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.