Martínez-Vilalta J., Vanderklein D., Mencuccini M. (2007) Tree height and age-related decline in growth in Scots pine (Pinus sylvestris L.). Oecologia. 150: 529-544.EnllaçDoi: 10.1007/s00442-006-0552-7
Growth and seasonal water use was measured amongst trees growing in an old growth Scots pine forest in the Scottish Highlands. Three sites which differed in their recent management history and contained old and naturally regenerated young trees growing together were monitored in the field. Our results showed a clear decrease in growth efficiency with age, from values of around 0.25 kg m-2 leaves year-1 in approximately 25-year-old trees to less than 0.1 kg m-2 leaves year-1 in trees over 200 years old. When the old trees in one of the field sites were released from competition by thinning, their growth efficiency reverted to that of coexisting young trees, indicating that the decline in growth was reversible. This is consistent with the results of a parallel study showing that cambial age had no effect on the physiology or growth of grafted seedlings originating from the same population studied here (Mencuccini et al. 2005). Our detailed study of tree water use in the field showed an overall decrease in whole-tree hydraulic conductance and stomatal canopy conductance with tree height in the unthinned stands, in agreement with the hydraulic limitation hypothesis. However, the effect of this reduction in hydraulic efficiency on growth was comparatively small, and old trees also showed consistently lower nitrogen concentrations in needles, suggesting that hydraulic and nutritional factors combined to produce the decline in growth efficiency with age observed in the studied populations. © 2006 Springer-Verlag.
Marull J., Pino J., Mallarach J.M., Cordobilla M.J. (2007) A Land Suitability Index for Strategic Environmental Assessment in metropolitan areas. Landscape and Urban Planning. 81: 200-212.EnllaçDoi: 10.1016/j.landurbplan.2006.11.005
This paper presents the Land Suitability Index (LSI), a transparent, modular hierarchical system of cartographic indices aimed at delivering Strategic Environmental Assessment (SEA) of developmental land uses for regional planning (European Directive 2001/42/EC). The LSI evaluates land suitability by combining three main sub-indices concerning (i) the vulnerability of the biosphere, lithosphere, and hydrosphere to impacts arising from implementing development proposals; (ii) the natural heritage value of the target area; and (iii) its contribution to terrestrial ecological connectivity. We have used the LSI to evaluate the impact of municipal urban plans in the Barcelona Metropolitan Region (BMR). For this case study, we provide redundancy and sensitivity analyses, and a partial validation using independent studies. Results showed noticeable inconsistencies between the municipal plans and the values of the LSI and its main sub-indices. There was moderate redundancy between sub-indices but considerable sensitivity to changes in input variables. Validation showed a high degree of coincidence with previous, independent, studies as regards connectivity. The quantitative and cartographic approach adopted by the methodology facilitates conveying the results to planners and policy makers. In addition, successive iterations to check the impact related to different alternative planning scenarios can be quickly performed. We therefore propose its application to other metropolitan areas. © 2006 Elsevier B.V. All rights reserved.
Vanderklein D, Martínez-Vilalta J, Lee S, Mencuccini M (2007) Plant size, not age, regulates growth and gas exchange in grafted Scots pine trees. Tree physiology 27: 71-79.
García H, Tarrasón D, Mayol M, Male-Bascompte N, Riba M (2007) Patterns of variability in soil properties and vegetation cover following abandonment of olive groves in Catalonia (NE-Spain). Acta Oecologica 31: 316-324.
Morand-Ferron J., Sol D., Lefebvre L. (2007) Food stealing in birds: brain or brawn?. Animal Behaviour. 74: 1725-1734.EnllaçDoi: 10.1016/j.anbehav.2007.04.031
Kleptoparasitism, the stealing of food items already procured by others, is a widespread foraging strategy in animals, yet the reasons why some taxa have evolved this strategy and others have not remain unresolved. It has been hypothesized that kleptoparasitism should be more profitable, and hence have more often evolved, in lineages featuring certain characteristics, such as a large body mass, an enlarged brain or a dependence on vertebrate prey. Alternatively, the evolution of kleptoparasitism could have been facilitated in certain ecological contexts, such as open habitats or mixed-species foraging groups. Here, we test these hypotheses for the evolution of food stealing with a comparative analysis in birds, using information on 856 field reports of interspecific kleptoparasitism from all over the world. In multivariate analyses controlling for common ancestry, the probability that a family uses kleptoparasitism was positively associated with residual size of the brain, habitat openness and the presence of vertebrate prey in the diet, but showed no association with body size or participation in mixed-species foraging groups. The conclusion that kleptoparasitism is associated more closely with cognition than with aggression is further supported by the finding that kleptoparasites have a larger residual brain size than their respective hosts, while their body size is not significantly larger. By emphasizing the central role of cognitive abilities in avian kleptoparasitism, our results offer a novel perception of avian food stealing, which in the past was primarily seen in terms of 'brawn' rather than 'brains'. © 2007 The Association for the Study of Animal Behaviour.
Moya D., Espelta J.M., Verkaik I., López-Serrano F., De Las Heras J. (2007) Tree density and site quality influence on Pinus halepensis Mill. reproductive characteristics after large fires. Annals of Forest Science. 64: 649-656.EnllaçDoi: 10.1051/forest:2007043
In Spain, many Pinus halepensis Mill. forests have been seriously affected by significant forest fires in the past decade, in 1994 alone, more than 100 000 ha were burned in Eastern Spain. In order to study the reproductive characteristics of P. halepensis after forest fires, six locations were selected in four areas affected by serious fires in the summer of 1994, and the following different precipitation zones were studied: dry-subhumid, dry and semi-arid. Ten years after the fires, data relevant to the production of pine cones: serotinous (grey), mature (brown), immature (green) and opened cones, was collected from areas with natural post-fire regeneration. Various cone and seed characteristics, such as pine cone seed number and weight, and germination percentage, were measured. The results showed greater production of cones and strobili in high-density sites. The biggest cone sizes (volume) and seed number per cone were related to site quality (dry-subhumid precipitation zone). Also, viability and germination percentages were higher with better site quality, with significant differences in values for serotinous and non-serotinous cones. Despite these differences, the canopy seed bank was large enough to ensure regeneration in this area for this age stand. © INRA, EDP Sciences, 2007.
Munné-Bosch S., Peñuelas J., Llusià J. (2007) A deficiency in salicylic acid alters isoprenoid accumulation in water-stressed NahG transgenic Arabidopsis plants. Plant Science. 172: 756-762.EnllaçDoi: 10.1016/j.plantsci.2006.12.005
Previous studies have shown that salicylic acid is an essential component of the plant resistance to pathogens and participates in the plant response to adverse environmental conditions. The present study was aimed at better understanding the response of salicylic acid-deficient transgenic NahG Arabidopsis plants to water deficit conditions, with an especial emphasis on the effects of salicylic acid on isoprenoid accumulation. Total monoterpene contents, chlorophylls and α-tocopherol (which contain a diterpene phytyl moiety in their molecule) and the tetraterpenes, carotenoids, were measured in wild type and NahG Arabidopsis plants exposed to 2 weeks of water deficit. The results show that a salicylic acid deficiency in NahG tansgenic lines suppressed the water stress-induced loss of chlorophylls and carotenoids observed in the wild type. α-Tocopherol accumulation was also affected in NahG plants, which showed lower levels of this antioxidant both under irrigated and water stress conditions. In addition, accumulation of monoterpenes was suppressed in NahG plants both under irrigated and water stress conditions, although the effects were more apparent under stress and, as this was more severe. We conclude that salicylic acid affects isoprenoid accumulation in leaves specially under water stress conditions. © 2007 Elsevier Ireland Ltd. All rights reserved.
Ogaya R., Peñuelas J. (2007) Tree growth, mortality, and above-ground biomass accumulation in a holm oak forest under a five-year experimental field drought. Plant Ecology. 189: 291-299.EnllaçDoi: 10.1007/s11258-006-9184-6
A holm oak forest was exposed to an experimental drought during 5 years to elucidate the growth responses of the dominant species Quercus ilex, Arbutus unedo and Phillyrea latifolia. Soil water availability was partially reduced, about 15% as predicted for this area for the next decades by GCM and ecophysiological models, by plastic strips intercepting rainfall and by ditch exclusion of water runoff. The stem diameter increment was highly correlated with annual rainfall in all species, and drought treatment strongly reduced the diameter increment of Q. ilex (41%) and specially of A. unedo (63%), the species showing higher growth rates. Stem mortality rates were highly correlated with previous stem density, but drought treatment increased mortality rates in all species. Q. ilex showed the highest mortality rates (9% and 18% in control and drought plots, respectively), and P. latifolia experienced the lowest mortality rates (1% and 3% in control and drought plots, respectively). Drought strongly reduced the increment of live aboveground biomass during these 5 years (83%). A. unedo and Q. ilex experienced a high reduction in biomass increment by drought, whereas P. latifolia biomass increment was insensitive to drought. The different sensitivity to drought of the dominant species of the holm oak forest may be very important determining their future development and distribution in a drier environment as expected in Mediterranean areas for the next decades. These drier conditions could thus have strong effects on structure (species composition) and functioning (carbon uptake and biomass accumulation) of these Mediterranean forests. © 2006 Springer Science+Business Media B.V.
Ogaya R., Peñuelas J. (2007) Seasonal ultrasonic acoustic emissions of Quercus ilex L. trees in a Mediterranean forest. Acta Physiologiae Plantarum. 29: 407-410.EnllaçDoi: 10.1007/s11738-007-0048-z
Ultrasonic acoustic emissions were measured in Quercus ilex trees of a Mediterranean forest in Catalonia (NE Spain) each season from summer of 2004 to autumn of 2005. Acoustic emissions were maximum during hot and dry summer periods. Acoustic emissions started below 17% soil moisture, 0.85 RWC, and 2.5 MPa leaf water potential. They were negatively correlated with soil moisture and leaf water potential. The relationship between acoustic emissions and leaf water potential was the strongest, indicating that xylem tension is the most important factor inducing both cavitation (acoustic emissions) and a decrease in leaf water potential. Future increase of xylem cavitation derived from climate change may result in growth and survival limitations for this species in the drier southern limits of its current distribution. © 2007 Franciszek Górski Institute of Plant Physiology, Polish Academy of Sciences.
Ogaya R., Peñuelas J. (2007) Species-specific drought effects on flower and fruit production in a Mediterranean holm oak forest. Forestry. 80: 351-357.EnllaçDoi: 10.1093/forestry/cpm009
A holm oak forest was exposed to an experimental drought (reduction of 15 per cent soil moisture as predicted for this area for the next decades by General Circulation Models and ecophysiological models) during 7 years to elucidate the reproductive responses of the dominant species Quercus ilex L., Arbutus unedo L. and Phillyrea latifolia L. Soil moisture was partially reduced by plastic strips intercepting rainfall and by ditch exclusion of water runoff. During the period studied, meteorological conditions and soil moisture were continuously monitored, together with flower and fruit production in the three dominant species. In Q. ilex and A. unedo, flower and specially fruit production were strongly correlated with annual rainfall, but not in P. latifolia. The experimental drought reduced flower and fruit production in Q. ilex by 30 per cent and 45 per cent, respectively. Reductions in flower and fruit production were not significant in A. unedo and were not observed in P. latifolia. A decrease in production of reproductive structures and the different response of the species studied to a decrease in water availability could induce important changes in the competitive ability of the different species and in the long term in the community species composition and future distribution of these Mediterranean species. © Institute of Chartered Foresters, 2007. All rights reserved.
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