Carbon in heartwood, sapwood and bark along stem profile in three Mediterranean Pinus species

Context 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). Aims 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. Methods Wood samples from a permanent plantation in northern Spain were examined for C concentration and wood bulk density. Results 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.Instituto Universitario de Gestión Forestal Sostenibl

Potential climatic influence on maximum stand carrying capacity for 15 Mediterranean coniferous and broadleaf species

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.Industrial PhD project [grant DI-15-07722]Torres Quevedo programme [grant PTQ-12-05409

Análisis de datos selvícolas con R

La cuantificación de la selvicultura permite medir y comparar los tratamientos selvícolas y sus efectos sobre los bosques. Así, dos conceptos a menudo distantes para la mayoría de las personas como son los bosques y los números pueden hacernos reflexionar sobre diversos aspectos de interés para la gestión de los bosques. Entre otras preguntas que podemos hacernos destacan dos: 1. ¿Tiene sentido cuantificar los procesos que ocurren en los bosques? 2. ¿Qué aporta la cuantificación de los procesos forestales a la toma de decisiones? Si la respuesta a la primera pregunta es sí y a la segunda podemos responder diciendo que lo que aporta la cuantificación es relevante para la selvicultura, entonces debemos disponer de herramientas avanzadas para el análisis forestal. Una de estas herramientas es el programa informático de análisis estadístico R. Con este manual se pretende dotar de una herramienta de apoyo a las clases de grado y máster relacionadas con los aspectos cuantitativos de la selvicultura.Departamento de Producción Vegetal y Recursos Forestale

Can mixed forests sequester more CO2 than pure forests in future climate scenarios? A case study of Pinus sylvestris combinations in Spain

Producción CientíficaAdapting 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 BUCL

Cuantificación de carbono en pinares (Pinus nigra Arn., Pinus pinaster Ait., Pinus sylvestris L.) y rebollares

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

Modelo de probabilidad de germinación del pino negral "Pinus pinaster" Ait. tras incendio

El fuego es un factor determinante en los ecosistemas forestales. El conocimiento de la respuesta de la especie Pinus pinaster resulta fundamental a la hora de establecer cualquier acción encaminada a una mejor, y más rápida, recuperación del ecosistema tras un incendio forestal. En el presente trabajo hemos comprobado que las semillas de Pinus pinaster responden eficazmente a los choques térmicos de corta duración, 1 minuto, a lo largo de todo el régimen de temperaturas estudiado. Sin embargo, en la simulación de fuegos de larga duración, las temperaturas iguales o superiores a 130 ºC producen efectos letales al proceso de regeneración del ecosistema. La competencia ejercida por Cistus laurifolius puede ser significativa debido a su estrategia reproductiva. El manejo de las masas arbóreas de pino negral después del fuego, debe considerar el efecto que el fuego prescrito puede incorporar en la gestión forestal sostenible

Effect of heat shock on the germination of seeds of the species Acacia senegal L. and Acacia seyal Del. from sub-Saharan Africa (Ethiopia).

Producción CientíficaAim of the study: Understanding post-fire germination of tree species in arid and semi-arid zones of sub-Saharan Africa.Area of study: Ethiopian Acacia senegal L. and Acacia seyal Del. forests.Material and methods: Seeds were subjected to heat shocks at combinations of four temperatures (60º, 90º, 120º and 150ºC) and three exposure times (1, 5 and 10 minutes). A control was also included, resulting in a total of thirteen treatments. After the application of the heat shocks, the viability of no germinated seeds was assessed after immersion in a Tetrazolium solution. A mixed and a logistic model were used to analyse the influence of heat shock on germination.Main results: Results showed that germination depended on the species, the heat shock treatment and their interaction. Both species showed similar germination results at temperatures below 90ºC in all exposure times, however, germination in Acacia senegal was statistically higher in most of the heat shocks. On the other hand, germination probability decreased in both species, when the exposure time increased, although with a different behaviour. In 1 minute of time of exposure, the germination probability was higher than 60% in the two species throughout the temperature range. However, at 5 minutes of time and temperature smaller than 90°C, the probability of germination was higher than 70% in A. senegal and 50% in A. seyal. Although germination in both species was impacted by the different heat shocks, non-germinated seeds were viable.Research highlights: This paper showed, according to these results, that heat shock would negatively influence the regeneration of both species, and especially for A. seyalAgencia Española de Cooperación Internacional para el Desarrollo (MAEC-AECID [584953])Programa Nacional de Selección e Incorporación de Personas, programm [PTQ-12-05409

Competition and climate influence in the basal area increment models for Mediterranean mixed forests

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.Peer reviewe

Species Mixing Proportion and Aridity Influence in the Height–Diameter Relationship for Different Species Mixtures in Mediterranean Forests

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.Forestry, Faculty ofNon UBCForest Resources Management, Department ofReviewedFacultyResearche

Fungal and bacterial communities in Tuber melanosporum plantations from northern Spain

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