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Light Detection and Ranging (LiDAR) is a remote sensing technique with multiple uses throughout scientific fields. It can also be used to transfer point data measured in the field to broader spatial scales, which might enable the evaluation of habitats over large areas and define biodiversity hotspots. Our study took place in Cabañeros National Park, which is situated in the Mediterranean, namely, central Spain, and its vegetation is dominated by forest and impenetrable scrubland. LiDAR was used to detect veteran trees as key elements for a highly diverse saproxylic community. The saproxylic beetle community inhabiting tree hollows was studied among different forest types and habitats to determine its preferences. We identified potential hotspots for the saproxylic beetle community of tree hollows both inside and outside of the park, as well as the connectivity of suitable habitat patches. This was based on the species response to the spatial partitioning of the landscape. We found that not all potentially suitable forest types hosted the same saproxylic diversity or similar species compositions. In addition, forest distribution and connectivity inside and outside of the park also varied highly among forest types and habitats, where the most diverse deciduous oak forest was also the least connected together with the riparian forest. The evergreen oak forest could act as a habitat linkage for most of the threatened and less mobile species in the park. However, the low connectivity of the most diverse forest types in the park surroundings can compromise the persistence of saproxylic diversity in the near future. We concluded that LiDAR data were an effective tool for estimating saproxylic beetle diversity distribution over large-scale areas in the context of landscapes with low accessibility. Additionally, this tool allowed us to identify the most threatened forest types and critical patches for connectivity persistence where management practices capable of accelerating tree veteranisation could help to increase adequate forest connectivity in the region. Financial support was provided by the Ministerio de Ciencia e Innovación, Spain (PID2020-115140RB-I00) granted to EM. This study was also supported by the programme Erasmus + and by UHK specific research project (2116/2020) granted to PR.

Este artículo está sujeto a una licencia CC BY 4.0, Understanding the impact of land use and land cover change on surface energy and water budgets is increasingly important in the context of climate change research. Eddy covariance (EC) methods are the gold standard for high temporal resolution measurements of water and energy fluxes, but cannot resolve spatial heterogeneity and are limited in scope to the tower footprint (few hundred meter range). Satellite remote sensing methods have excellent coverage, but lack spatial and temporal resolution. Long-range unmanned aerial systems (UAS) can complement these other methods with high spatial resolution over larger areas. Here we use UAS thermography and multispectral data as inputs to two variants of the Two Source Energy Balance Model to accurately map surface energy and water fluxes over a nutrient manipulation experiment in a managed semi-natural oak savanna from peak growing season to senescence. We use energy flux measurements from 6 EC stations to evaluate the performance of our method and achieve good accuracy (RMSD ≈ 60 W m− 2 for latent heat flux). We use the best performing latent heat estimates to produce very high-resolution evapotranspiration (ET) maps, and investigate the drivers of ET change over the transition to the senescence period. We find that nitrogen and nitrogen plus phosphorus treatments lead to significant increases in ET (P < 0.001) for both trees (4 and 6%, respectively) and grass (12 and 9%, respectively) compared to the control. These results highlight that the high sensitivity and spatial and temporal resolution of a UAS system allows the precise estimation of relative water and energy fluxes over heterogeneous vegetation cover., This research was supported by the DAAD/BMBF program Make Our Planet Great Again – German Research Initiative Project MONSOON (grant number 57429870).

11Pág., The necessity for accurate biomass estimates is greater than ever for the sustainable management of forest resources, which is an increasingly pressing matter due to climate change. The most used method to estimate biomass for operational purposes is through allometric equations. Typically, each country develops their own models to be applied at the local scale because it is more convenient. But, for Quercus suber, a joint regional model can be more beneficial, since the species is distributed across the Mediterranean and is challenging to account for due to felling limitations and the nature of mature cork biomass itself. We found that these characteristics are reflected in the biomass datasets and compatibility was, perhaps, the largest impediment to such a model. The use of dummy variables to differentiate between countries, as well as compromises in the limits of biomass compartments, allowed us to develop two joint models to estimate aboveground biomass in Portugal, Spain and Tunisia. One model as a function of diameter and another as a function of diameter and total tree height. In addition, we developed a separate model for roots (modelling efficiency of fitting = 0.89), since it was not possible to assure additivity of the whole tree. All coefficients were estimated using Seemingly Unrelated Regressions (SUR) and model fitting assured additivity in the aboveground compartments—leaves and woody biomass (modelling efficiency of fitting = 0.89 and 0.93, respectively). This work proves that it is possible to have a biologically sound and efficient model for the three countries, despite differences in the observed allometric patterns., This research was funded by the Forest Research Centre, a research unit funded by Fundação para a Ciência e a Tecnologia I.P. (FCT), Portugal (UIDB/00239/2020). Catarina Jorge was funded by Fundação para a Ciência e a Tecnologia I.P. (FCT), under scholarship UI/BD/150757/2020.

Forests of the Mediterranean Basin provide a wide range of provisioning and regulating services that are currently jeopardised by land-use change. Although many ecosystem services are mediated by insects, most of the studies that have focused on how to enhance diversity in traditionally managed forests are about plants and vertebrates. Quercus pyrenaica woodlands of the Western Iberian Peninsula constitute a scenario in which traditional human practices (i.e., extensive livestock grazing, pollarding, firewood, forest thinning, etc.), and their progressive abandonment, have generated differences in landscape that affect habitat and microhabitat structures. We used saproxylic beetles (deadwood-dependent species) as biological indicators because they are the most diverse taxa and provide important ecosystem services related to deadwood decomposition, forest pest control and pollination. We modelled the response of two taxonomic (species richness and abundance), one ecological (species diversity of order 1) and two functional (functional richness and redundancy) diversity metrics to the environmental variables that result from traditional management or its abandonment at habitat and microhabitat levels. We included 16 explanatory variables related to forest structure, tree microhabitats and abiotic factors, which were grouped into eight principal components. Linear regression was the best fitting model for data. The resulting models were used to perform diversity predictions in different scenarios. We found that abandonment of some traditional forest management activities in the Mediterranean Region reduced taxonomic saproxylic beetle diversity, which may be further aggravated by climate change. We suggest minimal management actions to improve taxonomic and ecological saproxylic beetle diversity related to habitat and tree management (i.e., maintenance of >20% scrub coverage, >20 m3/ha of deadwood on soil and >20 hollow trees/ha). However, actions that boost saproxylic biodiversity do not ensure the community’s higher functional resilience. We should also promote tree microhabitat diversity to reduce the vulnerability of saproxylic beetle functions to environmental changes. Financial support was provided by the Ministerio de Economía y Competitividad (Projects CGL2016-78181-R) and Ministerio de Ciencia e Innovación (PID2020-115140RB-I00) granted to EM and EG. This research forms part of Sandra Martínez Pérez’s PhD studies granted by ’Ministerio de Economía, Industria y Competitividad’ (BES-2017-080278).

The dehesa is an anthropic complex ecosystem typical of some areas of Spain and Portugal, with a key role in soil and biodiversity conservation and in the search for a balance between production, conservation and ecosystem services. For this reason, it is essential to have tools that allow its characterization, as well as to monitor and support decision-making to improve its sustainability. A multipurpose and scalable tool has been developed and validated, which combines several low-cost technologies, computer vision methods and RGB aerial orthophotographs using open data sources and which allows for automated agroforestry inventories, identifying and quantifying units with important ecological significance such as: trees, groups of trees, ecosystem corridors, regenerated areas and sheets of water. The development has been carried out from images of the national aerial photogrammetry plan of Spain belonging to 32 dehesa farms, representative of the existing variability in terms of density of trees, shrub species and the presence of other ecological elements. First, the process of obtaining and identifying areas of interest was automated using WMS services and shapefile metadata. Then, image analysis techniques were used to detect the different ecological units. Finally, a classification was developed according to the OBIA approach, which stores the results in standardized files for Geographic Information Systems. The results show that a stable solution has been achieved for the automatic and accurate identification of ecological units in dehesa territories. The scalability and generalization to all the dehesa territories, as well as the possibility of segmenting the area occupied by trees and other ecological units opens up a great opportunity to improve the construction of models for interpreting satellite images.

Wood-pastures are socio-ecological systems covering vast areas in Europe. Although used for grazing and production of various forest goods, wood-pastures harbour a rich biodiversity and are usually considered as High Nature Value Farmlands. However, socio-economic pressures are driving the transformation of these valuable landscapes from multi-functional, heterogeneous habitats to homogeneous areas through either intensification or land abandonment. We investigated how changes in management intensity influence the taxonomic diversity, functional diversity and functional composition of birds in these landscapes using generalized linear models. In contrast to taxonomic diversity, functional diversity decreased significantly towards shrub-dominated and less heterogeneous areas related to the abandonment of grazing and/or understory management practices. Grassland and generalist species, and associated guilds such as granivores, ground-nesters and ground-foragers are almost absent less managed areas. On the other hand, shrub-dominated areas favour forest species, particularly understory/canopy foragers and arboreal nesters, although the forest guild is still well-represented in actively managed, heterogeneous areas. Our results indicate the abandonment of wood-pasture management affects the prevalence of grassland and generalist species, leading to functional diversity loss and potentially reduced ecosystem functioning. We suggest non-intensive, active management is needed to maintain habitat heterogeneity and canopy openness, enhancing trait diversity in wood-pastures.

9 páginas.- 5 figuras.- 1 tabla.- 70 referencias.- Supplementary material associated with this article can be found, in the online version, at doi:10.1016/j.agrformet.2021.108425, Soil respiration (RS) is one of the most important carbon fluxes in terrestrial ecosystems, and it is considered as a keystone in predicting ecosystem functioning. Changes in climate and land use may alter RS, triggering feedbacks between RS and other ecosystem components. Different factors might simultaneously alter RS, but the consequences of the interactive effects for ecosystems functioning remain poorly understood. Here, the impact of the expected changes in climate were analysed in a factorial field study over two consecutive years in a Mediterranean savannah ecosystem. We assessed how the interaction of changes in climate with grazing legacy and habitat structure influences RS. We simulated different climate scenarios (ambient, drier, warmer, and drier and warmer conditions) forecasted for the study area at three adjacent sites with different grazing legacies (high, medium, and low) and for the two most important habitat types (open grasslands and under tree canopy). We also considered other factors that could affect RS, such as soil organic C, microbial biomass or net primary productivity, unravelling the direct and indirect effects of the factors controlling RS over time by using structural-equation models (SEMs). Overall, RS was higher under tree canopy than in open grasslands, and high grazing intensity tended to alter RS differently through seasons. Warming scenario consistently increased RS, while drought reduced it (especially in moist seasons), with a moderate increase of RS resulting from the combination of warming and drought. Tree canopy modulated the impact of climate on RS. The SEM analyses identified soil moisture, temperature, grazing legacy and canopy as the main factors controlling RS, although they presented seasonal variations in the size and direction of their effects. Thus, the projected changes in climate can deeply alter ecosystem functioning of carbon sequestration, although their impact can be modulated by canopy cover and management activities. © 2021, LM was supported by the fellowships II5B and IV2 from VI-PPIT -U. Sevilla. MTD was supported by a postdoctoral fellowship from U. Sevilla (V Plan Propio de Investigación), IMPR by a postdoctoral “Ramón & by a FPI contract (BES-2016-078248). This research was funded by the MICINN projects DECAFUN (CGL2015-70123-R) and MEADCLIM (PID2019-108288RA-I00).

This work assesses damage caused by Coraebus undatus (Fabricius) (Coleoptera: Buprestidae) and Reticulitermes grassei Clément (Blattodea: Rhinotermitidae) in managed cork oak forests from the southern Iberian Peninsula. Lesions were diagnosed and quantified in relation to the following features: height and orientation in the trunk, diameter at breast height, solar exposure, understory presence and orography. The distribution patterns of lesions in the study area across 12 plots and in the trunk of the trees were also analyzed. The study was performed in “Sa de Hornachuelos” Natural Park (Córdoba, Spain) and the research area encompassed 12 environmentally-restored sampling plots. Data were recorded from 2007 to 2014, with yearly sampling from late June to mid-September, corresponding to the cork extraction period, since lesions caused by these insects are well distinguishable promptly after bark removal. The results reveal that C. undatus has low population levels and a non-uniform distribution pattern in the study area as well as in the trunk of the tree. It shows preference for medium height but not by any trunk orientation. R. grassei also shows low infestation levels and a preference to affect the trunk’s base. Comparatively, C. undatus showed higher infestation levels than R. grassei. The location of damage was also different, since galleries made by C. undatus predominated at intermediate trunk heights while those of R. grassei were more frequent at lower heights. Our results further showed a low co-occurrence of both species in the same tree trunks, which could be explained in terms of overlapping in the distribution areas of both species. These results provide background information that will enable natural resources managers to detect changes and trends of these species and inform future management decisions.

Cork oaks highly infested by Cerambyx welensii emit an amount of limonene at dusk, when C. welensii adults become active. In contrast, emissions by neighboring cork oaks free of C. welensii are dominated by pinene-type compounds. The activity of the woodborer Cerambyx welensii Kuster is a key factor in the decline of Quercus suber L. dehesas. This study aimed to estimate whether trees highly infested by C. welensii exhibited a peculiar emission profile, with known antennally active compounds. Monoterpenes were sampled in situ in 2006 (day/late evening) and 2008 (early evening) from Q. suber stratified by whether or not trees were highly infested by C. welensii and analyzed by gas chromatography. Limonene, α-pinene, β-pinene, sabinene, and myrcene accounted for over 87.2% of overall monoterpene emissions. Monoterpene composition and emission rates differed between the two groups, both during daytime and early evening, with a high presence of limonene in infested trees and dominance of pinene-type compounds in non-infested trees. This work evidenced differences in foliar monoterpene emissions between Q. suber trees highly infested by C. welensii and non-infested trees, with a high presence of limonene in the former and dominance of pinene-type compounds in non-infested trees. We hypothesize that the detection—especially during the onset of insects daily flight—of certain compounds (e.g., limonene), together with the detection of specific ratios of several monoterpenes (e.g., those of limonene to pinene-type compounds), has a role in the intraspecific host selection by C. welensii.

Agroforestry systems, in which trees are integrated in arable or pasture land, can be used to enable sustainable food, material, and energy production (i.e. provide provisioning ecosystem services) whilst reducing the negative environmental impacts associated with farming. However, one constraint on the uptake of agroforestry in Europe is a lack of knowledge on how specific agroforestry designs affect productivity. A process-based biophysical model, called Yield-SAFE, was used: (1) to quantify the food, material and biomass energy production of four contrasting case study systems in Europe in a common energy unit (MJ ha−1), and (2) to quantify how tree density determined the supply of provisioning ecosystem services. The Yield-SAFE model was calibrated so that simulated tree and crop growth fitted observed growth data for reference monoculture forestry, pasture, and arable systems. The modelled results showed that including trees in pasture or arable systems increased the overall accumulated energy of the system in comparison with monoculture forestry, pasture, and arable systems, but that the accumulated energy per tree was reduced as tree density increased. The greatest accumulated energy occurred in the highest tree density agroforestry system at all the case study sites. This suggests that the capture of environmental resources, such as light and water, for obtaining provisioning services is most effective in high density agroforestry systems. Further modelling should include tree canopy effects on micro-climatic and the impact this has on pasture, crop, and livestock yields, as well as the impact of tree density on the economic value and management of the different systems.

Tree–grass ecosystems are widely distributed. However, their phenology has not yet been fully characterized. The technique of repeated digital photographs for plant phenology monitoring (hereafter referred as PhenoCam) provide opportunities for long-term monitoring of plant phenology, and extracting phenological transition dates (PTDs, e.g., start of the growing season). Here, we aim to evaluate the utility of near-infrared-enabled PhenoCam for monitoring the phenology of structure (i.e., greenness) and physiology (i.e., gross primary productivity—GPP) at four tree–grass Mediterranean sites. We computed four vegetation indexes (VIs) from PhenoCams: (1) green chromatic coordinates (GCC), (2) normalized difference vegetation index (CamNDVI), (3) near-infrared reflectance of vegetation index (CamNIRv), and (4) ratio vegetation index (CamRVI). GPP is derived from eddy covariance flux tower measurement. Then, we extracted PTDs and their uncertainty from different VIs and GPP. The consistency between structural (VIs) and physiological (GPP) phenology was then evaluated. CamNIRv is best at representing the PTDs of GPP during the Green-up period, while CamNDVI is best during the Dry-down period. Moreover, CamNIRv outperforms the other VIs in tracking growing season length of GPP. In summary, the results show it is promising to track structural and physiology phenology of seasonally dry Mediterranean ecosystem using near-infrared-enabled PhenoCam. We suggest using multiple VIs to better represent the variation of GPP., The authors acknowledge the Alexander von Humboldt Foundation for supporting this research with the Max-Planck Prize to Markus Reichstein. Y.L. and M.M. gratefully acknowledge financial support from the China Scholarship Council. We are also thankful for financial support from the Spanish Ministry of Economy and Competitiveness through the FLUXPEC project “Monitoring changes in water and carbon fluxes from remote and proximal sensing in a Mediterranean dehesa ecosystem” (CGL2012-34383). The development of PhenoCam has been supported by the Northeastern States Research Cooperative, NSF’s Macrosystems Biology program (award EF-1065029 and EF-1702697), DOE’s Regional and Global Climate Modeling program (award DE-SC0016011), and the US National Park Service Inventory and Monitoring Program and the USA National Phenology Network (grant number G10AP00129 from the United States Geological Survey). The authors thank Sujan Koirala for relevant technical assistance and comments on graphics. The authors thank two anonymous reviewers and the editor for constructive comments to improve the earlier manuscript. The authors thank Andrew Durso for final proofreading for English.

Mapping the land-cover pattern dominated by complex Mediterranean silvo-pastoral systems with an accuracy that enables precise monitoring of changing tree-cover density is still an open challenge. The main goal of this paper is to demonstrate the implementation and effectiveness of the Forest Canopy Density (FCD) model in producing a remote sensing-based and detailed map of montado canopy density over a large territory in southern Portugal. This map will make a fundamental contribution to accurately identifying and assessing High Nature Value farmland in montado areas. The results reveal that the FCD model is an effective approach to estimating the density classes of montado canopy (overall accuracy = 78.0 %, kappa value = 0.71). The study also shows that the FCD approach generated good user’s and producer’s accuracies for the three montado canopy-density classes. Globally, the results obtained show that biophysical indices such as the advanced vegetation index, the bare soil index, the shadow index and the thermal index are suitable for estimating and mapping montado canopy-density classes. These results constitute the first remote sensing-based product for mapping montado canopy density that has been developed using the FCD model. This research clearly demonstrates that this approach can be used in the context of Mediterranean agro-forestry systems.

Modern alley cropping designs, with trees aligned in rows and adapted to operating farming machinery, have been suggested for Europe. This paper explores the potential for adoption of cork oak (Quercus suber L.) agroforestry in Portugal and estimates the potential carbon sequestration. Spatial modeling and Portuguese datasets were used to estimate target areas where cork oak could grow on farmland. Different implementation scenarios were then modeled for this area assuming a modern silvoarable agroforestry system (113 trees ha−1 thinned at year 20 for establishing 50 trees ha−1). The YieldSAFE process-based model was used to predict the biomass and carbon yield of cork oak under low and high soil water holding capacity levels. Approximately 353,000 ha are available in Portugal for new cork oak alley cropping. Assuming implementation rates between 10 % of the area with low soil water capacity (60 mm: 15 cm depth, coarse texture) and 70 % of the area with high soil water holding capacity (1,228 mm: 200 cm depth, very fine texture), then carbon sequestration could be 5 × 106 and 123 × 106 Mg CO2 respectively. Due to higher yields on more productive land, scenarios of limited implementation in high productivity locations can sequester similar amounts of carbon as wide implementation on low productivity land, suggesting that a priori land classification assessments can improve the targeting of land and financial incentives for carbon sequestration.

Dehesas are man-made systems composed by evergreen oaks (Quercus ilex and Quercus suber) scattered over a grassland understorey. They cover about 3.1 million ha in the southwest of the Iberian Peninsula and are to be preserved under the EU Habitats Directive due to the high levels of plant and animal diversity they maintain. The main current threat to long-term dehesa farming is a chronic absence of natural tree regeneration. We test whether dehesa abandonment would promote natural regeneration, how size structure of tree populations change after abandonment, and whether shrub encroachment would enhance seedling recruitment by measuring the size structure of mature tree populations, shrub cover and seedling density in 17 dehesa farms of known date of abandonment. Size structures were approximately bell-shaped in farms abandoned less than 16 years ago, progressively approaching afterwards the inverse J-shaped distribution typical from holm oak forests. Proportions of young mature trees changed with age of abandonment according to a logistic growth function. Proportions typical from forests (70-80%) were reached 30 years after abandonment, whereas balanced numbers of young and old trees were reached 20-25 years after abandonment. Short-term seedling recruitment was not related to age of abandonment or to covers of most dominant shrubs and was positively related to cover of mature trees and of Cytisus multiflorus, a nurse shrub for holm oak seedlings. Synthesis and applications Conservation of dehesas and their associated biodiversity values should be based on financing temporal abandonment of productive dehesa farming for 20 years, keeping land in good agricultural condition by re-opening the encroached plots after tree recruitment (i.e. rotational set-aside). The proposed measure has the additional advantages of easy monitoring and straightforward evaluation of its effectiveness. © 2007 Elsevier B.V. All rights reserved.

[ES] Según la guía de buenas prácticas del Panel Intergubernamental de Expertos en Cambio Climático (IPCC), las técnicas de teledetección son adecuadas para la estimación de los sumideros de carbono a partir de la estimación de la biomasa. En este trabajo se ha utilizado una serie temporal de imágenes Landsat para estimar la cantidad de biomasa del pasto en una zona de dehesa al NE de la provincia de Cáceres (España) en el período 1985-2010. A partir de las imágenes de biomasa obtenidas se ha analizado la evolución de los stocks de carbono en la cubierta herbácea. Se realizaron muestreos de campo de biomasa, así como de radiometría, en cuatro parcelas ubicadas dentro de la zona de estudio para la calibración del modelo. Se aplicó un modelo de regresión lineal entre los datos de campo e índices espectrales para la estimación de biomasa a partir de las imágenes Landsat. El índice EVI obtuvo los mejores ajustes (R2=0.79). Se aplicó un factor de carbono de 50% de la biomasa para la estimación de los stocks de carbono en la cubierta herbácea. Los valores promedios de biomasa mostraron sensibilidad a los cambios extremos de las series temporales de precipitación y temperatura., [EN] According to the Intergovernmental Panel on Climate Change Good Practice Guidance (IPCC GPG), remote sensing techniques are suitable for the estimation of carbon sinks, through the estimation of above ground biomass. In this work we used a Landsat time series to estimate grass biomass in a wooded grassland ecosystem located Northeast Cáceres (Spain) from 1985 to 2010. From the results of the estimation of biomass, we analyzed the evolution of carbon stocks in grasslands. Field sampling of biomass were performed, as well as field spectroscopy, in four plots located within the study site for model calibration. Linear regression models between field data and spectral indices were applied for estimating biomass from Landsat data. EVI was the best index for biomass estimation (R2=0.79). A carbon fraction of 50% of the biomass was applied for the carbon stock estimation. The average values of biomass were found to be sensitive to extreme changes in time series of precipitation and temperature., Agradezco a la Fundación Carolina por la beca otorgada para desarrollar el Máster en Tecnologías de la Información Geográfica en la Universidad de Alcalá, del cual se desprende este trabajo. Al Servicio Geológico de los Estados Unidos (USGS) por la disponibilidad de las imágenes Landsat. A Jeffrey Masek por facilitar el acceso a la herramienta de pre-procesamiento de LEDAPS y a la Agencia Estatal de Meteorología (AEMET) por la cesión de los datos meteorológicos. Este trabajo se ha realizado en el contexto de las actividades del proyecto BIOSPEC (CGL2008- 02301/CLI) financiado por el Ministerio de Ciencia e Innovación español

The quantification of terrestrial carbon pools is important for the modeling of carbon fluxes in forest ecosystems. As a contribution to the understanding of the factors that influence the carbon sequestration capacity of Mediterranean forest soils, the present study focuses on the quantification of the superficial soil carbon stocks in evergreen oak stands (Quercus ilex L.) representative of its distribution area in Mainland Spain and to analyze the influence of site factors (climate and topography) and the soil chemical properties in the topsoil carbon storage capacity. For that purpose, 103 Quercus ilex stands were studied grouped in four main formations 40 wooded grassland ecosystems with scattered oak trees (dehesas), 14 open Holm oak stands, 28 mixed Holm oak forests and 21 dense Holm oak forests. The soil organic carbon stocks (SOCS) in the upper organo-mineral soil layer ranged between 1. 4-15.6 kg m -2 and total soil carbon stocks (TSCS) between 1.4-17. 9 kg m -2. Tree density was a significant factor for SOC storage in the soil. The wooded grassland dehesas presented the minimum superficial SOC stocks (3.6 kg m -2), while dense Holm oak forests reached the maximum average values (7.6 kg m -2). Maximum SOCS (>10 kg m -2) were measured in the mixed and dense Holm oak forests over soils with calcareous substrates. Summer mean temperature (R = -0.46; P < 0.001) was the climatic variable that most influenced the SOCS. Soil properties had stronger positive correlations with SOCS than site factors nitrogen concentrations (R = 0.70; P < 0.001), clay content (R = 0.62; P < 0.001), soluble calcium (R = 0.60; P < 0.001) and magnesium (R = 0.42; P < 0.001). Climatic and topographic variables together explained 30 % of the SOCS variability. An increase up to 63 % was obtained by including soil variables. Under Mediterranean climate conditions, the soil properties that enhance the organic matter protection achieve a notable relevance. The soil carbon storage is favored by large organic matter inputs, high soil clay contents, a calcium-saturated soil matrix and reduced summer aridity. © 2012 Springer-Verlag.

The Portuguese montado is an agro-silvo pastoral system quite similar to the dehesa in Spain, and covering in Portugal most of the Southern region of the country, Alentejo. The trees in the montado are cork oh holm oak, and the system is mostly acknowledged due to the cork production, but also due to its singular savanna like land cover pattern, its multiple and complementary productions, the support of a diversity of ecosystems services and its biodiversity. The present special issue covers the diversity of components of the montado and of perspectives required to understand and assess the functioning of the system. This Editorial introduces the montado system, describes its extension and similarities to the dehesa in Spain, and addresses the multiple productions and externalities of the montado. It also refers to the several components of the system. It focus on the uniqueness and values of this system, stressing its potential and threats, and the requirements for integrated knowledge production. In the end of the Editorial, each one of the papers that compose the special issue are presented.

International audience; In this study we analyzed heterogeneity in nutrient cycling induced by trees in Mediterranean annual grasslands, comparing years of higher and lower than average precipitation and analyzing the effects of two different solar radiation scenarios. * Organic matter and consequently upper soil N, K, Ca and Mg were significantly greater in those locations receiving the highest levels of solar radiation, and as expected from many other studies in the literature, there was an increase in all macronutrients (except P) as well as pH below the canopy. * Contrary to what was expected, plant nutrient concentrations did not directly reflect those found in the soil, with the exception of K. The studied grassland responded to increased nutrient availability by enhancing growth and changing botanical composition rather than by increasing plant nutrient concentrations. Hence, the total amount of accumulated nutrients in the ecosystem was larger below the tree than outside it, although this is mainly a consequence of plant growth enhancement. The levels of Ca, Mg, and Na in plants decreased during the driest year, and the N content was mostly determined by the composition of the grass. * Temporal nutrient variability, particularly within-years, explained most of the variability in plant nutrient concentration, while spatial variability induced by trees was determined to be of secondary importance. These results are significant for ecosystem nutrient modelling.; Dans cette étude, nous avons analysé l'hétérogénéité du cycle des nutriments induite par les arbres dans les prairies méditerranéennes annuelles, en comparant les années à précipitations supérieures et inférieures à la moyenne et en analysant les effets de deux scénarios de rayonnements solaires différents. * La matière organique et par conséquent N, K, Ca et Mg des horizons supérieurs du sol étaient significativement plus élevés dans les stations recevant le plus de rayonnement solaire. Comme prévu à partir de nombreuses autres études dans la littérature, une augmentation de tous les macronutriments (sauf P) et aussi du pH a été observée sous la canopée des arbres. * Contrairement à ce qui était prévu, les concentrations de nutriments dans les végétaux n'ont pas reflété directement celles trouvées dans le sol, à l'exception de K. Les prairies étudiées ont répondu à un accroissement de la disponibilité en éléments nutritifs par une augmentation de la croissance et un changement de la composition botanique plutôt que par une augmentation des concentrations de nutriments dans les plantes. Par conséquent, les quantités totales de nutriments accumulées dans l'écosystème étaient plus importantes sous les arbres qu'en plein découvert, bien que cela soit principalement une conséquence de l'amélioration de la croissance des plantes. Les niveaux de Ca, Mg, et Na dans les plantes ont diminué au cours de l'année la plus sèche et la teneur en nutriments azotés était largement déterminée par la composition de l'herbe. * La variabilité temporelle intra-annuelle des éléments nutritifs expliquait la plus forte part de la variabilité de la concentration en nutriments des plantes annuelles, tandis que la variabilité spatiale induite par les arbres était d'importance secondaire. Ces résultats sont importants pour la modélisation des éléments nutritifs dans les écosystèmes.

Changing biotic and abiotic stress mediate in plant-plant interactions resulting in positive to neutral or negative effects, and these effects can change with gradients of stress or through plant dynamics. Here we studied the variability in annual grass production and composition induced by gradients of intercepted light by trees in years of contrasting precipitation in Mediterranean holm oak open woodlands. Although trees reduce the light radiance received by the pasture community, the presence of trees generally had a positive effect on pasture production in average climatic years where soil fertility was low. However, the interaction changed with increasing abiotic water stress. In a dry year, the increase in fertility could not be utilized and the effect of the crown was neutral. The effect of shade turned out to be beneficial for growth, contrary to the situation in an average climatic year. Light insolation was positive for legume biomass. There was high variability in functional components over the course of the growing period and from 1 year to another. Under low levels of other biotic stresses such as livestock grazing or root competition, the limiting factor among light, soil moisture or soil nutrients may determine whether facilitation or competition occurs. © 2009 Springer Science+Business Media B.V.

International audience; Tree recruitment in Mediterranean savannas is generally hampered, in contrast with the original oak forests where these savannas are derived from. We asked whether this difference in recruitment success can be explained by differential post-dispersal survival. For one year we monitored experimentally cached holm oak acorns in a savanna - forest ecosystem in Central Spain, and recorded cache pilferage, type of pilferer, boar rooting, seedling emergence, seedling survival and the cause of mortality.* Cache pilferage was significantly lower in savanna (8%) than in forest (21%). However, the higher cache survival was more than offset by lower seedling emergence and, particularly, by nine times higher seedling mortality in savanna, mainly due to desiccation. Wild boar rooting did not differ between experimental caches and controls without acorns, indicating that individual cached acorns do not trigger rooting activity.* Our results indicate that the difference in post-dispersal survival between savanna and forest is due to lower emergence and, primarily, higher seedling mortality in savanna, not to higher cache pilferage. Absence of safe sites such as shrubs, abundantly present in the forest, may well explain the lack of recruitment in the savanna. Management measures appear necessary for long-term persistence of Mediterranean savannas in general.; Le recrutement des arbres dans les savanes méditerranéennes est généralement entravé, ce qui contraste avec les forêts de chênes originelles dont ces savanes sont issues. Nous nous sommes demandé si cette différence dans le succès du recrutement pouvait être expliqué par une différence de survie post-dissémination. Pendant une année, nous avons suivi expérimentalement des glands de chêne vert cachés dans un écosystème de savane forestière en Espagne centrale, et nous avons enregistré les chapardages des caches, les types de chapardage, la fouille des sangliers, l'émergence des semis, la survie des semis et les causes de la mortalité* Le chapardage dans les caches a été significativement plus faible dans la savane (8 %) que dans la forêt (21 %). Toutefois, la survie plus élevée dans les caches été plus que compensée par une baisse de l'émergence des semis et, en particulier, par une mortalité des semis neuf fois plus élevée dans la savane, principalement due à la dessiccation. La fouille des racines par les sangliers n'est pas différente entre les caches expérimentales et les témoins sans glands, indiquant que les mises en cache des glands ne déclenchent pas activité de fouille des racines.* Nos résultats indiquent que la différence de survie post-dissémination entre la savane et la forêt est due à la baisse d'émergence et en premier lieu, à une mortalité plus élevée des semis dans la savane, et non pas à des chapardages des caches plus élevés. L'absence de sites abris tels que les arbustes, très présents dans la forêt, peut expliquer l'absence de recrutement dans la savane. Des mesures de gestion apparaissent nécessaires pour une persistance à long terme des savanes méditerranéennes.

Mixed systems of agriculture incorporating combinations of trees and crops have formed key elements of the landscape of Europe throughout historical times, and many such systems continue to function in the present day. In many cases they represent formerly widespread traditional systems in decline and a number have already become extinct or exist only in a threatened state. The causes are both practical and economic. The agricultural subsidy regime within the European Union is presently unfavourable towards silvoarable practices, which has been a major factor in their recent decline. The silvoarable systems of Europe can be split into two classes according to location – northern Europe and the Mediterranean. The latter contains not only a greater area of silvoarable cultivation, but also a greater diversity of systems due to the broader range of commercial tree and crop species grown. In general, the systems of northern Europe are limited by light, whilst those of the Mediterranean are limited by the availability of water. Mixed systems of agriculture present an opportunity for future European rural development and have the potential to contribute towards the increased sustainability of agriculture and enhancement of biodiversity, whilst preserving landscapes that are both culturally important and aesthetically pleasing. A better understanding of the legacy of traditional silvoarable systems, combined with the formulation of a consistent definition and specific European policy towards them will be invaluable in ensuring that the benefits of mixed agriculture are fully exploited in the future.

This paper tries to think about the environmental and agricultura european policies applied to the montainous «dehesas» of Sierra Morena. After setting up the regulation principles of the traditional dehesas its breaking up after the economic development stage was analized. The opportunities of reequilibrium for this agrosystem making use of the european community policy were also investigated. The main conclusion of this study was that the european applied measures have not produced, so far, the expected positive effects. The programs that fall most heavily on this system (cattle aids, reforestation programs, compensating indemnifications...) have not been conceived for the dehesas recuperation as a whole. This is why the effect can only be noticiable separately on each element without looking at the repercussions over the system alltogether. Finally, positions are taken towards a wide sense strategy for this agrosystem recuperation based on the ancient wisdom of its inhabitants about this landscape and territory., Este artículo es una reflexión sobre las aplicaciones de las políticas agroambientales comunitarias en las dehesas de Sierra Morena. Tras la presentación de los principios reguladores de las dehesas tradicionales y el análisis de su desarticulación en la etapa desarroUista, se intenta averiguar las posibilidades que ofrecen las políticas comunitarias para restablecer este agrosistema. La principal conclusión del estudio es que las medidas aplicadas no están produciendo el efecto positivo esperado. Los programas con una mayor incidencia (primas ganaderas, programa de reforestación, indemnizaciones compensatorias...) no han sido diseñados pensando en la recuperación de la dehesa, de haí que no pasen de incidir de manera aislada en cada uno de sus componentes, sin tener en cuenta las repercusiones sobre el conjimto. En definitiva, se termina abogando por la búsqueda de una estrategia globalizadora para la recuperación de este agrosistema, cimentada en la secular sabiduría que tienen de este espacio y estos paisajes sus pobladores de siempre. [fr] Cet article est une réflexion sur les applications des politiques agro-environementales communautaires dans les «dehesas» de Sierra Morena. Après la presentation des principes régulateurs des «dehesas» traditionelles et l'analyse de sa desarticulation lors de l'étape de développemente (années 60), nous essayons de vérifier les possibilitésqu'offrent les politiques communautaires pour rétablir cet agrosystème. La pricipale conclusion de l'étude est que les mesures appliquées ne produisent pas l'effect attendu. Les programmes ayant le plus d'incidence (prime à l'élevage, programme de reforestation, indemnisations compensatoires...) n'ont pas été développés en pensant à la récupération de la «dehesa» comme systèmes à part entière, ce qui ne veut pourtant pas dire qu'ils n'aient pas une influence isolée sur chacun de ses composants, mais ils n'ont pas de répercution sur l'ensemble. Enfln, nous terminons en plaidant pour la recherche d'une stratégie globalisante permettant la sauvegarde de cet agro-système, ancrée dans la culture ancestrale de ses populations et traduite dans l'espace et les paysages.

The agro-silvopastoral system 'montado' is mostly dominated by Mediterranean evergreen oaks such as, cork oak (Quercus suber L.) and holm oak (Quercus rotundifolia). The 'montado' production system management aims the maintenance of a balanced sustainable land use to cope with the Mediterranean climate variability. One important issue in cork oak forests is the control shrub growth in order to prevent forest fire hazard, which is of high risk in Mediterranean climate. In this article, two shrub control systems are compared and the results show that although soil disking is more profitable than shrub cutting, the results are reversed, if one considers the carbon sequestration. This means that besides the great economic sustainability of cork oak dependence on the price of cork, the profitability of different shrub control methods depend also on the way society valuates other goods and services provided by cork oak forest.

We present a review on the state-of-the-art of fruit prodution in Western Iberia woodlands («dehesas»), and particularly in Q. ilex (holm oak) «dehesas». This threatened ecosystem is of very high ecological and economical importance. Quercus sp. fruits (acorns) are essential for wildlife, and for pig fattening in «dehesas». In the first part of this review we briefly describe the phenology of the holm oak and the factors affecting acorn morphology and chemical composition. In the second half we analyze the main known factors reported in the literature that determine acorn production: pruning, stand characteristics, and site (weather and soil). We make several suggestions to improve future research and detect the existing gaps in the undertanding of acorn production. Fruit production is highly variable, both between and within years and individuals. The mean production in «dehesas» (mean density circa 50 trees/ha) is around 250-600 kg/ha (≈100 g/canopy-m2, CV > 100%). Acorn morphology is also very variable, with mean sound acorn size around 3.5 × 1.6 cm, CV ≈ 10% (3.5 g/acorn, CV > 50%). Silviculture plays an essential role in acorn production. Acorn production per tree seems to be negatively related to density. The effect of pruning is less clear: production seems to be reduced in the first and second years after pruning. After the third year it is not possible to discern from the literature whether there is any response to pruning or not. Weather and soil (site) also impact production and their effects should be explored in future management. The influence of genetics is unknown and should also be addressed. Longer data series are necessary. The dasometric features of the stands need to be characterized, in order to better understand production and compare results from different locations. Much research is still required to understand the functioning of fruiting in these woodlands. El alto interés ecológico y económico de la producción de fruto en las dehesas ibéricas, concretamente las de encina (Quercus ilex), nos ha movido a realizar una revisión del estado actual de conocimientos. Los frutos (bellotas) de Quercus sp. resultan esenciales para la fauna salvaje y el engorde de ganado porcino en las dehesas. En la primera parte de este trabajo se describen brevemente las características fenológicas de la especie, así como los factores que influyen en la variabilidad morfológica y la composición bromatológica del fruto. En la segunda parte se analizan los factores fundamentales estudiados en la bibliografía que determinan la producción: la poda, las características dasométricas (densidad y distribución diamétrica) y la influencia del sitio (suelo y clima). Se realizan sugerencias para mejorar futuras líneas de trabajo, así como se subrayan áreas de conocimiento deficitarias. La producción es muy variable tanto intra- como interanualmente. La producción media en las dehesas ibéricas (densidades medias alrededor de 50 pies/ha) es de unos 250-600 kg/ha (100 g/m2 de copa, CV > 100%), presentando las bellotas una morfología muy variable, con valores medios en bellotas sanas alrededor de 3,5 × 1,6 cm (CV ≈ 10%), correspondientes a 3,5 g/bellota (CV > 50%). Los tratamientos selvícolas juegan un papel fundamental, estando posiblemente la producción de bellota por árbol negativamente relacionada con la densidad de la masa arbórea. El efecto de la poda sobre la producción presenta cierta controversia. Parece que se reduce los primeros uno o dos años, no siendo concluyentes los resultados a partir del tercer año. El clima y el suelo (sitio) también influyen en la producción, aunque sus efectos deben ser estudiados con mayor detalle en futuros trabajos. De igual modo, la influencia del factor genético se desconoce y debería ser estudiada. El nivel de conocimiento alcanzado hasta ahora es del todo insuficiente, siendo necesarias series temporales más largas para caracterizar la producción de fruto. Es estrictamente necesario multiplicar el esfuerzo realizado si queremos llegar a comprender las razones que determinan la producción de fruto en este ecosistema y así ser capaces de optimizar de un modo sostenible un recurso tan valioso. La sistematización del modo en que se ofrecen los resultados y el uso de métodos de estimación validados y fiables, resulta fundamental para poder comparar posteriormente diferentes estudios y responder a cuestiones específicas.

Plant species richness has been recorded, at 4 m² scale, in different grassland communities in "dehesas" of S.W. Spain. The importance of the physical and biotic heterogeneity caused by the scattered oak trees on the (gamma) diversity of the savanna-like vegetation is discussed. The herbaceous communities under the oak trees are less diverse than in the open grassland, but show a distinct species composition, thereby augmenting the total species richness for the "dehesa" landscape. Most of the species registered in both contrasted habitats, oak understory and open grassland, exhibit therophyte life-form, and belong to one of the three dominant families : Gramineae, Leguminosae and Compositae. Within the grasses, Eu-Mediterranean species are the most numerous in both habitat., La richesse spécifique a été mesurée, sur une aire de 4 m, dans différentes communautés herbacées de "dehesa" du sud-ouest de l'Espagne. On discutera dans cet article l'importance de l 'hétérogénéité physique et biotique engendrée par la présence d'arbres (Chêne-vert) sur la diversité (gamma) de ce type de végétation savannoide. La diversité des communautés herbacées est plus faible sous l'arbre qu'en dehors, mais leur composition spécifique est différente. Il en résulte une augmentation de la richesse spécifique totale du paysage de "dehesa". La majorité des espèces rencontrées dans les deux situations contrastées, sous l'arbre et en dehors, sont des thérophytes et appartiennent à l'une des trois familles dominantes : Gramineae, Leguminosae et Compositae. Parmi les graminées, les espèces eu-méditerranêennes prédominent dans les deux cas., Marañon Teodoro. Plant species richness and canopy effect in the savanna-like "dehesa" of S.-W. Spain. In: Ecologia mediterranea, tome 12 n°1-2, 1986. pp. 131-141.