Search

Land abandonment promotes forest expansion into abandoned agricultural lands in Europe. This process leads to changes that affect several ecosystem services, but it is considered a low‐cost strategy to restore soil functions in past agricultural lands. Soil microbial communities play a key role in restoring functions. However, the relationship among forest expansion, microbial communities, and soil functioning is unclear.In this study, we used a Juniperus thurifera expansion gradient on abandoned agricultural lands in Alto Tajo National Park (Spain) to discover the changes elicited by the soil microbial communities and their functions along this gradient considering two microhabitats, under the canopy and open areas. Specifically, our objectives were (i) to analyse how soil properties (organic matter and pH), microbial communities (using PLFAs‐NFLAs) and enzymatic activities (related to C, N and P cycling) varied along the forest expansion gradient and between microhabitats and (ii) to decipher the pathways by which soil properties control the carbon and nutrient cycling in soils.The forest expansion gradient had a direct negative effect on phosphatase activity. The microhabitat showed a positive direct effect on organic matter content, pH, actinomycetes and arbuscular mycorrhizal fungi biomass and on soil C and P cycling. Moreover, the biomass of gram‐positive bacteria determined the biomass of other microbial groups.Synthesis and Applications: Though its effectiveness is variable, passive restoration can be more effective than active restoration. Our research indicates that passive tree colonisation of past agricultural land is enough to achieve soil functionality similar to a mature forest for most variables studied. However, some variables would need more time to reach mature forest levels, such as total microbial biomass and organic matter content. Therefore, to support ecosystem recovery, the management of this applied forest ecology strategy requires continuous monitoring of newly established trees and soil to elucidate the time needed to achieve mature soil properties. [ABSTRACT FROM AUTHOR]

Ecologists have long recognized that seed dispersal mutualisms trigger natural regeneration and range expansion of animal‐dispersed trees. Yet we lack empirical studies addressing whether frugivore activity influences founder effects, which reduce genetic diversity at the colonization front of expanding populations.Here, we evaluate the contribution, from both demographic and genetic perspectives, of animal frugivores dispersing seeds across an expansion gradient. We used DNA barcoding for frugivores identification and highly polymorphic genetic markers (SSRs) for maternal analysis of juniper seeds to investigate how (1) stand maturity, (2) microhabitat types and (3) foraging patterns shape the distribution of the maternal progenies along this gradient.We expect both reduced seed rain density and low numbers of source trees contributing to the seed rain at the colonization front, with limited availability of local fruiting trees. We also anticipated that large‐sized frugivore species would promote maternally rich seed rain due to their ability to mix seed progenies during digestive processing and move further distances across the landscape.Contrary to our expectations, we found that all identified frugivores produced dense and genetically diverse seed rains across the expansion gradient, even at the colonization front, characterized by scarce fruiting trees.Synthesis: Our findings shed light on the fundamental and applied implications of plant–frugivore interactions in shaping highly diverse second‐growth forests. These results emphasize the necessity of preserving plant–animal mutualistic interactions to ensure the persistence and expansion of natural tree populations, particularly in formerly fragmented landscapes [ABSTRACT FROM AUTHOR]

The phyllosphere is a wide and complex ecosystem that provides a key support for microbial diversity. Fungal communities inhabiting the leaf are functionally variable and play important roles on plant performance. Factors conditioning the arrival and colonization of fungal communities will determine the phyllosphere fungal composition. Plant identity, leaf functional traits and host plant phylogeny have been shown to be regulators of the microbial colonization of the leaves, and can be considered as biotic filters determining the assembly of phyllosphere fungal communities. By high‐throughput sequencing we analysed the phyllosphere fungal communities from 38 Mediterranean woody plant species in two forests of south‐eastern Iberian Peninsula. We analysed the effect of plant species and site on fungal community composition. We also tested the effect of leaf functional traits and plant phylogeny on plant species differences in their fungal communities, and on the structure of the plant–fungus interaction network. Plant species account for a larger proportion than site in the variability of the composition of phyllosphere fungal communities. Leaf traits and host phylogeny influence the arrival and colonization of phyllosphere fungal communities across plant species. Plants with pubescent leaves and phylogenetically closer harbour more similar communities of decomposers, pathogens and epiphytes. Leaf habit (i.e. evergreen versus deciduous) also influences the community composition of decomposer and epiphytic fungi. Leaf carbon, leaf water content and leaf mass per area affect differentially each functional guild. Plant–fungus interaction networks present a modular structure in which plants belonging to the same module share more fungal species and are phylogenetically closer. We provide evidence that even though phyllosphere fungal communities are complex ecosystems, fungi with contrasting relationships with the plant (decomposers, epiphytes and pathogens) respond similarly to a common subset of leaf traits that impose physical limitations to the assembly of phyllosphere fungal communities. [ABSTRACT FROM AUTHOR]

Forests provide a wide range of provisioning, regulating and cultural services of great value to societies across the Mediterranean basin. In this study, we reviewed the scientific literature of the last 30 years to quantify the magnitude of projected changes in ecosystem services provision by Mediterranean forests under IPCC climate change scenarios. We classified the scenarios according to the temperature threshold of 2℃ set by the Paris Agreement (below or above). The review of 78 studies shows that climate change will lead to a general reduction in the provision of regulating services (e.g. carbon storage, regulation of freshwater quantity and quality) and a general increase in the number of fires, burnt areas and generally, an increase in climate‐related forest hazards (median + 62% by 2100). Studies using scenarios above the 2℃ threshold projected significantly more negative changes in regulating services than studies using scenarios below this threshold. Main projected trend changes on material services (e.g. wood products), were less clear and depended on (i) whether or not the studies considered the interaction between the rise in temperatures and other drivers (e.g. forest management, CO2 fertilization) and (ii) differences in productivity responses across the tree species evaluated. Overall, the reviewed studies projected significant reductions in range extent and habitat suitability for the most drought‐sensitive forest species (e.g. −88% Fagus sylvatica), while the amount of habitat available for more drought‐tolerant species will remain stable or increase; however, the magnitude of projected change for these more xeric species was limited when high‐end extreme climatic scenarios were considered (above Paris Agreement). Our review highlights the benefits that climate change mitigation (to keep global mean temperature increase <2℃) can bring in terms of service provision and conservation of Mediterranean forests. [ABSTRACT FROM AUTHOR]

Questions: The assembly of plant communities depends strongly on mechanisms that determine the recruitment of different plant species. Studying recruitment using a trait‐based approach may help in the search for general or dominant mechanisms involved in this process. Here, we try to disentangle what traits of saplings and established (canopy) plants can be considered as functional for recruitment, and whether the complementarity of these functional traits may be a driver of the plant community assembly. Location: Regional. Two pine–oak forest communities in Sierra Sur de Jaén and one in Sierra de Segura, southeast of the Iberian peninsula. Methods: In each forest community, we established three 50 m × 50 m plots, where we identified the saplings of each species recruiting under the canopy of each species or in open interspaces. The study focuses on 37 woody species. Measures of 18 traits were conducted for 30 saplings and 10 adults of each species. Results: Seed mass and the ratio height:basal diameter of saplings were positively associated with species abundance in the sapling bank under vegetation, while abundance in the sapling bank in open interspaces was only related to the type of mycorrhizal association. On the other hand, some traits of adult plants (leaf mass per unit area [LMA], seed dispersal mechanism, leaf habit and branch density) favour the recruitment of other species in their close proximity. However, we found only circumstantial evidence of canopy/recruit trait complementarity affecting recruitment. Conclusions: Our results suggest that the assembly of canopy–recruit interactions is primarily driven by the filtering effect of canopy species on recruitment, through traits that affect both seed arrival and soil properties. Species abundance in the sapling bank was related to resource acquisition traits. We did not find any clear evidence supporting that trait complementarity is involved in the interaction between canopy and recruit species. [ABSTRACT FROM AUTHOR]

Rising ozone (O3) concentrations, coupled with an increase in drought frequency due to climate change, pose a threat to plant growth and productivity which could negatively affect carbon sequestration capacity of Northern Hemisphere (NH) forests. Using long‐term observations of O3 mixing ratios and soil water content (SWC), we implemented empirical drought and O3 stress parameterizations in a coupled stomatal conductance–photosynthesis model to assess their impacts on plant gas exchange at three FLUXNET sites: Castelporziano, Blodgett and Hyytiälä. Model performance was evaluated by comparing model estimates of gross primary productivity (GPP) and latent heat fluxes (LE) against present‐day observations. CMIP5 GCM model output data were then used to investigate the potential impact of the two stressors on forests by the middle (2041–2050) and end (2091–2100) of the 21st century. We found drought stress was the more significant as it reduced model overestimation of GPP and LE by ~11%–25% compared to 1%–11% from O3 stress. However, the best model fit to observations at all the study sites was obtained with O3 and drought stress combined, such that the two stressors counteract the impact of each other. With the inclusion of drought and O3 stress, GPP at CPZ, BLO and HYY is projected to increase by 7%, 5% and 8%, respectively, by mid‐century and by 14%, 11% and 14% by 2091–2100 as atmospheric CO2 increases. Estimates were up to 21% and 4% higher when drought and O3 stress were neglected respectively. Drought stress will have a substantial impact on plant gas exchange and productivity, off‐setting and possibly negating CO2 fertilization gains in future, suggesting projected increases in the frequency and severity of droughts in the NH will play a significant role in forest productivity and carbon budgets in future. [ABSTRACT FROM AUTHOR]

Abstract: Over the past 15 years, 3 million hectares of forests have been converted into shrublands or grasslands in the Mediterranean countries of the European Union. Fire and drought are the main drivers underlying this deforestation. Here we present a conceptual framework for the process of fire‐induced deforestation based on the interactive effects of fire and drought across three hierarchical scales: resistance in individuals, resilience in populations, and transitions to a new state. At the individual plant level, we review the traits that confer structural and physiological resistance, as well as allow for resprouting capacity: deforestation can be initiated when established individuals succumb to fire. After individuals perish, the second step toward deforestation requires a limited resilience from the population, that is, a reduced ability of that species to regenerate after fire. If individuals die after fire and the population fails to recover, then a transition to a new state will occur. We document trade‐offs between drought survival and fire survival, as embolism resistance is negatively correlated with fire tolerance in conifers and leaf shedding or drought deciduousness, a process that decreases water consumption at the peak of the dry season, temporally increases crown flammability. Propagule availability and establishment control resilience after mortality, but different hypotheses make contrasting predictions on the drivers of post‐fire establishment. Mycorrhizae play an additional role in modulating the response by favoring recovery through amelioration of the nutritional and water status of resprouts and new germinants. So far, resprouter species such as oaks have provided a buffer against deforestation in forests dominated by obligate seeder trees, when present in high enough density in the understory. While diversifying stands with resprouters is often reported as advantageous for building resilience, important knowledge gaps exist on how floristic composition interacts with stand flammability and on the “resprouter exhaustion syndrome,” a condition where pre‐fire drought stress, or short fire return intervals, seriously restrict post‐fire resprouting. Additional attention should be paid to the onset of novel fire environments in previously fire‐free environments, such as high altitude forests, and management actions need to accommodate this complexity to sustain Mediterranean forests under a changing climate. [ABSTRACT FROM AUTHOR]

Abstract: Questions: What are the differences in tree growth and resilience in response to extreme droughts between three co‐existing pine tree species? Are growth–resilience components more influenced by intrinsic (age, tree height) or extrinsic factors (mass effects or functional diversity of the neighbourhood)? Is the tree's vulnerability to drought buffered by the functional diversity of the surrounding plant community? Location: Mediterranean forest, northeast Spain. Methods: Trees from three co‐existing pine species with different drought tolerances (Aleppo pine – Pinus halepensis Mill.; Black pine – Pinus nigra subsp. salzmannii (Dunal) Franco; Scots pine – Pinus sylvestris L.) were sampled. The average age of the studed pines was ~30 years. Radial growth from 1980 to 2015 was measured and the pines’ responses to the most severe recent droughts (2005 and 2012) were studied by relating different growth resilience components (Rt, resistance; Rc, recovery; RRs, relative resilience) with intrinsic (age and height) and extrinsic factors of the neighbouring community around each tree. The considered extrinsic factors were CWM and niche complementarity of tree (height), leaf (specific leaf area, leaf dry matter content) and wood (wood specific gravity) traits. The way in which these factors affected growth resilience to drought was assessed. Results: For the whole study period we found lower growth of Scots pine than Aleppo pine, but similar resilience components (except for higher Rt in 2005 for the former species). Despite each drought year resulting in distinct responses, the growth resilience to drought was mostly dependent on tree age for Aleppo pine, while functional diversity modulated a high percentage of the resilience variance of Scots pine. Black pine had an intermediate strategy. CWM explained, in general, less variance of the resilience components than functional diversity. Conclusions: The positive effect of surrounding functional diversity on Scots pine could be related to a greater resistance to drought, likely due to improved resource acquisition favouring its performance at the dry limit of its distribution area. Intrinsic tree features, mass effects and functional diversity differently shape growth resilience to different droughts for co‐existing tree species. [ABSTRACT FROM AUTHOR]

Tree populations at the low-altitudinal or -latitudinal limits of species' distributional ranges are predicted to retreat toward higher altitudes and latitudes to track the ongoing changes in climate. Studies have focused on the climatic sensitivity of the retreating species, whereas little is known about the potential replacements. Competition between tree species in forest ecotones will likely be strongly influenced by the ecophysiological responses to heat and drought. We used tree-ring widths and δ13C and δ18O chronologies to compare the growth rates and long-term ecophysiological responses to climate in the temperate-Mediterranean ecotone formed by the deciduous Fagus sylvatica and the evergreen Quercus ilex at the low altitudinal and southern latitudinal limit of F. sylvatica (NE Iberian Peninsula). F. sylvatica growth rates were similar to those of other southern populations and were surprisingly not higher than those of Q. ilex, which were an order of magnitude higher than those in nearby drier sites. Higher Q. ilex growth rates were associated with high temperatures, which have increased carbon discrimination rates in the last 25 years. In contrast, stomatal regulation in F. sylvatica was proportional to the increase in atmospheric CO2. Tree-ring δ18O for both species were mostly correlated with δ18O in the source water. In contrast to many previous studies, relative humidity was not negatively correlated with tree-ring δ18O but had a positive effect on Q. ilex tree-ring δ18O. Furthermore, tree-ring δ18O decreased in Q. ilex over time. The sensitivity of Q. ilex to climate likely reflects the uptake of deep water that allowed it to benefit from the effect of CO2 fertilization, in contrast to the water-limited F. sylvatica. Consequently, Q. ilex is a strong competitor at sites currently dominated by F. sylvatica and could be favored by increasingly warmer conditions. [ABSTRACT FROM AUTHOR]

Aim Production of wood charcoal is an ancient form of anthropogenic forest use that existed for millennia in Mediterranean countries and only vanished in the last century. As a result, thousands of abandoned charcoal kiln platforms still occur in present-day woodlands. Because of peculiar light and soil properties, the understorey vegetation at these platforms may differ from the surrounding stands. Our study investigated, for the first time, the effects of abandoned kiln platforms on understorey vegetation diversity, composition and biomass production in forests of a Mediterranean area. Location Tuscany, central Italy. Methods One 3 × 3 m kiln plot on charcoal kiln area and one 3 × 3 m control plot in the surrounding stands were established in 59 representative sites located in three major forest types dominated by evergreen sclerophylls, deciduous oaks and beech. In each plot, diversity and composition of the understorey community were analysed, together with soil factors (content of C, N, C:N ratio, pH) and light conditions (PAR). A 50 × 50 cm frame was randomly placed in each plot to measure biomass production. Results The charcoal kiln habitat positively affected understorey diversity and above-ground biomass, as well as the content of C, C:N ratio, pH and light availability. Significant compositional differences between the two plot types occurred, although to a variable extent for the three forest types. Graminoids were more abundant on kiln plots, and 12 indicator species were found for this habitat in deciduous oak forests. Higher values of cover and biomass showed the lack of detrimental effects of wood charcoal accumulation on understorey productivity. Conclusions Long-term wood charcoal production in Mediterranean woodlands has caused long-lasting effects on the understorey via persistent changes in abiotic factors. Hence, former kiln platforms represent anthropogenic microhabitats that increase biodiversity and fine-scale heterogeneity of forest ecosystems. Conservation measures are advocated to preserve them against various external threats. [ABSTRACT FROM AUTHOR]

Human activities are historical ecological drivers, and we need to better understand their effects on ecosystems. In particular, they have been very important in the shaping of the Mediterranean biodiversity hotspot. Researchers and managers nonetheless lack knowledge concerning the impacts of their combinations and their current intensity on the structure of forest ecosystems of the southern part of the Mediterranean basin. In this study, we have develped a new methodology in order to understand the impacts of combined pastoral and woodcutting activities on the forest structure of the still ill-described but ecologically and economically important Moroccan Middle Atlas cedar forests. In a 40 000 ha forest, we chose 103 sites and sampled human activities through proxies and forest structures through circumference and vertical structures. A typology of sites yielded four human activity types: dominant pastoral activities, dominant oak cutting or cedar cutting activities, and an intermediate mid-disturbance type. This typology did not depend on altitude or substrate, confirming that the ecosystem structures linked to the different types depend more on human activities than on main environmental parameters. Pastoral activities modified forests the most, converting them to parklands with reduced canopies and low dynamics but high tree maturation. Woodcutting activities induced gap dynamics, favoring Cedrus atlantica in favorable environmental conditions and Quercus ilex otherwise, while they affected vertical structure depending on the local environment and competition for light and soil resources. Moderately disturbed stands showed forest maturation with low competition for light. Unlike previous studies, we found no evidence of a general degradation of cedar forests due to local human activities. However, cedar logging has reduced standing basal area regionally and one third of the sites may have vulnerable cedar populations due to pastoral activities and to unfavorable environmental conditions. These results can direct future research and management needs for a better protection of Mediterranean forests and parklands and their biodiversity, although to be effective such efforts must also partner with sociogeographical studies. [ABSTRACT FROM AUTHOR]

Aim Recently, increasing attention has been devoted to the development of sustainable forestry practices aimed at finding a balance between the maintenance and enhancement of different forest resources. However, the long-term, large-scale effects of conservation-oriented forest management on vertebrates have been poorly studied. We tested the hypothesis that conservation-oriented forest management, being conceived to mimic the dynamics of a natural forest succession more closely than does traditional forestry, causes a less severe long-term impact on the distribution of forest vertebrates. Location Molise region, Central Italy. Methods We proposed a hybrid modelling framework based on the integration of a forest dynamic model (' LANDIS- II') with species distribution models (SDMs). The framework was applied on four forest specialist vertebrates (tiny salamander, slow worm , Eurasian nuthatch and Leisler's bat) and included three components: forest dynamic model ( FDM), SDMs and spatial pattern analysis ( SPA). FDM was used to simulate spatially explicit patterns of forest succession for the current time and for 2050, imposing three alternative forestry scenarios. The simulated forest succession patterns were analysed through SPA to calculate spatialized landscape metrics that were adopted as environmental predictors for SDMs. Landscape trajectories were calculated on current and future species distributions predicted with SDMs to evaluate the effect of alternative forestry practices on their extent and fragmentation. Results Forest management mainly affected the spatial configuration rather than the extent of the species potential distributions. Conservation-oriented forest management was more favourable than traditional forestry in increasing the extent and reducing the fragmentation of the studied species' distributions. Main conclusions Conservation-oriented forest management, by mimicking the dynamics of a natural forest succession more closely than did traditional practices, favoured elements, such as forest unevenness, species richness, aggregation of patches and variability in their distances, which emerged as fundamental characteristics for preserving the long-term persistence of forest vertebrates. [ABSTRACT FROM AUTHOR]

Aim As a consequence of multiple cycles of deforestation and reforestation, most forest landscapes in Europe consist of a complex mosaic of patches of different successional ages. Despite the biogeographical distinctiveness of the Mediterranean region, studies on the effects of forest age on plant species diversity and composition are almost lacking for this area. This paper evaluates the influence of forest successional age on plant species richness and composition in various forest types of Mediterranean Italy. Location The Natura 2000 network of Siena Province, Tuscany, Italy. Methods Occurrence data on vascular plant species in 208 forest plots were obtained from a larger data set sampled with a stratified random design. The forest successional age of each plot was quantified through a series of historical maps. Species richness and composition were related to the age of the forest by means of GIS techniques and univariate and multivariate statistical analyses. Results Total species richness markedly decreased with increasing successional age due to a significant decrease in the richness of open-habitat species which was not matched by increasing richness of mature forest species. Successional age was the key factor in controlling species richness, while local environmental properties emerged as the main factors shaping community composition. The different forest types showed different temporal trends of species richness and composition and different hierarchies of explanatory factors. Main conclusions Forest successional age emerged as an important factor affecting both species richness and composition, even within the same forest type. Thus, the classification and prioritization of Mediterranean forests exclusively based on present physiognomy or environmental variables causes loss of information about species richness and composition; this could be detrimental for biodiversity conservation. [ABSTRACT FROM AUTHOR]

The East Mediterranean region is a global biodiversity hotspot for vertebrates and plants. Although oaks ( Quercus) are the dominant tree species in semi-natural Mediterranean forests, the insect species richness associated with East Mediterranean oak forest has been insufficiently studied., Species richness and composition of the saproxylic beetle assemblage, including its seasonal variation, of a stand of old oaks ( Quercus calliprinos) in northern Israel was investigated. Flight-interception traps were used to sample beetles over a period of 2 years. In addition, a set of pitfall traps was placed in the trunk hollows in the second year of the study., Fifty-two saproxylic beetle species were found associated with oaks in the field study. Among them, two saproxylic click-beetle species were previously unknown to science, and eight species represent new records for Israel. Both the number of species and the number of individuals showed two distinct phenological peaks during the year., A preliminary list of saproxylic beetles inhabiting oaks in Israel was prepared and biogeographical distribution, host plants, habitat guild, and activity period are presented for each species. Together with our own data, the literature survey conducted for 19 beetle families established that at least 124 saproxylic beetle species are associated with oaks in Israel while about 40% of them are unique to the Levantine region. As most localities with old-growth oak forest structures are small and isolated, ongoing management should have high priority despite the fact that these forests already receive protection. [ABSTRACT FROM AUTHOR]

Patterns of forest biodiversity are shaped by a complex set of processes operating over different spatial scales. Climate may largely determine species richness at regional scales, but biotic interactions and disturbance events are known to be important at local scales. The interactions between these local and regional processes are poorly understood, complicating efforts to manage for biodiversity., In this study, we used Spanish forest inventory data, together with hierarchical Bayesian models, to analyse how different harvest intensities affect patterns of species richness in a 152 000 km2 area in central Spain. Particularly, we quantified the interacting effects of locally applied silvicultural disturbances, of those applied in the surrounding landscape, and of the regional climate on native tree species richness., Our study supports the overall hypothesis that a hierarchical set of processes influence species richness, with regional climate contributing to shape the impacts of local harvesting practices and other environmental variables (topography and productivity)., In particular, we found that partial harvesting in both coniferous and broad-leaved Mediterranean forests may support greater tree species richness than complete harvesting and no management. However, this effect depended on the ecosystem and the surrounding landscape, being much less likely in semi-arid regions under water stress conditions and in landscapes dominated by managed forests (and particularly by completely harvested stands)., In general, forest stands exhibited increased tree species richness when surrounded by species-rich riparian forests, probably due to metacommunity dynamics and/or ecological history (land uses) of the area., Synthesis and applications. The effects of forest management on local species richness were shaped by coarse climate conditions and by the type and extent of other management practices in the surrounding landscapes. Therefore, to develop effective forestry management plans that optimize local diversity, we need to (i) apply regionally tailored practices with lower harvest intensities in areas of greater hydric stress; (ii) avoid the extensive application of a single silvicultural system over large areas and (iii) preserve a mosaic of species-rich forests that can act as sources of colonizers to enrich the regenerating stands nearby. [ABSTRACT FROM AUTHOR]

Most large-scale multispecies studies of tree growth have been conducted in tropical and cool temperate forests, whereas Mediterranean water-limited ecosystems have received much less attention. This limits our understanding of how growth of coexisting tree species varies along environmental gradients in these forests, and the implications for species interactions and community assembly under current and future climatic conditions. Here, we quantify the absolute effect and relative importance of climate, tree size and competition as determinants of tree growth patterns in Iberian forests, and explore interspecific differences in the two components of competitive ability (competitive response and effect) along climatic and size gradients. Spatially explicit neighborhood models were developed to predict tree growth for the 15 most abundant Iberian tree species using permanent-plot data from the Spanish Second and Third National Forest Inventory (IFN). Our neighborhood analyses showed a climatic and size effect on tree growth, but also revealed that competition from neighbors has a comparatively much larger impact on growth in Iberian forests. Moreover, the sensitivity to competition (i.e. competitive response) of target trees varied markedly along climatic gradients causing significant rank reversals in species performance, particularly under xeric conditions. We also found compelling evidence for strong species-specific competitive effects in these forests. Altogether, these results constitute critical new information which not only furthers our understanding of important theoretical questions about the assembly of Mediterranean forests, but will also be of help in developing new guidelines for adapting forests in this climatic boundary to global change. If we consider the climatic gradients of this study as a surrogate for future climatic conditions, then we should expect absolute growth rates to decrease and sensitivity to competition to increase in most forests of the Iberian Peninsula (in all but the northern Atlantic forests), making these management considerations even more important in the future. [ABSTRACT FROM AUTHOR]

Six Italian research sites, representative of Mediterranean and mountain forests and equipped with eddy covariance towers, were used in this study to test the performance of the CENTURY 4.5 model in predicting the dynamics of soil organic carbon (SOC) changes during the commitment periods (CP) of the Kyoto Protocol (2008-2012; 2013-2017). We show that changes in SOC stocks over short periods of time are difficult to detect, and explore the potential for models to be used for reporting SOC changes for forests that will remain forests, under Article 3.4 of the Kyoto Protocol. As the eddy covariance flux sites have been active for 10 yr on average, being initiated over the period between 1996 and 1998, the model was evaluated by comparing the modelled SOC stocks with those directly measured at each site in different years. Since long term series of observed values for soil carbon were not available, the validation of other model outputs such as net primary production (NPP) and soil nitrogen stocks, gives some confidence in long term simulations. Once the model performance was evaluated, two climate change scenarios, A1F1 (world markets-fossil fuel intensive) and B2 (local sustainability), were considered for prediction of C stock changes during the commitment periods of the Kyoto Protocol. In general, despite the need to consider the uncertainties in the direct measurements, at each site model fit with measured SOC stocks was good, with the simulated values within the standard deviation of the measurements. In this regard, the similarity between the SOC measured in 2008 and that predicted for the two forthcoming commitment periods points out the difficulty of detecting carbon stock changes by direct measurements, given the closeness in time to the present of the commitment periods. In any case, all sites show positive variations that are possibly related to the fertilization effects of increasing CO and to longer growing seasons, since no change in management occurred. Compared with the SOC measured in 2008, at the end of the second commitment period, the modelled SOC variations were smaller than 2% in the Mediterranean forests and comprised between 2% and 7% in the mountain forests. These variations, although small, indicate it might be possible to statistically detect differences after 10 yr in mountain forests with a reasonable number of samples. In conclusion, this work shows that since SOC stock changes are minimal within both CP, models can be effective tools for estimating future changes in SOC amounts, as an alternative to, or in support of, direct measurements when a short period of time is considered. [ABSTRACT FROM AUTHOR]

The article presents a study which evaluates the plant regeneration and plantation diversity of pines with the use of abiotic and biotic factors in southern Spain. The study analyzed the sapling and seedling density and plant species richness of pine trees. It shows that a diverse and abundant seedling bank was seen at low-to-mid-altitude plantations while monospecific seedling bank was found in high-altitude plantations. It advises to have active management in high-density plantations.

Destruction and fragmentation of habitats represent one of the most important threats for biodiversity. Here, we examined the effects of fragmentation in Mediterranean forests on the epiphytic lichen Lobaria pulmonaria (Lobariaceae). We tested the hypothesis that not only the level of fragmentation affects L. pulmonaria populations, but also the quality of the habitat and the nature of the surrounding matrix affect them. The presence and abundance of the lichen was recorded on 2039 trees in a total of 31 stands. We recorded habitat quality and landscape variables at three hierarchical levels: tree, plot, and patch. We found that L. pulinonaria tends to occur in trees with larger diameters in two types of surveyed forests. In Quercus pyrenaica patches, the mean diameter of colonized trees was smaller, suggesting the importance of bark roughness. Factors affecting the presence and cover of the lichen in each type of forest were different. There was a strong positive influence of distance from a river in beech forests, whereas proximity to forest edge positively affected in oak forests. The influence of the surrounding matrix was also an important factor explaining the epiphytic lichen abundance. [ABSTRACT FROM AUTHOR]

It has commonly been argued that many territorial species select their breeding sites following an ideal despotic distribution model, in which the most productive, high-quality territories are more frequently occupied. Theoretical and empirical studies have shown that this occupancy pattern may have population regulatory consequences, leading to density dependence in heterogeneous habitats. During a 9-year research project in a forested area of south-eastern Spain, we tested some of the predictions of the ideal despotic distribution model and the site-dependent population regulation theory in a migratory raptor species, the booted eagle Hieraaetus pennatus. Contrary to the predictions of the despotic model, our results showed that the temporal pattern of territorial occupation did not differ from randomness, and that the territory occupancy rate was not significantly related to the reproductive parameters considered. At population level, the breeding variables were density independent, suggesting the absence of site-dependent regulation. In addition, we were unable to find significant differences in the habitat characteristics between high-quality and low-quality territories, classified according to the criteria of both occupancy frequency and average productivity. Overall, our results suggest that booted eagles select their territories at random, probably due to the lack of strong environmental heterogeneity, and that occupancy rate is not a good measure of territory quality for the population studied. [ABSTRACT FROM AUTHOR]

The capacity of Phytophthora ramorum to colonize the inner bark of 18 native and two exotic tree species from the Iberian Peninsula was tested. Living logs were wound-inoculated in a growth chamber with three isolates belonging to the EU1 and two to the NA1 clonal lineages of P. ramorum. Most of the Quercus species ranked as highly susceptible in experiments carried out in summer, with mean lesion areas over 100 cm2 in Q. pubescens, Q. pyrenaica, Q. faginea and Q. suber and as large as 273 cm2 in Q. canariensis, ca. 40 days after inoculation. Quercus ilex ranked as moderately susceptible to P. ramorum, forming lesions up to 133 cm2 (average 17·2 cm2). Pinus halepensis and P. pinea were highly susceptible, exhibiting long, narrow lesions; but three other pine species, P. pinaster, P. nigra and P. sylvestris, were resistant to slightly susceptible. No significant difference in aggressiveness was found between the isolates of P. ramorum. In addition, there was evidence of genetic variation in susceptibility within host populations, and of significant seasonal variation in host susceptibility in some Quercus species. The results suggest a high risk of some Iberian oaks to P. ramorum, especially in forest ecosystems in southwestern Spain, where relict populations of Q. canariensis grow amongst susceptible understory species such as Rhododendron ponticum and Viburnum tinus. One isolate of P. cinnamomi used as positive control in all the inoculations was also highly aggressive to Iberian oaks and Eucalyptus dalrympleana. [ABSTRACT FROM AUTHOR]

Aim To explore potential shifts in vegetation and fire regime in some dominant forest types in the north-eastern part of the Mediterranean basin under climate change. Location Two altitudinal gradients in the continental part of Greece. Methods We developed a forest gap dynamics simulator that provides feedback from the stand to its water balance and flammability status. The model is used to simulate vegetation dynamics in two mountainous areas, currently found under different aridity conditions. Two climatic change scenarios (Intergovernmental Panel on Climate Change A1 and B2) were applied to explore differences in the response of the established forest types. In addition we explicitly accounted for the role of fire, under both current and altered climate patterns. Results Fire was identified to play a significant role in low-altitude sites. Its significance increased with the severity of the climate change scenario. Elevational shifts of the dominant species were simulated for each site, while in some cases these changes were associated with a shorter fire cycle and a frequent resetting of processes of vegetation change. Main conclusions Our simulations suggest a greater vulnerability of mountainous Mediterranean drier areas regarding compositional alteration and flammability trends. Changes in vegetation could take place through both a discrete and synergistic realization of changes in the drought stress and fire frequency. [ABSTRACT FROM AUTHOR]

The estimation of the carbon balance in ecosystems, regions, and the biosphere is currently one of the main concerns in the study of the ecology of global change. Current remote sensing methodologies for estimating gross primary productivity are not satisfactory because they rely too heavily on (i) the availability of climatic data, (ii) the definition of land-use cover, and (iii) the assumptions of the effects of these two factors on the radiation-use efficiency of vegetation (RUE). A new methodology is urgently needed that will actually assess RUE and overcome the problems associated with the capture of fluctuations in carbon absorption in space and over time. Remote sensing techniques such as the widely used reflectance vegetation indices (e.g. NDVI, EVI) allow green plant biomass and therefore plant photosynthetic capacity to be assessed. However, there are vegetation types, such as the Mediterranean forests, with a very low seasonality of these vegetation indices and a high seasonality of carbon uptake. In these cases it is important to detect how much of this capacity is actually realized, which is a much more challenging goal. The photochemical reflectance index (PRI) derived from freely available satellite information (MODIS sensor) presented for a 5-year analysis for a Mediterranean forest a positive relationship with the RUE. Thus, we show that it is possible to estimate RUE and GPP in real time and therefore actual carbon uptake of Mediterranean forests at ecosystem level using the PRI. This conceptual and technological advancement would avoid the need to rely on the sometimes unreliable maximum RUE. [ABSTRACT FROM AUTHOR]

The oxygen stable isotope composition ( δ18O) of CO2 is a valuable tool for studying the gas exchange between terrestrial ecosystems and the atmosphere. In the soil, it records the isotopic signal of water pools subjected to precipitation and evaporation events. The δ18O of the surface soil net CO2 flux is dominated by the physical processes of diffusion of CO2 into and out of the soil and the chemical reactions during CO2–H2O equilibration. Catalytic reactions by the enzyme carbonic anhydrase, reducing CO2 hydration times, have been proposed recently to explain field observations of the δ18O signatures of net soil CO2 fluxes. How important these catalytic reactions are for accurately predicting large-scale biosphere fluxes and partitioning net ecosystem fluxes is currently uncertain because of the lack of field data. In this study, we determined the δ18O signatures of net soil CO2 fluxes from soil chamber measurements in a Mediterranean forest. Over the 3 days of measurements, the observed δ18O signatures of net soil CO2 fluxes became progressively enriched with a well-characterized diurnal cycle. Model simulations indicated that the δ18O signatures recorded the interplay of two effects: (1) progressive enrichment of water in the upper soil by evaporation, and (2) catalytic acceleration of the isotopic exchange between CO2 and soil water, amplifying the contributions of ‘atmospheric invasion’ to net signatures. We conclude that there is a need for better understanding of the role of enzymatic reactions, and hence soil biology, in determining the contributions of soil fluxes to oxygen isotope signals in atmospheric CO2. [ABSTRACT FROM AUTHOR]

The role of species diversity on ecosystem resistance in the face of strong environmental fluctuations has been addressed from both theoretical and experimental viewpoints to reveal a variety of positive and negative relationships. Here we explore empirically the relationship between the richness of forest woody species and canopy resistance to extreme drought episodes. We compare richness data from an extensive forest inventory to a temporal series of satellite imagery that estimated drought impact on forest canopy as NDVI (normalized difference vegetation index) anomalies of the dry summer in 2003 in relation to records of previous years. We considered five different types of forests that are representative of the main climatic and altitudinal gradients of the region, ranging from lowland Mediterranean to mountain boreal-temperate climates. The observed relationship differed among forest types and interacted with the climate, summarised by the Thorntwaite index. In Mediterranean Pinus halepensis forests, NDVI decreased during the drought. This decrease was stronger in forests with lower richness. In Mediterranean evergreen forests of Quercus ilex, drought did not result in an overall NDVI loss, but lower NDVI values were observed in drier localities with lower richness, and in more moist localities with higher number of species. In mountain Pinus sylvestris forests NDVI decreased, mostly due to the drought impact on drier localities, while no relation to species richness was observed. In moist Fagus sylvatica forests, NDVI only decreased in plots with high richness. No effect of drought was observed in the high mountain Pinus uncinata forests. Our results show that a shift on the diversity-stability relationship appears across the regional, climatic gradient. A positive relationship appears in drier localities, supporting a null model where the probability of finding a species able to cope with drier conditions increases with the number of species. However, in more moist localities we hypothesize that the proportion of drought-sensitive species would increase in richer localities, due to a higher likelihood of co-occurrence of species that share moist climatic requirements. The study points to the convenience of considering the causes of disturbance in relation to current environmental gradients and historical environmental constraints on the community. [ABSTRACT FROM AUTHOR]

A major debate in the study of biodiversity concerns its influence on ecosystem functioning. We compared whether wood production in forests was associated with tree functional group identity (i.e. deciduous, conifer or sclerophylous), tree species richness (1–≥ 5) and tree functional group richness (1–3) by comparing more than 5000 permanent plots distributed across Catalonia (NE Spain). Deciduous forests were more productive than coniferous and sclerophylous forests. Wood production increased with tree species richness. However, functional group richness increased wood production only in sclerophylous forests. When other forest structure, environmental variables and management practices were included in the analysis, tree functional group identity and species richness still remained significant, while functional species richness did not. Our survey indicates that across a regional scale, and across a broad range of environmental conditions, a significant positive association exists between local tree species richness and wood production at least in typical early successional Mediterranean-type forests. [ABSTRACT FROM AUTHOR]

• We analysed the ectomycorrhizal (ECM) fungal diversity in a Mediterranean old-growthQuercus ilexforest stand from Corsica (France), whereArbutus unedowas the only other ECM host.• On a 6400 m2 stand, we investigated whether oak age and host species shaped below-ground ECM diversity. Ectomycorrhizas were collected underQ. ilexindividuals of various ages (1 yr seedlings; 3–10 yr saplings; old trees) andA. unedo. They were typed by ITS–RFLP analysis and identified by match to RFLP patterns of fruitbodies, or by sequencing.• A diversity of 140 taxa was found among 558 ectomycorrhizas, with many rare taxa.Cenococcum geophilumdominated (35% of ECMs), as well as Russulaceae, Cortinariaceae and Thelephoraceae. Fungal species richness was comparable above and below ground, but the two levels exhibited< 20% overlap in fungal species composition.• Quercus ilexage did not strongly shape ECM diversity. The two ECM hosts,A. unedoandQ. ilex, tended to share few ECM species (< 15% of the ECM diversity). Implications for oak forest dynamics are discussed.New Phytologist(2005)doi: 10.1111/j.1469-8137.2005.01382.x© New Phytologist(2005) [ABSTRACT FROM AUTHOR]