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Intrinsic water use efficiency (WUEi) reflects the trade‐off between photosynthetic carbon gain and water loss through stomatal conductance and is key for understanding dryland plant responses to climate change. Stipa tenacissima is a perennial tussock C3 grass with an opportunistic, drought‐avoiding water use strategy that dominates arid and semiarid steppes across the western Mediterranean region. However, its ecophysiological responses to aridification and woody shrub encroachment, a major land‐use change in drylands worldwide, are not well‐understood.We investigated the variations in leaf stable isotopes (δ18O, δ13C, δ15N), nutrient concentrations (N, P, K), and culm water content and isotopic composition (δ18O, δ2H) of paired pure‐grass and shrub‐encroached S. tenacissima steppes along a 350 km aridity gradient in Spain (10 sites, 160 individuals).Culm water isotopes revealed that S. tenacissima is a shallow‐rooted grass that depends heavily on recent rainwater for water uptake, which may render it vulnerable to increasingly irregular rainfall combined with faster topsoil drying under climate warming and aridification. With increasing aridity, S. tenacissima enhanced leaf‐level WUEi through more stringent stomatal regulation of plant water flux and carbon assimilation (higher δ13C and δ18O), reaching exceptionally high δ13C values (−23‰ to −21‰) at the most arid steppes. Foliar N concentration was remarkably low across sites regardless of woody shrub encroachment, evidencing severe water and N co‐limitation of photosynthesis and productivity. Shrub encroachment decreased leaf P and K but did not affect S. tenacissima water status. Perennial grass cover decreased markedly with both declining winter rainfall and shrub encroachment suggesting population‐level rather than individual‐level responses of S. tenacissima to these changes.The fundamental physiological constraints of photosynthetic C3 metabolism combined with low foliar N content may hamper the ability of S. tenacissima and other drought‐avoider species with shallow roots to achieve further adaptive improvements in WUEi under increasing climatic stress. A drought‐avoiding water use strategy based on early stomatal closure and photosynthesis suppression during prolonged rainless periods may thus compromise the capacity of semiarid S. tenacissima steppes to maintain perennial grass cover, sustain productivity and cope with ongoing climate aridification at the drier parts of their current distribution. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Flowering phenology is important in the adaptation of many plants to their local environment, but its adaptive value has not been extensively studied in herbaceous perennials. We used Arabis alpina as a model system to determine the importance of flowering phenology to fitness of a herbaceous perennial with a wide geographical range. Individual plants representative of local genetic diversity (accessions) were collected across Europe, including in Spain, the Alps and Scandinavia. The flowering behaviour of these accessions was documented in controlled conditions, in common-garden experiments at native sites and in situ in natural populations. Accessions from the Alps and Scandinavia varied in whether they required exposure to cold (vernalization) to induce flowering, and in the timing and duration of flowering. By contrast, all Spanish accessions obligately required vernalization and had a short duration of flowering. Using experimental gardens at native sites, we show that an obligate requirement for vernalization increases survival in Spain. Based on our analyses of genetic diversity and flowering behaviour across Europe, we propose that in the model herbaceous perennial A. alpina, an obligate requirement for vernalization, which is correlated with short duration of flowering, is favoured by selection in Spain where the plants experience a long growing season. [ABSTRACT FROM AUTHOR]

Catchment hydrological responses to precipitation inputs, particularly during exceptionally large storms, are complex and variable, and our understanding of the associated runoff generation processes during those events is limited. Hydrological monitoring of climatically and hydrologically distinct catchments can help to improve this understanding by shedding light on the interplay between antecedent soil moisture conditions, hydrological connectivity, and rainfall event characteristics. This knowledge is urgently needed considering that both the frequency and magnitude of extreme precipitation events are increasing worldwide as a consequence of climate change. In autumn 2018, we installed water level sensors to monitor stream water and near‐stream groundwater levels at two Mediterranean forest headwater catchments with contrasting hydrological regimes: Font del Regàs (sub‐humid climate, perennial flow regime) and Fuirosos (semi‐arid climate, intermittent flow regime). Both catchments are located in northeastern Spain, where the extratropical cyclone Gloria hit in January 2020 and left in ca. 65 h outstanding accumulated rainfalls of 424 mm in Font del Regàs and 230 mm in Fuirosos. During rainfall events of low mean intensity, hydrological responses to precipitation inputs at the semi‐arid Fuirosos were more delayed and more variable than at the sub‐humid Font del Regàs. We explain these divergences by differences in antecedent soil moisture conditions and associated differences in catchment hydrological connectivity between the two catchments, which in this case are likely driven by differences in local climate rather than by differences in local topography. In contrast, during events of moderate and high mean rainfall intensities, including the storm Gloria, precipitation inputs and hydrological responses correlated similarly in the two catchments. We explain this convergence by rapid development of hydrological connectivity independently of antecedent soil moisture conditions. The data set presented here is unique and contributes to our mechanistic understanding on how streams respond to rainfall events and exceptionally large storms in catchments with contrasting flow regimes. [ABSTRACT FROM AUTHOR]

Xylella fastidiosa is the causal agent of plant diseases that cause massive economic damage. In 2013, a strain of the bacterium was, for the first time, detected in the European territory (Italy), causing the Olive Quick Decline Syndrome. We simulate future spread of the disease based on climatic-suitability modeling and radial expansion of the invaded territory. An economic model is developed to compute impact based on discounted foregone profits and losses in investment. The model projects impact for Italy, Greece, and Spain, as these countries account for around 95% of the European olive oil production. Climatic suitability modeling indicates that, depending on the suitability threshold, 95.5 to 98.9%, 99.2 to 99.8%, and 84.6 to 99.1% of the national areas of production fall into suitable territory in Italy, Greece, and Spain, respectively. For Italy, across the considered rates of radial range expansion the potential economic impact over 50 y ranges from 1.9 billion to 5.2 billion Euros for the economic worst-case scenario, in which production ceases after orchards die off. If replanting with resistant varieties is feasible, the impact ranges from 0.6 billion to 1.6 billion Euros. Depending on whether replanting is feasible, between 0.5 billion and 1.3 billion Euros can be saved over the course of 50 y if disease spread is reduced from 5.18 to 1.1 km per year. The analysis stresses the necessity to strengthen the ongoing research on cultivar resistance traits and application of phytosanitary measures, including vector control and inoculum suppression, by removing host plants. [ABSTRACT FROM AUTHOR]

Agricultural field margins are often recommended as a cost-effective and efficient method for wild bee conservation, in response to the threat imposed by global pollinator declines as a result of intensive agricultural practices. In this study we compared margin characteristics and wild bee community structure from sites with landscapes of varying agricultural intensity in order to (i) investigate if field margins are valuable for wild bee conservation in all types of landscapes, and (ii) determine which biotic and abiotic margin characteristics best support wild bee abundance and community richness. Margin surveys and wild bee community sampling, comprising pan traps and observations of foraging activity, were carried out over three years at 27 cereal field margins in Catalonia, Spain. Generalized linear models indicated a strong inverse relationship between surrounding landscape diversity and wild bee abundance. The proportion of Halictidae bees (common generalists) increased with decreasing landscape complexity. Floral richness exhibited a positive association with number of foraging bees and morphospecies richness, and was positively correlated with the proportion of shrubs and trees represented in the margins. It was observed that wider margins held a higher proportion of perennial plants and a lower proportion of Halictidae bees. Our study suggests that field margins are more crucial in intensively farmed areas than in heterogeneous landscapes where foraging resources are more abundant. Maintaining wide margins with high flowering plant richness, comprising perennial and shrub species, best supports a dense and diverse bee community. In more diverse landscapes, conservation efforts focused on maintaining the quality of existing natural patches may be most effective. [ABSTRACT FROM AUTHOR]

In common with the single extant species of the water fern Regnellidium, Regnellidium diphyllum, megaspores of Eocene and Oligocene representatives of this genus are characterized by having twisted, leaflike folds forming an acrolamella around the triradiate suture. The fossil and modern megaspores also have very similar wall ultrastructure and sculpture, and the morphology of the attached microspores of both is indistinguishable. Specimens of one of the species of the Cretaceous megaspore genus Molaspora--namely, Molaspora lobata, with attached microspores from Spain--and spores in the sporocarp Regnellidium upatoiensis from Georgia, United States, share some characters with those of extant Regnellidium, but the surface ornament of the microspores and the ultrastructure of the megaspore and microspore walls are different. The inner layer of the inner perine of M. lobata megaspores is thinner than the outer layer and of more compact, spongiose construction than that of Eocene and Oligocene Regnellidium spores from Eurasia and extant R. diphyllum. The microspores attached to or associated with M. lobata have a reticulate surface formed from muri of an outer perine layer and a thick, two-layered exine, whereas those of fossil and Recent Regnellidium have a closely packed rugulate--papillate sculpture and a thin exine that consists of a single, slightly spongiose layer . These characteristics, therefore, distinguish the Cretaceous fossils from Eocene--Recent members of this group. On the basis of available morphological characters of megaspores and microspores, M. lobata is interpreted as sister taxon to Regnellidium or to the Regnellidium þ Pilularia clade. The geographically widespread records of Molaspora, some species of possibly related Arcellites, and fossil megaspores attributable to Regnellidium show that the parent plants of all of these reproductive organs were widely dispersed in the geological past and that the current distribution of Regnellidium--which is restricted to Brazil, Uruguay, and Argentina--is relict. [ABSTRACT FROM AUTHOR]

Abstract: Astragalus nitidiflorus is an endangered perennial, but short-lived legume of SE Spain, which has been re-found after 100 years. To identify possible weak points that might contribute to its rarity and hamper its conservation, this paper presents data concerning location, habitat, demographic features and reproductive biology of the species. Censuses of three cohorts of seedlings show that the seedling stage is the most critical in the life cycle. The adult plants show a long flowering season with a high degree of synchrony. Despite the low reproductive success of the species, the annual seed production is very high due to the high floral production. The data show that A. nitidiflorus is a facultative xenogamous species, but the presence of pollinators can enhance fruit set. The viability of the species is not limited by the flowering and fruiting process, however the maintenance of the habitat in the early successional stages seems to be the critical point for long-term survival of the species. [Copyright &y& Elsevier]

We evaluated the ecological success of the manual removal of Carpobrotus species, a putative hybrid complex of a South African perennial mat-forming plant, by comparing treated, noninvaded, and invaded plots across coastal Andalucía in southern Spain. As a measure of the management effectiveness, we quantified the density of Carpobrotus seedlings and resprouts in treated plots one year after treatment. Response of the plant community to removal was assessed by com- paring native species richness, cover, diversity, and species composition among treatments. Removal greatly reduced to a great extent Carpobrotus density. However, successful control will require repeated hand-pulling treatments. Treated plots had a significant increase in species richness, especially annual plants, compared to invaded plots, but both had the same native plant cover and diversity. We found similar species composition between removal and noninvaded plots, indicating that revegetation is not necessary. Long-term monitoring is necessary to determine whether these observed patterns of community response are transient or stable through succession. [ABSTRACT FROM AUTHOR]

Abstract: In recent decades a large proportion of agricultural lands have been abandoned in European countries, mainly in semi-arid or mountain Mediterranean areas. Environmental processes in old fields have attracted the attention of many scientists, but several issues remain unanswered. This study seeks to identify the edaphic factors determining changes in perennial-plant communities in old fields of a Mediterranean semi-arid area (Baza Basin, SE Spain) and elucidate the main relationships between these communities. For this goal, we mapped all old fields in this study area and calculated the surface area occupied by each community (single and mixed). Floristic data and soil samples were collected for all the communities, through a stratified sampling, and the data were subjected to several statistical treatments (ANOVA, DCA, CCA, Spearman correlation). The joint study of floristic and edaphic variables confirmed that the soil determines mainly the establishment of vegetation in old fields of this area. Specifically, salinity, moisture, and gravel content accounted for most of the floristic variation. The results may be useful for old-field management, for example, to identify areas that should not be cultivated due to salinity or to the high ecological value. [Copyright &y& Elsevier]

The question of whether or not perennial plants senesce at the organism level remains unresolved. The aim of this study was to unravel whether or not plant age can influence the production and composition of seeds. Flower and seed production was examined in 3-, 8-, and 13-year-old Cistus albidus plants growing in experimental plots corresponding to the F2, F1, and F0 generations of the same population. Furthermore, the phytohormone, fatty acid, and vitamin E content of the seeds was evaluated, and their viability was examined. Whether or not age-related differences in seed quality were observed in a natural population in the Montserrat Mountains (NE Spain) was also tested. The results indicate that under controlled conditions, the oldest plants not only produced fewer flowers, but also had higher rates of embryo abortion in mature seeds. However, germination capacity was not negatively affected by plant ageing. Seeds of the oldest plants contained significantly higher salicylic acid, jasmonic acid, and vitamin E levels compared with those from younger plants. Despite vigour (in terms of plant growth) being severely reduced due to harsh environmental conditions in the natural population, the oldest individuals produced seeds with no decline in viability. Seed biomass was instead positively correlated with seed viability. In conclusion, increased plant size may explain the loss of seed viability in the experimental field, but older smaller individuals in natural populations can escape senescence in terms of seed viability loss.