Gredos Range Research Articles

Holocene vegetation and fire dynamics in the supra-Mediterranean belt of the Gredos Range (central Iberian Peninsula)

High-resolution pollen, macrofossil and charcoal data, combined with multivariate analysis, were used to reconstruct Holocene vegetation and fire dynamics at Manaderos. The studied mire is located in a highly valued location in the supra-Mediterranean belt of the Gredos Range (central Iberian Peninsula). The record started at 1260 calendar years (cal yrs) BP, according to eight radiocarbon dates, with the occurrence of an open Quercus pyrenaica forest and Pinus nigra stands. The palynological data show a dramatic change ∼380 cal yrs BP, when the oak forest was progressively replaced by a maritime pine one. The interpretation of this record is related to an increase in agricultural and livestock activities and changes in the role of fire, thus Pyrenean oak canopy was consumed by fires providing openings for Pinus pinaster, better adapted to fire. The results are compared with other sequences from the Spanish Central System in order to better understand the past dynamics of the main forest constituents and to provide a critical view of the role of fire, anthropic dynamics and climatic events.

Geomorphology of glaciated gorges in a granitic massif (Gredos range, central Spain)

ABSTRACTA detailed geomorphological map on a 1:10,000 scale is presented for a high mountain area in Gredos range (Iberian Central System). Only few detailed geomorphological maps of the range are available despite the wide diversity of landforms. The map was created with the aid of aerial photographs, satellite images, and 3D images and verified with field surveys. The landforms resulting were classified using the IGUL (Institute of Geography, University of Lausanne) legend system combined with the legend proposed by Peña et al. (1997). As a result, 40 landforms distributed over an area of 40 km2 have been identified. The map shows the spatial distribution of different geomorphological processes that have modeled a wide variety of landforms. This variety of processes and landforms identified demonstrated that geomorphological cartography obtained by combining traditional image interpretation and GIS technology facilitates the production of geomorphological maps and the obtaining of valuable data for identify and understand surface processes and landforms.

Reconstructing past arboreal cover based on modern and fossil pollen data: A statistical approach for the Gredos Range (Central Spain)

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 study sites in the Gredos Range (central Spain) over the last 3000 yr based on multivariate statistical analysis (cluster analysis and non-metric multidimensional scaling, NMDS) of 186 modern pollen samples, modern vegetation data and six detailed fossil pollen records. The integrated approach allows distinguishing eight modern vegetation 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 of the fossil pollen sites in the Gredos Range. This estimated arboreal cover shows a higher level of landscape openness than suggested by the original pollen percentages data. Our results show that the evolution of the arboreal cover through time differs along an altitudinal gradient, with a decrease in arboreal cover during the Roman and Visigoth periods (2000–1240 cal BP) at low altitudes and only during the Christian/Feudal period (850–500 cal BP) at high altitudes. The applied methodology, integrating fossil pollen data with modern pollen and vegetation data in one NMDS, allows reconstructing past arboreal cover in a quantitative way.

Resilience, vulnerability and conservation strategies in high-mountain pine forests in the Gredos Range, central Spain

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-mountain Pinus sylvestris/P. nigra forests and derived Cytisus broom 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/nigra pollen 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 by ca. 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.

Intense precipitation events in the Central Range of the Iberian Peninsula

Abstract. Intense orographic precipitation associated with the Central Range was analysed using data of maximum accumulated precipitation in 24 h, occurring between 1958 and 2010. The 18 selected episodes were associated with a southwesterly tropospheric flow, a low-level jet, and high moisture flux at low levels. The observed moisture flux was higher than 100 (m g(s kg)−1) and the dry and wet Froude numbers were greater than 1. The selected area to study this synoptic situation was Gredos, broad and high range, which is located in the eastern part of the Central Range and generates a leeward orographic shadow. The effect of the Central Range on the spatial distribution of precipitation on the Iberian Peninsula plateau results in a sharp increase in precipitation in the south of the Central Range, followed by a decrease to the north of this range.

Paleofire Dynamics in Central Spain during the Late Holocene: The Role of Climatic and Anthropogenic Forcing

ABSTRACTThe use of fire and, consequently, its severity and incidence on the environment have grown steadily during the last millennia throughout the Mediterranean. This issue can be assessed in several mountain ranges of central Iberia where changes in the management policy on anthropic activities and exploitation of high‐mountain environments have promoted a remarkable increase on fire frequency. Our research focuses on fire dynamics throughout the last 3,000 years from three peat bog charcoal records of the Gredos range (central Iberia). Our aim is to reconstruct past fire regimes according to forest vegetation typology (Castanea sativa, Pinus pinaster, and Pinus sylvestris). Charcoal influx shows low values between 3,140 and 1,800 cal. year bp when forests were relatively dense in both high and mid‐mountain areas. Fire appeared synchronous between 1,800 and 1,700 cal. year bp for Lanzahíta and Serranillos and around 1,400–1,240 cal. year bp for the three sites, suggesting anthropogenic fire control between the Late Roman and Visigothic periods that can be related to the cultivation of olive trees in the valleys and a greater human impact in high‐mountain areas. By contrast, during the Muslim period (1,240–850 cal. year bp), fire dynamics becomes asynchronous. Later, fires turn again coeval in the Gredos range during the Christian period (850–500 cal. year bp) and can be also correlated with drought phases during the Late Medieval Warm Episode. In short, our study demonstrates that fire activity has been enormously variable during the late Holocene in response to both short‐term and long‐term regional and global climate, vegetation dynamics, and land use changes. Copyright © 2017 John Wiley & Sons, Ltd.

The dialectic between deciduous and coniferous forests in central Iberia: A palaeoenvironmental perspective during the late Holocene in the Gredos range

Pollen analyses supported by fifteen AMS 14C dates from Fuente de la Leche (1382 m) and Fuente del Pino Blanco (1343 m) peat sequences, in the Gredos range (central Spain), are used to reconstruct the late Holocene vegetation history in this mountain region. These results are compared with other sequences from the Spanish Central System in order to better understand the past dynamics of the main forest constituents and to provide a critical view of the dialectic between conifers and deciduous forests. The vegetation record at Fuente de la Leche starts at 3000 cal yr BP, with the occurrence of rather closed forests composed of Pinus sylvestris and Betula. Pinus sylvestris was the dominant pollen taxa for almost the entire period. However, during the last 850 years, Pinus sylvestris forests were progressively replaced by Quercus pyrenaica woodlands and grasslands, as a result of a high pastoral pressure, until forming mixed woodlands ∼400 years ago. The interpretation of Fuente del Pino Blanco record is that dramatic changes started about 265 years ago. Prior to this date, an open canopy woodland included species (Alnus glutinosa, Quercus pyrenaica) whose distributions no longer exist in the studied area. We suggest that the increase in agricultural (rye and other cereals) and livestock activities forced a change in the role of fire in the supramediterranean belt of the Gredos range, thus Pyrenean oak canopy was consumed by fires, providing openings for Pinus pinaster and broom communities better adapted to fire.

Holocene treeline history of a high-mountain landscape inferred from soil charcoal: The case of Sierra de Gredos (Iberian Central System, SW Europe)

Unravelling the precise Holocene altitudinal fluctuation of the highland vegetation communities (>1800 m asl) in the Gredos Range (Central System, Spain) is challenging owing to the complexity of the long-term human-environmental interactions in the area. Aiming at improving the knowledge of these highland dynamics, a pedoanthracological analysis was conducted on six soil profiles located on the northern slope of the central sector of the Gredos Range, following an altitudinal transect between 2200 and 1700 m asl in the Las Pozas valley. The soil charcoal analysis revealed the long-term stability of the Leguminosae shrublands, which have dominated the landscape over 1800 m asl since the Early Holocene. The highest ancient timberline was stimated to be at approximately 1700 m asl in this valley, from the Early Holocene until the beginning of the Late Holocene. This ancient forest contained Pinus gr. sylvestris, with significant numbers of deciduous Quercus. However, scattered individuals or small groves of pioneer deciduous taxa (Betula sp., Populus sp., Salix sp., Maloideae and Prunus sp.) were found to have thrived over the timberline during the Early and Middle Holocene, especially between 1900 and 2000 m asl. The highest treeline was marked by Betula at 2100 m asl. Elevated values of charcoal concentration reflect the intense fire regime of the area. The pattern of fire events accumulation periods that can be inferred from the 23 dated charcoal samples is consistent with previous data, which supports an increase in fire frequency around 2000 cal yr BP, during the first reported period of significant human influence.

Syntaxonomical update on the relict groves of Scots pine (Pinus sylvestris var. iberica) and Spanish black pine (Pinus nigra subsp. salzmannii) in the Gredos range (central Spain)

Pure and mixed high-mountain pine forest vegetation of the Gredos range (central Spain) was studied using 57 releves and multivariate analyses (hierarchical cluster analysis and detrended correspondence analysis). Classification of the releves resulted in 7 vegetation units, 3 of which were ranked as associations and only one as subassociation. DCA diagrams of releves and taxa indicated that floristic differentiation was attributed mainly to factors such as altitude. Differential taxa of vegetation units were chosen based on their phi coefficient values. The statistic discrimination of some of these vegetation units has allowed us to propose a new association and a new subassociation of other community described in a previous paper.

Landscape dynamics and human impact on high-mountain woodlands in the western Spanish Central System during the last three millennia

A multi-proxy palaeoenvironmental study (pollen, non-pollen palynomorphs, charcoal particles) of a mire, located in the western Spanish Central System (Gredos range), was undertaken to trace historic human activities related to woodland clearance and past land-uses at high altitudes during the last three millennia. The results of this study constrained by 4 AMS radiocarbon measurements are combined with archaeological data and compared with similar research carried out at the same altitude in mountains of central Iberia. The pollen data indicate that high-mountain areas were dominated by birch and pine woodlands until c. 2350years. From this date on a strong forest decline is recorded during the Late Iron Age and a deeper one c. 1500years ago in the Visigothic period, which may be related to increasing grazing activities and/or the occurrence of anthropogenic fires. Cereals and faba beans were cultivated in the surrounding valley since c. 2900cal BP, while chestnut, walnut and olive tree are documented mainly from the Roman period onwards.

Exploring seven hundred years of transhumance, climate dynamic, fire and human activity through a historical mountain pass in central Spain

A high-altitude peat sequence from the heart of the Spanish Central System (Gredos range) was analysed through a multi-proxy approach to determine the sensitivity of high-mountain habitats to climate, fire and land use changes during the last seven hundred years, providing valuable insight into our understanding of the vegetation history and environmental changes in a mountain pass close to a traditional route of transhumance. The pollen data indicate that the vegetation was dominated by shrublands and grasslands with scattered pines in high-mountain areas, while in the valleys cereals, chestnut and olive trees were cultivated. Strong declines of high-mountain pines percentages are recorded at 1540, 1675, 1765, 1835 and 1925 cal AD, which may be related to increasing grazing activities and/or the occurrence of anthropogenic fires. The practice of mountain summer farming and transhumance deeply changed and redesigned the landscape of the high altitudes in central Spain (Gredos range) since the Middle Ages, although its dynamics was influenced in some way by climate variability of the past seven centuries.

Unraveling the naturalness of sweet chestnut forests (Castanea sativa Mill.) in central Spain

This paper describes the patterns and processes of vegetation change and fire history in the Late Holocene (c. 3,140 cal bp) palaeoecological sequence of El Tiemblo, in a mountainous area in central Spain (Gredos range, Spanish Central System), and provides the first Iberian pollen sequence undertaken within a Castanea sativa-dominated woodland. These new data reassess not only the autochthonous nature of the species in the region and in the Iberian Peninsula, but also the naturalness of well-developed sweet chestnut forests. The study focuses on anthropogenic dynamics linked both to the effects of livestock husbandry and the use of fire for forest clearance. With this aim, non-pollen palynomorphs (coprophilous fungi ascospores) and charcoal accumulation rate are useful indicators for assessing the increasing role of human influence on vegetation.

2000 years of pastoralism and fire shaping high-altitude vegetation of Sierra de Gredos in central Spain

article i nfo The palynological record of Puerto de Serranillos provides insights into the late Holocene vegetation history of Sierra de Gredos in the Central Mountain System of the Iberian Peninsula. Overgrazing around the timberline has occurred at least throughout the past two millennia, related to the human management of the landscape. Before the 12th century AD, Pinus sylvestris forests were dominant with a diversity of accompanying trees and understorey. The current landscape of the Gredos Range is clearly anthropogenic, and includes a combination of forest patches, pastures, dense shrubby formations and prostrate junipers, overall generated during the transition between the 17th and 18th centuries AD, when continued human activity in the mountain pine forests, using fire and intensifying grazing practices, caused a progressive deforestation, and the expansion of the current fire-prone scrub.

Human genetic variation in the Sierra de Gredos mountain (central Spain): study of several polymorphisms.

The variation in the third component of human complement (C3) and orosomucoid (ORM1) serum proteins, and 6-phosphogluconate dehydrogenase (6PGD), adenosine deaminase (ADA), esterase D (ESD), and acid phosphatase (ACP1) red cell enzymes was examined in two samples from autochthonous populations living on either side of the Sierra de Gredos range in Central Spain. These results support only a moderate differentiation between Gredos subpopulations, which is discussed in relation to other Iberian Peninsula groups. Allele frequencies in Gredos show a remarkable heterogeneity as contrasted with other Iberian populations for most of the markers examined; relatively high C3*S, ORM1*F, ADA*1, ESD*2, and ACP1*C gene frequencies are characteristics of Gredos samples. This differentiation was more marked for the Northern Gredos population and could be related to the geographical peculiarities of this region.