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Deadwood is a large global carbon store with its store size partially determined by biotic decay. Microbial wood decay rates are known to respond to changing temperature and precipitation. Termites are also important decomposers in the tropics but are less well studied. An understanding of their climate sensitivities is needed to estimate climate change effects on wood carbon pools. Using data from 133 sites spanning six continents, we found that termite wood discovery and consumption were highly sensitive to temperature (with decay increasing >6.8 times per 10°C increase in temperature)—even more so than microbes. Termite decay effects were greatest in tropical seasonal forests, tropical savannas, and subtropical deserts. With tropicalization (i.e., warming shifts to tropical climates), termite wood decay will likely increase as termites access more of Earth’s surface. This study received support from the following sources: US National Science Foundation (NSF) DEB-1655759 (A.E.Z.); US NSF DEB-2149151 (A.E.Z.); US NSF DEB-1713502 (M.A.); US NSF DEB-1713435 (M.A.); US NSF DEB-1647502 (N.A.B.); US NSF DEB-1546686 (G.G.); US NSF DEB-1831952 (G.G.); George Washington University (A.E.Z.); USDA Forest Service (G.G.); Centre College Faculty Development Funds (M.L.G.); Australia Terrestrial Ecosystem Research Network National Collaborative Research Infrastructure Strategy (P.R.G., M.K., M.L., M.M.B., R.P.S., J.S., L.B.H., M.N., S.M.P., T.J.W., and S.K.A.); Royal Society-FCDO Africa Capacity Building Initiative (C.L.P., G.W.Q., S.A.-B., K.B., F.E.O., and M.P.R.); New Phytologist Foundation (A.T.A.); Fondecyt grant 1160329 (C.D.); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Brasil (CAPES) (E.v.d.B., A.S.Mou., R.F.M., F.F.S., T.M.C.-S., R.S.O., and A.M.D.); Department of Ecology and Conservation of the Federal University of Lavras (T.M.C.-S.); CNPq (E.v.d.B. and R.S.O.); FAPEMIG (E.v.d.B.); Australian Academy of Science 2017 Thomas Davies Research Grant (J.R.P.); Australian Research Council DP160103765 (W.K.C., J.R.P., and A.E.Z.); UK National Environment Research Council NE/L000016/1 (L.A.A.); Fundação de Amparo à Pesquisa do Estado de São Paulo, Brazil NERC - FAPESP 19/07773-1 (R.S.O. and A.M.D.); Environment Research and Technology Development Fund ERTDF, JPMEERF15S11420 of the Environmental Restoration and Conservation Agency of Japan (A.S.Mor. and K.O.); COLCIENCIAS no. FP44842-046-2017 (J.M.P.); Spanish government PID2019-110521GB-I00 (J.Pe., G.P., and R.O.); Catalan government grant SGR 2017-1005 (J.Pe., G.P., and R.O.); Fundación Ramón Areces ELEMENTAL-CLIMATE (J.Pe., G.P., and R.O.); National Agency for the Promotion of Research, Technological Development and Innovation, Scientific and Technological Research Project 2018-01561 PICT 2018-01561 (F.P.T.); ANID PIA/BASAL FB210006 (A.Fa.); Millennium Science Initiative Program NCN2021-050 (A.Fa.); iDiv German Research Foundation DFG–FZT 118, 202548816 (N.E.); and European Research Council Horizon 2020 research and innovation program no. 677232 (N.E.).

Predicting the seasonal dynamics of ecosystem carbon fluxes is challenging in broadleaved evergreen forests because of their moderate climates and subtle changes in canopy phenology. We assessed the climatic and biotic drivers of the seasonality of net ecosystem–atmosphere CO2 exchange (NEE) of a eucalyptus-dominated forest near Sydney, Australia, using the eddy covariance method. The climate is characterised by a mean annual precipitation of 800 mm and a mean annual temperature of 18 ∘C, hot summers and mild winters, with highly variable precipitation. In the 4-year study, the ecosystem was a sink each year (−225 g C m−2 yr−1 on average, with a standard deviation of 108 g C m−2 yr−1); inter-annual variations were not related to meteorological conditions. Daily net C uptake was always detected during the cooler, drier winter months (June through August), while net C loss occurred during the warmer, wetter summer months (December through February). Gross primary productivity (GPP) seasonality was low, despite longer days with higher light intensity in summer, because vapour pressure deficit (D) and air temperature (Ta) restricted surface conductance during summer while winter temperatures were still high enough to support photosynthesis. Maximum GPP during ideal environmental conditions was significantly correlated with remotely sensed enhanced vegetation index (EVI; r2 = 0.46) and with canopy leaf area index (LAI; r2 = 0.29), which increased rapidly after mid-summer rainfall events. Ecosystem respiration (ER) was highest during summer in wet soils and lowest during winter months. ER had larger seasonal amplitude compared to GPP, and therefore drove the seasonal variation of NEE. Because summer carbon uptake may become increasingly limited by atmospheric demand and high temperature, and because ecosystem respiration could be enhanced by rising temperatures, our results suggest the potential for large-scale seasonal shifts in NEE in sclerophyll vegetation under climate change.

Stomatal response to environmental conditions forms the backbone of all ecosystem and carbon cycle models, but is largely based on empirical relationships. Evolutionary theories of stomatal behaviour are critical for guarding against prediction errors of empirical models under future climates. Longstanding theory holds that stomata maximise fitness by acting to maintain constant marginal water use efficiency over a given time horizon, but a recent evolutionary theory proposes that stomata instead maximise carbon gain minus carbon costs/risk of hydraulic damage. Using data from 34 species that span global forest biomes, we find that the recent carbon‐maximisation optimisation theory is widely supported, revealing that the evolution of stomatal regulation has not been primarily driven by attainment of constant marginal water use efficiency. Optimal control of stomata to manage hydraulic risk is likely to have significant consequences for ecosystem fluxes during drought, which is critical given projected intensification of the global hydrological cycle. W.R.L.A. acknowledges funding for this research from NSF 1714972 and from the USDA National Institute of Food and Agriculture, Agricultural and Food Research Initiative Competitive Programme, Ecosystem Services and Agro-Ecosystem Management, grant no. 2017-05521. We thank T. Brodribb and one anonymous reviewer for their insightful reviews, B. Medlyn and Y.S. Lin for sharing data and R. Norby for providing Vcmax data for several species. We appreciate the assistance from Marion Feifel in collecting data of leaf photosynthetic parameters of five European tree species. S.L. acknowledges financial support from the China Scholarship Council (CSC). VRD acknowledges funding from a Ram on y Cajal fellowship (RYC-2012-10970). B.T.W. was supported by the Next Generation Ecosystem Experiments-Tropics, funded by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research. DJC acknowledges funding from the National Science Centre, Poland (NN309 713340).

Over the past 15 years, 3 million hectares of forests have been converted into shrublands or grasslands in the Mediterranean countries of the European Union. Fire and drought are the main drivers underlying this deforestation. Here we present a conceptual framework for the process of fire‐induced deforestation based on the interactive effects of fire and drought across three hierarchical scales: resistance in individuals, resilience in populations, and transitions to a new state. At the individual plant level, we review the traits that confer structural and physiological resistance, as well as allow for resprouting capacity: deforestation can be initiated when established individuals succumb to fire. After individuals perish, the second step toward deforestation requires a limited resilience from the population, that is, a reduced ability of that species to regenerate after fire. If individuals die after fire and the population fails to recover, then a transition to a new state will occur. We document trade‐offs between drought survival and fire survival, as embolism resistance is negatively correlated with fire tolerance in conifers and leaf shedding or drought deciduousness, a process that decreases water consumption at the peak of the dry season, temporally increases crown flammability. Propagule availability and establishment control resilience after mortality, but different hypotheses make contrasting predictions on the drivers of post‐fire establishment. Mycorrhizae play an additional role in modulating the response by favoring recovery through amelioration of the nutritional and water status of resprouts and new germinants. So far, resprouter species such as oaks have provided a buffer against deforestation in forests dominated by obligate seeder trees, when present in high enough density in the understory. While diversifying stands with resprouters is often reported as advantageous for building resilience, important knowledge gaps exist on how floristic composition interacts with stand flammability and on the “resprouter exhaustion syndrome,” a condition where pre‐fire drought stress, or short fire return intervals, seriously restrict post‐fire resprouting. Additional attention should be paid to the onset of novel fire environments in previously fire‐free environments, such as high altitude forests, and management actions need to accommodate this complexity to sustain Mediterranean forests under a changing climate. Erasmus Mundus Master Course Mediterranean Forestry Natural Resources Management (MEDfOR) Ramón y Cajal fellowship. Grant Number: RYC‐2012‐10970 Spanish Government. Grant Number: AGL2015‐69151‐R

En los últimos 15 años, 3 millones de hectáreas de bosques se han convertido en matorrales o pastizales en los países mediterráneos de la Unión Europea, siendo el fuego y la sequía los principales motores de esa deforestación. Se analiza la deforestación inducida por los efectos conjuntos del fuego y la sequía en tres escalas jerárquicas: resistencia en individuos, resiliencia de poblaciones y transiciones a un nuevo estado. A nivel individual se analiza la resistencia estructural y fisiológica y la capacidad de rebrote. Cuando los individuos perecen, el segundo paso hacia la deforestación es una resiliencia limitada de la población, esto es, una baja capacidad para regenerarse tras el fuego. Si los individuos mueren y la población no se recupera, se producirá una transición a un nuevo estado de vegetación. Las especies con capacidad de rebrote proporcionan un papel amortiguador contra la deforestación en bosques dominados por especies que regeneran sexualmente y carecen de banco de semillas. Aunque la diversificación de rodales con especies rebrotadoras suele ser ventajosa para incrementar la resiliencia de la masa, existen lagunas de conocimiento sobre cómo la composición de la masa afecta a la inflamabilidad, a la resistencia frente a la sequía y sobre el "síndrome de agotamiento de los rebrotes". La gestión debe adaptarse para mantener los bosques mediterráneos bajo un clima cambiante, prestando además mayor atención a la aparición de nuevos riesgos de incendios en zonas antes libres de ellos, como los bosques de montaña.

En los últimos 15 años, 3 millones de hectáreas de bosques se han convertido en matorrales o pastizales en los países mediterráneos de la Unión Europea, siendo el fuego y la sequía los principales motores de esa deforestación. Se analiza la deforestación inducida por los efectos conjuntos del fuego y la sequía en tres escalas jerárquicas: resistencia en individuos, resiliencia de poblaciones y transiciones a un nuevo estado. A nivel individual se analiza la resistencia estructural y fisiológica y la capacidad de rebrote. Cuando los individuos perecen, el segundo paso hacia la deforestación es una resiliencia limitada de la población, esto es, una baja capacidad para regenerarse tras el fuego. Si los individuos mueren y la población no se recupera, se producirá una transición a un nuevo estado de vegetación. Las especies con capacidad de rebrote proporcionan un papel amortiguador contra la deforestación en bosques dominados por especies que regeneran sexualmente y carecen de banco de semillas. Aunque la diversificación de rodales con especies rebrotadoras suele ser ventajosa para incrementar la resiliencia de la masa, existen lagunas de conocimiento sobre cómo la composición de la masa afecta a la inflamabilidad, a la resistencia frente a la sequía y sobre el "síndrome de agotamiento de los rebrotes". La gestión debe adaptarse para mantener los bosques mediterráneos bajo un clima cambiante, prestando además mayor atención a la aparición de nuevos riesgos de incendios en zonas antes libres de ellos, como los bosques de montaña.

There is increasing evidence that the circadian clock is a signif- icant driver of photosynthesis that becomes apparent when environmental cues are experimentally held constant. We studied whether the composition of photosynthetic pigments is under circadian regulation, and whether pigment oscillations lead to rhythmic changes in photochemical efficiency. To address these questions, we maintained canopies of bean and cotton, after an entrainment phase, under constant (light or darkness) conditions for 30–48 h. Photosynthesis and quantum yield peaked at subjective noon, and non-photochemical quenching peaked at night. These oscillations were not associ- ated with parallel changes in carbohydrate content or xantho- phyll cycle activity. W e observed robust oscillations of Chl a/b during constant light in both species, and also under constant darkness in bean, peaking when it would have been night dur- ing the entrainment (subjective nights). These oscillations could be attributed to the synthesis and/or degradation of tri- meric light-harvesting complex II (reflected by the rhythmic changes in Chl a/b), with the antenna size minimal at night and maximal around subjective noon. Considering together the oscillations of pigments and photochemistry, the observed pattern of changes is counterintuitive if we assume that the plant strategy is to avoid photodamage, but consistent with a strategy where non-stressed plants maximize photosynthesis. The authors acknowledge the support of the following re- search grants: UPV/EHU-GV IT-624-13 and IT-1018-16 from the Basque Government and CTM2014-53902-C2-2-P from the Spanish Ministry of Economy and Competitiveness (MINECO) and the ERDF (FEDER). This study benefited from the CNRS human and technical resources allocated to the Ecotrons Research Infrastructures as well as from the state allocation ‘Investissement d’Avenir’ ANR-11-INBS- 0001, ExpeER FP7 Transnational Access programme, Ramón y Cajal fellowships (RYC-2012-10970 to V.R.D. and RYC-2008-02050 to J.P.F.), the Erasmus Mundus Master Course Mediterranean Forestry and Natural Resources Management (MEDfOR) and internal grants from UWS- HIE to V.R.D. and ZALF to A.G. EHU postdoctora ellowship and JdC-Incorporation fellowship (IJCI-2014- 22489) to B.F.M. are also acknowledged. We remain indebted to E. Gerardeau, D. Dessauw, J. Jean, P. Prudent (Aïda CIRAD), J.-J. Drevon, C. Pernot (Eco&Sol INRA), B. Buatois, A. Rocheteau (CEFE CNRS), S. Devidal, C. Piel, O. Ravel and the full Ecotron team, J. del Castillo, P. Martín, A. Mokhtar, A. Pra, S. Salekin (UdL), S. García-Muñoz (IMIDRA), Z. Kayler and K. Pirhofer-Walzl (ZALF) for out- standing technical assistance during experiment setup, plant cultivation or subsequent measurements.

Sponsored Collection. Changing perspectives on daylight: Science, technology, and culture

Circadian resonance, whereby a plant's endogenous rhythms are tuned to match environmental cues, has been repeatedly shown to be adaptive, although the underlying mechanisms remain elusive. Concomitantly, the adaptive value of nocturnal transpiration in C3 plants remains unknown because it occurs without carbon assimilation. These seemingly unrelated processes are interconnected because circadian regulation drives temporal patterns in nocturnal stomatal conductance, with maximum values occurring immediately before dawn for many species. We grew individuals of six Eucalyptus camaldulensis genotypes in naturally lit glasshouses and measured sunset, predawn and midday leaf gas exchange and whole-plant biomass production. We tested whether sunrise anticipation by the circadian clock and subsequent increases in genotype predawn stomatal conductance led to rapid stomatal opening upon illumination, ultimately affecting genotype differences in carbon assimilation and growth. We observed faster stomatal responses to light inputs at sunrise in genotypes with higher predawn stomatal conductance. Moreover, early morning and midday stomatal conductance and carbon assimilation, leaf area and total plant biomass were all positively correlated with predawn stomatal conductance across genotypes. Our results lead to the novel hypothesis that genotypic variation in the circadian-regulated capacity to anticipate sunrise could be an important factor underlying intraspecific variation in tree growth.

El empleo de isótopos estables en el ámbito de la ecología forestal ha ido creciendo progresivamente en las últimas dos décadas. Cabe esperar que esta tendencia se mantenga en el futuro, ya que éstos aportan una visión integradora de cómo las plantas, hoy y en el pasado, han interaccionado con el medio así como con otros organismos. Su implementación es particularmente relevante en climas secos debido a la fuerte limitación de recursos que en ellos acontece. Tras una breve introducción sobre las bases teóricas de los isótopos estables en fisiología vegetal, esta revisión destaca, sobre diferentes escalas espaciales y temporales, los últimos avances en ecología forestal empleando esta metodología y con un énfasis especial en los sistemas áridos y semiáridos. The use of stable isotope techniques in forest ecology research has grown steadily over the last two decades. This trend will continue, as stable isotopes can serve as valuable integrators of how plants have interacted, today and in the past, with their physical environment or with other organisms. This is particularly relevant in dry areas due to the strong limitation of resources. After a brief introduction about the theoretical background of stable isotopes in plant physiology, this review highlights recent advances in forest ecology that have embraced this methodology, at different spatial and temporal scales, and with special emphasis on arid and semi-arid systems.

The occurrence of large, high-intensity wildfires requires plant biomass, or fuel, that is sufficientlydry to burn. This poses the question, what is“sufficiently dry”? Until recently, the ability to address this questionhas been constrained by the spatiotemporal scale of available methods to monitor the moisture contents ofboth dead and live fuels. Here we take advantage of recent developments in macroscale monitoring of fuelmoisture through a combination of remote sensing and climatic modeling. We show there are clear thresholdsof fuel moisture content associated with the occurrence of wildfires in forests and woodlands. Furthermore, weshow that transformations in fuel moisture conditions across these thresholds can occur rapidly, within amonth. Both the approach presented here, and ourfindings, can be immediately applied and may greatlyimprovefire risk assessments in forests and woodlands globally.

Plant traits—the morphological, anatomical, physiological, biochemical and phenological characteristics of plants—determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait‐based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits—almost complete coverage for ‘plant growth form’. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait–environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives. Funding Information: Max Planck Institute for Biogeochemistry; Max Planck Society; German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig; International Programme of Biodiversity Science (DIVERSITAS); International Geosphere-Biosphere Programme (IGBP); Future Earth; French Foundation for Biodiversity Research (FRB); GIS ‘Climat, Environnement et Société' France; UK Natural Environment Research Council (NERC); AXA Research Fund

Centro de Investigación Forestal (CIFOR), Progress in high-throughput phenotyping and genomics provides the potential to understand the genetic basis of plant functional differentiation. We developed a semi-automatic methodology based on unmanned aerial vehicle (UAV) imagery for deriving tree-level phenotypes followed by genome-wide association study (GWAS). An RGB-based point cloud was used for tree crown identification in a common garden of Pinus halepensis in Spain. Crowns were combined with multispectral and thermal orthomosaics to retrieve growth traits, vegetation indices and canopy temperature. Thereafter, GWAS was performed to analyse the association between phenotypes and genomic variation at 235 single nucleotide polymorphisms (SNPs). Growth traits were associated with 12 SNPs involved in cellulose and carbohydrate metabolism. Indices related to transpiration and leaf water content were associated with six SNPs involved in stomata dynamics. Indices related to leaf pigments and leaf area were associated with 11 SNPs involved in signalling and peroxisome metabolism. About 16-20% of trait variance was explained by combinations of several SNPs, indicating polygenic control of morpho-physiological traits. Despite a limited availability of markers and individuals, this study is provides a successful proof-of-concept for the combination of high-throughput UAV-based phenotyping with cost-effective genotyping to disentangle the genetic architecture of phenotypic variation in a widespread conifer., This work was supported by the Spanish Government, grant number RTI2018-094691-B-C31 (MCIU/AEI/FEDER, EU). We thank Ricardo Alía (CIFOR-INIA) for providing the genotypic data. We thank three anonymous reviewers whose insightful comments and suggestions helped to improve the manuscript. The authors declare no conflicts of interest.AGL2015-68274-C3-3-R, 14 Pág.

Les pertorbacions com el foc i la sequera són naturals a la conca mediterrània, però per la situació actual d'escalfament global i absència de gestió forestal, els episodis de sequera cada cop són més freqüents i severs. Aquests episodis de sequera, acompanyats de l'abandonament de les zones rurals de l'últim mig segle, han afavorit el desenvolupament d'una gran quantitat i continuïtat de vegetació (combustible des del punt de vista dels incendis) més seca i morta (disponible). Aquesta major quantitat de combustible i més sec generen uns incendis de major intensitat. A part d'aquests aspectes relacionats amb el canvi global, la mateixa fisiologia de les espècies forestals, pot afavorir les pèrdues d'aigua a través de la transpiració nocturna o cuticular, per exemple, malgrat que la seva regulació encara resulta ser una gran desconeguda avui en dia. S'ha indicat com aquests dos processos poden augmentar encara més la falta d'aigua, sobretot en condicions d'estrès, el que augmentaria el risc d'incendis i podria dificultar la recuperació de la vegetació després de la pertorbació. En aquest sentit, s'ha apuntat que les adaptacions fisiològiques per resistir la sequera poden arribar a ser antagòniques amb les adaptacions per resistir els incendis. Aquesta tesi doctoral busca unir els processos fisiològics responsables per la resistència a la sequera amb la resposta de les plantes als incendis i, en particular, el rebrot. Amb aquesta finalitat s'han combinat una sèrie d'estudis bibliogràfics i meta-analítics amb estudis de camp. Hem constatat com adaptacions a la sequera, com ara la resistència a l'embolisme poden estar negativament relacionades amb la resistència als incendis de baixa intensitat. Però, la recuperació del rebrot després d'incendis d'alta intensitat que eliminen la biomassa arbòria depenen de què el grau d'embolisme hagi estat limitant. Hem documentat com la variació en la conductància cuticular pot, efectivament, augmentar de forma considerable l'estrès hídric sobretot en espècies perennes i, finalment, hem realitzat una síntesi global sobre els factors que expliquen les pèrdues d'aigua nocturnes. Perturbaciones como el fuego y la sequía son naturales en la cuenca mediterránea, pero el calentamiento global y la ausencia de gestión forestal favorecen que los episodios de sequía sean cada vez más frecuentes y severos. Estos episodios de sequía, acompañados del abandono de las zonas rurales durante el último siglo, han favorecido el desarrollo de una gran cantidad y continuidad de vegetación (combustible desde el punto de vista de los incendios) que está cada vez más y, por tanto, más disponible para las llamas. Esta mayor cantidad de combustible seco aumenta la probabilidad de que sufrir grandes incendios. Aparte de estos aspectos relacionados con el cambio global, la propia fisiología de las especies forestales puede favorecer las pérdidas de agua a través de la transpiración nocturna o cuticular, por ejemplo, aunque su regulación resulta todavía una gran desconocida a día de hoy. Se ha indicado como estos dos procesos pueden aumentar todavía más la falta de agua, sobretodo en condiciones de estrés, lo que aumentaría el riesgo de incendios y podría dificultar la recuperación de la vegetación tras la perturbación. En este sentido, se ha apuntado que las adaptaciones fisiológicas para resistir a la sequía pueden llegar a ser antagónicas con las adaptaciones para resistir a los incendios Esta tesis doctoral busca unir los procesos fisiológicos responsables por la resistencia a la sequía con la respuesta de las plantas a los incendios y, en particular, el rebrote. A tal fin se han combinado una serie de estudios bibliográficos y meta-analíticos con estudios de campo. Hemos constatado como adaptaciones a la sequía, tales como resistencia al embolismo pueden estar negativamente relacionadas con la resistencia a los incendios de baja intensidad. Sin embargo, la recuperación del rebrote tras incendios de alta intensidad que eliminan la biomasa arbórea depende del grado de embolismo antes del incendio. Hemos documentado también como la variación en la conductancia cuticular puede, efectivamente, aumentar de forma considerable el estrés hídrico sobretodo en especies perennes y, finalmente, hemos realizado una síntesis global sobre los factores que explican la apertura estomática nocturna. Disturbances such as fire and drought are natural in the Mediterranean basin, but global warming and lack of forest management interact to enhance drought episodes that are becoming more frequent and severe. These drought episodes, accompanied by the abandonment of rural areas over the last century, have favoured the development of a large vegetation (fuel) loads that are increasingly drier and, consequently, more available to the fire. This increasing amount of dry fuel is consequently enhancing the probability of suffering a large fire. In addition to global change factors, some physiological traits may favour water losses through nocturnal or cuticular transpiration, for instance, although their regulation is still largely unknown at present. It has been pointed out how these two processes can further increase water scarcity, especially under stressful conditions, which would increase the risk of fire and could hinder the recovery of vegetation after disturbance. In this sense, it has been suggested that physiological adaptations to resist drought may become antagonistic to adaptations to resist fire. This PhD thesis seeks to link the physiological processes responsible for drought resistance with the response of plants to fire and, in particular, resprouting. To this end, a series of bibliographical and meta-analytical studies have been combined with field studies. I found that adaptations to drought, such as resistance to embolism, can be negatively related to resistance to low intensity fire. However, resprouting recovery after high-intensity fires that remove aboveground biomass depends on the degree of hydrcaulic conductance before the perturbation. I have documented how variation in cuticular conductance can indeed considerably increase water stress, especially in perennial species and, finally, I have performed a global synthesis on the factors that explain nocturnal stomatal conductance.

Els incendis forestals constitueixen una de les majors pertorbacions ecològiques a nivell mundial i, especialment, a les regions mediterrànies. Per anticipar-se a situacions de perill, aquest treball proposa l’aplicació espacial d’un índex de risc d’incendis forestals definit pel contingut mínim d’humitat dels combustibles fins morts (FM) i la relació existent amb l’àrea cremada després d’un incendi. El model emprat per predir FM requereix, únicament, del dèficit de pressió de vapor, llur valor s’obté de les dades en quadrícula de temperatura i humitat relativa. Per Universitat de Lleida obtenir això, es van provar les següents tècniques d’interpolació: regressió lineal (RL), ponderació per l’invers de la distància (IDW) i kriging ordinari (OK). Dins de la RL es van avaluar dues funcions diferents (RL1 i RL2) amb l’elevació, la latitud i la longitud com a variables d’entrada. L’estudi es va realitzar en el territori espanyol de la Península Ibèrica i les Illes Balears, i durant juny i juliol de 2018. Els millors resultats es van obtenir amb la tècnica d’OK amb enfocament localitzat. El producte final és una aplicació automatitzada de predicció de FM que busca ser operativa entre els cossos d’extinció d’incendis forestals. Los incendios forestales constituyen una de las mayores perturbaciones ecológicos a nivel mundial y, en especial, en las regiones mediterráneas. Para anticiparse a situaciones de peligro, este trabajo propone la aplicación espacial de un índice de riesgo de incendios forestales definido por el contenido mínimo de humedad de los combustibles finos muertos (FM) y la relación existente con el área quemada tras un incendio. El modelo empleado para predecir FM requiere únicamente del déficit de presión de vapor, cuyo valor se obtiene de los datos en cuadrícula de temperatura y humedad relativa. Para ello, se probaron las siguientes técnicas de interpolación: regresión lineal (RL), ponderación por el inverso de la distancia (IDW) y kriging ordinario (OK). Dentro de la RL se evaluaron dos funciones diferentes (RL1 y RL2) con la elevación, la latitud y la longitud como variables de entrada. El estudio se realizó en el territorio español de la Península Ibérica y las Islas Baleares, y durante junio y julio de 2018. Los mejores resultados se obtuvieron con la técnica de OK con enfoque localizado. El producto final es un aplicativo automatizado de predicción de FM que busca ser operativo entre los cuerpos de extinción de incendios forestales. Forest fires constitute one of the greatest ecological disturbances worldwide and, especially, in the Mediterranean regions. To anticipate situations of danger, this project suggests the spatial application of a forest fire risk index defined by the minimum moisture content of dead fine fuels (FM) and the existing relationship with the area burned after a fire. The model used to predict FM only requires the vapor pressure deficit, which value is obtained from the gridded temperature and relative humidity data. For this, the following interpolation techniques were tested: linear regression (RL), inverse distance weighted (IDW) and ordinary kriging (OK). Within the RL, two different functions (RL1 and RL2) were evaluated with elevation, latitude and longitude as input variables. The study was conducted in the Spanish territory of the Iberian Peninsula and the Balearic Islands during June and July 2018. The best results were obtained with the OK technique through localized approach. The final product is an automated FM prediction application that seeks to be operative among forest firefighting bodies.