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Producción Científica, Adapting forests to climate change is a critical issue for forest management. It requires an understanding of climate effects on forest systems and the ability to forecast how these effects may change over time. We used Spanish Second National Forest Inventory data and the SIMANFOR platform to simulate the evolution of CO2 stock (CO2 Mg · ha−1) and accumulation rates (CO2 Mg · ha−1 · year−1) for the 2000–2100 period in pure and mixed stands managed under different Shared Socioeconomic Pathways (SSPs) in Spain. We hypothesized that (1) the more optimistic climate scenarios (SSP1 > > SSP5) would have higher CO2 stock and accumulation rates; (2) mixed stands would have higher CO2 stock and accumulation rates than pure stands; and (3) the behavior of both variables would vary based on forest composition (conifer–conifer vs. conifer–broadleaf). We focused on Pinus sylvestris L., and its main mixtures with Pinus nigra, Pinus pinaster, Fagus sylvatica and Quercus pyrenaica. The SSP scenarios had correlating CO2 stock values in which SSP1 > SSP2 > SSP3 > SSP5, ranging from the most optimistic (SSP1) to the most pessimistic (SSP5). Though pure stands had higher CO2 stock at the beginning, differences with regard to mixed stands were drastically reduced at the end of the simulation period. We also found an increase in the aboveground CO2 proportion compared to belowground in conifer–broadleaf mixtures, while the opposite trend occurred in conifer–conifer mixtures. Overall CO2 accumulation rates decreased significantly from the beginning to the end of the simulation period, but our results indicated that this decline would be less drastic in mixed stands than in pure ones. At the end of the simulation period, CO2 accumulation rates were higher in mixed stands than in pure stands for all mixtures, fractions (aboveground and belowground) and SSPs. Knowing the evolution of mixed forests in different climate scenarios is relevant for developing useful silvicultural guidelines in the Mediterranean region and optimizing forestry adaptation strategies. Better understanding can also inform the design of management measures for transitioning from pure stands to more resource efficient, resistant and resilient mixed stands, in efforts to reduce forest vulnerability in the face of climate change. This work highlights the importance and benefits of mixed stands in terms of CO2 accumulation, stand productivity and species diversity., Ministerio de Economía y Competitividad (proyecto de investigación de Doctorado Industrial - [Beca DI-15–07722]), Programa Torres Quevedo (Beca PTQ-12–05409)., Publicación en abierto financiada por el Consorcio de Bibliotecas Universitarias de Castilla y León (BUCLE), con cargo al Programa Operativo 2014ES16RFOP009 FEDER 2014-2020 DE CASTILLA Y LEÓN, Actuación:20007-CL - Apoyo Consorcio BUCLE

BackgroundForest resilience should be improved to promote species adaptation and ensure the future of forests. Carbon stock is considered an indicator of resilience, so it is necessary to determine forest carbon stocks and how to improve them through forest management. The main objective of this study was to analyse biomass production and distribution among the components of four-year-old Pinus pinaster and Pinus halepensis trees. Young trees from a Nelder wheel experimental site were harvested and analysed. The effect of density could be included in the biomass analysis thanks to the Nelder wheel design. We tested densities from 1000 to 80000 seedlings/ha and analysed biomass by fitting different equations: (i) linear regressions to analyse biomass production; (ii) Dirichlet regressions to estimate the biomass proportions of each component and (iii) allometric equations to predict the biomass content of each component.ResultsResults from this innovative approach showed that density was a significant factor for Pinus halepensis. We observed a general increase of total biomass at lower densities and this positive effect increased root biomass proportion at the expense of aboveground biomass. Also, a new set of equations was developed for estimating above- and below-ground biomass in young Pinus pinaster and Pinus halepensis trees.Conclusionswe note the importance of belowground biomass and its value in total biomass production (approximately 20% of total biomass for both species). The effect of density on biomass production was only significant for Pinus halepensis, but the effect of density would have been different if root biomass had not been considered in the present study. Lower densities increased root biomass proportion at the expense of aboveground biomass. Currently, this positive effect is especially important in promoting management to improve tree resilience.

Tuber melanosporum (Ascomycota, Pezizales) is an ectomycorrhizal fungus that produces highly appreciated hypogeous fruiting bodies called black truffles. The aim of this paper was to research the composition of ectomycorrhiza-associated fungal and bacterial communities in T. melanosporum oak plantations. Results of this paper showed the competitive effect of T. melanosporum on other fungal species, especially other mycorrhizal and pathogenic species. T. melanosporum was shown to be associated mainly with bacteria, some of them important for their properties as mycorrhizal helper bacteria. A dendrogram analysis of co-occurrence showed that T. melanosporum tended to co-occur with the following bacteria species: Singulisphaera limicola, Nannocistis excedens and Sporosarcina globispora. In addition, it was linked to fungal species such as Mortierella elongata, M. minutissima, Cryptococcus uzbekistanensis, C. chernovii and C. aerius. This study provides an exhaustive analysis of the diversity, structure and composition of fungal and bacterial communities associated with T. melanosporum to enhance understanding of the biology, composition and role of these communities in truffle plantations.

13 Pág., Competition plays a key role controlling tree growth in mixed forests. Contrary to monocultures, quantifying species mixing influence on tree growth suppose a challenge since the presence of two or more species requires to estimate the degree of intra- and inter-specific competition among trees. Moreover, it is well known that aridity can also influence tree growth, especially in the Mediterranean Basin. In the present context of climate change, it is essential to take into account species mixing and aridity uncertainty in the design of sustainable management guidelines for Mediterranean mixed forests. To achieve that, data from Spanish National Forest Inventory was used in this study to fit new mixed-effects basal area increment (BAI) models for 29 two-species compositions in Spain. A wide range of different competition structures (intra-specific, inter-specific, size-symmetric and size-asymmetric) and aridity conditions (in terms of the De Martonne Index) were included and tested into the BAI models. Parameter estimations were obtained for all possible species, mixtures and combinations by Maximum Likelihood (ML). Models with all the coefficients being significant (p < 0.05) were first selected. Among these models, we used Akaike Evidence Ratios for selecting the best one by species for each mixture. The best model for each species and mixture was used to analyze the competition and climatic influence on tree growth. Regarding competition influence, a common trend among mixtures was found with higher productivity in mixed than pure stands, suggesting that BAI values may increase with the increment of species diversity. Based on intra and inter-specific competition indexes, competition seemed to be the most representative biological interaction in conifer-conifer mixtures, since neutralism and facilitation may occur more frequently in conifer-broadleaved and broadleaved-broadleaved mixtures. Our findings also suggested that tree growth may be significantly limited by arid conditions, excepting for Pinus halepensis and Pinus pinea. Our rigorous modelling approach successfully uncovered not only possible mixing effect among various species but also help us to understand the effect of aridity on tree growth. Thus, models presented in this study can be used in the design and implementation of management and adaptation guidelines under future climate change scenarios., The authors would like to thank the Spanish Ministry of Economy and Competitiveness for funding this research through Industrial PhD project [grant DI-15-07722] and the Torres Quevedo programme [grant PTQ-12-05409]. The authors are also grateful to the Ministry for Ecological Transition and the WorldClim team for sharing and providing the data used in this study.

Producción Científica, Long-term field-data series were used to fit a mushroom productivity model. Simulations enabled us to predict the consequences of management and climate scenarios on potential mushroom productivity. Mushrooms play an important ecological and economic role in forest ecosystems. Human interest in collecting mushrooms for self-consumption is also increasing, giving forests added value for providing recreational services. Pinus pinaster Ait. is a western Mediterranean species of great economic and ecological value. Over 7.5% of the total European distribution of the species is found on the Castilian Plateau in central Spain, where a great variety of mushrooms can be harvested. The aim of this study was to model and simulate mushroom productivity in Maritime pine (Pinus pinaster Ait.) ecosystems in northern Spain under different silvicultural and climatic scenarios. A mixed model was fitted that related total mushroom productivity to stand and weather variables. The model was uploaded to the SiManFor platform to study the effect of different silvicultural and climatic scenarios on mushroom productivity. The selected independent variables in the model were the ratio between stand basal area and density as a stand management indicator, along with precipitation and average temperatures for September and November. The simulation results also showed that silviculture had a positive impact on mushroom productivity, which was higher in scenarios with moderate and high thinning intensities. The impact was highly positive in wetter scenarios, though only slightly positive and negative responses were observed in hotter and drier scenarios, respectively. Silviculture had a positive impact on mushroom productivity, especially in wetter scenarios. Precipitation had greater influence than temperature on total mushroom productivity in Maritime pine stands. The results of this paper will enable forest managers to develop optimal management approaches for P. pinaster forests that integrate Non-Wood Forest Products resources., European Union Seventh Framework Programme FP7 under Grant Agreement n 613762, Ministerio de Economía y Competitividad under Grant Agreement n 345151982-51982-45-514, Ministerio de Economía y Competitividad - Fondo Social Europeo (Grant PTQ-12-05409)

Agroforestry land-use systems in the Andean region have great socioeconomical and biophysical relevance due to the abundance of products and services they provide. Biomass estimation in these systems constitutes a priority concern as it facilitates assessment of carbon sink potential and functionality for biomass production. In this paper, a set of equations were fitted to enable easy and reliable estimation of the total aboveground biomass of four frequently used species in Andean agroforestry systems: Acacia melanoxylon L., Alnus acuminata Kunth., Buddleja coriacea Remy. and Polylepis racemosa Ruiz&Pav. The best models for each biomass component (stem, thick branches, thin branches and leaves) per species were fitted simultaneously according to SUR methodology (seemingly unrelated regressions). All models showed high goodness of fit statistics and more than 70% of the observed variation in biomass components was explained by the independent variables. The inclusion of height as a predictive variable in the models improved their predictive reliability and expanded the application range. The models developed here are useful for assessing the sustainability of agroforestry systems and could support governmental or non-governmental forest conservation incentive programs and initiatives.

Climate change projections for the Mediterranean basin predict a continuous increase in extreme drought and heat episodes, which will affect forest dynamics, structure and composition. Understanding how climate influences the maximum size-density relationship (MSDR) is therefore critical to designing adaptive silvicultural guidelines based on the potential stand carrying capacity of tree species. With this aim, data from the Third Spanish National Forest Inventory (3NFI) and WorldClim databases were used to analyze climate-related variations of the maximum stand carrying capacity for 15 species from the Pinus, Fagus and Quercus genera. First, basic MSDR were fitted using linear quantile regression and observed size-density data from monospecific 3NFI plots. Reference values for maximum stocking, expressed in terms of the Maximum Stand Density Index (SDImax), were estimated by species. Then, climate-dependent MSDR models including 35 annual and seasonal climatic variables were fitted. The best climate-dependent models, based on the Akaike Information Criteria (AIC) index, were used to determine the climatic drivers affecting MSDR, to analyze general and species-specific patterns and to quantify the impact of climate on maximum stand carrying capacity. The results showed that all the selected climate-dependent models improved the goodness of fit over the basic models. Among the climatic variables, spring and summer maximum temperatures were found to be key drivers affecting MSDR for the species studied. A common trend was also found across species, linking warmer and drier conditions to smaller SDImax values. Based on projected climate scenarios, this suggests potential reductions in maximum stocking for these species. In this study, a new index was proposed, the Q index, for evaluating the impact of climate on maximum stand carrying capacity. Our findings highlight the importance of using specific climatic variables to better characterize how they affect MSDR. The models presented in this study will allow us to better explain interactions between climate and MSDR while also providing more precise estimates concerning maximum stocking for different Mediterranean coniferous and broadleaf tree species.

Biomass equations have become a vital estimation tool and a prerequisite for studies on forest productivity, nutrient cycling and carbon sequestration. In this paper a new set of biomass equations were fitted for Eucalyptus globulus in Northern Spain. These equations allow us to estimate the total biomass and above- and below-ground fractions from the basal area and the height of the tree. A dummy variable was included in the model to calculate the root fraction of planted versus coppice stands. A descriptive study of the root system was also carried out to complete the information about this component. Root fraction plays an important role in forest structure, but is often omitted in carbon sequestration estimates due to the difficulties and cost associated with measurement. Our results indicated that root biomass accounted for 15% and 35% of total biomass in planted and coppice stands, respectively, at a shoot age equal to 9 years. We also found that the stand type and plantation age influenced the number of roots per root system, the volume of the root system and root length. This paper brings to light how coppice stands accumulate significant amounts of carbon in their root systems from the time a plantation is established. Such information makes it possible to orient ecosystem management towards potential for C fixation.

The woodlands in the south-west of the Argentinean pampas are dominated by Prosopis Caldenia Burkart (calden). The current deforestation rate of this woodlands is 0.82% per year. Different compensation initiatives have begun that recognize the role of forests as environmental service providers. The financial incentives they offer make it necessary to quantify the amount of carbon stored in the forest biomass. A model for estimating calden biomass was developed. Thirty-eight trees were selected, felled and divided into sections. An equation system was fitted using joint generalized regression to ensure the additivity property. A weighted regression was used to avoid heteroscedasticity. In these woodlands fire is the main disturbance and it can modify tree allometry, due this all models included the area of the base of the stem and tree height as independent variables since it indirectly collects this variability. Total biomass and the stem fraction had the highest R2_Adj. values (0.75), while branches with a diameter less than 7 cm had the lowest (0.58). Tree biomass was also analyzed by partitioning into the basic fractions of stem, crown, roots, and the root/shoot ratio. Biomass allocation was greatest in the crown fraction and the mean root/shoot ratio was 0.58. The carbon stock of the caldenales considering only calden tree biomass is 20.2 Mg ha−1. While the overall carbon balance of the region is negative (deforestation and biomass burning, the remnant forested area has increased their calden density and in an indirect way his carbon sequestration capacity could also be increased.

The quantity and characteristics of coarse woody debris (CWD) were examined in four distinct pine ecosystems of north-western (NW) Spain, NW Russia and the NW USA. The average CWD volume and biomass ranged from 3.76 m3 ha-1, 1.55 Mg ha-1 in pine plantations in NW Spain to 24.86 m3 ha-1, 6.69 Mg ha-1 in Scots pine forest in NW Russia to 55.35 m3 ha-1, 20.38 Mg ha-1 and 77.04 m3 ha-1, 28.84 Mg ha-1 in ponderosa and lodgepole pine forests in the NW USA. Despite differences in species, ecological conditions and management histories, in all four ecosystems the mean snag volume was less than that of logs, most of the CWD mass was in an intermediate degree of decay, and mature stands had the greatest amount of CWD mass, followed by middle-age and then young stands. The CWD ratio (ratio of dead to live wood volume) ranged from 2.8% to 126.6%, depending on pine ecosystem and stand age, and was influenced by the type of natural and human disturbance. The difference in CWD amount and distribution among the regions studied reflected differences in disturbance history and management practices. Only in NW USA was the sample size large enough to examine the effect of disturbance type on CWD amount and distribution. There, fire and insect damage were found to considerably influence the amount of CWD in both lodgepole and ponderosa pine forests. Comparison of how different factors affect the amount and distribution of CWD in different ecosystems could be useful in developing ecologically sustainable forest management guidelines.

Forest stand productivity is defined as the quantitative estimation of a specific area's potential to produce biomass over a determined period of time. The site index has been the predominant method used to evaluate forest stand productivity. Teak is one of the most accepted species within the international timber market due to the physical and aesthetic qualities of this wood. The aim of this study was to determine the site index of teak plantations. The study was conducted in teak plantations of Tabasco. Data were obtained from a network of 10 plantations consisting of 35 plots measured over four successive inventories (2003 to 2006). The data were fitted to five models, of which four were based on proposed finite difference equations and a non-integrated function. The most suitable of the five models was chosen, taking into account the goodness of fit, the residual analysis, and the validation with a data subsample from the plantation. The Sloboda model was finally selected, and the results obtained were compared with the model proposed by Upadhyay. This model proved to be a useful tool, not only in evaluating station quality but also in improving the planning and management of teak plantations in Tabasco. Resumen La productividad de una masa forestal es la estimación cuantitativa del potencial de un área para producir biomasa en un tiempo determinado. El índice de sitio ha sido el principal método para evaluar esta productividad en los rodales forestales. Entre las especies madereras, la teca es una de las especies que ha tenido mejor aceptación en el mercado a nivel internacional por las cualidades físicasyrestéticas de su madera. El objetivo de este trabajo fue determinar el índice de sitio en plantaciones de teca (Tectona grandis L.). El estudio se llevó a cabo en plantaciones de teca en el estado de Tabasco. Los datos se obtuvieron de una red de 10 plantaciones con 35 parcelas medidas en cuatro inventarios sucesivos (de 2003 a 2006). Se ajustaron cinco modelos, de los cuales cuatro se basaron en el planteamiento de ecuaciones en diferencias finitas y el otro en una función no integrada. De los cinco modelos, se eligió el más adecuado según la bondad del ajuste, el análisis de los residualesyrla validación con una submuestra de datos de las plantaciones. Se seleccionó el modelo de Slobodayrse compararon los resultados obtenidos con el modelo propuesto por Upadhyay utilizando la ecuación de Hossfeld IV Este modelo resultó ser una herramienta útil, no sólo para evaluar la calidad de estación, sino también para mejorar la planificaciónyrgestión de las plantaciones de teca en el Estado de Tabasco.

In the Mediterranean area, the role of forest as carbon sinks is particularly significant since usually ecosystem services provided by forests are frequently of greater value than their direct productions. In this chapter, how carbon sequestration changes over time and with different management regimes in Mediterranean pine forests are presented. The information come from a number of sources including: (i) carbon stock estimates under different management plans using a chronosequence trial in Pinus sylvestris forests; (ii) simulations based on the process model 3-PG of the effect of different thinning regimes on Pinus pinaster biomass under a climate change scenario; (iii) a comparison of the effect of different age structures in Pinus pinea forest using the PINEA growth model which includes the biomass allocated in cones and considers the different wood uses; and finally, (iv) a model for estimating coarse woody debris.

Aim of study: The aim of this study was to 1) estimate the amount of dead wood in managed beech (Fagus sylvatica L.) stands in northern Iberian Peninsula and 2) evaluate the most appropriate volume equation and the optimal transect length for sampling downed wood.Area of study: The study area is the Aralar Forest in Navarra (Northern Iberian Peninsula).Material and methods: The amount of dead wood by component (downed logs, snags, stumps and fine woody debris) was inventoried in 51 plots across a chronosequence of stand ages (0-120 years old).Main results: The average volume and biomass of dead wood was 24.43 m3 ha-1 and 7.65 Mg ha-1, respectively. This amount changed with stand development stage [17.14 m3 ha-1 in seedling stage; 34.09 m3 ha-1 inpole stage; 22.54 m3 ha-1 in mature stage and 24.27 m3 ha-1 in regular stand in regeneration stage], although the differences were not statistically significant for coarse woody debris. However, forest management influenced the amount of dead wood, because the proportion of mass in the different components and the decay stage depended on time since last thinning. The formula based on intersection diameter resulted on the smallest coefficient of variation out of seven log-volume formulae. Thus, the intersection diameter is the preferred method because it gives unbiased estimates, has the greatest precision and is the easiest to implement in the field.Research highlights: The amount of dead wood, and in particular snags, was significantly lower than that in reserved forests. Results of this study showed that sampling effort should be directed towards increasing the number of transects, instead of increasing transect length or collecting additional piece diameters that do not increase the accuracy or precision of DWM volume estimation.Keywords: snags; downed logs; stumps; fine woody debris; beech; line intersect sampling.

Indicators for sustainable forest management are considered to be key tools for the implementation of regional, national and international forest policies. The Montreal process identified the “maintenance of forest contribution to global carbon cycles” as an essential component in sustainable management of forest ecosystems. Carbon sink evaluations provide reference information to policy-makers, stakeholders, resource managers and concerned citizens about the sustainable use of our forests for present and future generations. Two forest areas in northern and central Spain (‘Paramos y Valles’ and Central Mountain Range) were chosen as pilot areas to test the use of the National Forest Inventory to calculate carbon biomass forest sink at operational level. Data from the Second and Third National Forest Inventory (2NFI and 3NFI, respectively), together with biomass equations were used. Total carbon biomass sink was calculated as a balance between carbon dioxide inputs and outputs in forest biomass. Tree growth between 2NFI and 3NFI, new plots and ingrowth (recruitment and upgrowth) biomass were considered as inputs, while forest harvesting and natural mortality were considered as outputs. In ‘Paramos y Valles’, 2.46 Mg CO2 ha−1 year−1 was fixed in the tree biomass of forest ecosystems from 2NFI to 3NFI, whereas in the Central Mountain Range the fixation was 0.72 Mg CO2 ha−1 year−1 in the period between inventories. The balance of CO2 in the two areas was positive in 3NFI, with more than four million Mg of CO2 accumulated in ‘Paramos y Valles’ and more than 72 million Mg of CO2 fixed in the Central Mountain Range. Forest ecosystems are carbon sinks in the tree biomass in the two areas considered.

Producción Científica, Aim of study: The aim of the study was to determine the baseline carbon stock in forest floor and mineral soils in pine and oak stands in acid soils in Northern Spain.Area of study: The study area is situated in northern Spain (42° N, 4° W) on “Paramos y Valles” region of PalenciaMaterial and methods: An extensive monitoring composed of 48 plots (31 in pine and 17 in oak stands) was carried out. Litter layers and mineral soil samples, at depths of 0-30 cm and 30-60 cm, were taken in each plot. An intensive monitoring was also performed by sampling 12 of these 48 plots selected taken in account species forest composition and their stand development stage. Microbial biomass C (CMB), C mineralization (CRB), and soil organic C balance at stand level were determined in surface soil samples of intensive monitoring.Main results: No differences in soil C content were detected in the two forest ecosystems up to 60 cm depth (53.0±25.8 Mg C ha-1 in Pinus spp. plantations and 60.3±43.8 Mg C ha-1 in oak stands). However, differences in total C (CT), CMB and CRB were found in the upper 10 cm of the soils depending on the stand development stage in each species forest composition (Pinus nigra, Pinus pinaster, Pinus sylvestris and Quercus pyrenaica). Plots with high development stage exhibited significant lower metabolic quotient (qCO2), so, meant more efficient utilization of C by the microbial community. The C content in the forest floor was higher in pine stands (13.7±0.9 Mg C ha-1) than in oak stands (5.4±0.7 Mg C ha-1). A greater turnover time was found in pine ecosystems vs. oak stands. In contrast, forest floor H layer was nonexistent in oak stands.Research highlights: Results about litterfall, forest floor and mineral soil dynamics in this paper can be used strategically to reach environmental goals in new afforestation programs and sustainable forest management approaches, Ministerio de Economía y Competitividad (Project AGL2011-29701-C02-02.)

Two experiments were performed to study the effect of fire and ash concentration on the germination of Pinus pinaster and Cistus laurifolius seeds. These experiments combined seven different temperatures, ranging from 70 °C up to 190 °C, and two times of exposure, 1 and 5 min. In addition to these treatments, a control treatment was performed in the absence of thermal shock. Following the heat treatments, seeds were introduced into a germination chamber in a randomized design and under controlled conditions of temperature and photoperiod. P. pinaster seeds responded positively in germination to thermal shocks of short duration (1 min) over the studied range of temperatures. Nevertheless, in the simulation of fires of long duration, temperatures equal to or higher than 130 °C, resulted in lethal effects on seeds. On the other hand, C. laurifolius seeds responded positively if the temperature was below 110 °C, independent of time of exposure. The effect of ash concentration was also tested but failed to produce significant differences in the germination rates of either species. The results of this study suggest prescribed fire could be incorporated in sustainable forestry practices following detailed studies of its direct and indirect effects.

El aumento de las concentraciones de gases efecto invernadero junto con los cambios de uso de la tierra está provocando un incremento de la temperatura de la Tierra. En este contexto, los bosques pueden ayudar a mitigar los efectos del cambio climático debido a su potencial como sumideros de carbono. Pero, ¿cuánto C puede almacenar una masa forestal?. Para responder esta pregunta se realizaron muestreos con el objetivo de cuantificar el contenido de C en la biomasa arbórea, el estrato arbustivo y de matorral, la madera muerta, la hojarasca y el suelo en dos ecosistemas forestales mediterráneos, pinares de repoblación [pinares de laricio (Pinus nigra Arn.), negral (Pinus pinaster Ait.) y silvestre (Pinus sylvestris L.)] y rebollares naturales (Quercus pyrenaica Willd.). Los resultados obtenidos han mostrado que los ecosistemas estudiados son sumideros, la selvicultura aplicada y la capacidad tecnológica del rodal determinan el carbono total que se retiene y se extrae en el ecosistema.

Understanding biological processes in forests is necessary to orientate ecosystem management towards potential C sequestration. To achieve this, information is required about changes in forest biomass C pools, including the stem components (bark, sapwood and heartwood). This study aimed to determine whether there are differences in C concentration in axial and radial directions within stem biomass in Pinus nigra, Pinus pinaster and Pinus sylvestris. Wood samples from a permanent plantation in northern Spain were examined for C concentration and wood bulk density. The results showed that C concentration was higher in heartwood than in sapwood in the three species. Pinus spp. sapwood C concentration increased along the stem, while the C concentration in heartwood tissue showed the opposite behavior. In bark, Pinus pinaster showed a decreasing trend, in contrast to Pinus nigra and Pinus sylvestris, where higher values were found at the base and top of the stem. Finally, wood bulk density decreased in heartwood, sapwood and bark areas when stem height increased. Estimating C content taking into account different anatomical parts and heights is important in considering the specificity of the different parts because of their potential commercial or ecological use in forest ecosystems.

International audience; Coarse woody debris (CWD) plays a substantial role in several ecological processes in forest ecosystems, providing a habitat for many organisms and participating in biogeochemical fluxes. Understanding CWD dynamics is important to classify adequate density, size and amount into different decay classes and to make decisions that include biodiversity and the carbon budget in practical forestry.* A two-step model has been developed to quantify CWD in Pinus spp. plantations in Northern Spain. The two-step approach was composed of a logistic model to predict the probability of CWD occurrence and linear models to quantify the two components considered, basal area of snags and volume of logs.* Site conditions, and climatic and stand variables were included in the models as independent variables. Good performance of the two-step model (R2snag = 39.9%, R2log = 62.8%) was observed.* Modelling CWD is a useful tool for simulating future scenarios in the current context of climate change. Models inform stakeholders properly about defining the best silvicultural options for the distribution of CWD under sustainable forest management.

18 Pág. (This article belongs to the Special Issue Climate Change Effect on Mixed-Species Forest Management), Estimating tree height is essential for modelling and managing both pure and mixed forest stands. Although height–diameter (H–D) relationships have been traditionally fitted for pure stands, attention must be paid when analyzing this relationship behavior in stands composed of more than one species. The present context of global change makes also necessary to analyze how this relationship is influenced by climate conditions. This study tends to cope these gaps, by fitting new H–D models for 13 different Mediterranean species in mixed forest stands under different mixing proportions along an aridity gradient in Spain. Using Spanish National Forest Inventory data, a total of 14 height–diameter equations were initially fitted in order to select the best base models for each pair species-mixture. Then, the best models were expanded including species proportion by area (mi ) and the De Martonne Aridity Index (M). A general trend was found for coniferous species, with taller trees for the same diameter size in pure than in mixed stands, being this trend inverse for broadleaved species. Regarding aridity influence on H–D relationships, humid conditions seem to beneficiate tree height for almost all the analyzed species and species mixtures. These results may have a relevant importance for Mediterranean coppice stands, suggesting that introducing conifers in broadleaves forests could enhance height for coppice species. However, this practice only should be carried out in places with a low probability of drought. Models presented in our study can be used to predict height both in different pure and mixed forests at different spatio-temporal scales to take better sustainable management decisions under future climate change scenarios., This research was funded by the SPANISH MINISTRY OF ECONOMY AND COMPETITIVENESS (MINECO), through an Industrial PhD Grant (grant number DI-15-07722) and the Project “CLU-2019-01-iuFOR Institute Unit of Excellence” of the University of Valladolid, funded by the Junta de Castilla and co-financed by the European Union (ERDF “Europe drives our growth”). In addition, this project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 734907.