
catchments (humid, A1B: -18%; B1: -10%; dry, A1B: +257%; B1: +9%) due to the expansion of permanent
cover vegetation in one case and annual crops in the other. Climate and land use changes had off-setting effects on
sediment export at the humid catchment (A1B: -29%; B1: -22%), as a result of reduced precipitation and cultivation
of more soil-protective crops. A different response was observed for the dry catchment (A1B: +222%; B1: +5%),
as the increase in sediment export associated with the cultivation of highly erosion-prone crops was not aggravated
by the higher rainfall amounts forecasted for winter months. The results of the present study highlight that indirect
impacts of climate change, like land use changes, might be similar or more severe than direct impacts
ScenaLand: a simple methodology for developing land use and management scenarios
Scenarios serve science by testing the sensitivity of a system and/or society to adapt to the
future. In this study, we present a new land use scenario methodology called ScenaLand.
This methodology aims to develop plausible and contrasting land use and management
(LUM) scenarios, useful to explore how LUM (e.g. soil and water conservation techniques)
may afect ecosystem services under global change in a wide range of environments. ScenaLand is a method for constructing narrative and spatially explicit land use scenarios that
are useful for end-users and impact modellers. This method is innovative because it merges
literature and expert knowledge, and its low data requirement makes it easy to be implemented in the context of inter-site comparison, including global change projections. ScenaLand was developed and tested on six diferent Mediterranean agroecological and socioeconomic contexts during the MASCC research project (Mediterranean agricultural soil
conservation under global change). The method frst highlights the socioeconomic trends
of each study site including emerging trends such as new government laws, LUM techniques through a qualitative survey addressed to local experts. Then, the method includes
a ranking of driving factors, a matrix about land use evolution, and soil and water conservation techniques. ScenaLand also includes a framework to develop narratives along with
two priority axes (contextualized to environmental protection vs. land productivity in this
study). In the context of this research project, four contrasting scenarios are proposed: S1
(business-as-usual), S2 (market-oriented), S3 (environmental protection), and S4 (sustainable). Land use maps are then built with the creation of LUM allocation rules based on
agroecological zoning. ScenaLand resulted in a robust and easy method to apply with the
creation of 24 contrasted scenarios. These scenarios come not only with narratives but also
with spatially explicit maps that are potentially used by impact modellers and other endusers. The last part of our study discusses the way the method can be implemented including a comparison between sites and the possibilities to implement ScenaLand in other
contexts.info:eu-repo/semantics/publishedVersio
Reductions in soil surface albedo as a function of biochar application rate: implications for global radiative forcing
Biochar can be defined as pyrolysed (charred) biomass produced for application to soils with the aim of mitigating global climate change while improving soil functions. Sustainable biochar application to soils has been estimated to reduce global greenhouse gas emissions by 71â130 Pg CO2-Ce over 100 years, indicating an important potential to mitigate climate change. However, these estimates ignored changes in soil surface reflection by the application of dark-coloured biochar. Through a laboratory experiment we show a strong tendency for soil surface albedo to decrease as a power decay function with increasing biochar application rate, depending on soil moisture content, biochar application method and land use. Surface application of biochar resulted in strong reductions in soil surface albedo even at relatively low application rates. As a first assessment of the implications for climate change mitigation of these biocharâalbedo relationships, we applied a first order global energy balance model to compare negative radiative forcings (from avoided CO2 emissions) with positive radiative forcings (from reduced soil surface albedos). For a global-scale biochar application equivalent to 120 t haâ1, we obtained reductions in negative radiative forcings of 5 and 11% for croplands and 11 and 23% for grasslands, when incorporating biochar into the topsoil or applying it to the soil surface, respectively. For a lower global biochar application rate (equivalent to 10 t haâ1), these reductions amounted to 13 and 44% for croplands and 28 and 94% for grasslands. Thus, our findings revealed the importance of including changes in soil surface albedo in studies assessing the net climate change mitigation potential of biochar, and we discuss the urgent need for field studies and more detailed spatiotemporal modelling.We thank L Montanarella (Joint Research Centre) for making this study possible, W Mehl for help with the spectroscopy work and P Drahota for the mineralogy analyses. We thank the Portuguese Fundação para a CiĂȘncia e a Tecnologia (FCT) for providing F G A Verheijen with a postdoctoral grant (SFRH/BPD/74108/2010), and further want to acknowledge the financial support of the Czech Science Foundation (under grant No. GA 526/09/1762), and the Marie Curie CIG grant (No. GA 526/09/1762). We thank two anonymous reviewers for strengthening the letter.publishe
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Helping stakeholders select and apply appraisal tools to mitigate soil threats: researchersâ experiences from across Europe
Soil improvement measures need to be ecologically credible, socially acceptable and economically affordable if they are to enter widespread use. However, in real world decision contexts not all measures can sufficiently meet these criteria. As such, developing, selecting and using appropriate tools to support more systematic appraisal of soil improvement measures in different decision-making contexts represents an important challenge. Tools differ in their aims, ranging from those focused on appraising issues of cost-effectiveness, wider ecosystem services impacts and adoption barriers/opportunities, to those seeking to foster participatory engagement and social learning. Despite the growing complexity of the decision-support tool landscape, comprehensive guidance for selecting tools that are best suited to appraise soil improvement measures, as well as those well-adapted to enable participatory deployment, has generally been lacking. We address this gap using the experience and survey data from an EU-funded project (RECARE: Preventing and REmediating degradation of soils in Europe through land CARE). RECARE applied different socio-cultural, biophysical and monetary appraisal tools to assess the costs, benefits and adoption of soil improvement measures across Europe. We focused on these appraisal tools and evaluated their performance against three broad attributes that gauge their differences and suitability for widespread deployment to aid stakeholder decision making in soil management. Data were collected using an online questionnaire administered to RECARE researchers. Although some tools worked better than others across case studies, the information collated was used to provide guiding strategies for choosing appropriate tools, considering resources and data availability, characterisation of uncertainty, and the purpose for which a specific soil improvement measure is being developed or promoted. This paper provides insights to others working in practical soil improvement contexts as to why getting the tools right matters. It demonstrates how use of the right tools can add value to decision-making in ameliorating soil threats, supporting the sustainable management of the services that our soil ecosystems provide
Measurement of the ratios of branching fractions and
The ratios of branching fractions
and are measured, assuming isospin symmetry, using a
sample of proton-proton collision data corresponding to 3.0 fb of
integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The
tau lepton is identified in the decay mode
. The measured values are
and
, where the first uncertainty is
statistical and the second is systematic. The correlation between these
measurements is . Results are consistent with the current average
of these quantities and are at a combined 1.9 standard deviations from the
predictions based on lepton flavor universality in the Standard Model.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-039.html (LHCb
public pages
- âŠ