Aim Mediterranean terrestrial ecosystems serve as reference laboratories for the investigation of global change because of their transitional climate, the high spatiotemporal variability of their environmental conditions, a rich and unique biodiversity and a wide range of socio-economic conditions. As scientific development and environmental pressures increase, it is increasingly necessary to evaluate recent progress and to challenge research priorities in the face of global change. Location Mediterranean terrestrial ecosystems.Methods This article revisits the research priorities proposed in a 1998 assessment.Results A new set of research priorities is proposed: (1) to establish the role of the landscape mosaic on fire-spread; (2) to further research the combined effect of different drivers on pest expansion; (3) to address the interaction between drivers of global change and recent forest management practices; (4) to obtain more realistic information on the impacts of global change and ecosystem services; (5) to assess forest mortality events associated with climatic extremes; (6) to focus global change research on identifying and managing vulnerable areas; (7) to use the functional traits concept to study resilience after disturbance; (8) to study the relationship between genotypic and phenotypic diversity as a source of forest resilience; (9) to understand the balance between C storage and water resources; (10) to analyse the interplay between landscape-scale processes and biodiversity conservation; (11) to refine models by including interactions between drivers and socio-economic contexts; (12) to understand forest-atmosphere feedbacks; (13) to represent key mechanisms linking plant hydraulics with landscape hydrology.Main conclusions (1) The interactive nature of different global change drivers remains poorly understood. (2) There is a critical need for the rapid development of regional-and global-scale models that are more tightly connected with largescale experiments, data networks and management practice. (3) More attention should be directed to drought-related forest decline and the current relevance of historical land use.

According to the competitive exclusion principle, species with low competitive abilities should be excluded by more efficient competitors, and yet they generally remain as rare species. Here, we describe the positive and negative spatial association networks of 326 disparate assemblages, showing a general organization pattern that simultaneously supports the primacy of competition and the persistence of rare species. Abundant species monopolize negative associations in about 90% of the assemblages. Contrarily, rare species are mostly involved in positive associations, forming small network modules. Simulations suggest that positive interactions among rare species and microhabitat preferences are the most likely mechanisms underpinning this pattern and rare species persistence. The

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Seeds of N. hispanicus have deep simple epicotyl morphophysiological dormancy (MPD), with the dormancy formula C(1b)B(root) - C(3)(epicotyl). This is the first study on seeds with simple MPD to show that embryos in advanced stages of growth can re-enter dormancy (secondary dormancy).

The influence of high temperatures on germination of four Cistus and five Halimium taxa is analysed. Seeds were heated to a range of temperatures (from 50ºC to 150ºC) and a range of exposure times (from 1 to 60 min), simulating those heat conditions registered on the soil surface during wildfires. After the thermal pretreatments, seeds were sown in plastic Petri dishes and monitored for germination over 60 days. For all the species, germination was increased significantly over the control set (untreated seeds) by at least one of the thermal pretreatments. Temperatures of 120 and 150ºC were the most efficient temperatures promoting seed germination, although germination was interrupted at 150ºC if exposure times were equal to or longer than 5 minutes for the majority of species. The preheating at 50ºC was effective on;y for C. populifolius, but only at long exposure times (60 min). H. atriplicifolium had the highest heat requirements for stimulating germination, requiring at least 120ºC for 5 min. H. halimifolium subsp. halimifolium seeds showed the highest heat resistance: the final germination level reached at 150ºC for 7.5 minutes ranged between 52.5 and 55.5%. The germination rates after preheating were much lower than in mechanically scarified seeds, and closely resembled those of the untreated seeds. In general, species sharing the same habitat showed different heat requirements in promoting germination. For C. crispus and H. halimifolium subsp. halimifolium, the experiment was carried out on seeds collected from two different localities. For both species the germination patterns were similar between populations, although some high temperature pretreatments showed different germination percentages.

In order to analyze the extent to which allelopathic action of Cistus ladanifer may influence the successional progression towards Mediterranean sub-climacic shrublands and the geographical distribution of other species, the inhibitory effect of Cistus ladanifer extracts on the germination of 20 Mediterranean species was analyzed. Five of the species tested were characteristic of maquis sub-climacic shrublands: Arbutus unedo, Adenocarpus argyrophyllus, Phillyrea angustifolia, Phillyrea latifolia, and Rhamnus alaternus. Tests were also carried out on 6 Cistaceae species in order to evaluate the auto-toxicity rate of allelopathic extracts: Halimium umbellatum subsp. viscosum, Halimium ocymoides, Cistus ladanifer, Cistus salvifolius, Cistus monspeliensis, and Cistus populifolius. Nine herbaceous species sharing the natural habitat with C. ladanifer were also examined. Results confirmed a clear inhibitory and delaying effect of aqueous C. ladanifer-leaf extracts on the germination of P. angustifolia, P. latifolia, R. alaternus, H. ocymoides, C. populifolius, Erysimum lagascae, Brassica barrelieri, Silene tridentata, and Moricandia moricandioides. Assays with soil collected below the canopy of the C. ladanifer community showed more pronounced inhibitory effect on sub-climacic shrub species than the aqueous extracts. In contrast, the opposite pattern was detected when analyzing the allelopathic effect of natural soil on Cistaceae and herbaceous species. Allelopathic compounds produced by C. ladanifer showed little auto-toxicity. The inhibitory effect of phytotoxic compounds accumulated in the jaral soil upon germination of A. unedo, B. barrelieri, and M. moricandioides was eliminated by heating soil at 150°C for 10 min. Phenolic compounds (i.e. ferulic, p-hydroxybenzoic, vanillic, p-coumaric, and caffeic acids) and terpenes (i.e.a and b-pinene) with allelopathic documented effect were detected in the aqueous extracts and soil samples used in the analyses. We suggest that the allelopathic effect of C. ladanifer may influence the composition and structure of Mediterranean communities where the species is present, since it hinders the establishment of some sub-climacic species and may reduce the area occupied by numerous herbaceous species.

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Seeds of Delphinium fissum subsp. sordidum are physiologically dormant at maturity, with underdeveloped embryos; thus they have morphophysiological dormancy (MPD). The aims of this study were to determine the requirements for embryo growth, dormancy break and germination, to characterise the type of seed dormancy and to evaluate the effects of light, seed age, pollination mechanism, and inter-annual and inter-population variability on germinative ability. After 3 months of incubation at 5°C (cold stratification) in darkness conditions, the mean embryo length increased from 5.6 to 2.07 mm, with 76% of seeds germinating. Conversely, embryos of seeds incubated during 3 months at 20/7 or 28/14°C hardly grew and no germination was recorded. Since cold stratification was the only requirement for the loss of MPD, and both dry storage in laboratory conditions and warm stratification prior to cold stratification shortened the cold stratification period required for germination, it could be concluded that D. fissum subsp. sordidum seeds have intermediate complex MPD. Cold stratification and incubation in darkness conditions promoted higher germination percentages than those in light. In addition, germinative ability increased with seed age up to 8 months (reaching 96% at 5°C in darkness), showed a pronounced inter-annual and inter-population variability, as well as a significant decrease in seeds coming from pollination by geitonogamy. High temperatures (25/10 or 28/14°C) induced seeds to secondary dormancy, so seedling emergence in the greenhouse was restricted to February-March. The requirements for dormancy break and germination reflect an adaptation to trigger germination in late winter. This study is the first one to document a gradual increase in germination percentage with seed age for plant species with intermediate complex MPD.