Quercus Ilex Forest Research Articles

Uncovering the dark side of agriculture: How land use intensity shapes soil microbiome and increases potential plant pathogens

Soil microbiome plays a critical role in maintaining key soil processes such as litter decomposition, nutrient cycling, and plant productivity. In this study, we aimed to investigate the variability of soil chemicals, microbial diversity, and composition in seven ecosystems i.e., Fagus sylvatica and Quercus ilex forests, a Mediterranean grassland and shrubland, a vineyard, a horticultural cultivation in open field and under greenhouse, across a gradient of land-use intensity in Southern Italy. Soil chemistry included pH, organic matter, total nitrogen, and C/N ratio, and soil microbiota was characterized by high-throughput sequencing of 16S and ITS genes. Our results showed that greenhouse soils had the highest pH, while Fagus had the lowest. Horticultural, greenhouse, and grassland soils had low levels of OM and total N, while shrubland had relatively high levels of OM, total N, and C/N ratio. Fagus soils, on the other hand, had the highest levels of OM, total N, and C/N ratio. Bacterial diversity was lowest in horticultural soils, whereas fungal diversity was highest in shrubland soils. Pseudomonadota were the predominant bacteria in Fagus, grassland, and vineyard soils, while Actinomycetota dominated in Quercus, shrubland, and greenhouse soils. However, Cyanobacteria was predominant in horticultural soils. On the other hand, the Ascomycota was predominant in all ecosystems except Quercus soils, where the Basidiomycota was dominant. Our bipartite network analysis revealed that bacteria are often the same in different ecosystems while fungi tend to be specific to a particular habitat. Moreover, in agricultural ecosystems, fungal pathogens belonging to Alternaria, Fusarium, Gibellulopsis, Stemphylium, Acremonium, and Curvularia are more abundant, especially in greenhouse. The findings of this study provide important insights into the variability of soil microbial diversity and community composition in different ecosystems, highlighting the essential role of preserving natural ecosystems while managing agricultural ones, given their higher abundance of pathogens.

Plant hydraulic modelling of leaf and canopy fuel moisture content reveals increasing vulnerability of a Mediterranean forest to wildfires under extreme drought.

Fuel moisture content (FMC) is a crucial driver of forest fires in many regions world-wide. Yet, the dynamics of FMC in forest canopies as well as their physiological and environmental determinants remain poorly understood, especially under extreme drought. We embedded a FMC module in the trait-based, plant-hydraulic SurEau-Ecos model to provide innovative process-based predictions of leaf live fuel moisture content (LFMC) and canopy fuel moisture content (CFMC) based on leaf water potential ( ). SurEau-Ecos-FMC relies on pressure-volume (p-v) curves to simulate LFMC and vulnerability curves to cavitation to simulate foliage mortality. SurEau-Ecos-FMC accurately reproduced and LFMC dynamics as well as the occurrence of foliage mortality in a Mediterranean Quercus ilex forest. Several traits related to water use (leaf area index, available soil water, and transpiration regulation), vulnerability to cavitation, and p-v curves (full turgor osmotic potential) had the greatest influence on LFMC and CFMC dynamics. As the climate gets drier, our results showed that drought-induced foliage mortality is expected to increase, thereby significantly decreasing CFMC. Our results represent an important advance in our capacity to understand and predict the sensitivity of forests to wildfires.

Early vegetation recovery of a burned Mediterranean forest in relation to post-fire management strategies

Abstract The risk of wildfires in the Mediterranean region is expected to increase with climate change. Fire is one of the main drivers of plant diversity and composition, triggering succession processes that vary according to the fire regime and species’ regeneration traits. Human management can modulate these processes to promote the recovery of the burned soil-vegetation system, through the application of practices such as salvage logging. Effects of these managements have been studied mostly for coniferous forests, with contrasting results, while little is known about the responses of evergreen broadleaved woodlands. Here, we analysed the 34-month recovery processes of a Quercus ilex forest and an adjacent Pinus pinaster stand in central Italy with respect to their diversity, composition and plant fire-related traits, in relation to three different management strategies applied after fire. These were: (1) no intervention (NT), (2) salvage logging and mulching (SM and SMP for the pine stand), (3) salvage logging, mulching and erosion control measures (e.g. fascines for hill slope stabilization; EC). Overall, the increase of post-fire vegetation cover was negatively affected by SM and EC treatments, while their effects on ɣ- and α-diversity were positive. Species diversity was significantly lower in pine than in broadleaved plots and compositional differences associated with forest type were significant. Abundance of woody species was higher in the unsalvaged sites, except for a few species (e.g. Q. ilex), while herbaceous plants were not affected. Species composition in managed plots was different from control plots after 10 and 22 months, while differences decreased after 34 months. Effects of management strategies on the frequency of resprouters as well as on the proportion of species with persistent vs transient soil seed bank were minor; these traits were mainly driven by forest type. Our findings suggest that non-treatment is the best post-fire management strategy for a fast recovery of woody species in typical Mediterranean broadleaved forests. However, the EC strategy promoted a high diversity level, while not apparently altering species composition compared with the natural post-fire succession process.

Linking functional traits with tree growth and forest productivity in Quercus ilex forests along a climatic gradient

Plant functional traits are highly plastic to changes in climatic factors and nutrient availability. However, the intraspecific plant response to abiotic factors and the overall effect on tree growth and productivity is still under debate. We studied forest productivity for 30 Quercus ilex subsp. ballota forests in Spain along a broad climatic gradient of aridity (mean annual precipitation from 321 to 858 mm). We used linear mixed models to quantify the effect of climatic and edaphic (soil nutrients, topography, and texture) factors on tree functional traits (leaf and branch traits), and subsequently, the effect of such functional traits and abiotic factors on the relative growth rate (RGR) of adult trees. We used piecewise structural equation models (SEMs) to determine the causal effect of intrinsic and extrinsic factors on forest productivity. Our results showed that tree functional traits were mainly explained by climatic and edaphic factors. Functional traits and tree biomass explained forest biomass and RGR, respectively, which ultimately explained forest productivity. In conclusion, intraspecific variability of functional traits has a significant effect on plant biomass and growth, which ultimately may explain forest productivity in Quercus ilex forests.

Inocybe brijunica sp. nov., a New Ectomycorrhizal Fungus from Mediterranean Croatia Revealed by Morphology and Multilocus Phylogenetic Analysis.

A new ectomycorrhizal species was discovered during the first survey of fungal diversity at Brijuni National Park (Croatia), which consists of 14 islands and islets. The National Park is located in the Mediterranean Biogeographical Region, a prominent climate change hot-spot. Inocybe brijunica sp. nov., from sect. Hysterices (Agaricales, Inocybaceae), is described based on morphology and multilocus phylogenetic data. The holotype collection was found at the edge between grassland and Quercus ilex forest with a few planted Pinus pinea trees, on Veli Brijun Island, the largest island of the archipelago. It is easily recognized by a conspicuous orange to orange–red–brown membranaceous surface layer located at or just above the basal part of the stipe. Other distinctive features of I. brijunica are the medium brown, radially fibrillose to rimose pileus; pale to medium brown stipe with fugacious cortina; relatively small, amygdaliform to phaseoliform, and smooth basidiospores, measuring ca. 6.5–9 × 4–5.5 µm; thick-walled, utriform, lageniform or fusiform pleurocystidia (lamprocystidia) with crystals and mostly not yellowing in alkaline solutions; cheilocystidia of two types (lamprocystidia and leptocystidia); and the presence of abundant caulocystidia only in the upper 2–3 mm of the stipe. Phylogenetic reconstruction of a concatenated dataset of the internal transcribed spacer region (ITS), the nuclear 28S rRNA gene (nrLSU), and the second largest subunit of RNA polymerase II (rpb2) resolved I. brijunica and I. glabripes as sister species.

Production and turnover of mycorrhizal soil mycelium relate to variation in drought conditions in Mediterranean Pinus pinaster, Pinus sylvestris and Quercus ilex forests.

In forests, ectomycorrhizal mycelium is pivotal for driving soil carbon and nutrient cycles, but how ectomycorrhizal mycelial dynamics vary in ecosystems with drought periods is unknown. We quantified the production and turnover of mycorrhizal mycelium in Mediterranean Pinus pinaster, Pinus sylvestris and Quercus ilex forests and related the estimates to standardised precipitation index (SPI), to study how mycelial dynamics relates to tree species and drought-moisture conditions. Production and turnover of mycelium was estimated between July and February, by quantifying the fungal biomass (ergosterol) in ingrowth mesh bags and using statistical modelling. SPI for time scales of 1-3months was calculated from precipitation records and precipitation data over the study period. Forests dominated by Pinus trees displayed higher biomass but were seasonally more variable, as opposed to Q.ilex forests where the mycelial biomass remained lower and stable over the season. Production and turnover, respectively, varied between 1.4-5.9kgha-1 d-1 and 7.2-9.9 times yr-1 over the different forest types and were positively correlated with 2-month and 3-month SPI over the study period. Our results demonstrated that mycorrhizal mycelial biomass varied with season and tree species and we speculate that production and turnover are related to physiology and plant host performance during drought.

Do Forest Fires Make Biotic Communities Homogeneous or Heterogeneous? Patterns of Taxonomic, Functional, and Phylogenetic Ant Beta Diversity at Local and Regional Landscape Scales

Biotic homogenization—the erosion of biological differences among ecosystems due to human disturbance—is a pervasive threat to forest landscapes given the current global biodiversity crisis. In Mediterranean forests, wildfire is a particularly common disturbance that affects biodiversity at local, regional, and global scales. However, little is known about how fire influences biotic homogenization. We analyzed the taxonomic, functional, and phylogenetic β-diversity of ground-dwelling ant communities across a large region in the Mediterranean. We tested the hypothesis that fire leads to community heterogenization at the local landscape scale but community homogenization at the regional landscape scale. We sampled ant communities in 5 pairs of burned and unburned plots at 21 study sites (n=210 plots) representing seven forest types in Catalonia (northeastern Iberian Peninsula). Ant species were characterized based on 10 functional traits and phylogenetic relatedness. We then calculated taxonomic, functional, and phylogenetic community dissimilarity indices at local and regional landscapes scales focusing on common versus rare species. Our results show that fire strongly affected community dissimilarity at the local landscape scale. Regardless of diversity type or species type, community dissimilarity was always greater among burned and unburned plots combined than among unburned plots alone, a pattern that was largely driven by Pinus nigra forests, Quercus ilex forests, and shrublands composed of resprouter species. At the regional landscape scale, community dissimilarity was the same among burned and unburned plots and among unburned plots. However, when we examined taxonomic data for common species and phylogenetic data for rare species, community dissimilarity was slightly lower among burned plots than it was among unburned plots and among burned and unburned plots. Fire clearly affected the degree of biotic homogenization within ant communities, and these effects depended on spatial scale, local vegetation type, diversity type, and species type. Overall, our results suggest that, in Mediterranean regions composed of diverse forest types, wildfire generates local environmental heterogeneity and, as a consequence, locally heterogeneous ant communities. These effects are more dramatic in forest types where fire increases habitat openness. At the regional scale, fire does not create heterogeneity, but might even render ant communities more homogeneous.

Improving the modelling and understanding of carbon-nitrogen-water interactions in a semiarid Mediterranean oak forest

Mediterranean drylands are often nutrient poor, but parameter requirements of forest ecosystem models are usually high. Therefore, there is a need for developing parsimonious nutrients models. In that sense, this study aims to contribute to a better understanding and modelling of the hydrological and biogeochemical (carbon and nitrogen) cycles and their interactions in semiarid conditions and to test the capability of a new parsimonious model to satisfactorily reproduce them. The proposed model (TETIS-CN) and two additional widely used models were implemented in a Quercus ilex forest, and no noteworthy differences were found. Results suggest that: (1) it is important to include carbon observations in the calibration process and to consider all the existing vegetation species in the simulation; (2) a fixed daily potential uptake may not be appropriate to reproduce plant nitrogen uptake; and (3) TETIS-CN, with a lower number of parameters, proved an acceptable tool.

Coastal landscape evolution of Corsica island (W. Mediterranean): palaeoenvironments, vegetation history and human impacts since the early Neolithic period

A multi-proxy investigation of sediment cores has enabled us to reconstruct the coastal environmental evolution of East-Central Corsica (the sites of Saint Florent, Piantarella-Bonifacio and Palo-Solenzara) for the last 8000 years. The analytical methods comprise pollen (five original pollen diagrams), weight loss-on-ignition measurements, laser granulometry, and ostracod identification. In addition, 26 radiocarbon dates are used to provide a robust chronostratigraphy for the sedimentary sequences. The assessment of coastal landscape dynamics enables us to define the major morphological changes and to evaluate the complex interplay between climatic forcing and anthropogenic activity on the vegetation history of Corsica, within an archaeological context, since the early Neolithic period (∼7.4 cal kyr BP). The major findings are that the first farmers reached Corsica by sea, and they encountered a coastal environment mainly composed of freshwater ponds located close to the shoreline. This specific paleoenvironmental feature offered a favourable location for agriculture and for the development of permanent settlements where a subsistence economy was developed. Since the Middle Holocene, postglacial sea-level rise has caused major changes in local coastal environments, often characterized by salt intrusion into freshwater bodies. At the transition between the Mid and Late Holocene (∼4.0 cal kyr BP), an increase in both salinity and aridity caused substantial landscape changes, mainly characterized by a further expansion of saline marshland, mainly occupied by Chenopodiaceae. The results also provide new insights into the role of Erica in the original Holocene vegetation of Corsica. Our data clearly indicate that an Erica arborea - Quercus ilex forest transition occurred before 6.3 cal kyr BP, significantly earlier than previously proposed. Finally, the earliest evidence of cereal cultivation is at ∼7350 cal kyr BP, and in addition we are better able to constrain the role of humans in the landscape dynamics of Corsica since the early Neolithic.

Effect of land use change on contents and distribution of monosacharides within density fractions of calcareous soil

In the last century, many calcareous soils in Castilla León (northwestern Spain) have been transformed from natural Quercus ilex forest to cropped land. During the past 40 years, cropping was abandoned and some of these soils has been reforested with Pinus halepensis. We studied how thEse land use changes affected the soil organic matter amount (C stocks) and characteristics. Density fractionation combined with ultrasonic dispersion enables separation and study of soil OM fractions, considered on the basis of the mechanisms of physical protection: non-physically protected OM (FF), OM occluded into aggregates (OF), and OM stabilized in organo-mineral complexes (DF). In the present study, whole soils and density fractions were analyzed for organic C amount (OC) and for carbohydrate content. The study aimed to describe the carbohydrate content in whole soils and its SOM density fractions to find out whether the carbohydrates can be used to explain the origin of SOM fractions and if they can depict its response to land management. We found a loss of 67% of the topsoil OC as a result of converting the natural Quercus ilex forest to cropped land, ∼100 years ago. After crop abandonment and soil reforestation with Pinus halepensis, the stock of topsoil OC increased. After ∼40 years of pine plantation, an average recovery of 71% of the previously lost OC had been recovered (43% loss of reference topsoil). The changes in OC stocks affected mainly the free fraction (FF) but also the organo-mineral (DF) one. Our results point to the role of physical protection in the C stocks but also that organo-mineral associations could be disrupted under a land use change. Monosaccharide content was significantly different (p < 0.01) among land uses. Gas chromatography analysis revealed significant differences in monosaccharide composition between land uses and also among density fractions. Whatever the fraction and land use considered, glucose was the dominant sugar monomer, followed by mannose and xylose.

Assessing the role of soil water limitation in determining the Phytotoxic Ozone Dose (PODY) thresholds

Phytotoxic Ozone Dose (PODY), defined as the accumulated stomatal ozone flux over a threshold of Y, is considered an optimal metric to evaluate O3 effects on vegetation. PODY is often computed through the DO3SE model, which includes species-specific parameterizations for the environmental response of stomatal conductance. However, the effect of soil water content (SWC) on stomatal aperture is difficult to model on a regional scale and thus often ignored. In this study, we used environmental input data obtained from the WRF-CHIMERE model for 14,546 grid-based forest sites in Southern Europe. SWC was obtained for the upper 10 cm of soil, which resulted in a worst-case risk scenario. PODY was calculated either with or without water limitation for different Y thresholds. Exclusion of the SWC effect on stomatal fluxes caused a serious overestimation of PODY. The difference increased with increasing Y (78%, 128%, 237% and 565% with Y = 0, 1, 2 and 3 nmol O3 m−2 s−1, respectively). This behaviour was confirmed by applying the same approach to field data measured in a Mediterranean Quercus ilex forest. WRF-CHIMERE overestimated SWC at this field site, so under real-world conditions the SWC effect may be larger than modelled. The differences were lower for temperate species (Pinus cembra 50–340%, P. sylvestris 57–363%, Abies alba 57–371%) than for Mediterranean species (P. pinaster 87–356%, P. halepensis 96–429%, P. pinea 107–532%, Q. suber 104–1602%), although a high difference was recorded also for the temperate species Fagus sylvatica with POD3 (524%). We conclude that SWC should be considered in PODY simulations and a low Y threshold should be used for robustness.

Baseline Mortality Analysis Reveals Legacy of Contrasting Land Use Practices on the Structural Sustainability of Endangered Moroccan and Spanish Mountain Forests

Disturbances can affect forest health and are important modulating factors of tree responses to environmental changes. However, standard methods are needed to assess and elucidate the relative effects of disturbance legacies on forest health among species. Here, structural sustainability was used to evaluate and to compare the impacts of contrasting disturbances on the health of Quercus ilex, Cedrus atlantica, and Abies pinsapo forest stands in Morocco and Spain. Disturbance effects on structural sustainability were related to type, severity, and land-use history, and showed inter-regional variability. Cedrus atlantica was structurally sustainable in its core distribution in Morocco, but not at its southern and northernmost geographical range limits. Quercus ilex was structurally sustainable in Morocco. Abies pinsapo was structurally sustainable at optimal elevation sites in Morocco (Rif Mts.), but considering the whole A. pinsapo dataset including Morocco and Spain, the species is structurally unsustainable due to excessive mortality. However, at the lower elevation plots in Spain, unsustainability was due to insufficient mortality. Although some forests were structurally sustainable, none of them were deemed healthy because none met their management objectives. Results also support the key role of disturbance regimes as drivers of forest structural sustainability and adaptive capacity.

Reducing the infectivity and richness of ectomycorrhizal fungi in a calcareous Quercus ilex forest through soil preparations for truffle plantation establishment: A bioassay study

In the early years of a black truffle plantation, the field proliferation of the nursery-inoculated fungi can be hampered by native ectomycorrhizal fungi colonising the seedling roots. Reducing the soil ectomycorrhizal infectivity in the planting hole before introducing the inoculated seedling could be an effective strategy to reduce this problem. Three bioassays were conducted to evaluate the impact of several soil preparations on the ectomycorrhizal infectivity and richness of a Quercus ilex soil in a truffle-producing region. Microwaves, quicklime, and acetic acid significantly decreased the percent root colonisation and morphotype richness of the native ectomycorrhizal fungi. However, they also decreased seedling survival or growth. Peracetic acid, hydrogen peroxide, and sodium hypochlorite did not show a significant negative effect on the soil ectomycorrhizal community. The results support the potential of soil preparation for reducing the ectomycorrhizal infectivity of forest soils, thus being a promising strategy to reduce the early colonisation by native fungi in truffle plantations. However, the indications of damage to the seedling development must be addressed.

Seasonal variations of ectomycorrhizal communities in declining Quercus ilex forests: interactions with topography, tree health status and Phytophthora cinnamomi infections

SeasonalvariationsinectomycorrhizalsymbiosisofQuercusilextreeswerestudied,withspecialemphasisontree health status, Phytophthora cinnamomi root infections and topography. Five Q. ilex forests in western Spain were selected,andca.40 000roottipsfrom3decliningand3non-decliningtreesperforestwereexamined.Ectomycorrhizal fungal abundance and P. cinnamomi root infections were quantified seasonally for 2 years, and an assessment was made of the water soil content and physiological status of trees during summer, the most stressful season. Seasonal changes in ectomycorrhizal fungal abundance were higher for Tomentella spp. than those for Russula spp. and Cenococcum geophilum, but these changes were not influenced by topography, tree decline status and P. cinnamomi root infections. Seasonal variations of non-vital tips were conditioned significantly by the decline status of trees. A higher proportion of non-vital tips and a lower proportion of vital non-mycorrhizal tips were observed in declining than in non-declining trees. Abundance of C. geophilum and Tomentella spp. was not influenced byP. cinnamomi root infections but by topography. Abundance of Russula spp. was not influenced byP.cinnamomirootinfectionsbutbythedeclinestatusoftrees.Therelationshipsfoundbetweentreephysiology and ectomycorrhizalabundance changed significantly depending on the decline status of trees. For thefirsttime, seasonal variations in ectomycorrhizae inP. cinnamomi-infectedQ. ilexforests are reported. The lowdiversityand abundance of ectomycorrhizal fungi associated with declining trees should be further studied in order to uncover causes or consequences of Q. ilex crown transparency.

The use of maps as a monitoring tool of protected area management

Leaf area index (LAI) of vegetation types developing inside the protected Estate of Castelporziano was analyzed in the year 2013 and compared with the previous studies carried out in the years 1995–1997. Our recent data do not show significant differences in the structure and LAI of the vegetation types not subjected to thinning with respect to the previous studies. The results on the whole highlight that the conservative management carried out in the Castelporziano Estate has had positive effects leading to a high number of large tree size in the forest stands. The multiple linear regression analysis shows that the photon flux density monitored at soil level is related to plant height (H), total plant basal area and LAI in the considered forest types. In addition, plants renewal was analyzed in some thinned and un-thinned areas of Quercus ilex forests and broadleaf mixed forests inside the Estate. The spatial patterns of light availability within these forest types influence the regeneration patterns of woody species: a higher seedling regeneration both in un-thinning and thinning areas was observed in Q. ilex evergreen forests (5.0 ± 2.0 and 1.0 ± 0.5 seedlings m−2, respectively) than in broadleaf mixed forests (0.40 ± 0.10 and 0.10 ± 0.03 seedlings m−2, respectively) due to the large germination capability of Q. ilex. LAI is a key parameter in evaluating ecosystem structure. The used maps may be considered a rapid and cost-effective method to have an overview on the functional state of the forest ecosystems as well as the possibility to highlight rapidly the occurrence of a local disturbance state. Old growth forests like those under study are important reference sites for conservation strategies involving a broad range of ecosystem services. These types of data may be useful to achieve a database for management projects in the Presidential Estate of Castelporziano.

Plant community response to drought-induced canopy defoliation in a Mediterranean Quercus ilex forest

Climate change has increased drought-induced tree die-off in many parts of the world, and future climate models expect a higher recurrence of these perturbations. However, few studies have addressed plant community recovery after drought events, particularly in Mediterranean forests. This study evaluates the consequences of drought-induced die-off of the dominant holm-oak (Quercus ilex) trees on composition, structure and recruitment of the plant community, 6 years after a severe drought episode in Montserrat mountain (Catalonia, NE Spain). We evaluated the relationship of the vegetation response variables to two parameters related to the die-off consequences: canopy openness, as a measure of radiation arriving to ground, and canopy defoliation weighed by plant size, as a measure of drought impact on dominant neighbor plants. We also included in our analyses topographic situation to account for the proximity to ridge summits. Six years after the drought episode, the main findings were as follows: (1) There was a general loss of canopy cover, but Q. ilex still remained as dominant; nevertheless, the small tree Phyllirea latifolia and the shrub Buxus sempervirens tended to increase its relative abundance in the upper vegetation canopy; (2) overall, in open canopy conditions, species richness was higher mostly due to the presence of shade-intolerant herbaceous plants and early successional shrubs, such as Cistus albidus; (3) die-off did not result in increasing recruitment of the dominant species but preexisting Q. ilex sprouts were taller in sites with more open canopy; (4) there was a negative relationship between weighed defoliation and understory height, including Q. ilex sprouts, that can be attributed to large drought impact to both understory and canopy holm-oaks in some microhabitats, such as sites with abundant outcrops. This study highlights the ways in which Q. ilex Mediterranean forests regenerate after drought-induced events of canopy die-off. This regeneration involves changes in community structure and composition involving the increase in species, mostly small shrubs and herbaceous plants, which are able to grow in habitats created by canopy openness, likely becoming dominant in the landscape, as well as the arrival of non-dominant shrubs and short trees to the canopy. Potential shift in vegetation may be facilitated by the lack of increasing recruitment of Q. ilex, but this may be counterbalanced by the ability of holm-oak canopy to resprout and because pre-established saplings grown more with canopy openness. Thus, if tree canopies do not recover in a certain amount of time after the drought episode, then defoliation could lead to permanent changes in diversity and composition of the community.

Human-derived landscape changes on the northern Etruria coast (western Italy) between Roman times and the late Middle Ages

Anthracological analysis has been carried out in three sites located on the Tyrrhenian coast of central Italy (ancient northern Etruria: the castle of Donoratico, the town of Populonia and the port of Alberese), spanning between the Roman Republican Period and the Late Middle Ages (3rd century bc–13th century ad). The integrated comparison of three different local charcoal data with the regional pollen and microcharcoal data available from northern Etruria showed well that vegetation changes are completely independent of climate and strictly connected to economic and social dynamics characterising the history of this part of central Italy. Indeed, Quercus ilex forests progressively retracted from the 3rd century bc in favour of open macchia formations just during the growing human impact of the Romanisation when intensive agriculture and livestock grazing characterised the economic system. The transition from macchia to deciduous Quercus forest at the end of the Roman Period from the mid-4th to the mid-5th centuries ad and long lasting until the 9th–10th centuries ad was related to economic and cultural factors which led to a phase of land abandonment. Finally, between the 11th and 13th centuries ad, the vegetation cover shifted again towards an open macchia environment at the same time of a re-settlement phase well evidenced also by intensive orcharding. Charcoal data also showed that the expansion of olive and chestnut in central Italy only began in the Late Medieval Period (11th century ad) and not in the Roman Period. This means that extensive cultivation of chestnut and olive has very recent origins and should be attributed to one and the same macro-factor such as the set-up of the economic establishment of the feudal system and the later political organism of the Medieval town.

Laboratory and field measurements of enantiomeric monoterpene emissions as a function of chemotype, light and temperature

Abstract. Plants emit significant amounts of monoterpenes into the earth's atmosphere, where they react rapidly to form a multitude of gas phase species and particles. Many monoterpenes exist in mirror-image forms or enantiomers. In this study the enantiomeric monoterpene profile for several representative plants (Quercus ilex L., Rosmarinus officinalis L., and Pinus halepensis Mill.) was investigated as a function of chemotype, light and temperature both in the laboratory and in the field. Analysis of enantiomeric monoterpenes from 19 Quercus ilex individuals from Southern France and Spain revealed four regiospecific chemotypes (genetically fixed emission patterns). In agreement with previous work, only Quercus ilex emissions increased strongly with light. However, for all three plant species no consistent enantiomeric variation was observed as a function of light, and the enantiomeric ratio of α-pinene was found to vary by less than 20% from 100 and 1000 μmol m−2 s−1 PAR (photosynthetically active radiation). The rate of monoterpene emission increased with temperature from all three plant species, but little variation in the enantiomeric distribution of α-pinene was observed with temperature. There was more enantiomeric variability between individuals of the same species than could be induced by either light or temperature. Field measurements of α-pinene enantiomer mixing ratios in the air, taken at a Quercus ilex forest in Southern France, and several other previously reported field enantiomeric ratio diel cycle profiles are compared. All show smoothly varying diel cycles (some positive and some negative) even over changing wind directions. This is surprising in comparison with variations of enantiomeric emission patterns shown by individuals of the same species.

Ectomycorrhizal fungal diversity in Quercus ilex Mediterranean woodlands: variation among sites and over soil depth profiles in hyphal exploration types, species richness and community composition

Understanding the factors underlying the distribution of biodiversity is a challenging issue in ecology. Here, we examined the distribution patterns of ectomycorrhizal fungal diversity across the soil profile in three Quercus ilex forests. Contact exploration type strongly dominated at all sites, but was most prevalent in the upper, organic-rich soil layers. At each site, three quarters of the ectomycorrhizal tips and 59 % of taxa were restricted to the ten first centimeters of the soil profile. The relative abundance of the dominant family Russulaceae increased with increasing soil depth. Species composition varied significantly among sites, with most species being rare. Species that occurred in only one of the three sites accounted for 78.9 % of all species, and 57.3 % of species were represented by a single ECM root tip. Our results suggest that (i) rare species at both local and regional scales contribute to the highly diverse fungal assemblages in Mediterranean forests and (ii) multi-sites studies including the whole soil profile are needed to provide comprehensive overviews of the taxonomic and functional diversities of ectomycorrhizal communities.

The ectomycorrhizal community in Mediterranean old-growth Quercus ilex forests along an altitudinal gradient

The Mediterranean coastal region is considered a “hot spot” of both biodiversity and climate change, as global average air temperatures and atmospheric CO2 concentrations are increasing with subsequent impacts on regional precipitation patterns. The main goal of this study, performed in the largest Mediterranean holm oak forests (Sardinia Island, Italy), was to verify whether the vitality of root tips and the composition of the ectomycorrhizal community of holm oak change with the altitudinal gradient. The results demonstrated that the altitude does not significantly affect the vitality and the degree of ectomycorrhization of the root tips, while significant differences were observed in the ectomycorrhizal community composition, correlated with both the altitude and the Southward exposition of the root systems, both associated to the increase of xeric and drought conditions at the soil level. This study should help to integrate the understanding of forest ecology and forecast modelling, to improve the management strategies of the Mediterranean oak forests in the future.