Cambio global y ambiente lumínico en ecosistemas forestales mediterráneos:Consideraciones ecológicas e implicaciones para la gestión

10 páginas, 5 figuras y una tabla. Se recoge el trabajo en un cuadernillo titulado "Actas de la I Reunión sobre Ecología, Ecofisiología y Suelos forestales". En el apartado "Agradecimientos. Gracias a Teodoro Marañón, Juan Arroyo, Regino Zamora, José María Gómez, David Riaño, Emilio Chuvieco, Adrián Escudero, Federico Castillo, Bosco Imbert, Lucía Ramírez, Alba Valladares, Beatriz Guzmán-Asenjo y Libertad González por su colaboración en el trabajo de campo."La información cuantitativa sobre la radiación disponible en el sotobosque es crucial para la comprensión de multitud de aspectos relacionados con la ecología y dinámica del bosque. Dado que la gestión es en buena medida la gestión de la luz, la combinación de estudios sobre ecofisiología, heterogeneidad lumínica, dinámica forestal y cambio global representa un punto de encuentro entre la ecología y la gestión forestal, algo muy necesario em ecosistemas mediterráneos donde las incertidumbres son grandes y las predicciones poco optimistas. En este trabajo se presentan resultados sobre la heterogeneidad temporal y espacial de la luz en el sotobosque de diversas formaciones forestales ibéricas (encinares, alcornocales, pinares, abedulares y hayedos). En general se observa que las formaciones mediterráneas tiene una mayor estructura espacial y una mayor heterogeneidad lumínica que los bosques no mediterráneos, que la radiación disponible bajo un dosel es inversamente proporcional a la tolerancia a la sombra de las especies arbóreas que lo componen y que el número de destellos de sol disminuye con la radiación total que llega al sotobosque (i.e. los destellos se hacen largos e intensos). Las implicaciones de estos resultados se interpretan considerando la información disponible sobre las respuestas de las plantas a la combinación de sombra y sequía, y sobre el papel de la heterogeneidad abiótica en la coexistencia de especies. Se propone que el cambio global conduce a un sotobosque mas oscuro y lumínicamente homogéneo, lo cual unido al incremento de aridez irá dando lugar a bosques huecos, pobres en especies y con escasa capacidad de regeneración natural.La financiación procede de la red temática GLOBIMED, y de los proyectos ECOFIARB y TALMED del Ministerio de Ciencia y TecnologíaPeer reviewe

Past, present and future methods of quantification in anatomical and ultrastructural studies of lichens

7 pages, figures, and tables statistics.This paper provides a general view of the state of the art in quantification methods for light and elctron microscopy, with especial reference to botany and lichenology.Peer reviewe

Efectos de la disponibilidad de agua y nutrientes en el patrón de acumulación de carbohidratos en plántulas de tres especies de Quercus

6 páginas, 2 figuras y 2 tablasSe pretende estimar el efecto de un eventual cambio climático y edáfico sobre el patrón de almacenamiento de carbohidratos en plántulas de un año de tres especies leñosas mediterráneas del género Quercus. Para ello se han cultivado las plántulas bajo tres condiciones contrastadas de fertilidad y tres de riego, experimento no factorial, durante una estación de crecimiento. Se espera que en los medios menos fértiles se acumule carbono en forma de reservas debido a la limitación en el crecimiento por falta de nutrientes. Asimismo, en condiciones de riego bajo, aumente la concentración de glucosa para contribuir al ajuste osmótico de las hojas. Por último, esperamos que Q. faginea, la especie de crecimiento más rápido, invierta mayor cantidad de carbono en crecimiento y por tanto acumule menos almidón. Las concentración de almidón en raíz y tallo de Q. ilex y Q. coccifera fue inversamente proporcional al nivel de fertilización. La concentración de glucosa foliar mostró mayores concentraciones en las plántulas que experimentaron déficit hídrico. La especie que más carbohidratos almacenó fue Q. faginea. Nuestro estudio sugiere, que el efecto de un incremento de aridez sobre el almacenamiento de carbohidratos depende, no sólo de la especie, sino también de la fertilidad del suelo sobre el que se asiente.Universidad de Alcalá. Alcalá de Henares y Centro de Ciencias Medioambientales. CSICPeer reviewe

Convergence in light capture efficiencies among tropical forest understory plants with contrasting crown architectures: a case of morphological compensation

10 páginas, 5 figuras y 4 tablasLeaf and crown characteristics were examined for 24 tree and herbaceous species of contrasting architectures from the understory of a lowland rainforest. Light-capture efficiency was estimated for the crowns of the different species with a three-dimensional geometric modeling program. Causal relationships among traits affecting light absorption at two hierarchical levels (leaf and whole crown) were quantified using path analysis. Light-capture and foliage display efficiency were found to be very similar among the 24 species studied, with most converging on a narrow range of light absorption efficiencies (ratio of absorbed vs. available light of 0.60– 0.75). Exceptionally low values were found for the climber vines and, to a lesser extent, for the Bromeliad Aechmea magdalenae. Differences in photosynthetic photon flux density (PFD) absorbed per unit leaf area by individual plants were mostly determined by site to site variation in PFD and not by the differences in crown architecture among individuals or species. Leaf angle, and to a lesser extent also supporting biomass, specific leaf area, and internode length, had a significant effect on foliage display efficiency. Potential constraints on light capture such as the phyllotactic pattern were generally offset by other compensatory adjustments of crown structure such as internode length, arching stems, and plagiotropy. The variety of shoot morphologies capable of efficiently capturing light in tropical forest understories is greater than initially thought, extending over species with very different phyllotactic patterns, crown architectures, leaf sizes, and morphologies.This research was supported by Mellon foundation/ Smithsonian Institution fellowships to FV and RWP, NSF Grant IBN 96-04424. Manuscript preparation was supported by a train and mobility grant given to FV by the Spanish Ministry of Education, Culture and Sports and a Professional Development Grant to JBS from the California State University.The authors thank Eduardo Sierra for help with the identification of the individuals studied, to Eloisa Lasso for help with data collection, and to Lourens Poorter for fitting criticisms. This research was supported by Mellon foundation/ Smithsonian Institution fellowships to FV and RWP, NSF Grant IBN 96-04424.Peer reviewe

Interactive effects of seed size and drought stress on growth and allocation of Quercus brantii Lindl. seedlings from two provenances

Quercus brantii is an important tree species in Zagros forests. Summer drought imposes severe limitations in Q. brantii forests, making reforestation with this species in general very difficult. This is further complicated by the limited ecophysiological information for this species. To improve our understanding of factors affecting the drought tolerance of Q. brantii at early critical life stages, we explored the influence of seed size and provenance on growth and survival of Q. brantii seedlings under drought. As expected, drought reduced growth and survival and increased the root-to-shoot ratio, with larger acorns rendering more vigorous growth than small ones. There was a positive correlation between seed size and root-to-shoot ratio under severe drought stress only for the provenance from the wetter region. Our results indicate that large seeds of Q. brantii from populations with good genetic material can render restoration programs in the Zagros forests more successful. © TÜBİTAK.Peer Reviewe

Species-specific water use by forest tree species: from the tree to the stand

Forests play a critical role in the hydrological cycle making the study of water use by trees and forest stands of prime importance in the global change context .Very negative effects of increasing and more intense droughts on forest vegetation have been described over the last decades. Symptoms of disease and decline have been associated with changed precipitation patterns in many forests particularly in European temperate and Mediterranean regions. Intra- and inter-specific differences in both physiology and morphology exert a large but not well understood influence on the water balance of forest ecosystems, further affecting their vulnerability to drought. Stand structure and composition influences rainfall interception, runoff and water fluxes of the whole ecosystem. Both expanding plantations of renovated interest for biofuel industry and natural and semi-natural forests must be managed in a sustainable way on the basis of their water consumption. We review the role of key drivers on forest water use such as species composition, tree canopy status of each of them and species specific sensitivity to soil water scarcity. Specifically we discuss the role of these factors for natural forest, but with references also to forest plantations. Water scarcity is expected to be one of the largest societal problems worldwide in the near future, so water use by natural and planted forest ecosystems has become a central subject in current research agendas.This work was supported by the INIA and Ministry of Economy and Competitiveness (grants SUM2008-00004-C03-01 and AGL2011-25365).Peer reviewe

Jack-of-all-trades effects drive biodiversity-ecosystem multifunctionality relationships in European forests

Fons van der Plas [et al.].- Received 8 September 2015, Accepted 19 February 2016, Published 24 March 2016There is considerable evidence that biodiversity promotes multiple ecosystem functions (multifunctionality), thus ensuring the delivery of ecosystem services important for human well-being. However, the mechanisms underlying this relationship are poorly understood, especially in natural ecosystems. We develop a novel approach to partition biodiversity effects on multifunctionality into three mechanisms and apply this to European forest data. We show that throughout Europe, tree diversity is positively related with multifunctionality when moderate levels of functioning are required, but negatively when very high function levels are desired. For two well-known mechanisms, ‘complementarity’ and ‘selection’, we detect only minor effects on multifunctionality. Instead a third, so far overlooked mechanism, the ‘jack-of-all-trades’ effect, caused by the averaging of individual species effects on function, drives observed patterns. Simulations demonstrate that jack-of-all-trades effects occur whenever species effects on different functions are not perfectly correlated, meaning they may contribute to diversity–multifunctionality relationships in many of the world’s ecosystems.Peer reviewe

Geomorphological significance of lichen colonization in a present snow hollow: Hoya del Cuchillar de las Navajas, Sierra de Gredos (Spain)

18 páginas, 12 figuras y 1 tablaThis paper discusses the results of a lichenometrical and geomorphological study of one of the few remaining active snow hollows in the central region of the Iberian Peninsula. The study area, located on a glacial shoulder, is called Hoya del Cuchillar de las Navajas. A protalus rampart occurs at the base of the hollow. Our studies, conducted between 1992 and 1998, were designed to determine the geomorphological characteristics of Hoya, the mobility of the deposits, and the characteristics of the snow cover. These data formed the basis for a study of the lichen colonization on the blocks and on the wall surrounding the snow hollow. All of the lichen species found were analyzed according to their abundance, distribution and the extent of their surface cover. Measurements of the diameter of the thalli of the species Rhizocarpon geographicum were also obtained. Thalli of this species were found to require a mean snow-free growing season of at least 95 days 13.5 weeks per year. Maximum mean thallus diameters indicate that the protalus rampart was formed during the Little Ice Age and became inactive 130 years ago.The staff of the Refugio Jose Antonio Elola (Laguna Grande de Gredos) is thanked for its cooperation and hospitality. We are indebted to Alicia Ferrero for her careful revision of the English manuscript. Financial support was provided by the Proyecto de Investigacion Multidisciplinar PR218 / 94-5653 (Universidad Complutense de Madrid)Peer reviewe

Forests are not immune to plant invasions: phenotypic plasticity and local adaptation allow Prunella vulgaris to colonize a temperate evergreen rainforest

El pdf del artículo es la versión post-print.In the South American temperate evergreen rainforest (Valdivian forest), invasive plants are mainly restricted to open sites, being rare in the shaded understory. This is consistent with the notion of closed-canopy forests as communities relatively resistant to plant invasions. However, alien plants able to develop shade tolerance could be a threat to this unique forest. Phenotypic plasticity and local adaptation are two mechanisms enhancing invasiveness. Phenotypic plasticity can promote local adaptation by facilitating the establishment and persistence of invasive species in novel environments. We investigated the role of these processes in the recent colonization of Valdivian forest understory by the perennial alien herb Prunella vulgaris from nearby populations in open sites. Using reciprocal transplants, we found local adaptation between populations. Field data showed that the shade environment selected for taller plants and greater specific leaf areas. We found population differentiation and within-population genetic variation in both mean values and reaction norms to light variation of several ecophysiological traits in common gardens from seeds collected in sun and shade populations. The colonization of the forest resulted in a reduction of plastic responses to light variation, which is consistent with the occurrence of genetic assimilation and suggests that P. vulgaris individuals adapted to the shade have reduced probabilities to return to open sites. All results taken together confirm the potential for rapid evolution of shade tolerance in P. vulgaris and suggest that this alien species may pose a threat to the native understory flora of Valdivian forest. © 2010 Springer Science+Business Media B.V.OG wants to acknowledge financial support provided by the Spanish Ministry for Education and Science grants RASINV GL2004-04884-C02 02/BOS (as part of the coordinate project RINVE). A CSIC CONICYT collaborative grant to FV and EG contributed to the development of this study.Peer Reviewe