Mitigating the stress of drought on soil respiration by selective thinning: Contrasting effects of drought on soil respiration of two oak species in a mediterranean forest

Chang, C.-T., Sperlich, D., Sabaté, S., Sánchez-Costa, E., Cotillas, M., Espelta, J.M., Gracia, C. (2016) Mitigating the stress of drought on soil respiration by selective thinning: Contrasting effects of drought on soil respiration of two oak species in a mediterranean forest. Forests. 7: 0-0.
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Doi: 10.3390/f7110263

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Aboveground and belowground biomass allocation patterns in two Mediterranean oaks with contrasting leaf habit: an insight into carbon stock in young oak coppices

Cotillas M., Espelta J.M., Sánchez-Costa E., Sabaté S. (2016) Aboveground and belowground biomass allocation patterns in two Mediterranean oaks with contrasting leaf habit: an insight into carbon stock in young oak coppices. European Journal of Forest Research. 135: 243-252.
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Doi: 10.1007/s10342-015-0932-9

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In the last decades, the global interest in the role of forests as carbon sinks has grown, and thus, studies aimed at estimating tree biomass have progressively increased. However, few surveys have focused on young coppices, although they are abundant worldwide in areas regenerating after disturbance (e.g. wildfire, clearcutting). In the Mediterranean Basin, young coppices are very frequent, and most of them are formed by evergreen and deciduous oaks (Quercus spp.). In this survey, we have studied the biomass allocation patterns of two oaks coexisting in coppices, the evergreen Quercus ilex and the deciduous Quercus cerrioides, comparing them in the light of their different leaf habit, which may influence their physiological performance in the context of climate change. We have also obtained allometric equations for each species and its components, which we have used to calculate the carbon stock in the sampled area, as an insight into the potential of young oak coppices to sequester carbon. The results indicate a higher biomass investment of Q. ilex in the stump and a higher leafiness and allocation to roots in Q. cerrioides. In the light of these differences, the evergreen Q. ilex could be defined as a “resource-saving” species in comparison with the more “resource-demanding” Q. cerrioides. The allometric equations were able to predict from 78 to 99 % of the variation in biomass using diameter as predictor variable for all the tree components aside of the stump. Overall carbon stock estimation in the young coppice of our study area was 43.2 Mg ha−1, of which 62 % is stored belowground. These results highlight the importance of biomass allocation in the belowground compartment in Mediterranean young oak coppices as a temporal carbon sink. Moreover, they provide evidence that these forests may store a relevant amount of carbon, often ignored in forest inventories. © 2016, Springer-Verlag Berlin Heidelberg.

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Assessment of the impacts of climate change on Mediterranean terrestrial ecosystems based on data from field experiments and long-term monitored field gradients in Catalonia

Peñuelas, J., Sardans, J., Filella, I., Estiarte, M., Llusià, J., Ogaya, R., Carnicer, J., Bartrons, M., Rivas-Ubach, A., Grau, O., Peguero, G., Margalef, O., Pla-Rabés, S., Stefanescu, C., Asensio, D., Preece, C., Liu, L., Verger, A., Rico, L., Barbeta, A., Achotegui-Castells, A., Gargallo-Garriga, A., Sperlich, D., Farré-Armengol, G., Fernández-Martínez, M., Liu, D., Zhang, C., Urbina, I., Camino, M., Vives, M., Nadal-Sala, D., Sabaté, S., Gracia, C., Terradas, J. (2016) Assessment of the impacts of climate change on Mediterranean terrestrial ecosystems based on data from field experiments and long-term monitored field gradients in Catalonia. Environmental and Experimental Botany. : 0-0.
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Doi: 10.1016/j.envexpbot.2017.05.012

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Balance between carbon gain and loss under long-term drought: Impacts on foliar respiration and photosynthesis in Quercus ilex L

Sperlich D., Barbeta A., Ogaya R., Sabaté S., Peñuelas J. (2016) Balance between carbon gain and loss under long-term drought: Impacts on foliar respiration and photosynthesis in Quercus ilex L. Journal of Experimental Botany. 67: 821-833.
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Doi: 10.1093/jxb/erv492

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Terrestrial carbon exchange is a key process of the global carbon cycle consisting of a delicate balance between photosynthetic carbon uptake and respiratory release. We have, however, a limited understanding how long-term decreases in precipitation induced by climate change affect the boundaries and mechanisms of photosynthesis and respiration. We examined the seasonality of photosynthetic and respiratory traits and evaluated the adaptive mechanism of the foliar carbon balance of Quercus ilex L. experiencing a long-term rainfall-exclusion experiment. Day respiration (R d) but not night respiration (R n) was generally higher in the drought treatment leading to an increased R d/R n ratio. The limitation of mesophyll conductance (g m) on photosynthesis was generally stronger than stomatal limitation (g s) in the drought treatment, reflected in a lower g m/g s ratio. The peak photosynthetic activity in the drought treatment occurred in an atypical favourable summer in parallel with lower R d/R n and higher g m/g s ratios. The plant carbon balance was thus strongly improved through: (i) higher photosynthetic rates induced by g m; and (ii) decreased carbon losses mediated by R d. Interestingly, photosynthetic potentials (V c,max, J max, and TPU) were not affected by the drought treatment, suggesting a dampening effect on the biochemical level in the long term. In summary, the trees experiencing a 14-year-long drought treatment adapted through higher plasticity in photosynthetic and respiratory traits, so that eventually the atypical favourable growth period was exploited more efficiently. © 2015 The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.

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