Mediterranean Climate Regions Research Articles

Winter Precipitation Changes in California Under Global Warming: Contributions of CO2, Uniform SST Warming, and SST Change Patterns

AbstractClimate models project a wetting winter over California, distinct from the drying in all other Mediterranean climate regions under warming. Dynamic effect via an eastward extension of the westerly jet stream over the North Pacific is the root cause for the wetting California. Utilizing four sets of prescribed‐SST (sea surface temperature) simulations, the relative effects of direct CO2 radiative forcing, uniform SST warming, and SST change patterns are investigated. The wetting winter is dominated by uniform SST warming mainly through its effect on the jet extension. As a fundamental response to the enhanced upper‐tropospheric warming in the tropics, the jet extension in coupled simulations is well reproduced under uniform SST warming and robust among models. An El Niño‐like SST warming pattern has a secondary contribution to the jet extension via atmospheric teleconnection, but with large inter‐model spread. Relative to the SST forcing, the direct CO2 radiative effect is negligible.

The biogeography of alien plant invasions in the Mediterranean Basin

AbstractAimsHumans have deeply eroded biogeographic barriers, causing a rapid spread of alien species across biomes. The Mediterranean Basin is a biodiversity hotspot but is also known as a hub of alien plant invasions, particularly in its European part. Yet, a comprehensive inventory of alien species in the area is missing and understanding of the drivers of Mediterranean invasions is poor. Here, we aim to identify the main alien plant species in the European part of the Mediterranean Basin and quantify their invasion success in order to understand the plant species flows from other biomes of the world.LocationThe Mediterranean region of Europe, Anatolia and Cyprus.MethodsWe analyzed 130,000 georeferenced vegetation plots from the European Vegetation Archive (EVA) and identified 299 extra‐European alien plant species. We identified their biomes of origin and quantified the mean geographic distance, trade exchange and climatic similarity from each biome to the study area. After estimating the invasion success of each species in the study area, we tested which biomes have donated more alien species than expected by chance and which drivers best explain these non‐random patterns.ResultsWe found that other Mediterranean climatic regions, as well as temperate and xeric biomes of the world, are the main donors of successful alien species to Mediterranean Europe, beyond what would be expected by chance. Our results suggest that climatic matching, rather than geographic proximity or trade, has been the most important driver of invasion. However, climatic pre‐adaptation alone also does not appear to predict the invasion success of established species in the study area.ConclusionsOur results highlight the need to pay special attention to alien plant species from the same or climatically similar biomes, but also suggest that further research is needed for early screening of the most problematic alien species.

Double‐ITCZ as an Emergent Constraint for Future Precipitation Over Mediterranean Climate Regions in the North Hemisphere

AbstractThe semiarid Mediterranean climate regions feature wet winter and dry summer, distinct from most other regions on Earth. In response to warming, climate models project increased precipitation in US Southwest (USSW) and decreased in Mediterranean basin (MED) during winter, but with marked uncertainty. Using a multimodel ensemble, we found that models with excessive double Intertropical Convergence Zone (ITCZ) biases tend to exaggerate the precipitation increase over USSW and understate the precipitation decrease over MED in the future. These relationships are attributed to the atmospheric circulation changes driven by the increased tropical rainfall and the weaker slowdown of the Atlantic Meridional Overturning Circulation under warming, respectively. Constraining the present‐day double‐ITCZ with observations, the projected wetting over USSW is reduced to no change and the drying over MED is intensified by 32%. A relative reduction in future precipitation has profound societal and economic implications for these regions already under severe water stress.

Utilisation of cover crops: implications for conservation agriculture systems in a mediterranean climate region of South Africa

PurposeCover crops can provide multiple agroecosystem services to crops produced in conservation agriculture systems. South African grain producers in the Mediterranean climate region are reluctant to integrate cover crops in rainfed systems since cover crops replace cash crops leading to financial losses. Using cover crops as fodder can help cover input costs, while providing a range of advantageous services to the cropping system. The aim of this study was to investigate how cover crop mixtures and the utilisation of cover crops affect soil quality, the quality and quantity of the mulch as well as wheat (Triticum aestivum L.) produced in the subsequent year.MethodsA two-year study was conducted in the Western Cape Province of South Africa. In Year 1, diverse legume and cereal-based cover crop mixtures were partially grazed, cut and material removed for haymaking, or left unutilised as a mulch. In Year 2, spring wheat (Triticum aestivum L.) was planted to investigate the effects of cover crop mixtures and utilisation method on subsequent spring wheat yield.ResultsCover crops used as hay or for grazing did not affect (P < 0.05) grain yield of wheat that followed in rotation. Legume-based cover crop mixtures increased (P < 0.05) wheat grain protein content regardless of utilisation method. Soil quality and nitrogen content improved (P < 0.05) when cover crops were grazed.ConclusionsCover cropping can be used by South African grain producers as an important agronomic tactic to improve system productivity and support sustainable intensification of rainfed cropping systems.

Framework for Climate Change Adaptation of Agriculture and Forestry in Mediterranean Climate Regions

Planning the adaptation of agriculture and forestry landscapes to climate change remains challenging due to the need for integrating substantial amounts of information. This information ranges from climate scenarios, geographical site information, socio-economic data and several possible adaptation measures. Thus, there is an urgent need to have a framework that is capable of organizing adaptation strategies and measures in the agriculture and forestry sectors in Mediterranean climatic regions. Additionally, this framework should provide a cause effect relation with climate vulnerability to adequately support the development of adaptation planning at municipal and local (farm) level. In this context, we propose to test and evaluate a framework for climate adaptation of the agriculture and forestry sectors, based on the local causal-effect relation between adaptation strategies and measures and the level of vulnerability reduction achieved for Mediterranean areas. The framework was developed based on the combination of the DPSIR (Driving forces, Pressures, State, Impacts, Responses) and Vulnerability frameworks and reviewed 162 practical adaptation measures, further organized into strategies, complemented by a set of efficacy indicators. The framework was tested with 70 stakeholders in six stakeholder workshops for the planning of two farms and one municipal climate adaptation study, that are now in actual implementation and monitoring. The framework is composed by a set of eight adaptation strategies in which adaptation measures are clustered and assessed using efficacy indicators. In the evaluation of the adaptation framework, 96% of stakeholders considered its content as good or very good and 89% considered the final outcomes as good or very good. Finally, the framework was also used to assess and compare the adaptation strategies and measures presented in the climate adaptation plans of the three case studies. On average, 52.2% of the adaptation measures selected by the three case studies are dedicated to Ecosystem Resilience, 30.9% to Adaptive Capacity, 9.1% to Microclimates, 7.4% to Protection, and 0.3% to Mitigation strategies. This framework was considered effective in supporting adaptation planning at farm and municipal levels and useful to assess and compare adaptation plans in the frame of vulnerability reduction. Future studies can further contribute to support adaptation planning in these sectors by using, developing and streamlining this framework to additional and different socio-ecological contexts.

Estimation of Reference Evapotranspiration during the Irrigation Season Using Nine Temperature-Based Methods in a Hot-Summer Mediterranean Climate

The FAO-56 Penman–Monteith (PM) equation is regarded as the most accurate equation to estimate reference evapotranspiration (ETo). However, it requires a broad range of data that may not be available or of reasonable quality. In this study, nine temperature-based methods were assessed for ETo estimation during the irrigation at fourteen locations distributed through a hot-summer Mediterranean climate region of Alentejo, Southern Portugal. Additionally, for each location, the Hargreaves–Samani radiation adjustment coefficient (kRs) was calibrated and validated to evaluate the appropriateness of using the standard value, creating a locally adjusted Hargreaves–Samani (HS) equation. The accuracy of each method was evaluated by statistically comparing their results with those obtained by PM. Results show that the calibration of the kRs, a locally adjusted HS method can be used to estimate daily ETo acceptably well, with RMSE lower than 0.88 mm day−1, an estimation error lower than 4% and a R2 higher than 0.69, proving to be the most accurate model for 8 (out of 14) locations. A modified Hargreaves–Samani method also performed acceptably for 4 locations, with a RMSE of 0.72–0.84 mm day−1, a slope varying from 0.95 to 1.01 and a R2 higher than 0.78. One can conclude that, when weather data is missing, a calibrated HS equation is adequate to estimate ETo during the irrigation season.

Acid-catalyzed fractionation of almond shells in γ-valerolactone/water

The fractionation of almond shells, an agro-industry residue available in some Mediterranean climate regions, was investigated using acid-catalyzed hydrolysis in γ-valerolactone (GVL)/water. A set of non-isothermal experiments at nominal temperatures of 120, 140, and 160 °C and sulfuric acid concentrations from 25 to 75 mM were developed using a constant 80% w/w GVL in water concentration and a reaction time of up to 120 min. GVL was an efficient medium and promoted solubilization of both lignin and hemicellulose, even at low temperature during the initial period of reactor heating, while cellulose conversion was limited. A temperature of 160 °C gave the highest extraction of lignin and hemicellulose, but recovery of hemicellulose carbohydrates was better below 140 °C. Sulfuric acid concentrations above 45 mM promoted excessive dehydration of xylose and glucose to furans and humins, which were recovered with lignin. A model was developed to describe the kinetics of lignin and hemicellulose solubilization. It distinguished three fractions of different reactivity in each polymer (lignin or hemicellulose): fast-reacting, slow-reacting, and unreactive. The amount of each fraction was correlated with acid concentration and reaction temperature. Activation energies and the other parameters in the model were obtained numerically by least-squares optimization using the data from the non-isothermal experiments. Activation energies for the fast-reacting and slow-reacting fractions of hemicellulose were 142 and 39.7 kJ mol−1, and for those of lignin 134 and 71.7 kJ mol−1, respectively. Acid concentration had a larger influence than temperature on establishing the amounts of slow-reacting hemicellulose and lignin, whereas temperature was the dominant variable concerning the fractions of non-reacting polymers.

Biology, Ecology, and Management of Hemipteran Pests in Almond Orchards in the United States

AbstractAlmond, Prunus dulcis (Miller) D. A. Webb, is an important tree nut crop cultivated primarily in the Mediterranean climatic regions. However, the United States, specifically the state of California, is the largest producer and exporter of almond nuts in the world. At least 60 species of insect pests attack almonds worldwide. Hemipterans can be important pests in almond orchards. Some hemipteran insect pests in almonds include lace bugs, plant bugs, stink bugs, and leaffooted bugs. These pests use needle-like mouthparts to pierce and feed upon fruits or other parts of the plant, causing direct or indirect crop damage. Nonetheless, the biology, life history, and management practices for many hemipteran pests of almonds are not available in the literature or come from research of these insects on other crops and host plants. In this article, we discuss the current understanding of biology, ecology, and management of hemipteran pests of almonds and outline future research to advance the integrated pest management of these pests in almond orchard systems.

Grapevine Responses to Heat Stress and Global Warming

The potential effects of the forthcoming climate change include the rising of the average annual temperature and the accumulation of extreme weather events, like frequent and severe heatwaves, a phenomenon known as global warming. Temperature is an important environmental factor affecting almost all aspects of growth and development in plants. The grapevine (Vitis spp.) is quite sensitive to extreme temperatures. Over the current century, temperatures are projected to continue rising with negative impacts on viticulture. These consequences range from short-term effects on wine quality to long-term issues such as the suitability of certain varieties and the sustainability of viticulture in traditional wine regions. Many viticultural zones, particularly in Mediterranean climate regions, may not be suitable for growing winegrapes in the near future unless we develop heat-stress-adapted genotypes or identify and exploit stress-tolerant germplasm. Grapevines, like other plants, have developed strategies to maintain homeostasis and cope with high-temperature stress. These mechanisms include physiological adaptations and activation of signaling pathways and gene regulatory networks governing heat stress response and acquisition of thermotolerance. Here, we review the major impacts of global warming on grape phenology and viticulture and focus on the physiological and molecular responses of the grapevine to heat stress.

Investigation of spatiotemporal variation of drought in Iran during the last five decades

The present study was conducted to assess the changes in Iran's drought severity for the duration of 1964 to 2014. For this purpose, the spatial distribution of drought was annually and seasonally evaluated using climate data from 26 synoptic stations over Iranian territory based on standardized precipitation index (SPI). In this regard, the climate classification in the study area was performed applying Dermartone method. Moreover, the annual and seasonal values of SPI were calculated for the whole Iranian territory and each climate region. The SPI index for monotonic trend was calculated in each climate region utilizing Mann-Kendall and Theil Sen estimators. Our results implied that the minimum and maximum values of SPI (-3.86 and 2.89, respectively) appeared during spring in dry and Mediterranean climate regions. In addition, the maximum and minimum values of annual continuous SPI appeared in 1999-2004 and 1974-1982, respectively. The maximum and minimum values of seasonal continuous SPI also appeared for a duration of 9 years during summers respectively in the period of 1977 to 1985 and springs in the period of 2006 to 2014. The application of Mann-Kendall and Theil Sen estimator analyses revealed that 9 out of 26 stations had a significant decreasing SPI trend. Moreover, the annual and seasonal time series in moderately dry regions indicated a meaningfully decreasing trend in winter and annual SPI. Additionally, winter, spring, autumn and annual values of SPI had a meaningful decreasing trend in the Mediterranean climate region. In dry and very wet climate regions, no obvious trend was detected for the annual or seasonal SPI index.

The response of Pinus species to ozone uptake in different climate regions of Europe

Abstract This study is focused on the research of selected Pinus species exposed to high ozone concentrations in the mountain environment. We noticed different values of modelled ozone doses (MOD) up-taken by Mountain pine (Pinus mugo Turra) in the High Tatra Mts (SK–HTMts) and Swiss stone pine (Pinus cembra L.) in the Alpes-Mercantour (FR–AlpMar) during the growing season 2019. The MOD values were obtained by multiplicative DO3SE model, while we also tested a new approach based on modification of input ozone data. The MOD values were obtained by multiplicative DO3SE model, while we also tested a new approach based on modification of input ozone data. Testing has shown that ozone input based on passive sampling may be used in MOD modelling for sites situated in the subalpine zone where the operation of active monitors is limited.. Presented results confirmed the assumption regarding stomatal ozone flux reduction due to the occurrence of soil drought in hot and dry summer weather typical for the Mediterranean climate region. Despite the limitation of stomatal flux, foliar ozone specific injury on two years needles of P. cembra was substantially higher in comparison to the incidence of ozone injury symptoms observed on two years needles of P. mugo in SK–HTMts. It may suggest low phytotoxicity of given MOD or efficient resistance of P. mugo against oxidative stress. In addition, the visible injury index (VINX) covering the broad effect of biotic and abiotic harmful agents was appraised on P. mugo. Percentage of affected surface indicated moderate deterioration of needle injury at the end of the growing season, particularly due to traces of mechanical damage.

Incorporating a Fresh Mixed Annual Ryegrass and Berseem Clover Forage Into the Winter Diet of Dairy Cows Resulted in Reduced Milk Yield, but Reduced Nitrogen Excretion and Reduced Methane Yield.

The winter diet of dairy cows in Mediterranean climate regions is usually a total mixed ration with a base of conserved summer crops such as corn silage and alfalfa hay. However, there is increased labor and financial cost related to this kind of feeding, which could be reduced if fresh forages were used in place of some of the conserved forage in the cow diet. The objective of our study was to evaluate the effect of including fresh mixed annual ryegrass and berseem clover into the diet of dairy cows on milk, nitrogen utilization, and methane emission. Twenty-four lactating dairy cows were split into two groups and offered either a diet similar to that usually offered to the cows (CON) or one where a mixture of fresh annual ryegrass and berseem clover was used to partially substitute the corn silage and alfalfa hay in the diet (MIX). Milk yield was recorded automatically, and methane emissions were estimated using the SF6 tracer technique. The MIX diet had lower crude protein concentration (148 vs. 170 g/kg DM) but higher DM digestibility (81.6 vs. 78.6%) than the CON diet. Compared to the cows offered the CON diet, milk yield was reduced when cows were fed the MIX diet (36.4 vs. 31.9 kg/d), but methane emissions (381 vs. 332 g/d) and nitrogen excretion were also reduced (238 vs. 180 g/d). Nitrogen use efficiency was unaffected (30.8%). In addition, milk from cows fed the MIX diet had a fatty acid profile considered to be more beneficial to human health than that of the milk from cows fed the CON diet. Increasing the protein concentration in the MIX diet, either by direct supplementation or increasing the proportion of legume in the mixed herbage, could overcome the reduction on milk and positively affect methane emission and N use efficiency.

White Leaf Spot Caused by Neopseudocercosporella capsellae: A Re-emerging Disease of Brassicaceae.

White leaf spot can cause significant damage to many economically important Brassicaceae crops, including oilseed rape, vegetable, condiment, and fodder Brassica species, and recently has been identified as a re-emerging disease. The causal agent, Neopseudocercosporella capsellae, produces foliar, stem, and pod lesions under favorable weather conditions. N. capsellae secretes cercosporin, a non-host specific, photo-activated toxin, into the host tissue during the early infection process. The pathogen has an active parasitic stage on the living host and a sexual or asexual saprobic stage on the dead host. Where the sexual stage exists, ascospores initiate the new disease cycle, while in the absence of the sexual stage, conidia produced by the asexual stage initiate new disease cycles. Distribution of the pathogen is worldwide; however, epidemiology and disease severity differ between countries or continents, with it being more destructive in Subtropical, Mediterranean, or Temperate climate regions with cool and wet climates. The pathogen has a wide host range within Brassicaceae. Brassica germplasm show varied responses from highly susceptible to completely resistant to pathogen invasion and significant susceptibility differences are observed among major crop species. Cultural practices only provide effective disease control when the climate is not conducive. An increase in the susceptible host population and favorable weather conditions have together favored the recent rise in white leaf spot disease occurrence and spread. The lack of understanding of variation in pathogen virulence and associated resistant gene sources within brassicas critically limits the potential to develop efficient control measures.

Architecture and storage in Mediterranean environments: Case studies from the Aegean and southern California

This paper offers a comparative look at the organization of built space and storage for sedentary communities in the world's Mediterranean climatic regions and assesses the variable expressions of certain underlying features that are held in common. Our analysis focuses on two primary case studies: the occupants of the Aegean Sea region from the Neolithic to Roman periods (ca. 6800 BCE-168 CE) and the coastal Chumash of southern California during the Late Period (1300–1782 CE). We show that in both regions, households took advantage of outdoor spaces as productive activity areas during the long periods of favorable weather each year. This incorporation of exterior spaces was typically structured using clear visual cues or architecture. Additionally, surplus food was acquired by individual households and stored to mitigate the inherent risks of interannual variability in precipitation and expected annual periods of lower yield (i.e., winter). Since storage was typically organized at the household level, the domestic architecture often incorporated dedicated space or built facilities to manage this surplus. By understanding such climatic influences on the regions' architecture and storage infrastructure, the distinct cultural qualities of these expressions can be better articulated. While it is not our contention that these attributes manifested identical outward architectural and material forms or were exclusive to Mediterranean environments, we suggest that the environment was an important influence on construction and storage decisions which could be adapted according to the local histories of their respective communities.

Bird-friendly wine country through diversified vineyards.

Vinecology, the integration of ecological and viticultural practices, focuses on the working landscapes of the Mediterranean-climate biomes to make wine-grape production compatible with species conservation. We examined how maintaining remnant native vegetation and surrounding natural areas in and around vineyards, two primary practices of vinecology, may influence bird community richness and composition across a vineyard landscape. We conducted bird surveys over spring and summer (October-January) at 120 sites across a wine-grape growing region in central Chile. The sites were equally divided across vineyards with and without remnant native vegetation, and sites had varying amounts of adjacent natural land cover. We used generalized linear mixed models to examine individual species responses to remnant vegetation in the vineyard at plot scale (within a 50-m radius) in the surrounding natural area (within a 500-1000 m radius). We used the Horn similarity index to explore overall community differences to quantify variations in endemic species, guild detection levels, and species richness between site types. At the plot scale, 9 out of 30 species were positively associated with the proportion of remnant vegetation and 3 species were negatively associated. Six were positively influenced by the proportion of native vegetation in the surrounding landscape and 3 species were negatively associated with proportion of native vegetation. Although overall total detections and richness were significantly greater in continuous mixed Mediterranean forest, 84.9% of these species were also detected in forest remnants within vineyards. Endemics, insectivores, granivores, and omnivores were all more abundant in vineyards with remnant native vegetation than in vineyards without remnant native vegetation. Our results show the value of maintaining and restoring natural vegetation remnants in vineyards as a tool for bird conservation that can be applied in working landscapes of the New World Mediterranean climate regions.

Dynamic modeling and performance assessment of single and double phase change material layer–integrated buildings in Mediterranean climate zone

Nowadays, latent heat storage is becoming an imperative in building sector since it plays a crucial role in conserving energy through controlling the thermal comfort level. In this field, different storage systems based on phase change material show great performances in terms of energy saving, leading to a significant improvement of occupant thermal comfort. In this work, the thermal behavior and energy efficiency of a residential house incorporating various phase change materials (RT18HC, RT21HC, RT25HC, and RT28HC) in Mediterranean climate region were investigated via numerical simulations. EnergyPlus software was used to analyze the thermal performance of phase change materials applied to the interior wall surfaces of a simplified building model in El Jadida city. The integration of different single and double phase change material layers has been evaluated based on various concepts such as the average temperature fluctuation reduction and the monthly energy saving. The study showed that low melting point phase change material outperforms in terms of heating load, while phase change material with high melting temperature favors the cooling performance. Moreover, the results show that double-layer systems formed by two distinct phase change materials exhibit higher performance than a single phase change material layer throughout the whole year. The annual energy saving rate reaches 41.42% and 55.41% when using single and double phase change material layers, respectively. Finally, we opted for an optimum double-layer system for lower energy consumption in the selected city.

Human-environmental interactions in Mediterranean climate regions from the Pleistocene to the Anthropocene

• Climate change poses great challenges for human welfare and biodiversity in Mediterranean Climate Regions. • Archaeological and paleoecological records document human responses to past climate change. • Past climatic deterioration was an important driver of socio-environmental change. • People actively altered ecosystems and landscapes in these regions for millennia. • Archaeological records provide key insights for preparing for climate and environmental challenges of the future. From mobile hunter-gatherers to a series of state societies, Mediterranean climate regions (MED) around the world have been critical areas for human and biological evolution for millennia. Comprised of five regions on six continents, the MED are important today for human settlement, global food production, transportation, industry, and tourism, but these regions are also extremely vulnerable to projected changes in their typically temperate climate towards more extreme conditions. Researchers and strategists are exploring the implications of these changes for present and future societies, but there has been limited comparative synthesis of past human responses to environmental and climatic change in the global MED and how these data may help prepare and plan for projected changes in the future. This review synthesizes archaeological and paleoenvironmental data, focusing on key demographic, social, economic, and cultural developments that occurred alongside and often in response to past climate and environmental disruption. Past climatic change influenced broader socio-environmental systems, in some cases acting as a driver of population collapse, large-scale abandonment, migration, and socio-political upheaval. These deep time data illustrate the importance of understanding Pleistocene-Holocene human-environmental interactions, land use, and climate change to help evaluate and plan for contemporary and projected environmental change.

Ecohydrological Separation Hypothesis: Review and Prospect

The ecohydrological-separation (ES) hypothesis is that the water used for plant transpiration and the water used for streams and groundwater recharge comes from distinct subsurface compartmentalized pools. The ES hypothesis was first proposed in a study conducted in the Mediterranean climate region, based on the stable isotope method in 2010. To date, the ES hypothesis has proven to be widespread around the world. The ES hypothesis is a new understanding of the soil water movement process, which is different from the assumption that only one soil reservoir in the traditional hydrology. It is helpful to clear the water sources of plants and establish a new model of the ecohydrological process. However, the theoretical basis and mechanism of the ES hypothesis are still unclear. Therefore, we analyzed the characteristics of ES phenomenon in different climatic regions, summarized the research methods used for the ES hypothesis, concluded the definitions of tightly bound water and mobile water, discussed the mechanism of isotopic differences of different reservoirs and their impacts on ES evaluation and pointed out the existing problems of the ES hypothesis. Future research should focus on the following three aspects: (a) detailed analysis of ES phenomenon characteristics of different plant species in different climatic regions; (b) further understanding of the ES phenomenon mechanism; (c) improvement of the experimental methods.

Hydrological drought insurance for irrigated agriculture in southern Spain

In Mediterranean-climate regions, irrigated agriculture is especially vulnerable to the risk of hydrological drought, and irrigators are particularly concerned about the negative effects of water supply failures. This paper proposes a new index-based drought insurance scheme to cover the risk of water supply failures in irrigated agriculture that overcomes the problems currently hindering the development of this kind of insurance, especially those related to arbitrariness in annual water allotments decision-making. Although the proposal is tailored to Spain, it can be easily adapted to other countries or regions because its main features can also be implemented worldwide. The scheme proposed is a promising instrument to help irrigators manage the risk related to hydrological droughts since it has been proved to be technically feasible. The main contribution of this paper is the innovative actuarial analysis implemented, which is aimed at calculating fair premiums. Considering that recent changes in the institutional framework (new demands, new storage capacity, and revised basin and drought management plans) make historical records unsuitable for this purpose, the actuarial analysis applied is based on a stochastic hydrological model able to simulate future hydrological situations under updated settings. Simulation results have shown that irrigated agriculture in southern Spain is expected to be more vulnerable to hydrological droughts. In fact, incidence rates are likely to increase because of the new institutional framework, leading to relatively high fair premiums. Only by implementing high ordinary deductibles can the hypothetical cost of commercial premiums be affordable for irrigators, accounting for less than 10% of their current variable costs.

SILVOLIVE, a Germplasm Collection of Wild Subspecies With High Genetic Variability as a Source of Rootstocks and Resistance Genes for Olive Breeding.

Wild subspecies of Olea europaea constitute a source of genetic variability with huge potential for olive breeding to face global changes in Mediterranean-climate regions. We intend to identify wild olive genotypes with optimal adaptability to different environmental conditions to serve as a source of rootstocks and resistance genes for olive breeding. The SILVOLIVE collection includes 146 wild genotypes representative of the six O. europaea subspecies and early-generations hybrids. These genotypes came either from olive germplasm collections or from direct prospection in Spain, continental Africa and the Macaronesian archipelago. The collection was genotyped with plastid and nuclear markers, confirming the origin of the genotypes and their high genetic variability. Morphological and architectural parameters were quantified in 103 genotypes allowing the identification of three major groups of correlative traits including vigor, branching habits and the belowground-to-aboveground ratio. The occurrence of strong phenotypic variability in these traits within the germplasm collection has been shown. Furthermore, wild olive relatives are of great significance to be used as rootstocks for olive cultivation. Thus, as a proof of concept, different wild genotypes used as rootstocks were shown to regulate vigor parameters of the grafted cultivar “Picual” scion, which could improve the productivity of high-density hedgerow orchards.