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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Growth response of mixed mediterranean oak coppices to rainfall reduction. Could selective thinning have any influence on it?

Cotillas M., Sabaté S., Gracia C., Espelta J.M. (2009) Growth response of mixed mediterranean oak coppices to rainfall reduction. Could selective thinning have any influence on it?. Forest Ecology and Management. 258: 1677-1683.
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Doi: 10.1016/j.foreco.2009.07.033

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Climate change is one of the major challenges for ecosystem conservation. One of the most vulnerable areas to climate change is the Mediterranean Basin which is expected to suffer important changes in temperature and precipitation in the next few decades, leading to a warmer and dryer climate. Therefore, it is necessary to determine species-specific responses to increased drought to predict possible future changes in the structure and composition of Mediterranean forests, as well as to identify appropriate management strategies to mitigate these effects. The main aim of this study has been to experimentally simulate the effects of a 15% reduction in annual rainfall on the survival and growth of two co-occurring Mediterranean oaks with contrasting leaf-habit (the evergreen Quercus ilex spp. ilex and the winter-deciduous Quercus cerrioides) and, to assess whether traditional selective thinning carried out in these mixed oak coppices (i.e. selection of one to few stems per stump) can modify the consequences of rainfall reduction. Soil moisture decreased under the rainfall reduction level while it increased in the thinned plots. Reduced rainfall did not influence tree mortality, but did lead to species-specific effects on height growth: no changes were observed in Q. ilex while height growth rate of Q. cerrioides decreased (c.a. 20%). Selective thinning improved tree growth (c.a. 50%) in stands both under natural and, and to a lesser extent, under reduced rainfall conditions. Nevertheless, the positive effects of thinning rapidly declined during our three years experiment, probably because the vigorous resprouting of thinned stumps. Our results show that the forecasted reduction in annual rainfall for the Western Mediterranean Basin can constrain the growth of some deciduous oaks in mixed oak coppices. Traditional selective thinning can increase soil moisture and encourage tree growth, thus partially mitigating this effect. However, the transient results observed in this experiment suggest the need to reconsider the intensity and the frequency of this traditional management practice in light of new climatic scenarios. © 2009 Elsevier B.V. All rights reserved.

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Patrones reproductivos en Quercus mediterráneos: Efecto del clima, del incremento de sequía y del resalveo sobre la producción de bellotas. V Congreso Forestal Español. Montes y Sociedad: Saber que hacer.

Sánchez Humanes B, Espelta JM, Camarero J, Sabaté S (2009) Patrones reproductivos en Quercus mediterráneos: Efecto del clima, del incremento de sequía y del resalveo sobre la producción de bellotas. V Congreso Forestal Español. Montes y Sociedad: Saber que hacer. S.E.C.F-Junta de Castilla y León. ISBN: 978-84-936854-6-1.

¿Puede la gestión forestal mitigar los efectos de un incremento de sequía en los montes mediterráneos? El caso de los bosques de encina y roble en el contexto del cambio climático. V Congreso Forestal Español. Montes y Sociedad: Saber que hacer.

Cotillas M, Espelta JM, Sabaté S (2009) ¿Puede la gestión forestal mitigar los efectos de un incremento de sequía en los montes mediterráneos? El caso de los bosques de encina y roble en el contexto del cambio climático. V Congreso Forestal Español. Montes y Sociedad: Saber que hacer. S.E.C.F-Junta de Castilla y León. ISBN: 978-84-936854-6-1.

Impactos del cambio climático sobre los bosques mediterráneos analizados en el marco de distintos proyectos de investigación. V Congreso Forestal Español. Montes y Sociedad: Saber que hacer.

Sabaté S, Espelta JM,Gracia C, Claramunt B, Cotillas de la Torre M, Keenan T, Sánchez Humanes B, Vayreda J, Plà E (2009) Impactos del cambio climático sobre los bosques mediterráneos analizados en el marco de distintos proyectos de investigación. V Congreso Forestal Español. Montes y Sociedad: Saber que hacer. S.E.C.F-Junta de Castilla y León. ISBN: 978-84-936854-6-1.

Resprouting dynamics.

Espelta JM, Sabaté S, Retana J (1999) Resprouting dynamics. In Rodá F, Retana J, Gracia C, Bellot J (eds) Ecology of Mediterranean evergreen oak forests. Springer, Berlin, pp. 61-73.