Mencuccini M, Martínez-Vilalta J, Hamid HA, Korakaki E, Vanderklein D (2007) Theoretical and methodological considerations on the importance of size-related versus age-related changes in tree growth Tree physiology 27: 463-473.
Jump A, Peñuelas J (2007) Els faigs es defensen del canvi climàtic. UAB DIVULGA 04/2007.
Bartolome J, Peñuelas J, Filella I, Llusià J, Broncano MJ, Plaixats J (2007) Mass scans from a proton transfer mass spectrometry analysis of air over Mediterranean shrubland browsed by horses. Journal Environmental Biologi 28: 697-700
Peñuelas J, Sardans J, Stefanescu C, Parella T, Filella I (2007) Transferencia de defenses de les plantes als herbívors. UAB DIVULGA 05/2007.
Asensio D, Peñuelas J, Ogaya R, Llusià J (2007) Seasonal soil and leaf CO2 exchange rates in a Mediterranean holm oak forest and their responses to drought conditions. Atmospheric Environment 41: 2447–2455.
Jump A.S., Hunt J.M., Peñuelas J. (2007) Climate relationships of growth and establishment across the altitudinal range of Fagus sylvatica in the Montseny Mountains, northeast Spain. Ecoscience. 14: 507-518.LinkDoi: 10.2980/1195-6860(2007)14[507:CROGAE]2.0.CO;2
A rise in elevation of the temperate biome has been reported in the mountains of northeast Spain. We aimed to determine the principal climatic factors limiting growth and establishment of the dominant temperate tree, Fagus sylvatica, across its altitudinal range and how its climate-response has varied over time. We determined the climate-response of the growth of adult trees and the establishment of juveniles using dendroecological methods at 3 sites along an elevational gradient spanning this species' full altitudinal distribution of approximately 1000-1650 in above sea level. We found strong altitudinal variation in growth and establishment responses to climate. The most common growth response was to high spring and summer temperature (April-July), which promoted growth and establishment at the upper treeline but had the opposite effect at low altitudes. Precipitation was strongly limiting for adult growth at the lower limit of F. sylvatica and declined in importance with increasing altitude. Sensitivity of growth to summer temperature increased over the second half of the 20th century. Future increases in summer temperature are likely to have negative consequences for growth and establishment at this species' low altitude, low latitude range-edge, particularly if temperature increase is not matched by increasing precipitation.
Jump A.S., Peñuelas J. (2007) Extensive spatial genetic structure revealed by AFLP but not SSR molecular markers in the wind-pollinated tree, Fagus sylvatica. Molecular Ecology. 16: 925-936.LinkDoi: 10.1111/j.1365-294X.2006.03203.x
Studies of fine-scale spatial genetic structure (SGS) in wind-pollinated trees have shown that SGS is generally weak and extends over relatively short distances (less than 30-40 m) from individual trees. However, recent simulations have shown that detection of SGS is heavily dependent on both the choice of molecular markers and the strategy used to sample the studied population. Published studies may not always have used sufficient markers and/or individuals for the accurate estimation of SGS. To assess the extent of SGS within a population of the wind-pollinated tree Fagus sylvatica, we genotyped 200 trees at six microsatellite or simple sequence repeat (SSR) loci and 250 amplified fragment length polymorphisms (AFLP) and conducted spatial analyses of pairwise kinship coefficients. We re-sampled our data set over individuals and over loci to determine the effect of reducing the sample size and number of loci used for SGS estimation. We found that SGS estimated from AFLP markers extended nearly four times further than has been estimated before using other molecular markers in this species, indicating a persistent effect of restricted gene flow at small spatial scales. However, our SSR-based estimate was in agreement with other published studies. Spatial genetic structure in F. sylvatica and similar wind-pollinated trees may therefore be substantially larger than has been estimated previously. Although 100-150 AFLP loci and 150-200 individuals appear sufficient for adequately estimating SGS in our analysis, 150-200 individuals and six SSR loci may still be too few to provide a good estimation of SGS in this species. Journal compilation © 2006 Blackwell Publishing Ltd.
Lin C., Owen S.M., Peñuelas J. (2007) Volatile organic compounds in the roots and rhizosphere of Pinus spp.. Soil Biology and Biochemistry. 39: 951-960.LinkDoi: 10.1016/j.soilbio.2006.11.007
Plant roots normally release a complex mixture of chemicals which have important effects in the rhizosphere. Among these different root-emitted compounds, volatile isoprenoids have received very little attention, yet they may play important and diverse roles in the rhizosphere, contributing to the regulation of microbial activity and nutrient availability. It is therefore important to estimate their abundance in the rhizosphere, but so far, there is no reliable sampling method that can be used to measure realistic rates of root emissions from plants growing in field conditions, or even in pots. Here, we measured root content of volatile isoprenoids (specifically monoterpenes) for Pinus pinea, and explored the feasibility of using a dynamic bag enclosure method to measure emissions from roots of intact pot-grown plants with different degrees of root cleaning. We also investigated a passive diffusion method for exploring monoterpenes in soil at incremental distances from mature Pinus sylvestris trees growing in field conditions. Total monoterpene content of P. pinea roots was 415±50 μg g-1 fresh wt in an initial screening study, and between 688±103 and 1144±208 μg g-1 dry wt in subsequent investigations. Emissions from shaken-clean roots of intact plants and roots of intact plants washed to remove remaining soil after shaken-clean experiments were 119±14 and 26±5 μg g-1 dry wt h-1, respectively. Emissions from intact roots in soil-balls were an order of magnitude lower than from shaken-clean roots, and probably reflected the amount of emitted compounds taken up by physical, chemical or biological processes in the soil matrix surrounding the roots. Although monoterpene content was not significantly different in droughted roots, emission rates from droughted roots were generally significantly lower than from well-watered roots. Finally, passive sampling of monoterpenes in the soil at different distances from mature P. sylvestris trees in field conditions showed significantly decreasing sampling rates with increasing distance from the trunk. We conclude that it is feasible to measure volatile isoprenoid emissions from roots but the method of root preparation affects magnitude of measured emissions and therefore must be decided according to the application. We also conclude that the rhizosphere of Pinus species is a strong and previously un-characterized source of volatile isoprenoid emissions and these are likely to impact significantly on rhizosphere function. © 2006 Elsevier Ltd. All rights reserved.
Lloret F., Lobo A., Estevan H., Maisongrande P., Vayreda J., Terradas J. (2007) Woody plant richness and NDVI response to drought events in Catalonian (northeastern Spain) forests. Ecology. 88: 2270-2279.LinkDoi: 10.1890/06-1195.1
The role of species diversity on ecosystem resistance in the face of strong environmental fluctuations has been addressed from both theoretical and experimental viewpoints to reveal a variety of positive and negative relationships. Here we explore empirically the relationship between the richness of forest woody species and canopy resistance to extreme drought episodes. We compare richness data from an extensive forest inventory to a temporal series of satellite imagery that estimated drought impact on forest canopy as NDVI (normalized difference vegetation index) anomalies of the dry summer in 2003 in relation to records of previous years. We considered five different types of forests that are representative of the main climatic and altitudinal gradients of the region, ranging from lowland Mediterranean to mountain boreal-temperate climates. The observed relationship differed among forest types and interacted with the climate, summarised by the Thorntwaite index. In Mediterranean Pinus halepensis forests, NDVI decreased during the drought. This decrease was stronger in forests with lower richness. In Mediterranean evergreen forests of Quercus ilex, drought did not result in an overall NDVI loss, but lower NDVI values were observed in drier localities with lower richness, and in more moist localities with higher number of species. In mountain Pinus sylvestris forests NDVI decreased, mostly due to the drought impact on drier localities, while no relation to species richness was observed. In moist Fagus sylvatica forests, NDVI only decreased in plots with high richness. No effect of drought was observed in the high mountain Pinus uncinata forests. Our results show that a shift on the diversity-stability relationship appears across the regional, climatic gradient. A positive relationship appears in drier localities, supporting a null model where the probability of finding a species able to cope with drier conditions increases with the number of species. However, in more moist localities we hypothesize that the proportion of drought-sensitive species would increase in richer localities, due to a higher likelihood of co-occurrence of species that share moist climatic requirements. The study points to the convenience of considering the causes of disturbance in relation to current environmental gradients and historical environmental constraints on the community. © 2007 by the Ecological Society of America.
Serra P, Zabala A, Pesquer L, Pons X (2007) Innovación en Cartografía y Fotointerpretación digital: retos y resultados. Comunicació a les V Jornadas Internacionales de Innovación Universitaria. Métodos docentes afines al EEES. Vicerrectorado de Política Científica y Profesorado de la Universidad E uropea de Madrid. CD-ROM (ISBN: 84-95433-22-2) http://corporativo.uem.es/es/que-es-la-uem/id/jornadas-internacionales-de-innovacion-universitaria
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