Predicting the future of forests in the Mediterranean under climate change, with niche- and process-based models: CO2 matters!.

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.

Projected Climate Change Impacts on Biodiversity in Mediterranean Ecosystems. In Atlas of Biodiversity Risk. Eds. Settele J, Penev L, Georgiev T, Grabaum R, Grobelnik V, Hammen V, Klotz S, Kühn I.

Peñuelas J, Estiarte M, Prieto P, Sardans J, Jump A Moreno JM, Torres I, Cespedes B, Pla E, Sabaté S, Gracia CA (2010) Projected Climate Change Impacts on Biodiversity in Mediterranean Ecosystems. In Atlas of Biodiversity Risk. Eds. Settele J, Penev L, Georgiev T, Grabaum R, Grobelnik V, Hammen V, Klotz S, Kühn I. Pensoft Publishers. Sofia-Moscow. ISBN 978-954-642-446-4 (print) and ISBN 978-954-642-447-1 (e-book).

Soil water stress and coupled photosynthesis-conductance models: Bridging the gap between conflicting reports on the relative roles of stomatal, mesophyll conductance and biochemical limitations to photosynthesis

Keenan T., Sabate S., Gracia C. (2010) Soil water stress and coupled photosynthesis-conductance models: Bridging the gap between conflicting reports on the relative roles of stomatal, mesophyll conductance and biochemical limitations to photosynthesis. Agricultural and Forest Meteorology. 150: 443-453.
Enllaç
Doi: 10.1016/j.agrformet.2010.01.008

Resum:

Various plant responses to water stress have been reported, but conflicting reports as to which limiting process is the most important and ecophysiologicaly relevant during water stressed periods make it difficult to confidently model terrestrial CO2 and water flux responses. It has become increasingly accepted that mesophyll conductance could play a role in regulating photosynthesis during periods of water stress. We adapt the Farquhar-BB-type canopy photosynthesis-conductance model coupling to incorporate mesophyll conductance, embed it in an ecophysiological forest model and use it to simulate the effects of seasonal soil water stress on canopy CO2 and water fluxes at a Mediterranean Quercus ilex forest. Tests of various hypotheses regarding the relative roles of stomatal conductance limitations (SCL), mesophyll conductance limitations (MCL) and biochemical limitations (BL) confirmed that during water stressed periods, applying only BL allows for the accurate simulation of CO2 and water fluxes. Neither SCL nor MCL alone could accurately reproduce the observed CO2 and water fluxes. However, a combination of both MCL and SCL was successful at reproducing water stress induced reductions in CO2 and water fluxes, suggesting that mesophyll conductance could bridge the gap between conflicting reports on the processes behind responses to water stress in the field. © 2010 Elsevier B.V.

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The importance of mesophyll conductance in regulating forest ecosystem productivity during drought periods

Keenan T., Sabate S., Gracia C. (2010) The importance of mesophyll conductance in regulating forest ecosystem productivity during drought periods. Global Change Biology. 16: 1019-1034.
Enllaç
Doi: 10.1111/j.1365-2486.2009.02017.x

Resum:

Water availability is the most limiting factor to global plant productivity, yet photosynthetic responses to seasonal drought cycles are poorly understood, with conflicting reports on which limiting process is the most important during drought. We address the problem using a model-data synthesis approach to look at canopy level fluxes, integrating twenty years of half hour data gathered by the FLUXNET network across six Mediterranean sites. The measured canopy level, water and carbon fluxes were used, together with an inverse canopy ecophysiological model, to estimate the bulk canopy conductance, bulk mesophyll conductance, and the canopy scale carbon pools in both the intercellular spaces and at the site of carboxylation in the chloroplasts. Thus the roles of stomatal and mesophyll conductance in the regulation of internal carbon pools and photosynthesis could be separated. A quantitative limitation analysis allowed for the relative seasonal responses of stomatal, mesophyll, and biochemical limitations to be gauged. The concentration of carbon in the chloroplast was shown to be a potentially more reliable estimator of assimilation rates than the intercellular carbon concentration. Both stomatal conductance limitations and mesophyll conductance limitations were observed to regulate the response of photosynthesis to water stress in each of the six species studied. The results suggest that mesophyll conductance could bridge the gap between conflicting reports on plant responses to soil water stress, and that the inclusion of mesophyll conductance in biosphere-atmosphere transfer models may improve their performance, in particular their ability to accurately capture the response of terrestrial vegetation productivity to drought. © 2009 Blackwell Publishing Ltd.

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Evaluation of growth slowdown nursery treatments on Prunus avium seedlings by means of allometric relationships and relative growth rates

Miguel C., Aranda X., de Herralde F., Sabaté S., Biel C., Savé R. (2010) Evaluation of growth slowdown nursery treatments on Prunus avium seedlings by means of allometric relationships and relative growth rates. Scandinavian Journal of Forest Research. 25: 51-59.
Enllaç
Doi: 10.1080/02827581.2010.485813

Resum:

To evaluate the effects of carbonic fertilization and apical brushing (brushing of shoot apices to induce a negative thigmonastic response) on Prunus avium growth under nursery, carbon dioxide (CO2) was fed to cherry trees. Later, carbonic fertilization was withdrawn and apical brushing was applied. Finally, the original conditions were reinstated. Height and trunk diameter, allometric relations with plant biomass and relative growth rate were followed. Contrary to expectations, apical brushing resulted in increased trunk diameter and, hence, growth rate. Carbonic fertilization did not produce differences in the initial growth, probably owing to the deciduous characteristics of the species. Continuous application of carbonic fertilization maintained growth rate, whereas no fertilization or its withdrawal reduced the growth rate, but acclimation of the CO2-fed plants appeared by the end of the growing period. No differences in root growth potential at the end of the assay were observed between treatments. In conclusion, owing to the observed acclimation, carbonic fertilization is not advised throughout the complete period of growth. The tested treatments did not help to adapt supply of plant material of this species to the demand for revegetation. However, growth-slowing treatments may be applied to P. avium without any negative effects on potential root growth. © 2010 Taylor & Francis.

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