Connolly, J., Sebastià, M.-T., Kirwan, L., Finn, J.A., Llurba, R., Suter, M., Collins, R.P., Porqueddu, C., Helgadóttir, Á., Baadshaug, O.H., Bélanger, G., Black, A., Brophy, C., Čop, J., Dalmannsdóttir, S., Delgado, I., Elgersma, A., Fothergill, M., Frankow-Lindberg, B.E., Ghesquiere, A., Golinski, P., Grieu, P., Gustavsson, A.-M., Höglind, M., Huguenin-Elie, O., Jørgensen, M., Kadziuliene, Z., Lunnan, T., Nykanen-Kurki, P., Ribas, A., Taube, F., Thumm, U., De Vliegher, A., Lüscher, A. (2018) Weed suppression greatly increased by plant diversity in intensively managed grasslands: A continental-scale experiment. Journal of Applied Ecology. 55: 852-862.EnlaceDoi: 10.1111/1365-2664.12991
Diaz-de-Quijano M., Kefauver S., Ogaya R., Vollenweider P., Ribas À., Peñuelas J. (2016) Visible ozone-like injury, defoliation, and mortality in two Pinus uncinata stands in the Catalan Pyrenees (NE Spain). European Journal of Forest Research. 135: 687-696.EnlaceDoi: 10.1007/s10342-016-0964-9
Ozone concentrations in the Pyrenees have exceeded the thresholds for forest protection since 1994. We surveyed the severity of visible O3 injuries, crown defoliation, and tree mortality of Pinus uncinata, the dominant species in subalpine forests in this mountain range, along two altitudinal and O3 gradients in the central Catalan Pyrenees and analysed their relationships with the local environmental conditions. The severity of visible O3 injuries increased with increasing mean annual [O3] when summer water availability was high (summer precipitation/potential evapotranspiration above 0.96), whereas higher [O3] did not produce more visible injuries during drier conditions. Mean crown defoliation and tree mortality ranged between 20.4–66.4 and 0.6–29.6 %, respectively, depending on the site. Both were positively correlated with the accumulated O3 exposure during the last 5 years and with variables associated with soil–water availability, which favours greater O3 uptake by increasing stomatal conductance. The results indicate that O3 contributed to the crown defoliation and tree mortality, although further research is clearly warranted to determine the contributions of the multiple stress factors to crown defoliation and mortality in P. uncinata stands in the Catalan Pyrenees. © 2016, Springer-Verlag Berlin Heidelberg.
Ribas A., Llurba R., Gouriveau F., Altimir N., Connolly J., Sebastia M.T. (2015) Plant identity and evenness affect yield and trace gas exchanges in forage mixtures. Plant and Soil. 391: 93-108.EnlaceDoi: 10.1007/s11104-015-2407-7
Aims: We explore the potential effect of plant diversity on yield and greenhouse gas exchanges in forage mixtures, identifying potential co-benefits between functions. Methods: Using the biodiversity-ecosystem function (BEF) modelling framework (Connolly et al. 2013), we analyse results from a field experiment where the relative sown proportion of three forage species (a grass, a legume, and a non-legume forb) was varied to obtain a gradient in species proportions and evenness. The exchange rates of N2O, CH4, NH3 and CO2 were measured, together with forage yield and soil inorganic N content. We conducted gas measurements 4 years after sward establishment during the expected period of highest emissions. Results: Results support the hypothesis that emission rates are affected by plant diversity. Sown evenness was found to decrease N2O exchange rates, and some evidence was found for a similar negative effect on CH4. Plant composition affected gas exchanges, with legume monocultures showing the highest emission rates for all gases. Diversity also increased yield and modulated NO3− and NH4+ soil concentrations. Conclusions: The integrated analysis of yield and emission response to species diversity allows the identification of a range of species proportions for which both functions are optimized. Diversifying forage legume-based systems could contribute to mitigation while improving ecosystem productivity. © 2015, Springer International Publishing Switzerland.
Kefauver S.C., Penuelas J., Ribas A., Diaz-De-Quijano M., Ustin S. (2014) Using Pinus uncinata to monitor tropospheric ozone in the Pyrenees. Ecological Indicators. 36: 262-271.EnlaceDoi: 10.1016/j.ecolind.2013.07.024
Field metrics were investigated using the conifer species Pinus uncinata for the biomonitoring of tropospheric ozone in the Pyrenees of Catalonia, Spain. The Ozone Injury Index (OII) was investigated piecewise for improvement as a biomonitoring field metric for using sensitive conifer species to monitor tropospheric ozone across variable environmental conditions. The OII employs a weighted average of visual chlorotic mottling (VI), needle whorl retention (RET), needle length (LGT), and crown death (CD). Of note, VI includes subcomponents VI-Amount (% of symptomatic needles) and VI-Severity (% of chlorotic mottling on symptomatic needles) and RET includes the FWHORL subcomponent (average fraction of needles retained per whorl). All components and subcomponents of the OII correlated better to multiple year ozone exposure compared to single year ozone exposure measurements. VI-Severity and FWHORL modeled over half the variability of the three year average of ambient ozone concentrations (P < 0.0001, R2 = 0.53, RMSE = 2.73). Combining the biomonitoring metrics with GIS models related to landscape-scale variability in plant water relations resulted in considerable improvement in the ozone exposure model explanatory power (P < 0.0001, R2 = 0.90, RMSE = 1.35) including the parameters VI-Amount, VI-Severity, elevation, slope and topographic curvature. © 2013 Elsevier Ltd. All rights reserved.
Achotegui-Castells A., Sardans J., Ribas À., Peñuelas J. (2013) Identifying the origin of atmospheric inputs of trace elements in the Prades Mountains (Catalonia) with bryophytes, lichens, and soil monitoring. Environmental Monitoring and Assessment. 185: 615-629.EnlaceDoi: 10.1007/s10661-012-2579-z
The biomonitors Hypnum cupressiforme and Xanthoria parietina were used to assess the deposition of trace elements and their possible origin in the Prades Mountains, a protected Mediterranean forest area of NE Spain with several pollution sources nearby. Al, As, Cd, Co, Cu, Cr, Ni, Pb, Sb, Ti, V, and Zn were determined in 16 locations within this protected area. Soil trace element concentrations were also ascertained to calculate enrichment factors (EF) and use them to distinguish airborne from soilborne trace element inputs. In addition, lichen richness was measured to further assess atmospheric pollution. EF demonstrated to be useful not only for the moss but also for the lichen. Cd, Cr, Cu, Ni, and Zn presented values higher than three in both biomonitors. These trace elements were also the main ones emitted by the potential sources of pollutants. The distance between sampling locations and potential pollution sources was correlated with the concentrations of Cu, Sb, and Zn in the moss and with Cr, Ni, and Sb in the lichen. Lichen richness was negatively correlated with lichen Cu, Pb, and V concentrations on dry weight basis. The study reflected the remarkable influence that the pollution sources have on the presence of trace elements and on lichen species community composition in this natural area. The study highlights the value of combining the use of biomonitors, enrichment factors, and lichen diversity for pollution assessment to reach a better overview of both trace elements' impact and the localization of their sources. © 2012 Springer Science+Business Media B.V.
Asensio D., Yuste J.C., Mattana S., Ribas À., Llusià J., Peñuelas J. (2012) Litter VOCs induce changes in soil microbial biomass C and N and largely increase soil CO 2 efflux. Plant and Soil. 360: 163-174.EnlaceDoi: 10.1007/s11104-012-1220-9
Aims: We investigated the effects of volatile organic compounds (VOCs) emitted by pine litter, specifically terpenes, on soil microbial biomass carbon and nitrogen and heterotrophic soil respiration under different microclimatic scenarios of water availability and temperature. Methods: Soil in glass jars (0.6 L headspace) was exposed to pine needle litter, avoiding any physical contact between soils and litter. Treatments were subjected to two moisture levels, control and drought (20 % and 10 % gravimetric soil water content respectively) and to different temperatures (temperature response curve from 5 °C to 45 °C). Results: In control soils, exposure to litter was associated with a significant decrease in microbial biomass carbon and ninhydrin extractable organic nitrogen, and with a significant increase in heterotrophic respiration (up to 46 %) under optimum temperature (25 °C). Drought, on the other hand, restricted the effects of litter exposure on heterotrophic respiration but exposure to litter was associated with a significant increase in microbial biomass nitrogen. We did not detect significant overall microbial consumption of terpenes in this study. Conclusions: These results suggest either that other VOCs not measured in the study were being consumed and/or that VOCs emissions were triggering strong changes in the composition and functioning of soil microbial communities. More studies under field conditions are needed to assess the magnitude of litter VOCs effects on carbon and nitrogen cycles. © 2012 Springer Science+Business Media B.V.
Díaz-De-Quijano M., Peñuelas J., Ribas A. (2011) Trends of AOT40 at three sites in the Catalan Pyrenees over the last 16 years. Journal of Atmospheric Chemistry. 68: 317-330.EnlaceDoi: 10.1007/s10874-012-9222-9
Ozone mixing ratios were monitored at three stations at different altitudes along the Catalan Pyrenees from 1994 to 2009. The AOT40 greatly exceeded the critical level for the protection of forest and semi-natural vegetation set by the UNECE's CLRTAP and the target value and long-term objective for the protection of vegetation set by the European Directive 2008/50/EC. The AOT40 showed an overall increasing trend over time with a slight decrease during the last 3 years, although longer-term records of ozone levels are required before affirming with certainty a declining or stabilising trend. These results indicate that plant life in the Pyrenean region can be at risk of ozone damage due to the high ozone mixing ratios detected. Nevertheless, more effort is warranted to determine the uptake of ozone by vegetation in this mountainous range. An ozone flux-based index that takes into account the local environmental conditions, plant phenology, and nocturnal uptake of ozone would provide a more accurate assessment of the risk from ozone for the particular vegetation in each area. © Springer Science+Business Media B.V. 2012.
Díaz-de-Quijano M., Peñuelas J., Ribas A. (2009) Increasing interannual and altitudinal ozone mixing ratios in the Catalan Pyrenees. Atmospheric Environment. 43: 6049-6057.EnlaceDoi: 10.1016/j.atmosenv.2009.08.035
Interannual, seasonal, daily and altitudinal patterns of tropospheric ozone mixing ratios, as well as ozone phytotoxicity and the relationship with NOx precursors and meteorological variables were monitored in the Central Catalan Pyrenees (Meranges valley and Forest of Guils) over a period of 5 years (2004-2008). Biweekly measurements using Radiello passive samplers were taken along two altitudinal transects comprised of thirteen stations ranging from 1040 to 2300 m a.s.l. Visual symptoms of ozone damage in Bel-W3 tobacco cultivars were evaluated biweekly for the first three years (2004-2006). High ozone mixing ratios, always above forest and vegetation protection AOT40 thresholds, were monitored every year. In the last 14 years, the AOT40 (Apr-Sept.) has increased significantly by 1047 μg m-3 h per year. Annual means of ozone mixing ratios ranged between 38 and 67 ppbv (38 and 74 ppbv during the warm period) at the highest site (2300 m) and increased at a rate of 5.1 ppbv year-1. The ozone mixing ratios were also on average 35-38% greater during the warm period and had a characteristic daily pattern with minimum values in the early morning, a rise during the morning and a decline overnight, that was less marked the higher the altitude. Whereas ozone mixing ratios increased significantly with altitude from 35 ppbv at 1040 m-56 ppbv at 2300 m (on average for 2004-2007 period), NO2 mixing ratios decreased with altitude from 5.5 ppbv at 1040 m-1 ppbv at 2300 m. The analysis of meteorological variables and NOx values suggests that the ozone mainly originated from urban areas and was transported to high-mountain sites, remaining aloft in absence of NO. Ozone damage rates increased with altitude in response to increasing O3 mixing ratios and a possible increase in O3 uptake due to more favorable microclimatic conditions found at higher altitude, which confirms Bel-W3 as a suitable biomonitor for ozone concentrations during summer time. Compared to the valley-bottom site the annual means of ozone mixing ratios are 37% larger in the higher sites. Thus the AOT40 for the forest and vegetation protection threshold is greatly exceeded at higher sites. This could have substantial effects on plant life at high altitudes in the Pyrenees. © 2009 Elsevier Ltd. All rights reserved.
Klumpp A., Ansel W., Klumpp G., Breuer J., Vergne P., Sanz M.J., Rasmussen S., Ro-Poulsen H., Ribas Artola A., Peñuelas J., He S., Garrec J.P., Calatayud V. (2009) Airborne trace element pollution in 11 European cities assessed by exposure of standardised ryegrass cultures. Atmospheric Environment. 43: 329-339.EnlaceDoi: 10.1016/j.atmosenv.2008.09.040
Within a European biomonitoring programme, Italian ryegrass (Lolium multiflorum Lam.) was employed as accumulative bioindicator of airborne trace elements (As, Cd, Cr, Cu, Fe, Ni, Pb, Sb, V, Zn) in urban agglomerations. Applying a highly standardised method, grass cultures were exposed for consecutive periods of four weeks each to ambient air at up to 100 sites in 11 cities during 2000-2002. Results of the 2001 exposure experiments revealed a clear differentiation of trace element pollution within and among local monitoring networks. Pollution was influenced particularly by traffic emissions. Especially Sb, Pb, Cr, Fe, and Cu exhibited a very uneven distribution within the municipal areas with strong accumulation in plants from traffic-exposed sites in the city centres and close to major roads, and moderate to low levels in plants exposed at suburban or rural sites. Accumulation of Ni and V was influenced by other emission sources. The biomonitoring sites located in Spanish city centres featured a much higher pollution load by trace elements than those in other cities of the network, confirming previously reported findings obtained by chemical analyses of dust deposition and aerosols. At some heavily-trafficked sites, legal thresholds for Cu, Pb, and V contents in foodstuff and animal feed were reached or even surpassed. The study confirmed that the standardised grass exposure is a useful and reliable tool to monitor and to assess environmental levels of potentially toxic compounds of particulate matter. © 2008 Elsevier Ltd. All rights reserved.
Klumpp A., Ansel W., Klumpp G., Calatayud V., Garrec J.P., He S., Peñuelas J., Ribas À., Ro-Poulsen H., Rasmussen S., Sanz M.J., Vergne P. (2006) Tradescantia micronucleus test indicates genotoxic potential of traffic emissions in European cities. Environmental Pollution. 139: 515-522.EnlaceDoi: 10.1016/j.envpol.2005.05.021
Urban atmospheres contain complex mixtures of air pollutants including mutagenic and carcinogenic substances such as benzene, diesel soot, heavy metals and polycyclic aromatic hydrocarbons. In the frame of a European network for the assessment of air quality by the use of bioindicator plants, the Tradescantia micronucleus (Trad-MCN) test was applied to examine the genotoxicity of urban air pollution. Cuttings of Tradescantia clone #4430 were exposed to ambient air at 65 monitoring sites in 10 conurbations employing a standardised methodology. The tests revealed an elevated genotoxic potential mainly at those urban sites which were exposed to severe car traffic emissions. This bioassay proved to be a suitable tool to detect local 'hot spots' of mutagenic air pollution in urban areas. For its use in routine monitoring programmes, however, further standardisation of cultivation and exposure techniques is recommended in order to reduce the variability of results due to varying environmental conditions. © 2005 Elsevier Ltd. All rights reserved.
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