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In a previous work we developed a mathematical model to explain the co-occurrence of evergreen and deciduous oak groups in the Mediterranean region, regarded as one of the distinctive features of Mediterranean biodiversity. The mathematical analysis showed that a stabilizing mechanism resulting from niche difference (i.e. different water use and water stress tolerance) between groups allows their coexistence at intermediate values of suitable soil water content. A simple formal derivation of the model expresses this hypothesis in a testable form linked uniquely to the actual evapotranspiration of forests community. In the present work we ascertain whether this simplified conclusion possesses some degree of explanatory power by comparing available data on oaks distributions and remotely sensed evapotranspiration (MODIS product) in a large-scale survey embracing the western Mediterranean area. Our findings confirmed the basic assumptions of model addressed on large scale, but also revealed asymmetric responses to water use and water stress tolerance between evergreen and deciduous oaks that should be taken into account to increase the understating of species interactions and, ultimately, improve the modeling capacity to explain co-occurrence. [ABSTRACT FROM AUTHOR]

Scientific community and policy-makers share the common interest in identifying and evaluating potential impacts of climate change on ecosystems, relying mainly on probabilistic methods of exploring the risks. In this perspective, the concept of ensemble forecasting makes possible to handle uncertainties associated with climate risk analysis by focusing on a range of potential or probable impact scenarios rather than actualizing a single case. In this paper, an ensemble of simulations based on the Lund-Potsdam-Jena (LPJ) model was used to investigate the uncertainty upon predictions of the future Euro-Mediterranean vegetation distribution, carbon dynamics, and water budget. Twenty simulations from past to future were based on the combination of different climate inputs, vegetation model parameterizations, and configurations. The evaluation of results combined the separate deterministic future projections from the LPJ model into a single probabilistic projection, associating a likelihood degree in accordance with the most recent Intergovernmental Panel on Climate Change terminology. Results projected a general critical situation in terms of water availability, made more serious if considering that also the occurrence of extreme-related events, e.g., fires, is expected to become more frequent as favored by more recurrent drought episodes. Although more uncomfortable climate conditions were projected for vegetation, net primary production (NPP) was predicted to increase due to the potential enrichment of CO in atmosphere and its fertilization effects on vegetation. The combination of rising NPP and fire frequency may shape the carbon cycle components, as the carbon losses by fire also were projected to increase. [ABSTRACT FROM AUTHOR]

We investigated the impact of land-cover changes on regional climate over the Euro-Mediterranean area. For this purpose, we compared a control simulation, which employs the present-day vegetation cover, with 2 different potential vegetation distributions performed with the regional climate model RegCM3 for the time period 1981-2000. The simulation results show how land-cover changes are able to modify both the thermodynamics and dynamics of the lower troposphere in central Europe, particularly during summer. Within some of the regions where land-cover change occurred, we found significant changes in heat fluxes, while weak changes were found in surface temperature and precipitation fields. Changes in vegetation composition modify the probability density function of the 2 m temperature, and hence land-cover changes may have a strong impact on extreme events. [ABSTRACT FROM AUTHOR]

1. We present ecosystem respiration data from two Mediterranean forest sites in central Italy (Castelporziano) and southern France (Puéchabon) in order to analyse the role of soil drought and decomposition dynamics using different models. 2. Ecosystem respiration was derived from continuous eddy covariance measurements. The entire data set was separated into 5-day periods. For each period a function depending on three parameters was fitted to the scatter of eddy CO[sub 2] flux versus photosynthetic photon flux density. The y intercept of each curve was taken as an estimate of the average night-time ecosystem respiration during the period. The ecosystem respiration was analysed with different regression models as a function of soil water content and temperature. 3. Ecosystem respiration ranged from 1 to 7 µmol m[sup -2] s[sup -1] and showed a clear seasonality, with low rates during drought periods and in winter. The regression model analysis revealed that in drier soil, ecosystem respiration was more sensitive to soil moisture than is expressed by the often used hyperbolic model. 4. In contradiction to a simple multiplicative model, the Q[sub 10] of ecosystem respiration was not independent of moisture, but increased from nearly 1.0 at low moisture to above 2.0 at field capacity. Several explanations are discussed. 5. Of the variance in ecosystem respiration, 70-80% was explained with a model where Q[sub 10] of ecosystem respiration is a function of soil water content. 6. For the Puéchabon site, a soil carbon-balance model predicted only small changes in litter pool size (max. 7%), which caused only minor changes in soil microbial respiration (0.1 µmol m[sup -2] s[sup -1]). In contrast, the contribution of microbial regrowth dynamics to ecosystem respiration is estimated to be substantial (≈ 1.6 µmol m[sup -2] s[sup -1]). The model predicted that soil microbial respiration probably provides the largest contribution to... [ABSTRACT FROM AUTHOR]

Abstract: In forest ecosystems, the external nitrogen (N) inputs mainly involve wet and dry depositions that potentially alter inorganic N availability in the soil and carbon (C) turnover. This study assesses the effect of a slow increase of inorganic N availability on microbial community activity and functionality in a Mediterranean forest soil. A four-month incubation experiment was performed with soil collected from the organic layer of a forest site and fertilized with a solution of ammonium nitrate. The fertilizer was supplied at an equivalent of 0, 10, 25, 50 and 75kgNha−1 (0, 0.3, 0.7, 1.3 and 2mgNg−1 for control N0 and treatments N1, N2, N3 and N4, respectively). The incubation was carried out under optimal conditions, with the addition of the nutritive solution in small aliquots once a week to mimic the phenomenon of N deposition. In order to isolate the effect of N, the pH of the NH4NO3 solutions was adjusted to soil pH, and phosphorus was added in order to prevent any nutrient limitation effect. Inorganic N, C-mineralization, the activity of one oxidative enzyme (o-diphenol oxidase) and 8 hydrolitic enzymes (α-glucosidase, β-glucosidase, N-acetyl-β-d-glucosaminidase, cellulase, leucine amino-peptidase, acid phosphatase, butyric esterase and β-xylosidase) and the community level physiological profile (CLPP) were measured and analyzed during the whole incubation and at the end of the experiment as a proxy for microbial decomposition activity. In the first month, the highest N availability (N4) repressed the microbial respiration activity but stimulated microbial enzymatic activity, suggesting a change of C-pathways from spilling to enzymes and biomass investment. The treatments N1, N2 and N3 had no effect in the same period. Throughout the incubation, a general stress condition affected all the treated soils. As a consequence, treated soils exhibited higher respiration rates than the control. This was accompanied by a loss of functional diversity and an end-detected decline in biomass C. Although at the end of incubation most of the soil features showed a clear correlation with the inorganic N pool, the organic C content was strongly affected by different patterns of microbial activity during the experiment: the highest N treatment (N4) showed a lower C loss than the N3 treatment. Overall, the experiment showed how inorganic N availability can potentially alter the C cycle in a Mediterranean forest soil. The effect is non linear, depending on microbial community dynamics, on the community’s ability to adapt given the time scale of the process, and on N supply amount. Our study also revealed a common pattern in the short-term response to N addition in other, similar ecosystems with different climatic conditions. [Copyright &y& Elsevier]

Background: In this study we compare outlier loci detected using a FST based method with those identified by a recently described method based on spatial analysis (SAM). We tested a panel of single nucleotide polymorphisms (SNPs) previously genotyped in individuals of goat breeds of southern areas of the Mediterranean basin (Italy, Greece and Albania). We evaluate how the SAM method performs with SNPs, which are increasingly employed due to their high number, low cost and easy of scoring., Results: The combined use of the two outlier detection approaches, never tested before using SNP polymorphisms, resulted in the identification of the same three loci involved in milk and meat quality data by using the two methods, while the FST based method identified 3 more loci as under selection sweep in the breeds examined., Conclusion: Data appear congruent by using the two methods for FST values exceeding the 99% confidence limits. The methods of FST and SAM can independently detect signatures of selection and therefore can reduce the probability of finding false positives if employed together. The outlier loci identified in this study could indicate adaptive variation in the analysed species, characterized by a large range of climatic conditions in the rearing areas and by a history of intense trade, that implies plasticity in adapting to new environments.