Search

Los pinsapares de Abies pinsapo son una de las formaciones boscosas más originales de la península ibérica. A pesar de la singularidad de estos ecosistemas, hasta el momento ningún análisis de microfósiles polínicos había sido emprendido en aquellos territorios donde esta especie, en peligro de extinción, aún pervive. Con este trabajo se presentan los primeros resultados en los que, haciendo uso del registro fósil, han podido ser identificados los impactos climáticos pasados y los cambios de uso de suelo histórico en la evolución de las poblaciones del sur de la península ibérica para el Holoceno final (1180 AD hasta el presente). Los resultados son comparados con las fluctuaciones climáticas y cambios en el manejo forestal documentados en los últimos ocho siglos. La secuencia de polen muestra una fase de estabilidad estructural y estado de conservación óptimo del pinsapar durante el Período Musulmán (~1180-1400 AD), etapa que se desarrolla en la Anomalía Climática Medieval (ACM). A continuación, se inicia un proceso de degradación de estos bosques en el Período Cristiano concurrente con la Pequeña Edad de Hielo, PEH (ca. 1400-1530 AD). El Período Moderno (1530-1800 AD; PEH) está vinculado a la gestión forestal intensiva, relacionada con la industria naval. Posteriormente, se registra una reducción y declive progresivo de estas formaciones que tiene como punto de partida la Edad Contemporánea (Período Industrial; PI) y que culmina con un paisaje profusamente deforestado en el Calentamiento Reciente (CR).

Precipitation is a key climate parameter of vegetation and ecosystems in the Iberian Peninsula. Here, we use a regional pollen–climate calibration model and fossil pollen data from eight sites from the Atlantic coast to southern Spain to provide quantitative reconstructions of annual precipitation trends and excursions and their regional patterns for the last 11 700 years. The Early Holocene (11 700 to 11 000 cal. a BP) was characterized by high precipitation values followed by a slowly declining trend until about 9000 cal. a BP in the south and about 8000 cal. a BP in the north. From 8000 to 6000 cal. a BP the reconstructed precipitation values are the highest in most records, especially in those located in the Mediterranean climatic region in the southern part of the peninsula, with maximum values nearly 100% higher than the modern reconstructed values. The results suggest a declining precipitation during the Late Holocene in the south, with a positive excursion at around 2500 cal. a BP, while in the north precipitation remained high until 500 cal. a BP. However, the Late Holocene climate reconstructions in the Iberian Peninsula are biased by intensifying human impact on vegetation. The statistical time series analyses using SiZer technique do not indicate any statistically significant high-frequency drought events in the region. In general, our results suggest regional differences in the precipitation patterns between the northern and southern parts of the peninsula, with a more distinct Middle Holocene period of high humidity in the south.

A set of 30 modern pollen samples collected in pine communities of the Gúdar Range (southeastern Iberian System) has been investigated to determine the relationships between pollen percentages and vegetation composition along a ~ 1000 m elevation transect. Pollen representation was estimated by comparing the presence of plant taxa from a recent vegetation survey with pollen spectra. Classification and ordination of modern pollen samples indicated the existence of eight vegetation units, which can be assigned to the six studied pine forest communities. Lowland forests are clearly discriminated from high-altitude ones. These analyses also allow separating Pinus nigra and P. pinaster communities according to their tree cover, and even those of P. sylvestris according to the bioclimatic belt they inhabit. We show that it is possible to obtain distinct pollen markers for Mediterranean pine forest communities. These results will also improve the reconstruction of pine forests from fossil pollen diagrams, as far as modern pollen rain studies are carried out in specific regions, an approach which can be extrapolated to other plant formations regardless the involved territory.

A new record from a long sediment core (S3) in Navamuño (1505 m asl, western Iberian Central System) provides the reconstruction of the vegetation history and environmental changes in the region between 15.6 and 10.6 ka cal BP, namely during the Late Glacial and the early Holocene, using a multiproxy analysis (pollen-based vegetation and climate reconstruction, sedimentary macrocharcoals, loss-on-ignition, magnetic susceptibility and X-ray fluorescence (XRF) measurements). The results are then compared with other sequences from the Iberian Central System and the whole Iberian Peninsula in order to better understand the past dynamics of the main forest constituents. The pollen record shows a shift from open pine forests ∼15.6–14.7 ka cal BP (Oldest Dryas) to mixed open pine-birch woodlands ∼14.7–14.0 ka cal BP (Bølling). Woodlands were succeeded by a steppe-like landscape until ∼13.4 ka cal BP (Older Dryas), which was replaced again by high-mountain pine forests and riparian woodlands ∼13.4–12.6 ka cal BP (Allerød). A great development of cold steppe grasslands linked to the decline of birch woodlands is documented ∼12.6–11.7 ka cal BP (Younger Dryas). The early Holocene (11.7–10.6 ka cal BP) was characterized by a progressive reforestation of the study area by pine and birch forests in the highlands and oak woods in the lowlands. Temperate tree taxa (Carpinus betulus, Castanea sativa, Corylus avellana, Fraxinus, Juglans, Tilia, and Ulmus) were also common but likely at lower elevations. Pollen of Fagus sylvatica was already recorded during the Late Glacial and the early Holocene. The marked increasing local fire activity during the warmer and wetter Allerød oscillation could be related to a rise in tree cover, supporting the climatically driven character of these fires. Nevertheless, the strong increase in fire activity during the Younger Dryas would probably be related to growing tree and shrub mortality, as well as to the wet/dry biphasic structure of this stadial

La diversidad vegetal de Sierra Nevada es resultado de múltiples procesos que han determinado que se haya producido la sucesión continuada de contingentes florísticos y comunidades vegetales de diverso origen a lo largo de su historia geológica. Gran parte de la flora actual de Sierra Nevada proviene de latitudes septentrionales de Europa ( elementos arctoterciarios), cuando aún los materiales que dieron lugar al macizo nevadense estaban unidos al este de la placa ibérica en el Oligoceno, lejos de su emplazamiento final al sur de Iberia. A finales de este período, y durante todo el Mioceno, el clima inicia una tendencia hacia la aridez y enfriamiento global que provoca la extinción de parte de la flora paleotropical de Iberia, y su progresiva sustitución por la flora arctoterciaria. Es cuando la vegetación del sureste peninsular se enriquece en elementos sabanoides, quedando relegados los bosques siempreverdes y semideciduos a las zonas de mayor disponibilidad hídrica. La alta montaña nevadense es ocupada por cinturones de coníferas, mientras que por la franja costera y lagunas salobres se distribuyen los manglares. La desecación parcial del Mediterráneo durante la crisis del Messiniense promueve la creación de puentes que constituyen importantes rutas migratorias para especies irano-turánicas y saharo-síndicas. Tras la apertura del Estrecho de Gibraltar en el Plioceno, se consolida la estacionalidad propia del clima mediterráneo, que dio lugar a una vegetación muy similar en estructura a la actual. Finalmente, el Cuaternario supone la culminación del lento proceso de enfriamiento iniciado en el Terciario, durante el cual la alternancia de períodos glaciales e interglaciales proporciona refugio a táxones arctoterciarios e induce la extinción de los últimos elementos paleotropicales. La reciente recuperación climática del Holoceno supuso la expansión de bosques de frondosas del género Quercus.

Current knowledge of climate change effects on forest ecology and species conservation should be linked to understanding of the past-time. Abies pinsapo forests constitute a model of an endangered ecosystem, highly vulnerable to ongoing warming, whose populations have been declining for centuries, while the drivers of this local depletion trend remain poorly understood. We hypothesized that long-term disturbances, both human- and natural-induced, have shaped A. pinsapo forests, contributing to these decline processes. Until today, studies using fossil pollen record to identify past climate impacts and land-use changes on A. pinsapo populations have not been done. Here, we investigate forests’ dynamics since the late Holocene (1180 cal. AD to present) in Southern Iberian Peninsula from a fossil pollen record by comparing the results obtained with climate fluctuations and land-uses changes. The pollen sequence shows a phase of stability during the Islamic Period (~1180–1400 cal. AD; ‘Medieval Climate Anomaly’), followed by increasing degradation at Christian Period concurrent with ‘Little Ice Age’ (LIA) (ca. 1487–1530 cal. AD). The Modern Period (1530–1800 cal. AD; LIA) is linked to intensive forest management, related to the naval industry. Afterwards, a progressive reduction is recorded during the Contemporary Age period (‘Industrial Period’) until ‘Recent Warming’. In short, historical severe forest management coupled with increasing aridity since LIA appear to influence A. pinsapo forest current species composition and poor structural diversity. These disturbances might be limiting the resilience of A. pinsapo forests under a climate change scenario. A selected forest management could promote a more complex forest structure.

The Iberian Central System (ICS) is a clue region to reveal Mediterranean/Atlantic inferences over Iberia. We present a multidisciplinary study from western Spain conducted in the Navamuño depression (ND), covering the last 16.8 ka (cal BP). A reconstruction of the palaeotemperature from the resulting geochemical data highlights four cold and dry intervals, namely, the Oldest Dryas, Older Dryas, Intra-Allerød Cold Period (IACP), and the Younger Dryas, along with warmer intervals: the Bølling (14.7–14 ka) and the Allerød (12.9–12.6 ka); however, the Greenland Interstadial GI-1c (13.4–13.1 ka) is barely distinguishable in the ND. Despite the shortage of biomass to sustain fire, the earliest charcoals are from ~14.4–13.8 ka. Evidence of ash/dust events overprinting the geochemical background starts at ~13.8–12.8 ka. Significant fire activity in the Early Holocene at ~11.7–10.6 ka affected the ND, matching the westernmost ICS data. This period includes short oceanic spells inferred from Cl peaks at ~10.9–10.2 ka and three cold intervals at 11.4, 9.3, and 8.2 ka disrupted the progressive temperature increase. The Mid-Holocene showed a continuously increasing trend towards an arid climate, peaking at 4.2 ka under a pervasive dust influx from North Africa, which has prevailed since almost ~7.9 ka. A prominent volcanic event at ~6.8–5.8 ka is in Navamuño and Roñanzas (Asturias, N Spain; Gallego et al., 2013) identified from heavy metal-rich layer, synchronous with the last known eruption of the Calatrava volcanic field (South-Central Spain; Poblete-Piedrabuena et al., 2019). This volcanic eruption could affect many other regions half north of Iberia. The pervasive presence of oceanic aerosols in the last three millennia (2.8 ka ~ ) allowed the formation of a Cl-rich peat layer during the Ibero-Roman humid period ~2.1 ka, before a changing around ~0.4 ka toward colder and drier conditions at the Little Ice Age (LIA) period., Ministerio de Ciencia, Innovación y Universidades, Andalusian Office of Economy and Knowledge, Spanish Ministry of Education, Culture, and Sports, Depto. de Geodinámica, Estratigrafía y Paleontología, Fac. de Ciencias Geológicas, TRUE, pub

Human impact on western Mediterranean mountains is gaining more attention, as they harbour a rich plant diversity threatened by global change. This paper presents an analysis of two pollen records from both sides of Sierra Nevada, the prime plant-diversity centre of the Mediterranean, spanning the last 5400 years. The analysis sought to answer the following key questions: When did natural systems transform to cultural landscapes? What was the intensity and extent of alterations driven by the diverse civilizations? A compilation of archaeological and paleaeoclimatic data supported this analysis, as well as a multi-proxy palaeoecological study using pollen, non-pollen palynomorphs and microcharcoal, searching for the imprint that diverse societies left on these mountains. Results suggest that human influences started earlier than expected, with a strong impact on forest cover, oriented more towards crops on the southern face and towards livestock on the northern one, whereas mining and metallurgy were initial key drivers of population dynamics. Irrigation has supported farming since at least the Islamic period. More recent anthropogenic control and land-use management have allowed a further spread of the tree cover. Proper conservation strategies need long-term perspectives, including palaeoecological studies. The preservation of traditional human activities like grazing, high-elevation cropping or irrigation systems become essential to maintain current biodiversity., Ministerio de Ciencia e Innovación (MICINN), Ministerio de Economía y Competitividad (MINECO)/Gobierno de Andalucia/Fondo Regional de Desarrollo Económico(FEDER), Plan Andaluz de Investigación, Desarrollo e Innovación (PAIDI 2020)//Fondo Europeo de Desarrollo Regional(FEDER), Depto. de Biodiversidad, Ecología y Evolución, Fac. de Ciencias Biológicas, TRUE, pub

Human impact on western Mediterranean mountains is gaining more attention, as they harbour a rich plant diversity threatened by global change. This paper presents an analysis of two pollen records from both sides of Sierra Nevada, the prime plant-diversity centre of the Mediterranean, spanning the last 5400 years. The analysis sought to answer the following key questions: When did natural systems transform to cultural landscapes? What was the intensity and extent of alterations driven by the diverse civilizations? A compilation of archaeological and paleaeoclimatic data supported this analysis, as well as a multi-proxy palaeoecological study using pollen, non-pollen palynomorphs and microcharcoal, searching for the imprint that diverse societies left on these mountains. Results suggest that human influences started earlier than expected, with a strong impact on forest cover, oriented more towards crops on the southern face and towards livestock on the northern one, whereas mining and metallurgy were initial key drivers of population dynamics. Irrigation has supported farming since at least the Islamic period. More recent anthropogenic control and land-use management have allowed a further spread of the tree cover. Proper conservation strategies need long-term perspectives, including palaeoecological studies. The preservation of traditional human activities like grazing, high-elevation cropping or irrigation systems become essential to maintain current biodiversity.

Human impact on western Mediterranean mountains is gaining more attention, as they harbour a rich plant diversity threatened by global change. This paper presents an analysis of two pollen records from both sides of Sierra Nevada, the prime plant-diversity centre of the Mediterranean, spanning the last 5400 years. The analysis sought to answer the following key questions: When did natural systems transform to cultural landscapes? What was the intensity and extent of alterations driven by the diverse civilizations? A compilation of archaeological and paleaeoclimatic data supported this analysis, as well as a multi-proxy palaeoecological study using pollen, non-pollen palynomorphs and microcharcoal, searching for the imprint that diverse societies left on these mountains. Results suggest that human influences started earlier than expected, with a strong impact on forest cover, oriented more towards crops on the southern face and towards livestock on the northern one, whereas mining and metallurgy were initial key drivers of population dynamics. Irrigation has supported farming since at least the Islamic period. More recent anthropogenic control and land-use management have allowed a further spread of the tree cover. Proper conservation strategies need long-term perspectives, including palaeoecological studies. The preservation of traditional human activities like grazing, high-elevation cropping or irrigation systems become essential to maintain current biodiversity.

This work presents the anthracological and archeopalynological results obtained within the project AGRIWESTMED (ERC AdG 230561), which has involved a comprehensive retrieval of archeobiological remains based on a systematic sampling strategy, beyond the recovery of the usual archeological materials. These surveys were conducted on three sites located in the North of Morocco: the cave of Kaf Taht-el-Ghar, 8 km southeast from Tetuan, and two caves within the El Khil complex, close to Tanger. Both plant micro- and macro-remains (charred wood) were studied through palynological and anthracological analyses, respectively., Our goal was to assess the vegetation composition of the area as well as the impact of human activities on the landscape. In Kaf Taht-el-Ghar the dynamics of vegetation and land use is recorded over the Paleolithic, Epipaleolithic, Neolithic and Historic times. Clear changes such as the demise of ancient Paleolithic pine and juniper woods during the Epipaleolithic and the subsequent spread of grasslands are shown. Other conifers like Abies pinsapo, Cedrus atlantica and Taxus baccata also disappeared from the pollen and charred wood records. In the palynological study, cereal and broad beans (Vicia faba) are already detected in the Early Neolithic, as well as a lowering of grazing pressure. Both cereal and broad beans, along with the development of grazing activities are also documented around El Khil caves since the Early Neolithic. Throughout the whole pollen and anthracological sequences a progressive retreat of the tree cover and an extensive spread of grasslands could be set as the main features of the vegetation dynamics in this area.

Pollen analyses supported byfifteen AMS14C dates from Fuente de la Leche (1382 m) and Fuente del PinoBlanco (1343 m) peat sequences, in the Gredos range (central Spain), are used to reconstruct the lateHolocene vegetation history in this mountain region. These results are compared with other sequencesfrom the Spanish Central System in order to better understand the past dynamics of the main forestconstituents and to provide a critical view of the dialectic between conifers and deciduous forests. Thevegetation record at Fuente de la Leche starts at 3000 cal yr BP, with the occurrence of rather closedforests composed ofPinus sylvestrisandBetula.Pinus sylvestriswas the dominant pollen taxa for almostthe entire period. However, during the last 850 years,Pinus sylvestrisforests were progressively replacedbyQuercus pyrenaicawoodlands and grasslands, as a result of a high pastoral pressure, until formingmixed woodlands ~400 years ago. The interpretation of Fuente del Pino Blanco record is that dramaticchanges started about 265 years ago. Prior to this date, an open canopy woodland included species (Alnusglutinosa,Quercus pyrenaica) whose distributions no longer exist in the studied area. We suggest that theincrease in agricultural (rye and other cereals) and livestock activities forced a change in the role offire inthe supramediterranean belt of the Gredos range, thus Pyrenean oak canopy was consumed byfires,providing openings forPinus pinasterand broom communities better adapted tofire.

BACKGROUND: High-mountain pine forests and broom communities in central Spain today have led to contrasting interpretations of their natural or human-induced origin. AIMS: We evaluated the vulnerability and resilience of high-mountainPinus sylvestris/P. nigra forests and derivedCytisusbroom scrub communities to climate and anthropogenic disturbances. METHODS: We assessed historical transitions from forest to scrub and their relation to climate and human influences, using a multi-proxy paleoenvironmental study (pollen, non-pollen palynomorphs, charcoal, magnetic susceptibility) in three mires in the Gredos Range, western Iberian Central System. RESULTS: High percentages of Pinus sylvestris/nigrapollen and the identification of their macro remains demonstrated that high-mountain pine forests have been present in the oromediterranean bioclimatic belt of the Gredos Range since the mid-Holocene. After that, a major human-induced decline, enhanced by climate conditions, has led to their gradual replacement by broom communities. CONCLUSIONS: Broom communities are derived from ancient pine forests that were intensively transformed by human activities after 700 cal year BP, and largely disappeared byca. 500 cal yr BP. Today’s landscape, dominated by broom scrub and grasslands with scattered stands of pines, shows high resilience and provides suitable refugia for a rich mountain biodiversity which deserves a further protection.

The use offire and, consequently, its severity and incidence on the environment have grown steadily during the last millennia throughout theMediterranean. This issue can be assessed in several mountain ranges of central Iberia where changes in the management policy on anthropicactivities and exploitation of high-mountain environments have promoted a remarkable increase onfire frequency. Our research focuses onfire dynamics throughout the last 3,000 years from three peat bog charcoal records of the Gredos range (central Iberia). Our aim is toreconstruct pastfire regimes according to forest vegetation typology (Castanea sativa,Pinus pinaster, andPinus sylvestris). Charcoal influxshows low values between 3,140 and 1,800 cal. yearBPwhen forests were relatively dense in both high and mid-mountain areas. Fireappeared synchronous between 1,800 and 1,700 cal. yearBPfor Lanzahíta and Serranillos and around 1,400–1,240 cal. yearBPfor the threesites, suggesting anthropogenicfire control between the Late Roman and Visigothic periods that can be related to the cultivation of olive treesin the valleys and a greater human impact in high-mountain areas. By contrast, during the Muslim period (1,240–850 cal. yearBP),firedynamics becomes asynchronous. Later,fires turn again coeval in the Gredos range during the Christian period (850–500 cal. yearBP)and can be also correlated with drought phases during the Late Medieval Warm Episode. In short, our study demonstrates thatfire activityhas been enormously variable during the late Holocene in response to both short-term and long-term regional and global climate, vegetationdynamics, and land use changes.

Quantifying and reconstructing past vegetation changes is an important step to fully understand human-environment interactions in the past. In this study we present a reconstruction of arboreal cover of six studysites in the Gredos Range (central Spain) over the last 3000 yr based on multivariate statistical analysis (clusteranalysis and non-metric multidimensional scaling, NMDS) of 186 modern pollen samples, modern vegetationdata and six detailed fossil pollen records. The integrated approach allows distinguishing eight modern vegeta-tion communities and linking the fossil pollen records with these vegetation communities as modern analogues.The information of the arboreal cover of the modern pollen sites was used to estimate the past arboreal cover ofthe fossil pollen sites in the Gredos Range. This estimated arboreal cover shows a higher level of landscape open-ness than suggested by the original pollen percentages data. Our results show that the evolution of the arborealcover through time differs along an altitudinal gradient, with a decrease in arboreal cover during the Roman andVisigoth periods (2000–1240 cal BP) at low altitudes and only during the Christian/Feudal period (850–500 calBP) at high altitudes. The applied methodology, integrating fossil pollen data with modern pollen and vegetationdata in one NMDS, allows reconstructing past arboreal cover in a quantitative way.

Cedrus atlantica (Atlas cedar) is a relict and endemic endangered species from northwestern African mountains, whose distribution range has undergone a dramatic reduction over recent decades. Long-term studies are needed for a better understanding of the development of its range as well as for assisting in the implementation of sustainable conservation measures. The multi-proxy analysis of a high-resolution fossil record of 180 cm depth allowed us to depict the final demise of an Atlas cedar population from the western Rif Mountains (Jbel Khesana), despite its high resilience during the last ~4000 years. Currently, Atlas cedar trees are not observed in Jbel Khesana but they still occur in the nearby area as scattered populations on a few mountain tops at altitudes higher than 1400 m a.s.l. Our data show an initial relatively stable period (~4000¿2400 cal. yr BP) followed by a phase where both climatic and human-induced disturbances cause an alternate dominance of oaks and Atlas cedars (2400~1550 cal. yr BP). Then, the increasing aridity and human activities favoured the depletion of Atlas cedar forests (~1550¿800 cal. yr BP). Our record shows that Atlas cedar forests have recovered after each deforestation event, which reveals a high resilience of the species until the mid-20th century, when they became extinct in the study area. The main driver of their local extinction may be attributed to the strong human pressure. Management measures of Atlas cedar in the Rif Mountains should aim at limiting intensive loggings and protecting the existing populations for their local regeneration.