La Fitotoxicitat de l'ozó troposfèric a Catalunya avaluada amb plantes de tabac biosensores

S'ha trohat fitotoxicitat de l'ozó vers el tabac a diverses localitats de Catalunya durant un estudi pilot desenvolupat des del març fins al setembre de 1994. A les zones costaneres l'ozó afecta fins i tot les varietats més resistents, com la Bel-B, cosa que no succeí a cap estació de l'interior. A la costa, a part de les concentracions més elevades del gas, la major humitat augmenta la conductància estomàtica i per tant l'efecte de l'ozó. Els espectres de reflectància de les fulles afectades mostraren valors majors en el vermell i menors en l'infraroig proper, la qual cosa en facilità la teledetecció.En un estudio piloto realizado en varias localidades de Cataluña desde marzo hasta septiembre de 1994, se encontró fototoxicidad del ozono en plantas de tabaco. En las zonas de la costa, el ozono afectó incluso a las variedades más resistentes, como la Bel-B, cosa que no ocurrió en ninguna de las estaciones del interior. En la costa, aparte de las mayores concentraciones de ozono, la humedad más elevada aumentó la conductancia estomática y por lo tanto el efecto del ozono. Los espectros de reflectancia de las hojas afectadas mostraron valores mayores en el rojo y menores en el infrarojo cercano, lo que facilitó la teledetección de los efectos del ozono.O3 phytotoxicity to tobacco was demonstrated in several rural locations in Catalonia during a pilot study from March to September 1994. At coastal locations, O3 injury was found even on O3 resistant cultivar Bel-B such injury did not occur in the interior of Catalonia. In the coast, there are higher concentrations of ozone and higher humidities that rise stomatal conductance, and therefore the ozone effect. Injured leaf reflectance spectra showed higher values in the red and lower values in the near infrared areas, opening interesting possibilities for remote sensing of ozone effects

Managing soil carbon for climate change mitigation and adaptation in Mediterranean cropping systems: A meta-analysis

Mediterranean croplands are seasonally dry agroecosystems with low soil organic carbon (SOC) content and high risk of land degradation and desertification. The increase in SOC is of special interest in these systems, as it can help to build resilience for climate change adaptation while contributing to mitigate global warming through the sequestration of atmospheric carbon (C). We compared SOC change and C sequestration under a number of recommended management practices (RMPs) with neighboring conventional plots under Mediterranean climate (174 data sets from 79 references). The highest response in C sequestration was achieved by those practices applying largest amounts of C inputs (land treatment and organic amendments). Conservation tillage practices (no-tillage and reduced tillage) induced lower effect sizes but significantly promoted C sequestration, whereas no effect and negative net sequestration rates were observed for slurry applications and unfertilized treatments, respectively. Practices combining external organic amendments with cover crops or conservation tillage (combined management practices and organic management) showed very good performance in C sequestration. We studied separately the changes in SOC under organic management, with 80 data sets from 30 references. The results also suggest that the degree of intensification in C input rate is the main driver behind the relative C accumulation in organic treatments. Thus, highest net C sequestration rates were observed in most eco-intensive groups, such as “irrigated”, “horticulture” and controlled experiments (“plot scale”)

Parameterization of the Stomatal Component of the DO3SE Model for Mediterranean Evergreen Broadleaf Species

An ozone (O3) deposition model (DO3SE) is currently used in Europe to define the areas where O3 concentrations lead to absorbed O3 doses that exceed the flux-based critical levels above which phytotoxic effects would be likely recorded. This mapping exercise relies mostly on the accurate estimation of O3 flux through plant stomata. However, the present parameterization of the modulation of stomatal conductance (gs) behavior by different environmental variables needs further adjustment if O3 phytotoxicity is to be assessed accurately at regional or continental scales. A new parameterization of the model is proposed for Holm oak (Quercus ilex), a tree species that has been selected as a surrogate for all Mediterranean evergreen broadleaf species. This parameterization was based on a literature review, and was calibrated and validated using experimentally measured data of gs and several atmospheric and soil parameters recorded at three sites of the Iberian Peninsula experiencing long summer drought, and very cold and dry winter air (El Pardo and Miraflores) or milder conditions (Tietar). A fairly good agreement was found between modeled and measured data (R2 = 0.64) at Tietar. However, a reasonable performance (R2 = 0.47–0.62) of the model was only achieved at the most continental sites when gs and soil moisture deficit relationships were considered. The influence of root depth on gs estimation is discussed and recommendations are made to build up separate parameterizations for continental and marine-influenced Holm oak sites in the future

Carbon isotope composition, macronutrient concentrations, and carboxylating enzymes in relation to the growth of Pinus halepensis Mill. when subject to ozone stress

12 páginas, 4 figuras.We present here the effects of ambient ozone (O3)-induced decline in carbon availability, accelerated foliar senescence, and a decrease in aboveground biomass accumulation in the Aleppo pine (Pinus halepensis Mill.). Aleppo pine seedlings were continuously exposed in open-top chambers for 39 months to three different types of O3 treatments, which are as follows: charcoal-filtered air, nonfiltered air (NFA), and nonfiltered air supplemented with 40 ppb O3 (NFA+). Stable carbon isotope discrimination (Δ) and derived time-integrated ci /ca ratios were reduced after an accumulated ozone exposure over a threshold of 40 ppb (AOT40) value from April to September of around 20,000 ppb·h. An AOT40 of above 67,000 ppb·h induced reductions in ribulose-1, 5-biphosphate carboxylase/oxygenase activity, aboveground C and needle N and K concentrations, the C/N ratio, Ca concentrations in twigs under 3 mm, and the aerial biomass, as well as increases in needle P concentrations and phosphoenolpyruvate carboxylase (PEPC) activity and the N and K concentrations in twigs under 3 mm. Macronutrients losses, the limitations placed on carbon uptake, and increases in catabolic processes may be the causes of carbon gain diminution in leaves which was reflected as a reduction in aboveground biomass at tree level. Stimulation of PEPC activity, the consequent decreased Δ, and compensation processes in nutrient distribution may increase O3 tolerance and might be interpreted as part of Aleppo pine acclimation response to O3 .This research was funded by the EU EV5V-CT93-0263 project. We are also grateful for the partial funding from Spanish Government projects CGL2006-02922/ CLI, CGL2009-07031/CLI, CGL2006-04025/BOS and Consolider Montes (CSD2008-00040) and Catalan Government project SGR 2009-458.Peer reviewe

Nitrogen dynamics in cropping systems under Mediterranean climate: a systemic analysis

International audienceWorldwide, Mediterranean cropping systems face the complex challenge of producing enough high-quality food while preserving the quantity and quality of scarce water for people and agriculture in the context of climate change. While good management of nitrogen (N) is paramount to achieving this objective, the efficient strategies developed for temperate systems are often not adapted to the specificities of Mediterranean systems. In this work we combined original data with a thorough literature review to highlight the most relevant drivers of N dynamics in these semiarid systems. To do so, we provide an analysis at nested scales combining a bottom–up approach from the field scale with a top–down approach considering the agro-food system where cropping systems are inserted. We analyze the structural changes in the agro-food systems affecting total N entering the territory; the contrasting response of yields to N availability under rainfed and irrigated conditions in a precipitation gradient; the interaction between N management and climate change adaptation; the main drivers affecting the release of Nr compounds (NO3-, NH3, NO, N2O) as compared with temperate systems; and finally, the behavior of N once exported to highly regulated river networks. We conclude that a sustainable N management in Mediterranean cropping systems requires the specific adaptation of practices to the particular local agroenvironmental characteristics with special emphasis on water availability for rainfed and irrigated systems. This approach should also include a systemic analysis of N inputs into the territory that are driven by the configuration of the agro-food system

Fertilization strategies for abating N pollution at the scale of a highly vulnerable and diverse semi-arid agricultural region (Murcia, Spain)

Overuse of N fertilizers in crops has induced the disruption of the N cycle, triggering the release of reactive N (Nr) to the environment. Several EU policies have been developed to address this challenge, establishing targets to reduce agricultural Nr losses. Their achievement could be materialized through the introduction of fertilizing innovations such as incorporating fertilizer into soils, using urease inhibitors, or by adjusting N inputs to crop needs that could impact in both yields and environment. The Murcia region (southeastern Spain) was selected as a paradigmatic case study, since overfertilization has induced severe environmental problems in the region in the last decade, to assess the impact of a set of 8 N fertilizing alternatives on crop yields and environmental Nr losses. Some of these practices imply the reduction of N entering in crops. We followed an integrated approach analyzing the evolution of the region in the long-term (1860–2018) and considering nested spatial- (from grid to region) and systems scales (from crops to the full agro-food system). We hypothesized that, even despite reduction of N inputs, suitable solutions for the abatement of Nr can be identified without compromising crop yields. The most effective option to reduce Nr losses was removing synthetic N fertilizers, leading to 75% reductions in N surpluses mainly due to a reduction of 64% of N inputs, but with associated yield penalties (31%–35%). The most feasible alternative was the removal of urea, resulting in 19% reductions of N inputs, 15%–21% declines in N surplus, and negligible yield losses. While these measures are applied at the field scale, their potential to produce a valuable change can only be assessed at regional scale. Because of this, a spatial analysis was performed showing that largest Nr losses occurred in irrigated horticultural crops. The policy implications of the results are discussed