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Worldwide, 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 combine original data with a thorough literature review to highlight the most relevant drivers of N dynamics in these semi-arid 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 (nitrate, ammonia, nitric oxide and nitrous oxide) compared with temperate systems and finally, the behavior of N once exported to highly regulated river networks. We conclude that sustainable N management in Mediterranean cropping systems requires the specific adaptation of practices to particular local agro-environmental characteristics with special emphasis on water availability for rainfed and irrigated systems. This approach should also include a systemic analysis of N input into the territory that is driven by the configuration of the agro-food system.

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.

Nitrogen emissions have grown in Spain during the last 15 years. As precipitation scavenges gases and aerosols from the atmosphere, an effect on rainwater concentrations can be expected. However, time-series studies on wet N concentrations in the Iberian Peninsula are very scarce. This paper aims to fill this gap by analysing weekly rainfall N concentrations at a set of rural sites in Catalonia (NE Spain) from 1995/1996 to 2007 and a forest site monitored from 1983 to 2007. The sites encompass a range of rural environments and climate conditions, from the inland pre-Pyrenees (Sort) to the Mediterranean coast (Begur) and from north (Sort and Begur) to central (Palautordera and La Castanya) and south Catalonia (La Senia). We found a 1-year cycle for concentrations of NH ₄ ⁺ and NO ₃ ⁻ whereby higher values were reached at the end of spring-early summer, except at the easternmost coastal site of Begur. Weekly NH ₄ ⁺ concentrations decreased with time at all sites (except at La Senia) whilst NO ₃ ⁻ concentrations increased at all sites during the same period. Rainfall SO ₄ ²⁻ concentrations decreased with time at all sites. The opposite trends in NO ₃ ⁻ and SO ₄ ²⁻ concentrations determined a shift in the relative acid contribution of those anions during the 12-13-year period. To interpret the increasing trend, mean annual NO ₃ ⁻ concentrations were regressed against NO₂ Spanish emissions and to some indicators of local anthropogenic activity. The increase at Sort and Palautordera showed good correlation with local anthropogenic indicators. Wet inorganic N deposition ranged between 4.2 and 6.7 kg ha⁻¹ year⁻¹. When including estimates of dry deposition, total annual deposition rose up to 10-20 kg ha⁻¹ year⁻¹, values that have been found to initiate adverse effects on Mediterranean-type forest ecosystems.

An experiment was carried out in open-top chambers located in eastern Spain. One-yr-old Pinus halepensis Mill. seedlings were exposed during three consecutive summers to the following ozone (O3) treatments: charcoal-filtered air (CFA), non-filtered air (NFA) or non-filtered air plus 40 nl l−1 O3, 9 h d−1, 5 d wk−1 (NFA+40). Seasonal variations in Aleppo pine performance were observed since reductions in chlorophyll and cellular peroxidase levels associated with increases in superoxide dismutase activity, were recorded during the summer. Similarly, a reduction in epoxidation state was found at midday during the summer, derived from an activation of the xanthophyll cycle associated to an increment in radiation and temperature levels. The first O3-induced effects were recorded in previous-year needles (1991) during the first summer exposure as an increase in extracellular and total peroxidase activities and in zeaxanthin levels in the NFA+40 treatment along with a trend to a higher SOD activity in this treatment. A carry-over effect was detected since a lower winter recovery of chlorophyll levels was found in the NFA+40 seedlings along with a reduction of xanthophyll levels. A reduction in chlorophyll levels was observed in the previous-year needles (1992) from the NFA+40 treatment at the end of the second fumigation period. Realistic ozone exposures induced alterations in plant antioxidative systems and plant pigments as shown in this paper. These observations together with the reductions in stomatal conductance and net photosynthesis recorded in the same experiment, indicate that Aleppo pine is a species sensitive to ozone.

We present here the effects of ambient ozone (O 3 )-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 O 3 treatments, which are as follows: charcoal-filtered air, nonfiltered air (NFA), and nonfiltered air supplemented with 40 ppb O 3 (NFA+). Stable carbon isotope discrimination (Δ) and derived time-integrated c i / c a 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 O 3 tolerance and might be interpreted as part of Aleppo pine acclimation response to O 3 .

The study reported was conducted to establish the impacts of photochemical oxidants (primarily ambient ozone, O3) on the yield of watermelon (Citrullus lanatus) at a site on the east coast of Spain. Fruit yield and quality were monitored in plots established in a commercial watermelon field exposed, in open-top chambers (OTCs), to non-filtered air (NFA; near-ambient levels of ozone) or charcoal-filtered air (decreased levels of photochemical oxidants including O3; CFA), or to ambient air (AA), during the 1988 and 1989 growing seasons. Ambient levels of O3 were found to exceed present UN-ECE (United Nations Economic Commission for Europe; Convention on Long-Range Transboundary Air Pollution) critical level guidelines for the protection of crop yield by approx. twofold in 1988 and by approx. fivefold in 1989. Plants exposed to NFA and AA developed visible O3 injury on the upper surface of sun-exposed older leaves, and fruit yield (annual marketable fruit weight and number) was found to be depressed in OTCs ventilated with NFA in comparison with those receiving CFA. Consistent with inter-annual variations in O3 exposure, greater yield losses were experienced in 1989 (39%) than in 1988 (19%), an effect mediated predominantly by a decline in fruit number rather than average fruit weight. Exposure to ambient levels of ozone also slightly decreased fruit quality (4–8% decline in soluble solids content). Leaf gas exchange measurements made in the field in 1988 revealed effects of O3 on fruit yield and quality to be associated with a decline in the net CO2 assimilation rate per unit leaf area under light saturation (Asat) and stomatal conductance to water vapour (gs), and enhanced rates of dark respiration. A/ci curves (where A is the net CO2 assimilation rate per unit leaf area and ci is the mole fraction of CO2 in the leaf intercellular air space) constructed for plants grown in laboratory-based closed chambers, and exposed to an accumulated O3 exposure similar to that experienced by plants in the field, suggested that the likely cause of the decline in photosynthetic capacity was (1) a decrease in the amount and/or activity of Rubisco and (2) an impaired capacity for regeneration of ribulose 1,5-bisphosphate, which was not mediated through changes in the photochemical efficiency of photosystem II (Fv/Fm, where Fv is variable chlorophyll a fluorescence and Fm is maximum chlorophyll a fluorescence). No shift in the relative stomatal limitation to photosynthesis was observed under the influence of O3, suggesting that the decline in gs induced by the pollutant in both field and laboratory was the result, and not the cause, of the decrease in Asat. Ozone exposure also caused a decrease in C isotope discrimination (approx. 0.5‰), a shift that revealed a departure from predicted theory based on supporting leaf gas exchange measurements. The study demonstrates that ambient levels of photochemical oxidants on the Spanish Mediterranean coast are high enough to adversely influence the yield and physiology of an economically important crop grown in the region, and the magnitude of the effects was greater than would be predicted from exposure–yield-loss relationships for grain and fodder crops in central and northern Europe. Implications for the derivation of UN-ECE ozone standards are discussed, along with the mechanistic basis of the observed yield decreases.

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.

Atmospheric carbon dioxide enrichment (eCO2) can enhance plant carbon uptake and growth1 5, thereby providing an important negative feedback to climate change by slowing the rate of increase of the atmospheric CO2 concentration6. Although evidence gathered from young aggrading forests has generally indicated a strong CO2 fertilization effect on biomass growth3 5, it is unclear whether mature forests respond to eCO2 in a similar way. In mature trees and forest stands7 10, photosynthetic uptake has been found to increase under eCO2 without any apparent accompanying growth response, leaving the fate of additional carbon fixed under eCO2 unclear4,5,7 11. Here using data from the first ecosystem-scale Free-Air CO2 Enrichment (FACE) experiment in a mature forest, we constructed a comprehensive ecosystem carbon budget to track the fate of carbon as the forest responded to four years of eCO2 exposure. We show that, although the eCO2 treatment of +150 parts per million (+38 per cent) above ambient levels induced a 12 per cent (+247 grams of carbon per square metre per year) increase in carbon uptake through gross primary production, this additional carbon uptake did not lead to increased carbon sequestration at the ecosystem level. Instead, the majority of the extra carbon was emitted back into the atmosphere via several respiratory fluxes, with increased soil respiration alone accounting for half of the total uptake surplus. Our results call into question the predominant thinking that the capacity of forests to act as carbon sinks will be generally enhanced under eCO2, and challenge the efficacy of climate mitigation strategies that rely on ubiquitous CO2 fertilization as a driver of increased carbon sinks in global forests. © 2020, The Author(s), under exclusive licence to Springer Nature Limited.

The hepatic portal vein is the main vascular route responsible for collecting blood from the liver, spleen, pancreas, stomach, gallbladder, and intestines. Its key function is to metabolize the components acquired from the blood. The objective of this study was to analyze the characteristics of HPV variants and understand the possible clinical considerations that arise with them. The databases Medline, Scopus, Web of Science, Google Scholar, Cumulative Index to Nursing and Allied Health Literature and Latin American and Caribbean Literature in Health Sciences were researched until January 2024. Tree authors independently performed the search, study selection and data extraction. Methodological quality was evaluated with an assurance tool for anatomical studies. Pooled prevalence was estimated using a random effects model. A total of 31 studies met the established selection criteria. In this study, 21 articles were included for the meta-analysis with a total of 51,244 subjects. Of these 21 articles, the topics studied came mainly from Europe and Asia, with three (n = 554; 1.08%) and 11 articles (n = 50,090; 97.75%) respectively, also having six articles from North America (n = 442; 0.86%) and one from Africa (n = 158; 0.31%), discarding the articles from Oceania and South America. For the HPV trifurcation variant, it was 8% (CI = 7-10%). Apropos the right posterior portal vein variant, as the primary tributary from the main HPV, it was 7% (CI = 4-11%). About the right anterior portal vein variant originating from the left portal vein, it was 4% (CI = 1-6%). Finally, the prevalence of the isolated variants was 2% (CI = 1-3%). The knowledge of HPV and its anatomical variants is of utmost importance for both medical professionals and anatomists, as it is one of the vessels that collects blood from many important viscera found in the abdominal cavity, any structural alteration could be crucial in diagnosis and surgical procedures.