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The proportion of planted forests in the Mediterranean Basin is one of the largest in the world. These plantations are dominated by pine species and present a series of characteristics such as low elevation, high competition or small tree size that make them more vulnerable to droughts. However, quantitative assessments of their post-drought growth resilience in accordance with species, site factors and tree characteristics are lacking. In this study we sampled 164 trees at four forest sites located in the drought-prone Sierra Nevada, southeastern Spain. We compared growth responsiveness to drought in rear-edge planted vs. relic natural Scots pine (Pinus sylvestris) and coexisting Pyrenean oak (Quercus pyrenaica) stands. Our objective was to characterize and compare the different growth responses to drought between species and sites and the effect of the main physiographic factors (altitude, aspect, and slope) on these responses since the influence of these factors on post-drought resistance and resilience has received little attention to date. Our results reveal that the planted pine sites with the lowest mean growth rates displayed greater resistance during drought, and that higher altitude was associated with improved resistance and/or resilience for all species and sites. Natural pine and Pyrenean oak stands were better adapted to the dry climatic conditions of the Mediterranean region where the study was undertaken, displaying greater resistance and/or resilience and lower influence of drought on growth in comparison to stands of planted pines. These results suggest that promoting the conservation of high-elevation pine plantations and enhancing the regeneration of natural pine and oak may improve the resistance and resilience of these drought-prone forest ecosystems.

The dynamics of mixed stands are more complex and less studied than those of monospecific stands. The objective of this work was to analyze the variables involved in seedling occurrence and seedling survival in mixed stands of Pinus pinaster and P. pinea in Mediterranean areas. From 2011 to 2016, regeneration of both species was monitored at two sites located in Central Spain. We installed 72 regeneration plots where seedling dynamics were monitored. All the trees in the study areas were measured and mapped. Additionally, we took hemispherical photographs in each regeneration plot. The average density of P. pinea seedlings over the study period was almost 20 times larger than that of P. pinaster. Our results indicate that the seedlings of both species grow under moderate light conditions. In addition, we found that the occurrence of seedlings of both species was related to the structure of the stand. P. pinea seedlings grew where the density and size of P. pinaster trees were low and where P. pinea trees provided moderately sheltered conditions, whereas the number of P. pinaster seedlings was related to under intermediate densities of P. pinaster trees. Furthermore, seedling survival was positively associated with age of the seedlings and negatively with the August average maximum temperature. The temporal continuity of mixed stands of P. pinea and P. pinaster in the study area is compromised by the observed lack of regeneration of P. pinaster.

The role of climatic extremes on forest dynamics is still not fully understood. This is the case for droughts in temperate forests where growth of tree species is more driven by tree-to-tree competition than by climate. In this study we examine whether droughts shape growth trends and forest dynamics in a temperate forest of beech, oak and birch located in the “Picos de Europa” National Park in northern Spain. We used a dendroecological approach to quantify climate-growth associations and to evaluate growth resilience after droughts. We detected growth releases and quantified the increase in the number of trees established following each drought. Beech was the dominant tree species. Tree growth was only weakly related to climate variables in the three species studied. Oak was more resistant to drought than the other two species in terms of growth, with beech displaying higher vulnerability to drought. A significant association is displayed by all three species among droughts, growth releases and tree establishment pulses. After 1923 and following the dry 1940s, beech presented a peak of growth releases, whereas growth releases in oak and birch were concentrated in the 1960s and 1990s, respectively. Drought-induced growth releases probably reflect gap formation, these gaps being filled by recruitment of the three species.

Over recent decades, forest management in Europe has increasingly moved towards the emulation of natural dynamics. Natural dynamics in beech-oak forests leads to the formation of monospecific beech stands, the oak usually being excluded or restricted to sites with poor growing conditions. However, beech is more vulnerable than oak to drought and high temperatures. In this study, we examine whether climate change could attenuate the dominance of beech and improve the competitive capacity of oak in an old-growth temperate forest located in the “Picos de Europa” National Park, northern Spain. We used a dendroecological approach to reconstruct the competitive capacity of beech and oak and developed a projection for the 21st century based on forecasted climate conditions under three different emission scenarios. Beech is the dominant tree species in the studied forest, where the disturbance regime has favored the replacement of oak by beech. In general oaks are older than beeches and most of the small trees are beeches. Our results show that this substitution process may weaken due to the vulnerability of beech to warmer and drier conditions. Climate change will benefit oak growth over beech over the course of the 21st century, as was observed in the late 20th century. However, the natural gap dynamic benefits beech due to its greater shade-tolerance. Therefore, if the resilience of the ecosystem is to be increased, management strategies favoring oak regeneration are necessary given the better adaptation of oak to climate change.

The data in this paper are related to the research article entitled “Assessing the percentage of cork that a stopper should have from a mechanical perspective” (González and Terrazas, 2018). This data article contains data on the mechanical properties of different types of wine stoppers: 18 types of micro-agglomerated stoppers, three types of natural stoppers, and one type of co-extruded synthetic closure. Mechanical properties were evaluated with different analysis: Compression test for the maximum radial compression force, the young’s moduli and the diameter recovery, relaxation test for the relaxation force and the extraction test for the displacement force.

The aim of this study was to evaluate the viability of near infrared spectroscopy (NIRS) to detect the anomaly known as yellow stain on cork granulate. Detecting this anomaly is crucial to the cork granulate stopper industry, since it is associated with the presence of 2,4,6-Trichloroanisole (TCA), this compound having been identified as the main agent responsible for cork offflavours. Samples for the NIRS spectra were prepared by mixing in different proportions cork granulate with high visual quality and cork granulate with yellow stain, obtaining 120 samples with 8 different percentages of yellow stain (0, 5, 10, 15, 25, 35, 50 and 100%). Two spectra per sample were collected using a Bruker MPA spectrophotometer and the partial least squares (PLS) method was used to obtain numerous equations. The best equation was obtained by utilizing the standard normal variate (SNV) spectral preprocessing, making use of only one specific part of the near infrared spectral range: 9400- 4250 cm-1. This equation shows a coefficient of determination (R²) of 99.42%, a root mean square error of cross validation (RMSECV) of 2.34%, and a residual prediction deviation (RPD) of 13.10. The critical level and the limit of detection are 3.8% and 7.6%, respectively. The calculated receiver operating characteristic (ROC) curves show great discrimination capacity and the area under the ROC curve (AUC) is higher than 0.93 in any case. This study demonstrates that NIRS provides a viable technique for detecting yellow stain in cork granulate.

The economic importance of cork in the Mediterranean region demands an accurate assessment of its production. Cork production is currently estimated by aggregating information provided by Regional Forest Services, but this approach results in a lack of robustness at the national level. The objective of the present study is to analyse the role of the Spanish National Forest Inventory (SNFI) as a potential source of data for quantifying cork weight at national level and the scope of National Forest Inventory data to define national trends in cork yield as well as to characterize the main types of cork producing forest stands in Spain. Data from the Second and Third SNFI are used together with the Spanish Forest Map. The results point to the suitability of SNFI to quantify cork production as long as the two main variables defining cork weight, namely cork thickness and debarking height, were correctly recorded in inventories. Although the Second SNFI complied with these requirements, from the Third SNFI the methodology changed, preventing the accurate estimation of cork weight. Based on this study recommendations are made to improve the estimation of cork weight at national level, e.g. to measure cork thickness in all the cork oaks in the plot and to take a sample of cork from the inventoried trees. This information would also make it possible to assess the cork quality in terms of cork thickness growth and to classify cork production in terms of suitability for producing high quality cork products.The economic importance of cork in the Mediterranean region demands an accurate assessment of its production. Cork production is currently estimated by aggregating information provided by Regional Forest Services, but this approach results in a lack of robustness at the national level. The objective of the present study is to analyse the role of the Spanish National Forest Inventory (SNFI) as a potential source of data for quantifying cork weight at national level and the sc

Sustainable production of wood is one of the main services provided by forest systems. Site productivity in the case of forests is often evaluated through the site quality. However, most of the works addressing the site quality have been done at local or regional scale. In this work, we aim to develop site quality models for five dominant species in Spanish forests (Fagus sylvatica, Pinus pinaster atlantica, Quercus pyrenaica, Pinus nigra, Pinus sylvestris) and create site quality maps at a national-scale from these models. First, we develop site quality models using site form (height-diameter relationship) as the reference index and the Spanish National Forest Inventory as dataset. Then, we fit spatial additive models entering physiographic and climatic variables in order to predict the site quality over the whole country. Additionally, we plot site form maps for the five species in order to describe spatial pattern in site quality at a national scale. Altitude and aspect appeared to be fundamental variables in the assessment of site quality. The accuracy of the spatial additive models ranged from 38.2% to 47.9%. The correspondence between the predicted and observed maps of site qualities is clear. Our results provide a tool which could be used by forest managers in land use planning as well as in forest policy decision-making at a national scale. We suggest that this method could be used in other countries and that the maps could be expanded to the European scale to assessing the way in which site quality varies across Europe always considering that the relationships between forest productivity and environmental variables could vary among biogeoclimatic zones.

[Key message], The effect of adult trees on sapling density distribution during the regeneration fellings is determined in a Pinus sylvestris L. Mediterranean forest using generalized additive models. [Context], Spatial pattern of adult trees determines the number of new individuals after regeneration fellings, which modify the light and air temperature under tree canopy. [Aims], We proposed a novel spatiotemporal model with a functional predictor in a generalized additive model framework to describe nonlinear relationships between the size of the adult trees and the number of saplings of P. sylvestris and to determine if the spatial pattern of the number of saplings remained constant or changed in time. [Methods], In 2001, two plots (0.5 ha) were set up in two phases of regeneration fellings under the group shelterwood method. We mapped the trees and saplings and measured their diameter and height. The inventories were repeated in 2006, 2010, and 2014. [Results], We found a negative association between the diameter of adult trees and number of saplings up to 7–8 m. Beyond these distances, the diameter of adult trees was not associated with the number of saplings. Our results indicate that the spatial pattern of the number of saplings remained quite constant in time. [Conclusion ], The generalized additive models are a flexible tool to determine the distance range of inhibition of saplings by adult trees.

Key message: Optimal management of cork oak forest stands was analyzed for different site indices and cork growth rates. Optimal debarking intervals varied during the rotation and were sometimes shorter or longer than the officially recommended range of 9–14 years. Context: Quercus suber L. is one of the most important multipurpose tree species in the Mediterranean area. Its main product is cork, appreciated for its elasticity, impermeability, and thermal insulation properties. Cork oaks are debarked at constant intervals, which vary from 9 to 14 years depending on the area. However, since the growth rate of cork is not constant during the rotation, it may be optimal to use variable debarking intervals. Aims: This study optimized the debarking and cutting schedules of Quercus suber stands and analyzed the influence of economic and stand-related factors on optimal management. Methods: The study employed a simulation system where the existing growth and yield models for Quercus suber were used with a non-linear derivative-free optimization algorithm. Discount rates and cork prices were tested as economic factors and cork growth rate and site productivity as stand-related factors. Results: The optimal debarking interval varied during the rotation. Increasing cork growth rate increased the optimal number of debarkings and shortened their interval. Decreasing discount rate increased the optimal number of debarkings during rotation while decreasing cork price decreased the number of debarkings. Conclusion: The profitability of the management of cork oak stands depends on site fertility and stand density; management is not profitable on poor sites or at high discount rates. This study is the first that simultaneously optimizes the cutting and debarking schedule of cork oak stands, allowing the debarking interval to vary.

Aim of study To present the evolution of the current multi-objective Spanish National Forest Inventory (SNFI) through the assessment of different key indicators on challenging areas of the forestry sector. Area of study Using information from the Second, Third and Fourth SNFI, this work provides case studies in Navarra, La Rioja, Galicia and Balearic Island regions and at national Spanish scale. Material and Methods These case studies present an estimation of reference values for dead wood by forest types, diameter-age modeling for Populus alba and Populus nigra in riparian forest, the invasiveness of alien species and the invasibility of forest types, herbivore preferences and effects on trees and shrub species, the methodology for estimating cork production, and the combination of SNFI4 information and Airborne Laser Scanning datasets with the aim of updating forest-fire behavior assessment information with a high degree of accuracy. Main results The results show the suitability and feasibility of the proposed methodologies to estimate the indicators using SNFI data with the exception of the estimation of cork production. In this case, additional field variables were suggested in order to obtain robust estimates. Research highlights By broadening the variables recorded, the SNFI has become an even more important source of forest information for the development of support tools for decision-making and assessment in diverse strategic fields such as those analyzed in this study. © 2017 INIA.

Aboveground biomass estimation in short-rotation forestry plantations is an essential step in the development of crop management strategies as well as allowing the economic viability of the crop to be determined prior to harvesting. Hence, it is important to develop new methodologies that improve the accuracy of predictions, using only a minimum set of easily obtainable information i.e., diameter and height. Many existing models base their predictions only on diameter (mainly due to the complexity of including further covariates), or rely on complicated equations to obtain biomass predictions. However, in tree species, it is important to include height when estimating aboveground biomass because this will vary from one genotype to another. This work proposes the use of a more flexible and easy to implement model for predicting aboveground biomass (stem, branches and total) as a smooth function of height and diameter using smooth additive mixed models which preserve the additive property necessary to model the relationship within wood fractions, and allows the inclusion of random effects and interaction terms. The model is applied to the analysis of three trials carried out in Spain, where nine clones at three different sites are compared. Also, an analysis of slash pine data is carried out in order to compare with the approach proposed by Parresol (Can J For Res 31:865-878, 2001).

The objective of this study was to evaluate the effectiveness of both Normal and two-parameter Weibull distributions in describing diameter distribution of Tetraclinis articulata stands in north-east Tunisia. The parameters of the Weibull function were estimated using the moments method and maximum likelihood approaches. The data used in this study came from temporary plots. The three diameter distribution models were compared firstly by estimating the parameters of the distribution directly from individual tree measurements taken in each plot (parameter estimation method), and secondly by predicting the same parameters from stand variables (parameter prediction method). The comparison was based on bias, mean absolute error, mean square error and the Reynolds’ index error (as a percentage). On the basis of the parameter estimation method, the Normal distribution gave slightly better results, whereas the Weibull distribution with the maximum likelihood approach gave the best results for the parameter prediction method. Hence, in the latter case, the Weibull distribution with the maximum likelihood approach appears to be the most suitable to estimate the parameters for reducing the different comparison criteria for the distribution of trees by diameter class in Tetraclinis articulata forests in Tunisia. © SISEF.

Pinus pinea is one of the most important tree species in the Mediterranean region due to the economic value of its edible seeds called “piñones”. Timber also represents an important source of income from this species. Generally, P. pinea stands have been managed to maximize either timber or seed production, optimization of the joint production of both products being rare. The difficulty in optimizing seed or joint production is the highly stochastic masting habit of P. pinea. The aim of the present study was to find the optimal management of P. pinea stands from the economic point of view when both seed and timber production are considered. A growth and yield model was employed to simulate the dynamics of P. pinea stands of the northern Iberian Peninsula. The novelty of the study is the implementation of a cone yield model that is able to predict expected cone harvests and seed yields when masting is stochastic. The model was linked with an optimization algorithm to obtain optimal schedules for two different stands. The results showed that seed production of P. pinea in the northern plateau of the Iberian Peninsula may increase the soil expectation value by more than 300 % in dense stands and 200 % in sparse stands. When seed yields were considered, rotation lengths were longer and thinnings were delayed. The results were highly sensitive to cone prices and discount rates. © 2016, Springer-Verlag Berlin Heidelberg.

The ability of trees to grow and survive during periods of water scarcity is determined by the water use strategy of each individual. In this study we evaluated how water use strategies can influence the establishment phase of three coexisting species in forests where harvesting intensity and silvicultural interventions have been reduced over recent decades. We conducted a greenhouse experiment between February and July, applying two watering regimes (moist and dry) to current year seedlings in 1.5 m high pots to avoid root growth constraint. At the same time, the physiological performance of seedlings of the same species was monitored under natural conditions in the field over a period of decreasing soil moisture. Our results indicated that resprouter species allocated more than 40% of total biomass to roots whereas the non-resprouter P. pinea allocated only 26%. The plasticity index for the root traits was highest in Q. ilex, in which the highest stomatal conductance was measured in early summer. The slowest growth and lowest root plasticity, root hydraulic conductance and leaf water potential were measured in J. oxycedrus. The three species exhibited a positive carbon balance under low water availability. Coexisting species displayed a continuum in the water use strategies adopted. P. pinea would be the least competitive species under the forecasted increasing drought conditions in contrast to J. oxycedrus, which presents traits more suited to coping with droughts. © 2016 Elsevier B.V.

The aim of this study was to evaluate the potential of near infrared spectroscopy (NIRS) in predicting the coefficient of porosity of raw and boiled cork samples used mainly for producing cork stoppers for wine bottling. The classification of cork planks is currently performed visually in the last stage of preprocessing after boiling in water. In this study, calibration models have been developed on 279 cork samples before and after boiling. Three models were obtained one which predicts the coefficient of porosity of unprocessed samples, a second one that predicts porosity in boiled samples and finally a model that predicts the coefficient of porosity of boiled samples from spectra of raw samples. The models obtained showed a coefficient of determination of 0.58, 0.59 and 0.52, respectively. These results show that the modified partial least squares models based on NIRS technology can be used for screening cork porosity, not only at the two stages of processing, but also to predict boiled porosity. This suggests that NIRS technology could be used for determining the coefficient of porosity in boiled cork planks, and could also provide a useful tree selection tool. © 2016, Springer-Verlag Berlin Heidelberg.

Land use change and global warming are important drivers in the distribution of tree species. The Mediterranean mountain forest ecosystems can be severely affected by climate change since an increment in temperature has been observed. The main aim of this work was to analyze shifts in the distribution and changes in the abundance of Pyrenean oak (Quercus pyrenaica Willd.) and Scots pine (Pinus sylvestris L.) in Mediterranean mountains over a period of 47 years (1965-2012) by using data from the National Forest Inventories, extending the Universal Kriging/Cokriging models to the space-time case for long-term forest inventory data analysis including climatic variables. Our results indicated that both the distribution and the abundance of Scots pine remained quite constant during the study period. Pyrenean oak increased its presence by 42% whereas its abundance doubled between 1965 and 2012. This movement took place towards both higher and lower altitudes. With regard to climatic factors, the kriging models showed a negative association between the presence of Scots pine and the temperature. However, we found a quadratic relationship between the Pyrenean oak and temperature, pointing to the occurrence of at intermediate altitudes. Additionally, we found significant relationships between the rainfall and the abundance of both species. Rainfall was positively related to the abundance of Scots pine and negatively to that of Pyrenean oak. Our results indicate that there has been a threefold increase in the area covered by mixed stands. However, successive land use changes as well as forest policies related to conservation have played an important role in the distribution of both species and therefore are taken into account in the discussion of these results. © 2016.

In recent years, proximal sensing data has increasingly been used to optimize forest inventories. In this paper we present a forest inventory methodology based on stereoscopic hemispherical images. An automated pixel-based approach and a user-guided “region growing” approach have been developed for image matching. To estimate the basal area, number of trees and mean diameter, the sampling probability is determined for each tree. The accuracy and precision of the estimates derived from stereoscopic hemispherical images was analyzed for a set of National Forest Inventory plots. The results revealed that tree matching depends on the species, the distance to the target tree and the diameter. The Pearson correlation coefficient was 0.86 for the mean diameter and 0.89 for the basal area, whereas for the number of trees per hectare it was 0.59. The proposed methods may be used in large scale forest inventories as a cost-efficient way of obtaining data on diameter distribution and basal area from field surveys following a two-stage scheme combined with remote sensing techniques. © 2016 American Society for Photogrammetry and Remote Sensing.

Thuya (Tetraclinis articulata (Vahl) Mast) is a Mediterranean forest species mainly occupying semiarid environments in North African countries, where it provides important ecological and economical services, such as biodiversity conservation, soil protection against erosion, fuelwood, timber for fencing, construction and handicraft, resins, etc. Despite the importance of the species, there is a severe lack of scientific knowledge as regards the management of these forests or modeling tools to support multifunctional forest management decision making. In the present work, we developed a stand-level integrated model for the management of Thuya forests in Tunisia. The model comprises a family of site index curves, built using the Generalized Algebraic Difference Approach (GADA) method, which provides predictions for stand growth, aboveground biomass, total and merchantable volumes, along with a non-linear system of stand level equations presented as stand density management diagrams (SDMD). The developed model has been used to define, characterize and compare four different management specific schedules for different site qualities and multifunctional objectives. © SISEF.

Key message In modelling regeneration patterns, parametric regression is recommended because it can account for the spatial and temporal correlation present in the data, whereas decision trees allow more complex interactions and can be used to reduce the number of variables. Context The establishment of seedlings after regeneration fellings is key to guaranteeing the development and persistence of the forest. Depending on the objective pursued, data available or type of forest, a number of different methods have been employed to assess the relationship between seedling establishment and both environmental and stand factors. Most authors have conducted their analyses using parametric regression or point pattern analysis. Aim We analysed the way in which light, stand conditions, edaphic and topographic variables affect the regeneration of Pinus sylvestris L. in Central Spain. We used different methods to analyse the same data set. The strengths and weaknesses of each method were discussed. Methods We used two parametric approaches generalized linear mixed model regression using a negative binomial followed by the variant explanatory variables reduction prior to regression as well as three nonparametric approaches not commonly employed in forest regeneration nonmetric multidimensional scaling, regression trees and random forests algorithm. Results The parametric regression identified a larger number of variables associated with the regeneration process and the inclusion of a random effect in the model allowing the consideration of the spatial variability among plots. However, decision trees captured the complex interaction among variables, which typical parametric methods were unable to detect. Conclusion: Different statistical methods gave similar insights into the underlying ecological process. However, different statistical premises with inference implications can be noticed. This may give misinterpretation of the model depending on the nature of the data. The choic

The composition of Mediterranean forests is expected to vary with ongoing changes in climate and land use. To gain a clearer understanding of the response to global change of growth and survival during regeneration it is necessary to take a closer look at the ecophysiological traits underlying seedling performance. Gas exchange, leaf water potential, chlorophyll fluorescence, soil moisture, temperature and global site factor were measured over 1 year in naturally regenerated young trees of three coexisting species (Pinus pinea, Quercus ilex and Juniperus oxycedrus) in two stands of different density. We modelled the photosynthetic response of plants to micro-climatic conditions via the parameterization of the non-rectangular hyperbolic model of photosynthesis, which relates gross photosynthesis to incident light through three biochemical parameters, and the subsequent expansion of these parameters as a function of environmental variables (light environment, soil moisture and temperature). We investigated the relationship between different photosynthetic performance and the species-specific strategies to cope with stress (stress tolerant or avoiders). The optimal light environment, defined through the global site factor (GSF), and the regeneration niche to maximize carbon assimilation differed between the three species. P. pinea showed high sensitivity to water availability in agreement with a drought avoidance strategy, attaining the maximum photosynthetic capacity of the three species following the spring rainfall. Q. ilex was the most thermophilic and light-demanding of the species. Under high light conditions, J. oxycedrus was more drought tolerant and displayed higher net CO2 assimilation than P. pinea over the course of a growing period. Optimal locations for P. pinea regeneration are below-crown environments, while for J. oxycedrus regeneration the optimal locations are open gaps. Q. ilex regeneration occupy open gaps where the other two species are unable to

The sustainable production of lignocellulosic biomass in Short Rotation Coppice (SRC) in the context of bioeconomic development in Europe demands an ever greater understanding of the plant material. Different species and, in some cases, different genotypes (Populus deltoides 'Baldo', Populus x canadensis 'Orion', 'Oudenberg', 'Ballottino' and 'I-214'; Robinia pseudoacacia 'Nyirsegi', Salix matsudana x Salix spp. 'Levante' and Platanus x hispanica 'Girona') were tested at four contrasting Mediterranean locations to determine the biomass yield after three years. Besides production, genotypic stability is a key factor in furthering our understanding of the plant material, with important implications for the management of plantations as well as for breeding. To study this factor, several stability models were compared (additive mixed model, Shukla's stability variance model, Finlay-Wilkinson and Eberhart-Russell models) and differences in the response capacity of the material were evaluated in the different environments. This evaluation of genotypic stability, based on the measurement of variances, was complemented by an analysis of the mean genotypic value and the variability in genotype productivity. Intrinsic water use efficiency was also evaluated as it is an important trait of plant material destined for use in Mediterranean conditions. S. matsudana x Salix spp. 'Levante' exhibited the highest production and showed an intermediate reactivity (stability) as well as high intrinsic water use efficiency under the conditions in which it was tested. P. x canadensis 'Orion' also displayed a good overall performance and was highly sensitive to improving environmental conditions. Conversely, R. pseudoacacia and P. x hispanica presented yields well below the average as well as low responsiveness to improved environmental conditions. Our findings will contribute to a better understanding of plant material, enabling improved recommendations for plantations the Mediterranean ar

In central Spain, post-transplant water stress produces high seedling mortality after the first summer following outplanting. Our study was designed to determine whether survival and performance of outplanted stone pine (Pinus pinea) and holm oak (Quercus ilex) seedlings in a burned area could be improved by summer irrigation and mulching and to identify whether there is a species-specific adaptive capacity to respond to treatment and environment. Seedlings were outplanted in March 2011 in 200 planting holes in an area of 1.1 ha. Mulch was added in June; irrigation started in July and was repeated every week until mid-September. The severity of the 2011 summer drought constrained growth rates and photosynthetic characteristics, mainly in the non-irrigated seedlings, whose survival at the end of the year after planting was approximately 2.5%. Stone pine and holm oak seedlings responded more to irrigation than to mulching in terms of shoot growth, biomass and survival. Furthermore, stone pine seedlings were found to be more responsive to the partial alleviation of summer drought than holm oak seedlings. Irrigation alone produced similar results to those obtained when both irrigation and mulching were employed. In conclusion, first year summer irrigation should be considered as a planned adaptation measure in the management of outplanted Mediterranean ecosystems, because once a gravimetrically measured soil moisture level as low as 2% is achieved seedling survival and physiological performance can be guaranteed. However, the repercussions for the potential persistence of both species in the area will not only be related to the recurrence and intensity of summer droughts but also to drought duration. © SISEF.

Forests play an important role in the mitigation of global warming, acting as carbon sinks. However, the effects of forest management on the carbon pools over the rotation period in Mediterranean areas are scarcely understood. The objective of this work is to assess the way in which two alternative management systems; one more intensive and the other more moderate (with less severe harvesting and more spread over time) affect the carbon stocks in the living tree biomass, coarse woody debris, forest floor and mineral soil in Mediterranean forests. For this purpose, two chronosequences were established covering the whole rotation period in two Pinus sylvestris L. forests. We conducted four forest inventories over a period of 15years, measuring the diameter and the height of all the trees higher than 1.3m in order to calculate the carbon stored in the living parts of the tree. Soil pits were excavated and we collected soil samples to estimate the soil organic carbon. We found that the temporal trends for living tree biomass were similar in both forests. However, the total living tree carbon stored at the end of the rotation period was greater in the forest with the longer rotation period and lighter thinning regime (345.5Mgha-1 of carbon) than in the intensively-managed forest (223.8Mgha-1 of carbon). On average, more carbon was found to be stored in the forest floor under the more intensive management system, whereas more carbon was present in the first 20cm of mineral soil under the moderate management system. Moreover, in each forest, the carbon stocks of the forest floor and in the uppermost cm of the soil remained constant over the rotation period. Therefore, management systems with longer rotation periods and moderate harvesting intensities are recommended to increase carbon fixation in Mediterranean forests. © 2015 Elsevier B.V.

Key message The effect of unexpected low temperature on coexisting species in inland locations was examined; frost tolerance simulation over a 2-year period was used to determine bottlenecks where competition can arise. Abstract The effect of frost events on natural regeneration of Mediterranean mixed forests under a scenario of climate change is not well known. The expected increase in mean annual temperature and the greater inter- and intra-annual variability in frosts occurrence can significantly damage natural regeneration leading to death, with a decisive effect on species composition and forest dynamics. We investigated seasonal variations in frost tolerance of three Mediterranean species (Pinus pinea, Quercus ilex and Juniperus oxycedrus) co-occurring in inland locations in Spain. Our aim was to assess seasonal inter-specific differences in frost sensitivity or tolerance. First, we applied the relative electrolyte leakage method (REL) to estimate the frost tolerance of these species every 3–4 weeks during the 9-month period in which frost events can occur in a year. Second, we explored the REL relationship with environmental variables impacting frost acclimation/deacclimation, i.e.;absolute minimum and maximum temperatures and photoperiod. Third, we built a REL model to predict seasonal variations in REL performance of young trees. We simulated REL through a 2-year period, thus defining seasonal bottlenecks in which the dynamics of regeneration can be affected by frost events. Our results showed contrasting behaviors between species, highlighting a greater sensitivity to cold of P. pinea compared to the other two species. The three species are most vulnerable in autumn; however, the different strategies to cope with unfavorable conditions adopted by Q. ilex and J. oxycedrus (e.g.;stress tolerance and/or resprouting ability) give these species a competitive advantage over P. pinea. © 2015, Springer-Verlag Berlin Heidelberg.