Suchergebnisse

16 Pags. This article as a Preface by the Editors belonging to a special issue of Catena titled "Geoecology in Mediterranean mountain areas. Tribute to Professor José María García Ruiz". The definitive version is available at: http://www.sciencedirect.com/science/journal/03418162 ; The origin of this special issue arose from a scientific meeting held in Logroño (Spain) in October 2014, under the theme Geoecology in extreme environments: mountains and semiarid areas ( Arnáez et al., 2014). The main motivation of the event was to recognise, on the occasion of his retirement, the outstanding contribution of Prof. José María García-Ruiz to the progress of Geoecology in Mediterranean mountain areas. Prof. García-Ruiz (Zaragoza, 1949) was lecturer, between 1974 and 1987, at the University of Cáceres and La Rioja. As staff Scientist and later Professor at the Spanish National Research Council (CSIC), he was Head of the Pyrenean Institute of Ecology (IPE-CSIC) (1987–1990) and Head of the Department of Global Change at the same institute, President of the Spanish Society of Geomorphology (1994–1996), besides a productive and tireless researcher. He has published more than 300 scientific articles, one third of them in international journals, and more than 35 books. He has participated in 40 research projects funded by the European Commission, Spanish and regional governments. With his enthusiasm and dedication he has inspired and encouraged a wide number of geographers and geomorphologists, including 10 PhD students and a great number of collaborators, most of them now working at different Universities and Research Centres around the world. ; Peer reviewed

22 páginas, 6 figuras, 1 tabla ; This work presents a palaeoenvironmental interpretation of the Upper Pleistocene–Holocene sedimentary sequence recorded in the Valsalada saline wetland system (Monegros, Central Ebro Basin). This morphosedimentary system developed on karstified, gypsiferous bedrock and was mainly fed by local saline groundwater. Based on geomorphological, sedimentological, palynological and radiocarbon data, three depositional units have been differentiated: 1) a lacustrine unit, which accumulated under cold/cool and humid environmental conditions at 41–40 kyr cal BP, 2) a fluvial unit that was deposited under arid climatic conditions with cold episodic periods from 14 to 3.5 kyr cal BP, and 3) an alluvial slope unit associated with arid climate with human influence during the Late Roman Period (1.5 kyr cal BP). The morphosedimentary evolution of the Valsalada system is strongly influenced by the geomorphic setting (small catchment with karstic depressions and low gradient slopes on gypsum), the hydrological availability (runoff and groundwater discharges) related to climate variability during the Late Pleistocene–Holocene, and the human activities developed in the area during historical times. The response of the Valsalada system displays a low sensitivity to short-term climatic changes but responds to major long-term climatic conditions, improving the regional paleoenvironmental picture of the Late Quaternary in NE Spain. ; This work was supported by projects CGL2006-08973/BTE, CGL2009-10455/BTE, CGL2009-07992 and CSD2007-00067 of the Spanish Government and the European Regional Development Fund. This is a contribution by PaleoQ, GCC and Cuencas Sedimentarias Continentales groups (Aragón Regional Government). We are grateful to the anonymous reviewers for their helpful comments. ; Peer reviewed

15 páginas, 5 figuras, 1 tabla.-- Artículo en prensa.-- El PDF del artículo es su versión post-print. ; We present a palaeoclimatic reconstruction of the last glacial cycle in Iberia (ca. 120,000–11,600 cal yrs BP) based on multi-proxy reconstructions from lake sediments with robust chronologies, and with a particular focus on abrupt climate changes. The selected lake sequences provide an integrated approach from northern Iberia exploring temperature conditions, humidity variations and land-sea comparisons during the most relevant climate transitions of the last glacial period. Thus, we present evidence that demonstrates: (i) cold but relatively humid conditions during the transition from MIS 5 to MIS 4, which prevailed until ca. 60,000 cal yrs BP in northern Iberia; (ii) a general tendency towards greater aridity during MIS 4 and MIS 3 (ca 60,000 to 23,500 cal yrs BP) punctuated by abrupt climate changes related to Heinrich Events (HE), (iii) a complex, highly variable climate during MIS 2 (23,500 to 14,600 cal yrs BP) with the "Mystery Interval" (MI: 18,500 to 14,600 cal yrs BP) and not the global Last Glacial Maximum (LGM: 23,000 to 19,000 cal yrs BP) as the coldest and most arid period. The last glacial transition starts in synchrony with Greenland ice records at 14,600 cal yrs BP but the temperature increase was not so abrupt in the Iberian records and the highest humidity was attained during the Allerød (GI-1a to GI-1c) and not during the Bølling (GI-1e) period. The Younger Dryas event (GS-1) is discernible in northern Iberian lake records as a cold and dry interval, although Iberian vegetation records present a geographically variable signal for this interval, perhaps related to vegetation resilience. ; The funding for this study mainly derives from LIMNOCLIBER (REN2003-09130-C02-02), LIMNOCAL (CGL2006-13327-C04-01), GRACCIE-CONSOLIDER (CSD2007-00067) and DINAMO (CGL2009- 07992) projects, provided by the Spanish Inter-Ministry Commission of Science and Technology (CICYT), and the VILLARQUEMADO (P196/2005) project from the Aragón Regional Government (DGA). A. Moreno acknowledges the funding from the "Ramón y Cajal" postdoctoral program. ; Peer reviewed

We investigate Lake Estanya's diatom and pollen records from the Late Glacial (LG) to the Early Holocene (EH), in order to compare limnological and vegetation responses to common climate forcing. The biotic changes recognized in this study largely agree with the hydrological evolution of the lake described previously for the same period. The diatom record shows high sensitivity to fluctuations in both lake level and salinity concentration as a consequence of climate shifts. In addition vegetation results indicate that the area could have played an important role as regional vegetation refuge. Shallow lake conditions during the Last Glacial Maximum (LGM) were punctuated by relatively deeper freshwaters between 19.3 and 18.6. cal. kyr BP and at 18.0. cal. kyr BP, as recorded by diatom shifts. A subsequent increasing aridity trend, coinciding with the Mystery Interval (MI), affected the diatom accumulation rates, which dropped to its minimum values between 17.2 and 14.7. cal. kyr BP. Particularly dry and cold conditions during the LGM and MI are supported by the largest values of steppic pollen taxa of the whole sequence, which account for up to 40%. However, relatively high values of Betula during the Heinrich Event 1 suggest a plausible regional vegetation refuge. Abrupt cooling and warming episodes within the LG triggered remarkable ecological threshold crossings in the diatom communities, especially during the stadial/interstadial episodes. At this point, the vegetation reflects the onset of warm conditions during the Bølling/Allerød with the partial substitution of Betula by Marcescent and Evergreen Quercus, which probably indicates the arrival of temperate taxa to the area and the likely migration of birch to higher altitudes. The Younger Dryas Stadial shows a complex ecological response. Diatoms are very poorly preserved, but aquatic taxa reach their highest values. An increase in Marcescent Quercus during this cold stage lends further support to the hypothesis that this is a regional vegetation refuge. Low lake levels recorded during the EH affected the development and preservation of diatom communities. A delay in the onset of humid conditions for the EH is also supported by the vegetation composition, characterized by the maximum expansion of Juniperus. © 2013 Elsevier B.V. ; This research has been funded through the projects LIMNOCLIBER (REN2003-09130-C02-02), IBERLIMNO (CGL2005-20236-E/ CLI), LIMNOCAL (CGL2006-13327-C04-01), PALEODIVERSITAS (CGL2006-02956/BOS), GLOBALKARST (CGL2009-08415), GRACCIE-CONSOLIDER (CSD2007-00067), DINAMO (CGL2009-07992), DINAMO2 (CGL2012-33063); provided by the Spanish Inter-Ministry Commission of Science and Technology (CICYT); and PIRINEOSABRUPT (PM073/2007), provided by the Diputación General de Aragón. Mario Morellón Marteles and Graciela Gil-Romera hold post-doctoral contacts funded by the "JAE-Doc/CSIC" ref.- and "Juan de la Cierva" (grant ref. JCI2009) programs respectively. Ana Pérez-Sanz has been supported by a PhD Fellowship provided by the Aragon Government. We also thank Beatriz Bueno and Aída Adsuar for lab assistance. Finally, we are grateful to Antonia Andrade Olalla for helping in initial pollen analyses and to Joan Gomà for assistance in diatom taxonomic determinations. Two referee's constructive criticism and suggestions helped improved a former version of this paper. ; Peer Reviewed

47 páginas, 2 tablas, 6 figuras ; A multiproxy study of sediments cores from Zoñar Lake (37º29'00''N, 4º41'22'' W, 300 m a.s.l.) supported by 11 14C AMS dates provides the first high-resolution centennial-scale reconstruction of past humidity changes in southern Spain during the last 4000 years. Arid periods occurred prior to 2.9 cal. kyr BP and during 1.3-0.6 cal. kyr BP (Medieval Climate Anomaly). The most humid period occurred during 2.6-1.6 cal. kyr BP encompassing the late Iron Age-Iberian and Roman epochs. Two humid periods of lower intensity occurred between 0.8 – 0.6 cal kyr BP (1200 – 1400 AD) and about 400 cal. yr BP (around 1600 AD) coinciding with the onset of the Little Ice Age. Humid conditions are synchronous with a decline in solar output and seem to correspond to atmospheric patterns similar to negative NAO phases. Arid conditions show better correlation with northern Africa climate evolution suggesting a possible link to subtropical dynamics. The geographic location of Zoñar Lake and the robust chronology provides an opportunity to improve our understanding of the climate evolution in mid latitudes during the Late Holocene and to evaluate subtropical and high latitude factors in Mediterranean climate evolution. ; Financial support for this study was provided by the Spanish Ministry of Science and Education (projects LIMNOCLIBER REN 2003-09130-CO2-02, IBERLIMNO CGL2004-20236-E, CALIBRE CGL2006-13327-C04/CLI and CGL-2006-2956-BOS) and Andalusian Government (PAI group RNM-328). A. Moreno acknowledges the funding from the European Commission's Sixth Framework Program (Marie Curie Outgoing International Fellowships, proposal 021673-IBERABRUPT).We thank comments and suggestions from Herb Wright, who helped with a previous version of the manuscript, Francisco Mezquita and Javier Marco for their advice on ostracod identification and José.S. Carrión and Noemí Fuentes for pollen samples preparation. We also thank Achim Brauer for his support and dedication during the varve counting. We are also very grateful to the LRC (Minnesota, USA), and particularly to Doug Schnuremberger, Mark Shapley and Anders Noren for making possible the 2004 expedition. A.C. Stevenson and an anonymous reviewer provided constructive criticisms and suggestions. ; Peer reviewed

The final version is available at: http://www.sciencedirect.com/science/journal/00310182 ; Although the Central Ebro Basin (Northeastern Iberian Peninsula) is both the northernmost semi-arid area in Europe and one of the regions with the largest biodiversity, it has been insufficiently studied in terms of past climate variability due to the scarcity of suitable sites for palaeoenvironmental analyses. Previous studies from ephemeral saline lakes in the area, mainly based on palynological data, show abrupt and rapid arid/humid transitions throughout the last glacial cycle highlighting a complex palaeohydrological evolution. New cores from two saline lakes (La Playa and La Salineta) in the Los Monegros area provide multi-proxy records including sedimentology, geochemistry, and pollen indicators. This study, together with a detailed and comprehensive review of the main saline records from the Central Ebro Basin, enables us tos reconstruct a comprehensive picture of the palaeoclimate evolution during the last glacial cycle. One of the main results of this study is the alternation of humid and dry phases as a characteristic of the climate evolution during the Lateglacial. Additionally, the study suggests an important role of the increased flow from the Pyrenean rivers during deglaciation in the hydrological balance of the Central Ebro Basin. It is found that the Early Holocene is the wettest period over the sequence studied contrasting with the arid Middle Holocene interval, which is frequently absent as a result of intense aeolian erosive processes. Although anthropogenic activity partially masks the climate signal from the palynological data in the uppermost part of the sequences studied, there are some sedimentological evidences for a climate change during the last 2000 years resulting in a recovery of average saline lake levels in the Central Ebro Basin. ; This work was part of the project "Arid periods in the Mediterranean area since the Last Glacial Maximum" (REN 2000-1136/CLI), and LIMNOCLIBER (REN 2003-09130-C02-02), funded by the CICYT, and the project "Environmental evolution and effects of the anthropogenic impact in the lacustrine complex of Bujaraloz–Sástago" (PO23/2001), funded by the Aragon regional government (DGA). We acknowledge the Pyrenean Institute of Ecology (CSIC) for financial support. ; Peer reviewed

18 páginas, 1 tabla, 3 figuras ; This paper reviews multi-proxy paleoclimatic reconstructions with robust age-control derived from lacustrine, dendrochronological and geomorphological records and characterizes the main environmental changes that occurred in the Southern Pyrenees during the last millennium. Warmer and relatively arid conditions prevailed during the Medieval Climate Anomaly (MCA, ca. 900–1300 AD), with a significant development of xerophytes and Mediterranean vegetation and limited deciduous tree formations (mesophytes). The Little Ice Age (LIA, 1300–1800 AD) was generally colder and moister, with an expansion of deciduous taxa and cold-adapted montane conifers. Two major phases occurred within this period: (i) a transition MCA–LIA, characterized by fluctuating, moist conditions and relatively cold temperatures (ca. 1300 and 1600 AD); and (ii) a second period, characterized by the coldest and most humid conditions, coinciding with maximum (recent) glacier advances (ca. 1600–1800 AD). Glaciers retreated after the LIA when warmer and more arid conditions dominated, interrupted by a short-living cooling episode during the late 19th to early 20th centuries. Some records suggest a response to solar activity with colder and slightly moister conditions during solar minima. Centennial-scale hydrological fluctuations are in phase with reconstructions of NAO variability, which appears to be one of the main climate mechanisms influencing rainfall variations in the region during the last millennium. ; This research has been funded by the Spanish InterMinistry of Science and Technology (CICYT), through the projects LIMNOCAL (CGL2006-13327-C04-01), GLOBALKARST (REN2003-09130-C02-02), GRACCIECONSOLIDER (CSD2007-00067), DINAMO (CGL2009-645- 07992) and CRYOMONT (CGL2010-19724). Additional support was provided by the Spanish National Parks Agency through the project HORDA (083/2009). M. Morell´on is supported by a Postdoctoral fellowship funded by the Spanish Ministry of Education and Science through FECYT (Spanish Foundation for Science and Technology), A. P´erez-Sanz is supported by a pre-doctoral fellowship funded by the Regional Aragonese Government and A. Moreno acknowledges the "Ram´on y Cajal" postdoctoral program for funding. Miguel Sevilla is acknowledged for his help with Fig. 1. We thank Gerardo Benito, William Fletcher, Lourdes L´opez-Merino and anonymous referee for their helpful comments and their criticism, which led to a considerable improvement of the manuscript. ; Peer reviewed

Evolution and change in agricultural practice is a major factor in the codification of social relations and represents one of the main resources employed by human societies to establish a durable relationship with their environment. Using a multi-proxy integrated approach, this paper seeks to decipher the long-term dynamics that have shaped agricultural landscapes in the Basque Country (N Spain). Social and economic indicators (archival records, toponymy and oral sources) are used along with geological core sampling (geochemistry, magnetic, palynological and carpological analyses) to reconstruct a diachronic sequence of human settlement and agricultural management in the village of Aizarna over the last ~1500 years. The oldest records obtained refer to non-agricultural human activities dating back to the Roman period. Later on, traces of agricultural landscape-transformation can be divided into four main phases: 1) the onset of terraced agriculture, defined by the clearance and terracing of previous forested areas during the Early Middle Ages; 2) a Late Medieval reorganisation, with new terraces being (re)constructed close to dispersed farmsteads, linked to the emergence of the modern rural landscape; 3) a new model of intensive polyculture developed during the Modern period as a consequence of the introduction of new crops of American origin; and 4) the mechanisation and commercialisation of the agricultural production over the 20th century. These results provide a valuable pathway for the investigation of currently inhabited rural contexts, and offer, for the first time in this region, an overview on long-term landscape construction in the Atlantic areas of the Basque Country. ; Fieldwork was funded by the Culture Department of the Provincial Government of Gipuzkoa, and by the Project "Peasant Agency and socio-political complexity in the northwest of the Iberian Peninsula during the Middle Ages" (Ministry of Economy, AEI/FEDER EU HUM2016-76094-C4-2-R), jointly participated in by the Research Group on Heritage and Cultural Landscapes (Basque Government, IT936-16) and the Group of Rural Studies (UPV/EHU-CSIC Associated Unit). Á. Carrancho acknowledges the financial support given by the Consejería de Educación, Junta de Castilla y León (project BU235P18) with also FEDER funding.

28 páginas, 4 figuras, 2 tablas ; The Central Ebro River Basin (NE Spain) is the most northern area of truly semi-arid Mediterranean climate in Europe and prehistoric human occupation has been strongly influenced by these unique environmental conditions. The Bajo Aragón region (SE Ebro River Basin) was intensively populated during the Early Holocene (9400 – 8200 cal. yr B.P.) but the settlements were abandoned abruptly at around 8200 cal. yr B.P. Modern climate conditions single out this region due to the harsh environment, characterized by the highest absolute summer temperatures of the Ebro River Basin. We propose that this "archaeological silence" was caused by the regional impact of the global abrupt 8.2 ka cold event. Available regional paleoclimate archives demonstrate the existence of an aridity crisis 8200 years ago that interrupts the humid Early Holocene. That environmental crisis would have forced hunter-gatherers groups from the Bajo Aragón to migrate to regions with more favourable conditions (i.e. more humid mountainous areas) and only return in the Neolithic. Coherently, archaeological sites persist during this crisis in the nearby Iberian Range (Maestrazgo) and the North Ebro River area (Pre-Pyrenean mountains and along the northwestern Ebro Basin). ; This work was part of the projects: "Palinología y Paleoclima: Cambios Climáticos y/o Antropogénicos y Evolución de la vegetación" funded by CSIC (Programa Intramural 2007-2008); "Los cambios climáticos abruptos y su influencia en los ecosistemas y las sociedades humanas en el Pirineo central y occidental" funded by the Aragón Regional Government (DGA) and two projects funded by the Spanish Inter-Ministry Commission of Science and Technology (CICYT): "Cambios climáticos rápidos en la Peninsula Ibérica basados en calibración de indicadores, series instrumentales largas y análisis de alta resolución de registros lacustres (Subproyecto CGL2006-13327-C04-01/CLI)" and "Cazadores-Recolectores del valle del Ebro (HUM 2005-02882)". A. Moreno, M. Morellón, M. Sebastián and MC. Sopena have benefited from a Marie Curie Outgoing International Fellowships (proposal 021673-IBERABRUPT), a DGA fellowship, a FPI fellowship and a FSE-MEC contract, respectively. ; Peer reviewed

30 páginas, 6 figuras ; Combined sedimentary facies, geochemical analyses and pollen spectra from lake records and sedimentological and palynological studies from slope deposits allow the characterization of vegetation and lake level status during glacial times in the central Ebro valley (NE Spain). These records show the presence of some increased effective moisture periods while regional vegetation was dominated by steppe taxa. The longest lake record comes from La Salineta, one of the saline lake in the Los Monegros area; the other lake sequence comes from a sinkhole in the Gállego river floodplain. The slope deposit from Valmadrid is the only periglacial deposit found in the central Ebro valley. Our data indicate that - at least for some intervals during full glacial times – when cold steppe vegetation dominated the region, some lakes experienced more positive water balance than today and run-off was also high. The data are coherent with the hypothesis that – at least for some periods- the ice-age climate of the western Mediterranean was characterized by cold winters, relative intense winter precipitation and summer droughts. Increased flow from the Pyrenean rivers during the early deglaciation could also play a significant role in the paleohydrological conditions in the central Ebro valley. However, La Salineta records also show the occurrence of arid periods during glacial times, indicating a complex picture of hydrological and moisture evolution in the central Ebro valley during the LGM. ; The research in the central Ebro valley was funded by the Aragonese Regional Government (Project PO23/2001: "Environmental evolution and human impact in the Bujaraloz-Sástago lake complex. Scientific bases for conservation and sustainable development of the Los Monegros saline lakes"), and the Spanish Government (CICYT Project REN2000 "Arid Periods in the Mediterranean areas of the Iberian Peninsula since the Last Glacial maximum: Chronology, characterization and paleoclimate implications" ). ; Peer reviewed

40 Pag., 2 Tabl., 6 Fig. The definitive version is available at: http://www.sciencedirect.com/science/journal/00335894 ; Palynological, sedimentological and stable isotopic analyses of carbonates and organic matter performed on the El Portalet sequence (1802 m a.s.l., 42°48′00N, 0°23′52W) reflect the paleoclimatic evolution and vegetation history in the central-western Spanish Pyrenees over the last 30,000 yr, and provide a high-resolution record for the late glacial period. Our results confirm previous observations that deglaciation occurred earlier in the Pyrenees than in northern European and Alpine sites and point to a glacial readvance from 22,500 to 18,000 cal yr BP, coinciding with the global last glacial maximum. The patterns shown by the new, high-resolution pollen data from this continental sequence, chronologically constrained by 13 AMS 14C dates, seem to correlate with the rapid climate changes recorded in Greenland ice cores during the last glacial–interglacial transition. Abrupt events observed in northern latitudes (Heinrich events 3 to 1, Oldest and Older Dryas stades, Intra-Allerød Cold Period, and 8200 cal yr BP event) were also identified for the first time in a lacustrine sequence from the central-western Pyrenees as cold and arid periods. The coherent response of the vegetation and the lake system to abrupt climate changes implies an efficient translation of climate variability from the North Atlantic to mid latitudes. ; This study was partially funded by projects REN 2000-1136/CLI, REN2003-02499-GLO and REN-2003-09130-CO202, by the CICYT and PI-17/00739/FS/01 (Fundación Séneca). Funding for P.G.S. was provided by the Spanish Government (post-doctoral grant in UPS-Toulouse, France). ; Peer reviewed

18 páginas, 7 figuras, 5 tablas.-- El PDF es la versión post-print del artículo. ; The multi-proxy analysis of sediment cores recovered in karstic Lake Estanya (42°02′ N, 0°32′ E; 670 m a. s. l., NE Spain), located in the transitional area between the humid Pyrenees and the semi-arid Central Ebro Basin, provides the first high-resolution, continuous sedimentary record in the region, extending back the last 21 000 years. The integration of sedimentary facies, elemental and isotopical geochemistry and biogenic silica, together with a robust age model based on 17 AMS radiocarbon dates, enables precise reconstruction of the main hydrological and environmental changes in the region during the last deglaciation. Arid conditions, represented by shallow lake levels, predominantly saline waters and reduced organic productivity occurred throughout the last glacial maximum (21–18 cal kyrs BP) and the lateglacial, reaching their maximum intensity during the period 18–14.5 cal kyrs BP (including Heinrich event 1) and the Younger Dryas (12.9–11.6 cal kyrs BP). Less saline conditions characterized the 14.5–12.6 cal kyrs BP period, suggesting higher effective moisture during the Bölling/Allerød. The onset of more humid conditions started at 9.4 cal kyrs, indicating a delayed hydrological response to the onset of the Holocene which is also documented in several sites of the Mediterranean Basin. Higher, although fluctuating, Holocene lake levels were punctuated by a mid Holocene arid period between 4.8 and 4.0 cal kyrs BP. A major lake-level rise occurred at 1.2 cal kyrs BP, conducive to the establishment of conditions similar to the present and interrupted by a last major water level drop, occurring around 800 cal yrs BP, which coincides with the Medieval Climate Anomaly. The main hydrological stages in Lake Estanya are in phase with most Western Mediterranean and North Atlantic continental and marine records, but our results also show similarities with other Iberian and northern African reconstructions, emphasizing peculiarities of palaeohydrological evolution of the Iberian Peninsula during the last deglaciation. ; This research has been funded through the projects LIMNOCLIBER (REN2003-09130-C02-02), IBERLIMNO (CGL2005-20236-E/ CLI), LIMNOCAL (CGL2006-13327-C04-01), PALEODIVERSITAS (CGL2006-02956/BOS), GRACCIE (CSD2007-00067); provided by the Spanish Inter-Ministry Commission of Science and Technology (CICYT); and PIRINEOSABRUPT (PM073/2007), provided by the Diputación General de Aragón. Additional funding for XRD analyses (Univ. of Cádiz) and geochemical analyses (EEZ-CSIC and MARUM Centre) was provided by the Aragonese Regional Government – CAJA INMACULADA by means of 2 travel grants. M. Morellón and J.P. Corella are supported by PhD contracts with the CONAIþ D (Aragonese Scientific Council for Research and Development) and A. Moreno and M. Rico hold post-doctoral contracts funded by the ESF ('Marie Curie programme') and the Spanish Ministry of Science and Innovation ('Juan de la Cierva programme'), respectively. ; Peer reviewed

Understanding long-term fire ecology is essential for current day interpretation of ecosystem fire responses. However palaeoecology of fire is still poorly understood, especially at high-altitude mountain environments, despite the fact that these are fire-sensitive ecosystems and their resilience might be affected by changing fire regimes. We reconstruct wildfire occurrence since the Lateglacial (14.7. cal. ka BP) to the Mid-Holocene (6. cal. ka BP) and investigate the climate-fuel-fire relationships in a sedimentary sequence located at the treeline in the Central Spanish Pyrenees. Pollen, macro- and micro-charcoal were analysed for the identification of fire events (FE) in order to detect vegetation post-fire response and to define biomass-fire interactions. mean fire intervals (mfi) reduced since the Lateglacial, peaking at 9-7.7. cal. ka BP while from 7.7 to 6. cal. ka BP no fire is recorded. We hypothesise that Early Holocene maximum summer insolation, as climate forcing, and mesophyte forest expansion, as a fuel-creating factor, were responsible for accelerating fire occurrence in the Central Pyrenees treeline. We also found that fire had long-lasting negative effects on most of the treeline plant communities and that forest contraction from 7.7. cal. ka BP is likely linked to the ecosystem's threshold response to high fire frequencies. © 2014 Elsevier B.V. ; This research has been funded by the projects DINAMO (CGL2009-07992) (funding EGPF — grant ref. BES-2010-038593 and MSC), DINAMO2 (CGL2012-33063), ARAFIRE (2012 GA LC 064), GRACCIE-CONSOLIDER (CSD2007-00067). GGR was funded by the Juan de la Cierva Program (grant ref. JCI2009-04345) and JAE-Doc CSIC Program, LLM was supported by a postdoctoral MINT fellowship funded by the Institute for the Environment (Brunel University), AMC is a Ramón y Cajal fellow (ref: RYC-2008-02431), APS holds a grant funded by the Aragon Government (ref. 17030G/5423/480072/14003) and JAE holds a grant funded by the Basque Country Government (BFI-2010-5). We are indebted to Beatriz Bueno and Aida Adsuar for sampling processing and laboratory analyses and to César Morales del Molino for productive discussions on the ideas of this paper. We are grateful to Steven M. Holland for providing the free software to calculate rarefaction (Analytic Rarefaction), which is available at http://strata.uga.edu/software/. ; Peer Reviewed

The sedimentological, geochemical and palynological analyses performed in the Conquezuela palaeolake (41°11′N; 2°33′W; 1124 m a.s.l.) provide a detailed, multiproxy palaeoenvironmental reconstruction in one of the key areas of inner Iberian Neolithic colonization. Combined with archaeobotanical and archaeological data from well-dated settlements along the Conquezuela–Ambrona Valley we investigate how environmental conditions may affect both socio-economic adaptations and livelihood strategies of prehistoric communities. The first evidences of early Neolithic occupation in the valley ca. 7250–6450 cal yr BP (5300–4500 BC) coincided with the onset of a period (7540–6200 cal yr BP, 5590–4250 BC) with higher water availability and warmer climate as alluvial environments were substituted by carbonate-wetland environments in the basin. The Conquezuela record supports an early Neolithic colonization of the inner regions of Iberia favored by warmer and humid climate features and with preferential settlement patterns associated to lakes. The maximum human occupation of the valley occurred during the mid–late Neolithic and Chalcolithic (6200–3200 cal yr BP, 4250–1250 BC) as evidenced by the high number of archaeological sites. Although a number of hydrological oscillations have been detected during this period, the intense landscape transformation at basin-scale, leading to a deforested landscape, was largely a consequence of widespread farming and pastoral practices. Socio-economic activities during Bronze, Iron and Roman times modified this inherited landscape, but the second largest ecosystem transformation only occurred during Mediaeval times when a new agrarian landscape developed with the expansion of stockbreeding transhumance. The current vegetation cover characterized by patches of holm and marcescent oaks and fields reflects an intense human management combining both extensive herding with agrarian activities in order to transform the previous forested landscape into a dehesa-like system. ; The funding for the present study derives from DINAMO2 (CGL-BOS 2012-33063) and AGRIWESTMED (ERC Grant Agreement #230561) projects, provided by the Spanish Inter-Ministry Commission of Science and Technology (CICYT) and the European Research Council under the European Union's Seventh Framework Programme (FP7/2007–2013). XRF data were obtained at the XRF Core Scanner Laboratory (CRG Marine Geosciences, University of Barcelona). Josu Aranbarri acknowledges the predoctoral funding provided by the Basque Country Government (ref: FI-2010-5). Graciela Gil-Romera hold a post-doctoral contract funded by "Juan de la Cierva" (ref: JCI2009-04345) program. Eduardo García-Prieto and Maria Leunda are supported by predoctoral FPI grants BES-2010-038593 and BES-2013-063753, respectively. We also thank Elena Royo for her help with the lab procedures and the two anonymous referees for their valuable suggestions. ; Peer reviewed

Palynological, sedimentological and geochemical analyses performed on the Villarquemado paleolake sequence (987 m a.s.l, 40°30′N; 1°18′W) reveal the vegetation dynamics and climate variability in continental Iberia over the last 13,500 cal yr BP. The Lateglacial and early Holocene periods are characterized by arid conditions with a stable landscape dominated by pinewoods and steppe until ca. 7780 cal yr BP, despite sedimentological evidence for large paleohydrological fluctuations in the paleolake. The most humid phase occurred between ca. 7780 and 5000 cal yr BP and was characterized by the maximum spread of mesophytes (e.g., Betula, Corylus, Quercus faginea type), the expansion of a mixed Mediterranean oak woodland with evergreen Quercus as dominant forest communities and more frequent higher lake level periods. The return of a dense pinewood synchronous with the depletion of mesophytes characterizes the mid-late Holocene transition (ca. 5000 cal yr BP) most likely as a consequence of an increasing aridity that coincides with the reappearance of a shallow, carbonate wetland environment. The paleohydrological and vegetation evolution shows similarities with other continental Mediterranean areas of Iberia and demonstrates a marked resilience of terrestrial vegetation and gradual responses to millennial-scale climate fluctuations. Human impact is negligible until the Ibero-Roman period (ca. 2500 cal yr BP) when a major deforestation occurred in the nearby pine forest. The last 1500 years are characterized by increasing landscape management, mainly associated with grazing practices shaping the current landscape. ; The funding for the present study derives from DINAMO (CGL-BOS 2009–07992), DINAMO2 (CGL-BOS 2012–33063), IBERIAN PALEOFLORA (CGL-BOS 2012–31717) and GRACCIE-CONSOLIDER (CSD2007-00067) projects, provided by the Spanish Inter-Ministry Commission of Science and Technology (CICYT). Josu Aranbarri acknowledges the predoctoral funding provided by the Basque Country Government (ref: FI-2010-5). Ana Moreno, Graciela Gil-Romera and Mario Morellón hold post-doctoral contracts funded by "Ramon y Cajal (ref: RYC-2008-02431)", "Juan de la Cierva (ref: JCI2009-04345)" and "JAE DOC CSIC (ref: JAEDOC-2011-026)" programms, respectively. Eduardo García-Prieto is supported by a predoctoral FPI grant (BES-2010-038593). We are very greateful to Aida Adsuar, Beatriz Bueno and Raquel López-Cantero for their assistance in core sampling and laboratory procedures. Josu Aranbarri thanks collegues from the Dipartimento di Biologia Ambientale, especially Alessandra Celant, for continuous encouragement. We would also like to thank Thomas M. Cronin, Anthony C. Stevenson and an anonymous reviewer for their valuable suggestions. ; Peer reviewed