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Worldwide, large wildfires are becoming increasingly common, leading to economic damages and threatening ecosystems and human health. Under future climate change, more frequent fire disturbance may push ecosystems into non‐forested alternative stable states. Fire‐prone ecosystems such as those in the Mediterranean Basin are expected to be particularly vulnerable, but the position of tipping points is unclear.We compare long‐term palaeoecological data from Sardinia with output from a process‐based dynamic vegetation model to investigate the mechanisms controlling the complex interactions between fire, climate, and vegetation in the past and the future.Our results show that past vegetation changes from Erica‐shrublands to mixed evergreen‐broadleaved Quercus ilex‐dominated forests were driven by a climate‐induced fire regime shift. By simulating vegetation dynamics under varying fire regimes, we could reproduce Holocene vegetation trajectories and mechanistically identify tipping points.Without an immediate reduction of greenhouse gas emissions, we simulate future expansion of fire‐prone Mediterranean maquis and increasing fire occurrence. Similarly, high anthropogenic ignition frequencies and plantations of non‐native, highly flammable trees could induce a shift to fire‐adapted Erica shrublands. However, our simulations indicate that if global warming can be kept below 2°C, Quercus ilex forests will be able to persist and effectively reduce fire occurrences and impacts, making them a valuable restoration target in Mediterranean ecosystems.Synthesis. By combining long‐term records of ecosystem change with a dynamic vegetation model, we show that past climate‐driven fire regime shifts were the main driver of vegetation change, creating alternative stable states that persisted over centuries. Projected future climate change exceeding Holocene variability leads to pronounced vegetation changes and increased fire risks in our simulations, requiring new fire management strategies to maintain current ecosystem services. [ABSTRACT FROM AUTHOR]

Climate and topography are among the most fundamental drivers of plant diversity. Here, we assessed the importance of climate and topography in explaining diversity patterns of species richness, endemic richness and endemicity on the landscape scale of an oceanic island and evaluated the independent contribution of climatic and topographic variables to spatial diversity patterns., We constructed a presence/absence matrix of perennial endemic and native vascular plant species (including subspecies) in 890 plots on the environmentally very heterogeneous island of La Palma, Canary Islands. Species richness, endemic richness and endemicity were recorded, interpolated and related to climate (i.e. variables describing temperature, precipitation, variability and climatic rarity) and topography (i.e. topographic complexity, solar radiation, geologic age, slope and aspect). We used multimodel inference, spatial autoregressive models, variance partitioning and linear regression kriging as statistical methods., Species richness is best explained by both climatic and topographic variables. Topographic variables (esp. topographic complexity and solar radiation) explain endemic richness, and climatic variables (esp. elevation/temperature and rainfall seasonality) explain endemicity. Spatial patterns of species richness, endemic richness and endemicity were in part geographically decoupled from each other., Synthesis . We identified several topography-dependent processes ranging from evolutionary processes (micro-refugia, in situ speciation, pre-adaptation to rupicolous conditions, dispersal limitations) to human-induced influences (introduced herbivores, fire, land use) that possibly shape the endemic richness pattern of La Palma. In contrast, climate mainly drives endemicity, which is connected to ecological speciation and specialization to local conditions. We highlight the importance of incorporating climatic variability into future studies of plant species diversity and endemism. The spatial incongruence in hot spots of species richness, endemic richness and endemicity emphasizes the need for an integrated conservation approach acknowledging different diversity measures to protect the complete spectrum of diversity. High-elevation islands such as La Palma are highly suitable to study drivers of diversity and endemism, as they offer environmental gradients of continental magnitude on the landscape scale of a single climatic mini-continent and a large array of in situ-speciated endemics. [ABSTRACT FROM AUTHOR]

Garajonay National Park in La Gomera (Canary Islands) contains one of the largest remnant areas of a forest formation once widespread throughout Europe and North Africa. Here, we aim to address the long-term dynamics (the last 9600 cal. years) of the monteverde forest (laurel forest and Morella-Erica heath) located close to the summit of the National Park (1487 m a.s.l.) and determine past environmental and human impacts., We used palaeoecological (fossil pollen, microscopic and macroscopic charcoal) and multivariate ecological techniques to identify compositional change in the monteverde forest in relation to potential climatic and human influences, based on the analysis of a core site at 1250-m elevation., The regional mid-Holocene change towards drier conditions was matched in this system by a fairly rapid shift in representation of key forest elements, with declines in Canarian palm tree ( Phoenix canariensis), Canarian willow ( Salix canariensis) and certain laurel forest taxa and an increase in representation of the Morella-Erica woody heath., Charcoal data suggest that humans arrived on the island between about 3000 and 1800 years ago, a period of minimal vegetation change. Levels of burning over the last 800 years are among the lowest of the entire 9600 years., Synthesis. A rapid climatic-induced shift of forest taxa occurred 5500 years ago, with a decrease in hygrophilous species in the pollen record. In contrast, we found no evidence of a significant response to human colonization. These findings support the idea that Garajonay National Park is protecting a truly ancient relict, comprising a largely natural rather than cultural legacy. [ABSTRACT FROM AUTHOR]

Herbivores and granivores represent one of the most influential drivers of plant abundance and population dynamics. Their effect can be, in turn, modulated by biotic or abiotic factors such as community composition, habitat characteristics or space heterogeneity., Recent approaches to the study of herbivore and granivore impacts on plants have considered the combined action of multiple herbivore species, the effect of herbivores on several plant life stages or the effect of environmental gradients on these interactions. However, studies addressing the effect of multiple herbivore species on different plant life stages are still lacking., We estimated the combined effect of multiple exotic herbivores ( European rabbits, Oryctolagus cuniculus; black rats, Rattus rattus; and house mouse, Mus musculus) on four different life stages of an endangered plant species ( Medicago citrina, Fabaceae). Mortality for seed, seedling and sapling was estimated at three types of plots (open, rat exclusion and rat + rabbit exclusion) replicated at four sites ( N = 3 per site and treatment) within Cabrera Island ( Balearic Islands, western Mediterranean). Browsing of reproductive adults was simulated under common-garden conditions ( Sóller Botanic Garden, Mallorca Island) and its effect on reproductive effort and success measured., European rabbits and black rats had complementary impacts on the different life stages of M. citrina. These included independent effects on different life stages (seed predation by rats, seedling predation by rabbits), which resulted in multiplicative increases in plant mortality, and concurrent effects on the same life stage (sapling predation). In addition, the simulated-herbivory experiment showed that a low rate of canopy removal (25% of initial biomass) already causes a strong decrease in fruit set (from 54% to 30%), but increasing rates of canopy removal do not increase this effect., Synthesis. Our results stress the importance of considering the combined effects of different herbivores on several life stages of the plant's life cycle and their consecutive effects on population dynamics. From an applied point of view, future reintroduction attempts of M. citrina in Cabrera Island should consider measures to either control the populations of both exotic herbivores or mitigate their impacts on the earlier recruitment stages of the plant (seeds, seedlings and saplings). [ABSTRACT FROM AUTHOR]

1 Species attributes have been used to explain invasion patterns assuming the prevalence of biological mechanisms, although this approach often suffers several methodological and conceptual limitations, such as local idiosyncrasies, differences among habitats, phylogenetic constraints and insufficient sample size.2 The relative importance of 15 species traits for explaining the abundance over 350 naturalized alien plant species was assessed across five Mediterranean islands (Corsica, Crete, Majorca, Malta and Sardinia). A comparative analysis accounting for phylogeny was used to examine variation in semi-quantitative estimates of species abundance in comparable habitats across the five island floras.3 Species were divided into those with affinity for semi-natural, agricultural and ruderal habitats. Both vegetative and reproductive attributes were evaluated for individual islands and averaged across all islands.4 Vegetative propagation, large leaf size, summer flowering, long flowering period and dispersal by wind or vertebrates were positively associated with average alien abundance across all five islands. Fewer significant trends were found in island-specific patterns.5 The relative importance of a few reproductive traits is reflected in over-representation of Caryophyllales, Asterales and Poales (late flowering, large seed size and anemochory). Although significant covariation in traits was found there was no evidence for well-defined invasive syndromes.6 Succulence was important in ruderal habitats, long flowering period in agricultural habitats and vertebrate seed dispersal in semi-natural habitats, suggesting that empty niches, avoidance of competitors and exploitation of mutualists, respectively, are important.7 The study highlights the importance of estimating invasion success across a wide region, but analyses of specific invasion stages are also needed. Reproductive traits, which may be more relevant for long-distance colonization, and vegetative traits, which determine local dominance and persistence, were, nevertheless, both related to abundance within islands.Journal of Ecology(2005)doi: 10.1111/j.1365-2745.2005.00979.x [ABSTRACT FROM AUTHOR]

Explores the interrelationship between island area, number of species and habitat diversity. Survey of dicotyledonous plant species on small islands near Shetland, Scotland; Positive correlations between species number, island area and number of habitat types; Existence of habitat types as a function of island size.

(1) A survey of the vegetation of eleven sites affected by herring gulls along the Aberdeenshire coast and on the Isle of May (Firth of Forth), and of adjacent unaffected areas, revealed that the vegetation of gull-affected sites consisted of a seasonal, species-poor community, in which annual and ruderal species predominated. Of particular prevalence were Atriplex hastata, Holcus lanatus, Poa annua, Rumex acetosa, R. crispus, Stellaria media and Tripleurospermum maritimum. By contrast, the vegetation on adjacent areas unaffected by gulls was generally a perennial grass sward in which Festuca rubra was the dominant species. (2) Observations from a hide at two study sites revealed that four principal gull activities affect the vegetation of breeding sites treading, the digging of scrapes and collecting of nest-materials, boundary clashes associated with gull territorial behaviour, and defecation. Each of these activities had an uneven spatial distribution within the colony area. Although all four activities exerted important influences on the vegetation, disturbance and destruction of vegetation associated with boundary clashes appeared to be a particularly significant activity for the plants occurring in gull colonies. (3) Experimental fieldwork involving the removal of vegetation (to simulate the ultimate effects of gull disturbance) also revealed the importance of disturbance. Annual plants (Stellana media, Atriplex patula and Senecio vulgaris) became established on an area formerly occupied by Holcus lanatus. (4) Mapping of the distribution of plant species within the two study sites over a 2-year period suggested that although gulls were responsible for the vegetation of the colonies as a whole, factors other than gull activities played a more significant role in determining the detailed distribution of plant species within the colonies. At the sites studied, differences in soil-nutrient concentrations and sea-spray deposition appeared to influence the... [ABSTRACT FROM AUTHOR]