Mycorrhizal induction of phenolic compounds and antioxidant properties of fungi and seedlings during the early steps of symbiosis.

Ectomycorrhizal (ECM) symbiosis plays a major role in nutrient cycling and the functioning of forest ecosystems. Trees with well developed ectomycorrhizas are more resistant to environmental stresses such as drought and to biotic stresses such as root pathogens. The establishment of ECM symbiosis is triggered by signals produced by both partners. These signals lead to morphological changes and a complex development of specific structures in both the plant root and the fungus. The development of the ECM fungi, Paxillus involutus and Pisolithus arhizus, in presence and absence of the symbiont – Pinus pinaster- was evaluated, as well as their antioxidant properties and phenolic compounds composition in response to the symbiotic association. ECM fungi grew less in the presence of Pinus pinaster, with Pisolithus arhizus being less affected in growth and thus being more adapted to this association. Protocatechuic acid was found only in Paxillus involutus, while Pinus pinaster roots, both in association and isolated, proved to have other phenolic acids, such as p-hydroxybenzoic and p-coumaric acids. The symbiosis between Paxillus involutus and Pinus pinaster had no major effects on the symbionts, while the association between Pisolithus arhizus and Pinus pinaster seems to generally decrease the antioxidant effects of both symbionts, despite the increase in p-coumaric and cinnamic acids in the ECM fungi

Potential climatic influence on the maximum stand carrying capacity of 15 Mediterranean conifers and broadleaves

Las proyecciones de cambio climático para la cuenca del Mediterráneo predicen un incremento continuo en episodios de sequía y calor extremos, afectando a la dinámica, estructura y composición de las masas forestales. En este contexto, resulta fundamental comprender cómo el clima influye en la relación tamaño-densidad máxima (recta de autoclareo) de estas masas con el fin de diseñar actuaciones de gestión forestal sostenible adaptadas a este nuevo escenario. Este estudio pretende avanzar en esta línea, analizando los potenciales impactos del clima en el Índice de Máxima Densidad (SDImax) de 15 especies forestales pertenecientes a los géneros Pinus, Fagus y Quercus. Para ello se utilizaron las bases de datos del Tercer Inventario Forestal Nacional Español (IFN3) y WorldClim. En primer lugar, se ajustaron rectas de autoclareo básicas mediante regresión cuantílica y se estimaron nuevos valores SDImax de referencia por especie. En un segundo paso, se seleccionaron 35 variables climáticas anuales y periódicas para ajustar rectas de autoclareo dependientes del clima. El mejor modelo climáticodependiente fue seleccionado para cada especie basándonos en el Indice de Información de Akaike con el fin de analizar las tendencias generales y específicas en la variación de SDImax. Para todas las especies de estudio, la influencia del clima sobre el SDImax fue significativa. Los resultados obtenidos mostraron una tendencia común en la variación de SDImax, con valores más pequeños vinculados a condiciones más secas y cálidas, lo que sugiere reducciones potenciales del stock de estas especies bajo futuros escenarios climáticos. En oposición a esta tendencia, el modelo de Pinus nigra sugiere que inviernos más suaves como efecto de incrementos en temperaturas mínimas podrían beneficiar a las especies en zonas de montaña. En general, el estrés hídrico (expresado a través del Indice De Martonne) fue un factor determinante afectando al SDImax de Fagus, mientras que cambios en las temperaturas de primavera y verano explicaron las variaciones SDImax de las especies del género Quercus. Las especies de Pinus se vieron indistintamente afectadas por potenciales variaciones de temperatura y humedad. Todos los modelos climático-dependientes seleccionados mejoraron los modelos básicos y los modelos ajustados en estudios similares, como aquellos que utilizan el Índice de Martonne como variable climática independiente. Nuestros hallazgos destacan la necesidad de utilizar variables climáticas periódicas para caracterizar mejor los impactos climáticos en el SDImax. Los modelos presentados en este estudio permitirán obtener estimaciones más precisas de la máxima densidad admisible por diferentes especies de coníferas y frondosas, proporcionando una herramienta avanzada para la gestión forestal sostenible de masas puras y mixtas mediterráneas bajo diferentes escenarios de cambio climático.Climate change projections for the Mediterranean basin predict a continuous increment in extreme drought and heat episodes, affecting forest dynamics, structure and composition. Understanding how climate influences the maximum size-density relationship (MSDR) is therefore critical to design adaptative 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 genus. First, basic MSDR were fitted using linear quantile regression and observed size-density data from monospecific 3NFI plots. Reference values of maximum stocking, expressed as SDImax, were estimated by species. In a second step, climatedependent MSDR models including 35 different annual and seasonal climatic variables were fitted. The best climate-dependent MSDR model was selected by species according to the Akaike Information Criteria in order to analyze general and species-specific trends in the SDImax variation. Results showed a common trend across species in SDIgenus variation with smaller SDImax values linked to drier and warmer conditions, suggesting potential reductions of the maximum stocking for this species based on projected climatic scenarios. Opposed to this trend, results for Pinus nigra suggest that milder winters as effect of increments in minimum temperatures could beneficiate mountainous species. Humidity (expressed as the De Martonne Index) was found as key driver affecting SDImax of Fagus species, since changes in spring and summer temperatures explained SDImax variations of Quercus species. Pinus species were indistinctively affected by temperature and water stress. All the selected climate-dependent models improved the goodness of fit over the basic and the business-as-usual models including the De Martonne Index as independent climatic variable. Our findings highlight the importance of using specific climatic variables to better characterize climatic impacts on the MSDR. Models presented in this study will allow to obtain more precise estimations of the maximum stocking for different coniferous and broadleaved species, providing an advanced tool for managing Mediterranean pure and mixed forests under different scenarios of climate change.Máster en Gestión Forestal basada en Ciencia de Dato

Xylem plasticity in Pinus pinaster and Quercus ilex growing at sites with different water availability in the Mediterranean region: relations between Intra-Annual Density Fluctuations and environmental conditions.

Fluctuations in climatic conditions during the growing season are recorded in Mediterranean tree-rings and often result in intra-annual density fluctuations (IADFs). Dendroecology and quantitative wood anatomy analyses were used to characterize the relations between the variability of IADF traits and climatic drivers in Pinus pinaster Aiton and Quercus ilex L. growing at sites with different water availability on the Elba island in Central Italy. Our results showed that both species present high xylem plasticity resulting in the formation of L-type IADFs (L-IADFs), consisting of earlywood-like cells in latewood. The occurrence of such IADFs was linked to rain events following periods of summer drought. The formation of L-IADFs in both species increased the hydraulic conductivity late in the growing season, due to their larger lumen area in comparison to "true latewood". The two species expressed greater similarity under arid conditions, as unfavorable climates constrained trait variation. Wood density, measured as the percentage of cell walls over total xylem area, IADF frequency, as well as conduit lumen area and vessel frequency, specifically in the hardwood species, proved to be efficient proxies to encode climate signals recorded in the xylem. The response of these anatomical traits to climatic variations was found to be species- and site-specific

Pine wilt disease: detection of the pinewood nematode (Bursaphelenchus xylophilus) as a tool for a pine breeding programme

The pinewood nematode (PWN), Bursaphelenchus xylophilus, is a serious quarantine pest first detected in Portugal and Europe in 1999. It is the causal agent of pine wilt disease (PWD). A resistance breeding programme has been initiated to contribute to control the evolution of the disease. Five hundred and four adult maritime pine, Pinus pinaster, trees were phenotypically selected as candidate trees for this programme from an area affected by PWD. To identify tolerance to the nematode, the selected trees were monitored monthly. Over the course of 1 year, 57 candidate trees died and were tested for the presence/absence of the PWN. As accuracy of detection is of major importance, an ITS-PCR-based method applied directly to wood from adult maritime pine trees was tested and compared with a standard morphological identification method. The results showed that the use of PCR to detect the pathogen provided more rapid and accurate results in comparison with the standard morphological identification. Thus, this method is suitable to be used in the survey of the breeding population for resistance/tolerance to PWD

The pinewood nematode, Bursaphelenchus xylophilus, in Madeira Island

The environmental conditions in Madeira Island are favorable for the presence and dissemination of the pinewood nematode (PWN), Bursaphelenchus xylophilus. Five hundred Pinus pinaster wood samples were collected in several forest areas and PWN was detected in 22.8 % of the samples. Bursaphelenchus xylophilus isolates from Madeira Island displayed the species-specific diagnostic characters. A morphological variation in the female tail terminus was detected. In most females, the tail presented a broadly rounded terminus and, occasionally, a digitate terminus with a terminal nipple-like extension resembling a mucro. PCR ITS-RFLP analysis revealed that Madeira Island isolates exhibited patterns specific to the species B. xylophilus and similar to virulent isolates. Amplified ITS regions were further sequenced and no genetic diversity was found for this genomic region among 17 Portuguese isolates (Madeira Island and Continental Portugal). Phylogenetic analysis revealed that Portuguese isolates grouped with isolates from China, Korea and one isolate from Japa

Climatic niche and neutral genetic diversity of the six Iberian pine species: a retrospective and prospective view

Quaternary climatic fluctuations have left contrasting historical footprints on the neutral genetic diversity patterns of existing populations of different tree species. We should expect the demography, and consequently the neutral genetic structure, of taxa less tolerant to particular climatic extremes to be more sensitive to long-term climate fluctuations. We explore this hypothesis here by sampling all six pine species found in the Iberian Peninsula (2464 individuals, 105 populations), using a common set of chloroplast microsatellite markers, and by looking at the association between neutral genetic diversity and species-specific climatic requirements. We found large variation in neutral genetic diversity and structure among Iberian pines, with cold-enduring mountain species (Pinus uncinata, P. sylvestris and P. nigra) showing substantially greater diversity than thermophilous taxa (P. pinea and P. halepensis). Within species, we observed a significant positive correlation between population genetic diversity and summer precipitation for some of the mountain pines. The observed pattern is consistent with the hypotheses that: (i) more thermophilous species have been subjected to stronger demographic fluctuations in the past, as a consequence of their maladaptation to recurrent glacial cold stages; and (ii) altitudinal migrations have allowed the maintenance of large effective population sizes and genetic variation in cold-tolerant species, especially in more humid regions. In the light of these results and hypotheses, we discuss some potential genetic consequences of impending climate change

Mechanical characterization of timber in structural sizes: bending and compression tests

This paper presents the results obtained in a series of tests on Pinus Pinaster Ait. timber specimens, using the prEN408:2000, to estimate the local and global Young’s modulus and strength both in bending and compression parallel to the grain. The results obtained are compared with the values presented in the Portuguese Nationally Determined Parameters of Eurocode 5, for the quality classes assign by Portuguese Standard NP4305:1994 by visual grading

Detailed morphobiometric studies of Bursaphelenchus xylophilus and characterisation of other Bursaphelenchus species (Nematoda: Parasitaphelenchidae) associated with Pinus pinaster in Portugal

Detailed studies on Bursaphelenchus xylophilus are provided in this contribution. Comparative observations between field and cultured populations of this species demonstrated significant size differences: cultured specimens overall displayed larger size in all morphometric parameters. A principal component analysis (PCA) of the individuals undergoing moulting allowed their separation in four groups namely J2-J3, J3-J4, J4F-F, and J4M-M; gonad length mean values of these four groups made possible to distinguish the non-moulting groups J2, J3, J4F, J4M and adults. Seven Bursaphelenchus species (B. hellenicus, B. leoni, B. pinasteri, B. sexdentati, B. teratospicularis, B. tusciae and B. xylophilus), associated with Pinus pinaster in Portugal, were charaterized, including biometrical measurements and ratios as well excised spicules observed under SEM; furthermore, B. hellenicus, B. pinasteri, B. sexdentati, B. tusciae and B. xylophilus were characterised on the basis of their ITS-RFLP profiles. B. sexdentati and B. xylophilus were the only species found in high numbers in some of the samples