Galiano L., Martínez-Vilalta J., Sabaté S., Lloret F. (2012) Determinants of drought effects on crown condition and their relationship with depletion of carbon reserves in a Mediterranean holm oak forest. Tree Physiology. 32: 478-489.LinkDoi: 10.1093/treephys/tps025
Severe droughts may increase physiological stress on long-lived woody vegetation, occasionally leading to rapid defoliation and progressive increase in mortality of overstorey trees. Over the last few years, episodes of drought-induced tree dieback have been documented in a variety of woodlands and forests around the world. However, the factors determining tree survival and subsequent recovery are still poorly understood, especially in resprouter species. We have studied the effects of a single drought episode on crown condition in a holm oak (Quercus ilex L.) forest located in NE Spain 7 years after the drought event. Generalized linear models were used to study the environmental correlates of forest crown condition 7 years after the drought event. Additionally, we evaluated the association between crown condition and the carbon and nutrient reserves stored in lignotubers 7 years after the drought. Our study reveals the multifactor nature of a drought-driven forest dieback in which soil depth and the characteristics of individual trees, particularly their number of stems, determined a complex spatial pattern of tree-level responses. This dieback was associated with a depletion of the carbon reserves in lignotubers 7 years after the episode, representing a reduction of up to 60 in highly drought-damaged trees. Interestingly, in the absence of new acute droughts, successive surveys in 2007-11 showed a direct association between carbon reserves depletion and further deterioration of crown condition. More frequent droughts, as predicted by climate change projections, may lead to a progressive depletion of carbon reserves and to a loss of resilience in Mediterranean resprouter species. © 2012 The Author.
Gracia C, Vanclay J, Daly H, Sabaté S, Gyenge J (2011) Securing Water for Trees and People: Possible Avenues. In: Water for Forests and People in the Mediterranean Region – A Challenging Balance. Birot Y, Gracia C, Palahí M (editors). What Science Can Tell Us 1 pp 83-91.
Gracia C, Sabaté S, Vayreda J, Sebastià T, Savé R, Alonso M, Vidal M (2011) Embornals. In: Segon Informe sobre canvi climàtic a Catalunya (Ed.Llebot Josep Enric). Institud d’Estudis Catalans i Generalitat de Catalunya. 1152 pp.
Keenan T., Maria Serra J., Lloret F., Ninyerola M., Sabate S. (2011) Predicting the future of forests in the Mediterranean under climate change, with niche- and process-based models: CO2 matters!. Global Change Biology. 17: 565-579.LinkDoi: 10.1111/j.1365-2486.2010.02254.x
Assessing the potential future of current forest stands is a key to design conservation strategies and understanding potential future impacts to ecosystem service supplies. This is particularly true in the Mediterranean basin, where important future climatic changes are expected. Here, we assess and compare two commonly used modeling approaches (niche- and process-based models) to project the future of current stands of three forest species with contrasting distributions, using regionalized climate for continental Spain. Results highlight variability in model ability to estimate current distributions, and the inherent large uncertainty involved in making projections into the future. CO2 fertilization through projected increased atmospheric CO2 concentrations is shown to increase forest productivity in the mechanistic process-based model (despite increased drought stress) by up to three times that of the non-CO2 fertilization scenario by the period 2050-2080, which is in stark contrast to projections of reduced habitat suitability from the niche-based models by the same period. This highlights the importance of introducing aspects of plant biogeochemistry into current niche-based models for a realistic projection of future species distributions. We conclude that the future of current Mediterranean forest stands is highly uncertain and suggest that a new synergy between niche- and process-based models is urgently needed in order to improve our predictive ability. © 2010 Blackwell Publishing Ltd.
Keenan T.F., Grote R., Sabaté S. (2011) Overlooking the canopy: The importance of canopy structure in scaling isoprenoid emissions from the leaf to the landscape. Ecological Modelling. 222: 737-747.LinkDoi: 10.1016/j.ecolmodel.2010.11.004
Isoprene and monoterpenes are highly reactive organic compounds, emitted by most plant species, which play an important role in air chemistry and air pollution. Different leaf-scale isoprenoid emission models are available. These models are scaled to the canopy through coupling them to terrestrial biogeochemical models and thus used to generate regional emissions inventories. Although the leaf scale models have been shown to perform similarly, large unexplained differences exist in regional emissions inventories. This may be explained in part by the complete lack of inter-comparisons of emission model estimates when scaled from the leaf to the canopy. In this paper we address this problem by coupling four different isoprene emission models (Guenther et al. model, Niinemets et al. model, BIM2 and the Martin et al. model) to two terrestrial biogeochemical model platforms (MoBiLE, GOTILWA+) that describe canopy structure differently. Simulations of isoprene emissions for the Puechabon Mediterranean holm oak stand are analysed, with both canopy photosynthesis models constrained using FLUXNET measurements. The results demonstrate that even with constrained canopy level photosynthesis, large model platform dependent within canopy differences can exist in both modelled photosynthesis and emissions. This results in large differences in modelled isoprenoid emissions, due to the relatively higher sensitivity of emissions to canopy microclimate, in particular temperature. This is the first time emission results from two biogeochemical platforms have been compared, and demonstrates that different canopy descriptions can lead to larger differences in modelled emissions than that attributable to the difference between the emission models themselves. This is an important aspect that has not been acknowledged by the emission modelling community. © 2010 Elsevier B.V.
Otero I., Boada M., Badia A., Pla E., Vayreda J., Sabaté S., Gracia C.A., Peñuelas J. (2011) Loss of water availability and stream biodiversity under land abandonment and climate change in a Mediterranean catchment (Olzinelles, NE Spain). Land Use Policy. 28: 207-218.LinkDoi: 10.1016/j.landusepol.2010.06.002
In the north rim of the Mediterranean region, where forest cover is increasing as a result of land abandonment and temperatures are rising as a result of climate change, there is increasing interest for the effects of such changes on the runoff of water courses. This is a paramount issue for the conservation of many freshwater habitats and species. In this work we studied the effects of both an increase in forest cover after depopulation and land abandonment and an increase in temperature on the runoff of a Mediterranean catchment and on the aquatic and semi-aquatic fauna species of the stream (Olzinelles valley, NE Spain). Although in our simulation no decreasing trend in runoff is detected, the monthly runoff-rainfall ratio is now 15% lower than 30 years ago, a fact that may be attributed to a drier period rather than to the small afforestation experienced by the catchment in the last decades. Other factors such as increasing temperatures, changing rainfall patterns and increasing canopy cover are discussed. The observed decrease in the water flow has caused the disappearance of white-clawed crayfish (Austropotamobius pallipes), Mediterranean barbel (Barbus meridionalis), chub (Squalius cephalus), European eel (Anguilla anguilla), and southern water vole (Arvicola sapidus). Our results suggest that in a progressively warmer climate, and especially after land abandonment processes, management of Mediterranean mountain areas should be oriented towards an appropriate distribution of agrarian and forest land-covers in terms of water availability. Down to the stream scale, the pools that keep water throughout the year should be conserved and extended to enhance its potential to maintain aquatic and semi-aquatic species populations. © 2010 Elsevier Ltd.
Pañella P, Lago Barreiro P, Sabaté S, i Sauras T (2011) Impacte de la gestió de la fusta cremada i del subsolat al Parc Natural de Sant Llorenç del Munt i l’Obac. VII Monografies de Sant Llorenç del Munt i l’Obac. Diputació de Barcelona. p. 157-174.
Bages T, Sabaté S (2011) Canvi Climàtic i Gestió Forestal: el moment de passar de la teoria a la pràctica. Silvicultura 63:10-13.
Sabaté S, Gracia C (2011) Water Processes in Trees: Transpiration and Photosynthesis. In: Water for Forests and People in the Mediterranean Region – A Challenging Balance. Birot Y, Gracia C, Palahí M (editors). What Science Can Tell Us 1 pp 72-75.
Keenan T, Serra J, Lloret F, Ninyerola M, Sabaté S (2010) Predicting the future of forests in the Mediterranean under climate change, with niche- and process-based models: CO2 matters!. Global Change Biology 17: 565-579. doi:10.1111/j.13652486.2010.02254.x.
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