Ramon Vallejo

Dr. Ramon Vallejo


Research Focus & Metrics

Academic Career Length

40Years (1987-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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12 December 2008 in International Journal of Wildland Fire
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JPJuli G. Pausas
Juli G. Pausas
JLJoan Llovet
Joan Llovet
ARAnselm Rodrigo
Anselm Rodrigo
RVRamon Vallejo
Ramon Vallejo
Evolutionary and paleoecological studies suggest that fires are natural in the Mediterranean basin. However, the important increase in the number of fires and area burned during the 20th century has created the perception that fires are disasters. In the present paper, we review to what extent fires are generating ecological disasters in the Mediterranean basin, in view of current fire regimes and the long-term human pressure on the landscapes. Specifically, we review studies on post-fire plant regeneration and soil losses. The review suggests that although many Mediterranean ecosystems are highly resilient to fire (shrublands and oak forest), some are fire-sensitive (e.g. pine woodlands). Observed erosion rates are, in some cases, relatively high, especially in high fire severity conditions. The sensitive ecosystems (in the sense of showing strong post-fire vegetation changes and soil losses) are mostly of human origin (e.g. extensive pine plantations in old fields). Thus, although many Mediterranean basin plants have traits to cope with fire, a large number of the ecosystems currently found in this region are strongly altered, and may suffer disasters. Post-fire disasters are not the rule, but they may be important under conditions of previous human disturbances.

1 January 2020 in Environmental Research Letters
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FMFrancisco Moreira
Francisco Moreira
DADavide Ascoli
Davide Ascoli
HSHugh Safford
Hugh Safford
MAMark A Adams
Mark A Adams
JOSE MANUEL MORENOJOSE MANUEL MORENO
JOSE MANUEL MORENO
Paulo FernandesPaulo Fernandes
Paulo Fernandes
During the last decades, climate and land use changes led to an increased prevalence of megafires in Mediterranean-type climate regions (MCRs). Here, we argue that current wildfire management policies in MCRs are destined to fail. Focused on fire suppression, these policies largely ignore ongoing climate warming and landscape-scale buildup of fuels. The result is a ‘firefighting trap’ that contributes to ongoing fuel accumulation precluding suppression under extreme fire weather, and resulting in more severe and larger fires. We believe that a ‘business as usual’ approach to wildfire in MCRs will not solve the fire problem, and recommend that policy and expenditures be rebalanced between suppression and mitigation of the negative impacts of fire. This requires a paradigm shift: policy effectiveness should not be primarily measured as a function of area burned (as it usually is), but rather as a function of avoided socio-ecological damage and loss.


1 March 2004 in Plant Ecology
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JPJuli G. Pausas
Juli G. Pausas
CBCarme Bladé
Carme Bladé
AVAlejandro Valdecantos
Alejandro Valdecantos
JSJosé P. Seva
José P. Seva
DFDavid Fuentes
David Fuentes
RVRamon Vallejo
Ramon Vallejo

1 December 2014 in Earth-Science Reviews
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Journal Article
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LCLucrezia Caon
Lucrezia Caon
RVRamon Vallejo
Ramon Vallejo
CRCoen J. Ritsema
Coen J. Ritsema
VGViolette Geissen
Violette Geissen

1 September 2003 in Journal of Experimental Botany
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Alberto VilagrosaAlberto Vilagrosa
Alberto Vilagrosa
JBJ. Bellot
J. Bellot
RVRamon Vallejo
Ramon Vallejo
EGEustaquio Gil-Pelegrín
Eustaquio Gil-Pelegrín
Seedling shrubs in the Mediterranean semi‐arid climate are subjected to intense droughts during summer. Thus, seedlings often surpass their limits of tolerance to water stress, resulting in the loss of hydraulic conductivity due to xylem cavitation. The response in terms of stomatal conductance, vulnerability to cavitation, leaf dieback, and survival were analysed in two co‐occurring seedlings of mastic tree (Pistacia lentiscus L.) and kermes oak (Quercus coccifera L.) during an intense drought period. Both species reacted to drought with steep decreases in stomatal conductance before the critical water potential brought about the onset of cavitation events. Q. coccifera showed wider safety margins for avoiding runaway embolism than P. lentiscus and these differences could be related to the particular drought strategy displayed by each species: water saver or water spender. The limits for survival, resprout capacity and leaf dieback were also analysed in terms of loss of conductivity. By contrast with previous studies, the species showing higher seedling survival in the presence of drought also showed higher susceptibility to cavitation and operated with a lower safety margin for cavitation. Both species showed a leaf specific conductivity (LSC) threshold below which leaf biomass had to be regulated to avoid runaway embolism. However, each species displayed a different type of response: P. lentiscus conserved total leaf area up to 100% loss of LSC, whereas Q. coccifera continuously adjusted leaf biomass throughout the drought period in order to maintain the LSC very close to the maximum values recorded without loss of conductivity. Both species maintained the capacity for survival until the loss of conductivity was very nearly 100%.