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Significance Forests are experiencing growing risks of drought-induced mortality in a warming world. Yet, ecosystem dynamics following drought mortality remain unknown, representing a major limitation to our understanding of the ecological consequences of climate change. We provide an emerging picture of postdrought ecological trajectories based on field indicators of forest dynamics. Replacement patterns following mortality indicate limited short-term persistence of predrought dominant tree species, highlighting the potential for major ecosystem reorganization in the coming decades. The great variability of the observed dynamics within and among species reinforces the primary influence of drought characteristics and ecosystem legacies, modulated by land use, management, and past disturbances, on ongoing drought-related species turnover and their potential implications for future forest biodiversity and ecosystem services., Forest vulnerability to drought is expected to increase under anthropogenic climate change, and drought-induced mortality and community dynamics following drought have major ecological and societal impacts. Here, we show that tree mortality concomitant with drought has led to short-term (mean 5 y, range 1 to 23 y after mortality) vegetation-type conversion in multiple biomes across the world (131 sites). Self-replacement of the dominant tree species was only prevalent in 21% of the examined cases and forests and woodlands shifted to nonwoody vegetation in 10% of them. The ultimate temporal persistence of such changes remains unknown but, given the key role of biological legacies in long-term ecological succession, this emerging picture of postdrought ecological trajectories highlights the potential for major ecosystem reorganization in the coming decades. Community changes were less pronounced under wetter postmortality conditions. Replacement was also influenced by management intensity, and postdrought shrub dominance was higher when pathogens acted as codrivers of tree mortality. Early change in community composition indicates that forests dominated by mesic species generally shifted toward more xeric communities, with replacing tree and shrub species exhibiting drier bioclimatic optima and distribution ranges. However, shifts toward more mesic communities also occurred and multiple pathways of forest replacement were observed for some species. Drought characteristics, species-specific environmental preferences, plant traits, and ecosystem legacies govern postdrought species turnover and subsequent ecological trajectories, with potential far-reaching implications for forest biodiversity and ecosystem services.

As global climate becomes warmer, the maintenance of the structure and function of Mediterranean forests constitutes a key challenge to forest managers. Despite the need for forest adaptation, an overall evaluation of the efficacy of current management strategies is lacking. Here we describe a theoretical framework for classifying management strategies, explicitly recognizing trade-offs with other, untargeted ecosystem components. We then use this framework to provide a quantitative synthesis of the efficacy of management strategies in the Mediterranean basin. Our review shows that research has focused on strategies aimed at decreasing risk and promoting resistance in the short-term, rather than enhancing long-term resilience. In addition, management strategies aiming at short-term benefits frequently have unintended consequences on other adaptation objectives and untargeted ecosystem components. Novel empirical studies and experiments focusing both on adaptation objectives and multiple responses and processes at the ecosystem level are needed. Such progress is essential to improve the scientific basis of forest management strategies and support forest adaptation in the Mediterranean basin. This work was funded by the ERA-NET FORESTERRA project INFORMED (29183). Additional support was obtained from the projects CGL2013-46808-R and EST_RES (AGL2015-70425-R) funded by the Spanish Ministry of Economy and Competitiveness. AVC acknowledges support from the EU through a Marie Skłodowska-Curie Fellowship. JMV benefits from an ICREA Academia award.

According to broad‐scale application of biogeographical theory, widespread retractions of species' rear edges should be seen in response to ongoing climate change. This prediction rests on the assumption that rear edge populations are “marginal” since they occur at the limit of the species' ecological tolerance and are expected to decline in performance as climate warming pushes them to extirpation. However, conflicts between observations and predictions are increasingly accumulating and little progress has been made in explaining this disparity. We argue that a revision of the concept of marginality is necessary, together with explicit testing of population decline, which is increasingly possible as data availability improves. Such action should be based on taking the population perspective across a species' rear edge, encompassing the ecological, geographical and genetic dimensions of marginality. Refining our understanding of rear edge populations is essential to advance our ability to monitor, predict and plan for the impacts of environmental change on species range dynamics. Fil: Vilà Cabrera, Albert. University of Stirling; Reino Unido Fil: Premoli Il'grande, Andrea Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Jump, Alistair. University of Stirling; Reino Unido

Species rear range edges are predicted to retract as climate warms, yet evidence of population persistence is accumulating. Accounting for this disparity is essential to enable prediction and planning for species' range retractions. At the Mediterranean edge of European beech-dominated temperate forest, we tested the hypothesis that individual performance should decline at the limit of the species' ecological tolerance in response to increased drought. We sampled 40 populations in a crossed factor design of geographical and ecological marginality and assessed tree growth resilience and decline in response to recent drought. Drought impacts occurred across the rear edge, but tree growth stability was unexpectedly high in geographically isolated marginal habitat and lower than anticipated in the species' continuous range and better-quality habitat. Our findings demonstrate that, at the rear edge, range shifts will be highly uneven and characterised by reduction in population density with local population retention rather than abrupt range retractions.

Vayreda, J., Martinez-Vilalta, J., Vila-Cabrera, A.. 2016. The Ecological Forest Inventory of Catalonia: a tool for functional ecology. Ecosistemas 25(3): 70-79. Doi.: 10.7818/ECOS.2016.25-3.08 This paper describes the particular characteristics of IEFC that makes it singular unique tool for the advance of forest ecological understanding. The IEFC stressed by sampling uncommon variables such as biomass and production of branches and leaves, growth curves or nutrient content in wood, bark, branches and leaves. This additional information allowed to carry out some functional studies. In this paper we briefly review the most relevant results regarding: i) the geographical distribution of functional traits across levels of organization and intraspecific and interspecific variability along environmental gradients; ii) the positive relationship between species richness and timber production in Mediterranean forests; iii) the trend to higher growth during most of the twentieth century reversed from year 1970 by lower water availability and; iv) stoichiometric relationships of nutrients by species and functional groups along environmental gradients. Today it is clear that the inclusion of these functional variables in a forest inventory is essential to better understand forest responses to environmental changes and evaluate the suitability of different management strategies.

Land-use changes are one of the major drivers of global change. In many developed countries socioeconomic changes have induced forest expansion during the last centuries, with still seldom explored implications for ecosystem services. We assessed the growth rate and the contribution of these “new forests” on C storage under the imprint of land-use history from Mediterranean to temperate forests in two biogeographical regions in the Iberian Peninsula, using data from 6422 plots of the Spanish National Forest Inventory (1986–2007) and the land-cover map of 1956 to distinguish among pre-existing and new forests (appeared after 1956). Almost a quarter of current forests were new forests and they represented 22% of the total C pool. New forests maintained similar C stocks than pre-existing ones (~45 Mg ha−1), but they are growing at rates 25% faster. Considering the whole Spanish forested territory, the new forest growth rate would offset around 9% of the rate of total C emitted in Spain between 1986 and 2007. The effects of land-use history on forest growth and C stocks varied with environmental conditions (for example, growth of new forests in areas with less water availability was higher than in pre-existing ones), supporting the idea that agricultural legacies may prevail in the long term. In a time when European forests exhibit the first signs of carbon sink saturation, our study endows a relevant ecological role to new forests appearing in the second half of the twentieth century.

International audience; Fire resistance traits drive tree species composition in surface‐fire ecosystems, but how they covary at different scales of variation and with the environment is not well documented. We assessed the covariation of bark thickness (BT), tree height, and crown base‐to‐height ratio across Alpine forests, after accounting for the effects of tree diameter and competition for light on individual trait variation. Traits consistently correlated across individuals and communities, although the variance of BT mainly occurred among species, whereas crown elevation traits varied mainly within species. Aridity, temperature, and competition contributed to explain the variation of fire resistance traits among and within species, driving a trade‐off between fire resistance and the ability to compete for light. Thick‐barked species (fire‐tolerant) that self‐prune their lower branches (flame‐avoiders) dominated the most fire‐prone and flammable communities in sub‐Mediterranean southern Alps, whereas thin‐barked tree species that grow tall (competition for light) dominated the least fire‐prone communities in the northern Alps. Our findings suggest a long‐term interaction between mountain tree species and fire regime. Higher allocation to trunk elongation occurs in moist and shade environments, while higher allocation to thicken the bark and distancing the crown base from surface fuels occurs in open‐canopy, dry forests where fire spreads with higher intensity.

Aim Characterizing the variation of functional traits in nature is a first step towards linking environmental changes to changes in ecosystem function. Here we aim to characterize the spatial variability of major plant functional traits along wide environmental gradients in Mediterranean and temperate forests, and assess to what extent this variability differs between two dominant families in Northern Hemisphere forests: Fagaceae and Pinaceae. Location Catalonia (north-east Iberian Peninsula). Methods Four functional traits were selected to incorporate information on both the leaf and the wood economic spectra: maximum tree height (Hmax), wood density (WD), leaf mass per area (LMA) and nitrogen content of leaves (Nmass). We quantified the variance distribution of each functional trait across three nested ecological scales: population, species and family. Through such scales, we explored the spatial variation of functional traits through climatic and biotic gradients, as well as the covariation among traits. Results Functional trait variability was distributed across all the ecological scales considered, but mostly at the family level, with functional traits differing markedly between Fagaceae and Pinaceae. Within families, variation in functional traits was similar or higher within species than between species. The spatial variability in functional traits was related to biotic and abiotic gradients, although this effect was quantitatively small compared with differences between families. Covariation among functional traits was not necessarily conserved across ecological scales. Trait covariation across all species was structured along the Hmax−WD and LMA−Nmass axes, but this structure was partially lost within families, where variation was mostly structured along the Hmax−LMA and WD−Nmass axes. Main conclusions Intraspecific variation emerges as a fundamental component of functional trait structure along wide environmental gradients. Understanding the sources of intraspecific variation, as well as how it contributes to community assembly and ecosystem functioning, thus becomes a primary research question.

Disentangling how variation in reproduction and growth is linked in plants across different ecological scales, and how allocation rules change in response to stress are fundamental aspects of life history theory. Although it is known that reproductive allocation is an allometric process and that environmental conditions can influence demographic traits, patterns of variation in vegetative and reproductive functions across and within individuals of tree species suffering drought-induced decline have rarely been documented. In this study we use Scots pine (Pinus sylvestris L.) as a model species to explore patterns of variation in cone production and growth in two declining populations at the southern edge of its distribution. A Bayesian approach was used to assess how these demographic traits vary as a function of drought effects and competition and covary across different ecological scales. The allometric trajectories relating tree size with cone production and growth differed along gradients of drought impacts and biotic interactions. Although reproduction and growth increased with tree size, cone production reached a maximum at intermediate sized trees and stabilized or decreased at larger sizes. Drought stress effects (defoliation at the tree level and overall decline at the plot level) and competition for resources reduced cone production and growth. Our results also showed differential effects of defoliation on cone production depending on tree size, with stronger effects on larger individuals. After accounting for these effects, much of the variation of demographic traits and correlations among them occurred at small ecological scales across individuals (i.e. within plots) and within individuals across years. This resulted in covariations between demographic traits among nearby individuals and within individuals through time, suggesting a consistent advantage in resource acquisition of some individuals within plots, and trade-offs between growth and cone production within trees across years. In conclusion, this study reports that drought-induced forest decline is associated with lower growth and cone production in Scots pine, which could contribute to explain the long-term impacts of drought in southern populations of this species and, in particular, its low regeneration capacity after severe drought.

Intense droughts combined with increased temperatures are one of the major threats to forest persistence in the 21st century. Despite the direct impact of climate change on forest growth and shifts in species abundance, the effect of altered demography on changes in the composition of functional traits is not well known. We sought to (1) quantify the recent changes in functional composition of European forests; (2) identify the relative importance of climate change, mean climate and forest development for changes in functional composition; and (3) analyse the roles of tree mortality and growth underlying any functional changes in different forest types. We quantified changes in functional composition from the 1980s to the 2000s across Europe by two dimensions of functional trait variation: the first dimension was mainly related to changes in leaf mass per area and wood density (partially related to the trait differences between angiosperms and gymnosperms), and the second dimension was related to changes in maximum tree height. Our results indicate that climate change and mean climatic effects strongly interacted with forest development and it was not possible to completely disentangle their effects. Where recent climate change was not too extreme, the patterns of functional change generally followed the expected patterns under secondary succession (e.g. towards late-successional short-statured hardwoods in Mediterranean forests and taller gymnosperms in boreal forests) and latitudinal gradients (e.g. larger proportion of gymnosperm-like strategies at low water availability in forests formerly dominated by broad-leaved deciduous species). Recent climate change generally favoured the dominance of angiosperm‐like related traits under increased temperature and intense droughts. Our results show functional composition changes over relatively short time scales in European forests. These changes are largely determined by tree mortality, which should be further investigated and modelled to adequately predict the impacts of climate change on forest function., Ministerio de Economía y Competitividad

To predict future changes in forest ecosystems, it is crucial to understand the complex processes involved in decline of tree species populations and to evaluate the implications for potential vegetation shifts. Here, we study patterns of decline (canopy defoliation and mortality of adults) of four Scots pine populations at the southern edge of its distribution and characterized by different combinations of climate dryness and intensity of past management. General linear and structural equation modeling were used to assess how biotic, abiotic, and management components interacted to explain the spatial variability of Scots pine decline across and within populations. Regeneration patterns of Scots pine and co-occurring oak species were analyzed to assess potential vegetation shifts. Decline trends were related to climatic dryness at the regional scale, but, ultimately, within-population forest structure, local site conditions, and past human legacies could be the main underlying drivers of Scots pine decline. Overall, Scots pine regeneration was negatively related to decline both within and between populations, whereas oak species responded to decline idiosyncratically across populations. Taken together, our results suggest that (1) patterns of decline are the result of processes acting at the plot level that modulate forest responses to local environmental stress and (2) decline of adult Scots pine trees seems not to be compensated by self-recruitment so that the future dynamics of these forest ecosystems are uncertain.

Aim Forest ecosystems dominated by fire-sensitive species could suffer shifts in composition under altered crown fire regimes mediated by climate change. The aims of this study were to: (1) study the spatio-temporal patterns and the climatic distribution of fires in Scots pine (Pinus sylvestris) forests during the last 31 years in north-eastern Spain, (2) evaluate the climatic vulnerability to fire of these forests in Spain, (3) analyse the regeneration of Scots pine after fire, and (4) predict the mid-term maintenance or replacement of Scots pine in burned areas. Location Catalonia (north-eastern Spain): the southern distribution limit of Scots pine. Methods We characterized the spatio-temporal and the climatic distribution of fires that occurred in Catalonia between 1979 and 2009. We used a generalized linear model to characterize the climatic vulnerability to fire of Scots pine in the whole of Spain. We assessed the regeneration of the species after crown fires in nine burned areas in Catalonia. The resulting data were integrated into a stochastic matrix model to predict the mid-term maintenance or replacement of Scots pine in burned areas. Results During the last three decades, Scots pine forests distributed in dry sites were most affected by fire. Our assessment of the vulnerability to fire of Scots pine forests in Spain as a whole, based on climatic and topographical variables, showed that 32% of these forests are vulnerable to fire, and that this proportion could increase to 66% under a conservative climate change scenario. Field data showed almost no regeneration of Scots pine after crown fires, and a limited capacity to recolonize from unburned edges, even in relatively old fires, with 90% of recruits located in the first 25 m from the edge. This process could be delayed by the elapsed time for new recruits to achieve reproductive maturity, which we estimated to be c. 15 years. Finally, our matrix model predicted the replacement of burned Scots pine forests by oak (Quercus sp.) forests, shrublands or mixed resprouter forests. Main conclusions Increased vulnerability to fire of Scots pine forests under future, warmer conditions may result in vegetation shifts at the southern edge of the distribution of the species.

The effect of high fire frequency on the species composition of Mediterranean-type plant communities is reported on the basis of shrubland stands located in Catalonia (Spain) that have experienced from 1 to 5 fires over the last 31 years. We focused on changes in the abundance of species, grouped according to post-fire regenerative traits (resprouting and seed germination) and life form (shrubs, herbaceous graminoids, and herbaceous non-graminoids). High fire frequency was related to a low abundance of obligate resprouter and obligate seeder shrubs. In the latter group, Cistus sp. disappeared in stands with high fire frequency and showed a maximum abundance in stands with low fire frequency. The abundance of facultative resprouter shrubs did not change with fire frequency. This group thus became dominant in the shrub layer at high fire frequency due to the low abundance of obligate resprouter and obligate seeder shrubs. These changes in the abundance of shrub species involve changes in the patterns of relative dominance of regenerative syndromes, in line with fire frequency. An examination of life forms revealed that the abundance of herbaceous non-graminoids and herbaceous graminoids was higher in stands with high fire frequency and the graminoid Brachypodium retusum was dominant at all fire frequencies. These results suggest a loss in the resilience of shrubs after frequent fires, leading to a simplification of vegetation structure, with a shift from shrubland to grassland-type communities, thereby probably enhancing a potential positive herb–fire feedback.Nomenclature: Bolos et al., 1990.

The southernmost European natural and planted pine forests are among the most vulnerable areas to warming-induced drought decline. Both drought stress and management factors (e.g., stand origin or reduced thinning) may induce decline by reducing the water available to trees but their relative importances have not been properly assessed. The role of stand origin - densely planted vs. naturally regenerated stands - as a decline driver can be assessed by comparing the growth and vigor responses to drought of similar natural vs. planted stands. Here, we compare these responses in natural and planted Black pine (Pinus nigra) stands located in southern Spain. We analyze how environmental factors - climatic (temperature and precipitation anomalies) and site conditions - and biotic factors - stand structure (age, tree size, density) and defoliation by the pine processionary moth - drive radial growth and crown condition at stand and tree levels. We also assess the climatic trends in the study area over the last 60. years. We use dendrochronology, linear mixed-effects models of basal area increment and structural equation models to determine how natural and planted stands respond to drought and current competition intensity. We observed that a temperature rise and a decrease in precipitation during the growing period led to increasing drought stress during the late 20th century. Trees from planted stands experienced stronger growth reductions and displayed more severe crown defoliation after severe droughts than those from natural stands. High stand density negatively drove growth and enhanced crown dieback, particularly in planted stands. Also pine processionary moth defoliation was more severe in the growth of natural than in planted stands but affected tree crown condition similarly in both stand types. In response to drought, sharp growth reduction and widespread defoliation of planted Mediterranean pine stands indicate that they are more vulnerable and less resilient to drought stress than natural stands. To mitigate forest decline of planted stands in xeric areas such as the Mediterranean Basin, less dense and more diverse stands should be created through selective thinning or by selecting species or provenances that are more drought tolerant. © 2013 Elsevier B.V., We are grateful for support from the Spanish FPU PhD Grant program (AP2007-04747) (Ministerio de Educación, Spain) and the financial support from University of Córdoba-Campus de Excelencia ceiA3 to the first author, and the MEC Project INTERBOS (CGL2008-04503-CO3-02), DIVERBOS (CGL2011-30285-C02-02); and AEMET (Agencia Estatal de Meteorologia) for providing meteorological data. We thank the support of “Agencia Andaluza del Agua y Medio Ambiente” (J.M. Ruiz-Navarro and all the members of “Red de Equilibrios Biológicos de Andalucía”) and Consejería de Medio Ambiente, Junta de Andalucía. We thank J.M. Grau, F. Artero, A. Carmen, M. Sanchez Gonzalez and M. Minaya for the laboratory and fieldwork support. MAZ and RSS were supported by SUM2008-00004-C03.01 (INIA) and CEXTREME; FP7-ENV-2008-1-226701. AFC and RSS were supported by INIA-RTA (RTA2010-00065-00-00). The first author thanks members of WSL for their useful comments. J.J. Camarero thanks ARAID and collaborative efforts within the Globimed network (http://www.globimed.net).

La conca Mediterrània és un territori especialment idoni per estudiar els impactes que tenen les pertorbacions relacionades amb els usos del territori i el canvi climàtic sobre la demografia dels seus boscos. En aquesta regió la disponibilitat d'aigua és un factor limitant en els boscos, on les sequeres són freqüents i es preveu que siguin més recurrents en el futur. La conca Mediterrània representa el límit meridional de distribució d'importants espècies arbòries de l'Hemisferi Nord, i aquestes poblacions són, probablement, particularment vulnerables a l'augment de l'aridesa. En aquest sentit, durant les últimes dècades un augment generalitzat en la defoliació dels boscos i episodis localitzats de mortalitats molt elevades s'han associat a períodes de sequera. D'altra banda, l'expansió i densificació dels boscos després de l'abandonament agrícola i de la gestió forestal tradicional han estat particularment intenses en aquesta regió durant l'últim segle. Aquests canvis poden resultar en un augment de la competència entre els individus pels recursos, amb una tendència pels processos de autotala, exacerbant la vulnerabilitat dels boscos durant episodis de sequera. A més, a la conca Mediterrània el foc determina la dinàmica i els patrons estructurals i paisatgístics de la vegetació, i l'aridesa determina la vulnerabilitat dels boscos al foc. El pi roig (Pinus sylvestris L.) és una de les espècies d'arbre més àmpliament distribuïdes de l'Hemisferi Nord. El límit sud-oest de l'àrea de distribució del pi roig es situa a la península Ibèrica, on es troben poblacions importants als Pirineus i algunes poblacions disperses en localitats més meridionals i seques. Durant el segle XX els boscos de pi roig s'han densificat i la seva àrea de distribució s'ha expandit notablement a causa dels canvis d'usos del sòl i de la gestió forestal. D'altra banda, hi ha indicis que durant les últimes dècades en aquesta regió les poblacions de pi roig estan patint episodis de mortalitat associats a sequera. A més, els focs de copa han afectat alguns dels seus boscos durant els últims anys. Amb aquesta tesi es pretén aprofundir en l’estudi dels patrons demogràfics de creixement, mortalitat, establiment i reproducció dels boscos de pi roig (Pinus sylvestris L.) al seu límit meridional (i sec) en resposta a les pertorbacions (incendis, sequeres, canvis en els usos del sòl), com aquests varien amb els gradients ambientals al llarg de diferents escales espacials i si aquests processos poden originar canvis en la vegetació. Els principals resultats de la tesi són: (1) Els boscos de pi roig a la península Ibèrica són climàticament vulnerables al foc, i aquesta vulnerabilitat podria augmentar substancialment com a conseqüència del canvi climàtic. Aquest fet, sumat a la maca de mecanismes efectius de regeneració de l’espècie, pot dur a canvis ràpids en la vegetació en zones actualment dominades pel pi roig. (2) Els processos de competència i autotala esdevenen els principals factors que expliquen els patrons demogràfics i, per tant, l’abandonament de les activitats agràries i forestals durant el segle XX són la principal pertorbació que explica els processos emergits. Tanmateix, les sequeres i les limitacions abiòtiques estan desencadenant processos de declivi, aparentment en boscos amb una estructura més desenvolupada, i.e. major abundància d’arbres grans. Malgrat que els efectes de la sequera són clars a escala local, i és previsible que es facin més perceptibles en el futur, no es detecta actualment un procés generalitzat de declivi a escala regional. (3) La regeneració del pi roig és en general baixa i, en particular, aquesta és encara menor en zones afectades per episodis de declivi, la qual cosa suggereix que es poden produir canvis en la vegetació a mig termini. Hi ha indicis que aquests canvis poden resultar de l’abandonament agrícola i dels canvis recents en els usos forestals. (4) El declivi a nivell de rodal i la defoliació a nivell d’individu afecten l’esforç reproductiu del pi roig, la qual cosa podria explicar, en part, el seu baix reclutament en zones afectades per episodis de declivi., The Mediterranean basin is an ideal area to study the impacts of disturbances related to land-use changes and climate change on the demography of forests. In this region, water availability is a limiting factor in forests, where droughts are common and are expected to be more frequent in the future. The Mediterranean basin represents the southern limit of distribution of important tree species in the Northern Hemisphere, and these populations are probably particularly vulnerable to increased aridity. During the last decades a widespread increase in defoliation of forests and localized episodes of high mortality have been associated to drought periods. Moreover, the expansion and densification of forests after agricultural abandonment and traditional forest management have been particularly strong in this region during the last century. These changes may result in increased competition for resources among individuals, with a tendency for self-thinning processes, exacerbating the vulnerability of forests during drought periods. In addition, in the Mediterranean basin, fire determines the dynamics and structural patterns of vegetation, and dryness determines the vulnerability of forests to fire. Scots pine (Pinus sylvestris L.) is one of the most widely distributed tree species in the Northern Hemisphere. The southwestern distribution limit of Scots pine is the Iberian Peninsula, with important populations located in the Pyrenees and some scattered populations in southern and dry locations. There have been important land use changes in the Iberian Peninsula during the last century, including the abandonment of agropastoral activities in mountain areas, the abandonment of forest exploitation, and a large-scale afforestation starting in the 1940s that intensified during the 1950s and has continued albeit at lower rates until recent decades. As a result, stand density has increased in many forests and the range of Scots Pine has expanded noticeably. Moreover, in recent decades Scots pine forest decline has been related to extreme drought episodes in several populations in the Iberian Peninsula, and crown fires have affected some populations. This thesis aims to study the demographic patterns of growth, mortality, reproduction and establishment of Scots pine (Pinus sylvestris L.) at the southern limit (dry) of its distribution in response to disturbances (fires, droughts, changes in land use). The main results of this thesis are: (1) Scots pine forests in the Iberian Peninsula are climatically vulnerable to fire, and this vulnerability could increase substantially as a result of climate change. This fact, added to the lack of effective mechanisms of regeneration, can lead to rapid changes in vegetation in areas currently dominated by Scots pine. (2) Competition and self-thinning are the main factors explaining demographic patterns. Therefore, the abandonment of agriculture and management during the last century are the main disturbances explaining the emerged processes. However, droughts and abiotic constraints are triggering Scots pine decline, apparently in forests with greater abundance of large trees. (3) Scots pine regeneration is lower in declining forests, suggesting that vegetation shifts could occur in the future. These changes could be result of recent land-use changes. (4) Drought stress affects the reproductive effort of individuals, which could contribute to the low recruitment in declining forests.