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We present a multiproxy characterization of a complex, polycyclic soil sequence from Les Alcusses, Moixent(Valencia, SE Spain). The area has abundant settlements dating from early Neolithic to Roman times. The sequence comprises six main units, dating back to 8.7-8.5kacalBP. We integrated mineralogy, inorganic (pH, grain size, elemental composition) and organic chemistry (pyrolysis gas chromatography/mass spectrometry, pyrolysis-GC/MS), micro-charcoal, pollen and non-pollen palynomorph (NPP) data. All data is contextualized within a framework of archaeological information and radiocarbon dating, with the aim of deciphering the Holocene environmental changes.We infer a shift from wetter and warmer, in the early-mid Holocene, to drier and cooler climatic conditions with increased fire occurrence, in the mid-late Holocene (particularly after 5.3kacalBP). Although the pollen record indicates a rapid forest retreat and expansion of grasslands for the Neolithic period, local proxies (molecular soil OM indicators and NPP) point to the presence of pine forest in the studied location well after the regional decline started. The same proxies suggest a sharp forest decline after about 7.0kacalBP. Strong soil erosion, likely linked both to climatic instability and the intensification of human exploitation, resulted in a hiatus from the late Neolithic to the Roman period. A certain climate amelioration, wetter conditions and land abandonment or, at least, lower human pressure, are suggested for the late Roman period/Early Middle Ages. Direct evidence of changes in soil properties due to agriculture was not detected in the sequence except for the upper soil unit studied, which reflects intense agricultural management (with the possible use of agrochemicals). © 2014 Elsevier Ltd.

Aluminium and Fe fractions were obtained in samples from two temperate podzols by selective extraction with NaOH (Aln, Fen), Na-dithionite-citrate (Ald, Fed), acid NH4-oxalate (Alo, Feo) and Na-pyrophosphate (Alp, Fep) following the traditional fractionation procedures, and also by the use of the chlorides of K (AlK), La (AlLa) and Cu (AlCu) as non-buffered extractants for Al. Carbon content was also determined in the Na-pyrophosphate extract (Cp). Soil sampling was done at high-resolution to allow a more detailed characterization of the vertical processes than the traditional sampling by whole soil horizons. Results showed that Alp and Fep make a large proportion of the Alo and Feo meaning that organoaluminic complexes dominated in the >active> metal pool instead of inorganic compounds. The degree of metal saturation of soil organic matter (estimated by the (Alp Fep)/Cp molar ratios) increases with depth, especially in the uppermost samples of spodic horizons (Bhs1) where it increases up to 0.1. Aluminium dominates in the adsorption positions of the organic matter in the spodic horizon (Fep/Alp ratios <0.5), except in the Bhs1 horizon (ratios >1), indicating that the immobilization of Fe containing complexes occurs 10-15cm above that of Al. The highly stable Al-OM complexes accounted on average for 60% of the organoaluminic associations (>70% in the Bhs horizons). The moderately stable complexes predominate in A horizons (57-77% in ACB1 and 37-48% in ACB2) and the largest proportions of low stability complexes were found in the uppermost samples of the spodic horizons (Bhs1) of both soils (9-21%), together with the highest Fep contents and a decrease in pH values. From a stepwise multiple regression model it is suggested that pH is the main variable accounting for the stability of Al-OM compounds together with C and organically bound Fe contents. It is suggested that the illuviation of unsaturated organic acids lower the pH in upper spodic horizons, leading to the

Pollen, non-pollen palynomorphs and charcoal from a colluvial soil surrounded by prehistoric petroglyphs (Campo Lameiro, NW Spain) were studied in order to assess the nature of human activities and their impact on Holocene vegetation patterns. Several phases of anthropogenic impact were observed. (i) Between 7.6 and 6.5 ka cal BP, synanthropic taxa (Urtica dioica type, Plantago lanceolata type) and coprophilous fungi (e.g. Sporormiella-type) are indicative of early (pre-agricultural) creation of small patches of pasture using fire, possibly for incipient animal husbandry or as part of a deliberate strategy to improve game availability. Such activities only had a minor effect on the deciduous Quercus-dominated forest established earlier during the Holocene Thermal Maximum. (ii) Between 5.9 and 4.8 ka cal BP a more intense signal indicative of pastoral activity was detected, corresponding to the Neolithic period. (iii) Between 4.8 and 3.4 ka cal BP, which fits within the hypothetical timeframe of petroglyph creation, the synanthropic and humidity (e.g. Cyperaceae, Mougeotia) indicators diminished while charcoal concentration increased, which can be explained by Mid-Holocene cooling/drying (Neoglaciation) in combination with reduced human impact, or by non-pastoral activities in the area possibly in association with the development of the rock art culture, converting pasture to protected open ground through anthropogenic fires. (iv) During the Late Bronze Age and Early Iron Age (3.4–2.5 ka cal BP), grazing pressure and fire regime intensity are high, coinciding with evidence of regional forest regression, despite an amelioration in climate. (v) Later phases, not corresponding to prehistoric rock art contexts, include a phase of heavy grazing and reduced fire frequency (from ca. 2.5 to 1.2 ka cal BP) as well as the near complete elimination of the deciduous woodland, the expansion of ericaceous shrubland and the evidence of local agriculture and afforestation. These res

The Holocene fire regime is thought to have had a key role in deforestation and shrubland expansion in Galicia (NW Spain) but the contribution of past societies to vegetation burning remains poorly understood. This may be, in part, due to the fact that detailed fire records from areas in close proximity to archaeological sites are scarce. To fill this gap, we performed charcoal analysis in five colluvial soils from an archaeological area (Campo Lameiro) and compared the results to earlier studies from this area and palaeo-ecological literature from NW Spain. This analysis allowed for the reconstruction of the vegetation and fire dynamics in the area during the last ca 11 000 yrs. In the Early Holocene, Fabaceae and Betula sp. were dominant in the charcoal record. Quercus sp. started to replace these species around 10 000 cal BP, forming a deciduous forest that prevailed during the Holocene Thermal Maximum until ∼5500 cal BP. Following that, several cycles of potentially fire-induced forest regression with subsequent incomplete recovery eventually led to the formation of an open landscape dominated by shrubs (Erica sp. and Fabaceae). Major episodes of forest regression were (1) ∼5500-5000 cal BP, which marks the mid-Holocene cooling after the Holocene Thermal Maximum, but also the period during which agropastoral activities in NW Spain became widespread, and (2) ∼2000-1500 cal BP, which corresponds roughly to the end of the Roman Warm Period and the transition from the Roman to the Germanic period. The low degree of chronological precision, which is inherent in fire history reconstructions from colluvial soils, made it impossible to distinguish climatic from human-induced fires. Nonetheless, the abundance of synanthropic pollen indicators (e.g. Plantago lanceolata and Urtica dioica) since at least ∼6000 cal BP strongly suggests that humans used fire to generate and maintain pasture.

[EN] We review research done on environmental changes in northwest (NW) Iberia spanning from the beginning to the late Holocene (7000–500 cal. BC). The type of archives (peat bogs, lake sediments, colluvium, soils, etc.) and proxies (pollen, element concentrations, isotopes, etc.) that were used to reconstruct changes on climate, soils, vegetation and atmospheric metal pollution are briefly described. Then we synthesize what the records suggest about the ecological history of NW Iberia. We identified four main phases: 7000–5000, 5000–3000, 3000–1500 and 1500-500 cal. BC. Each phase is determined by a set of environmental conditions, a combination of changes in climate, vegetation, soils and human impact. Human activities seem to have been involved in landscape changes in NW Iberia since at least 5000 cal. BC, with an increasing degree of anthropisation through time, which accelerated by 1500 cal. BC. The interaction between human activities and natural changes expressed as modifications in the vegetation cover, the elimination of the soil resources in many areas and its concentration in more localized, control-demanding sectors, as well as a progressive acidification and pollution of continental ecosystems. To a great extent, the present landscape in NW Iberia is the end product of these complex interactions, a cultural landscape., [ES] Revisamos la investigación llevada a cabo en relación a los cambios ambientales en el noroeste de la Península Ibérica que abarcan desde comienzos del Holoceno, hasta el Holoceno tardío (7000-500 cal. A. C). El tipo de archivos (turberas, sedimentos lacustres, coluviales, suelos, etc) y los datos inferidos (el polen, las concentraciones de elementos, isótopos, etc) que fueron utilizados para reconstruir los cambios en el clima, los suelos, la vegetación y la contaminación atmosférica por metales se describen brevemente. A continuación sintetizamos lo que sugieren los registros de la historia ecológica del noroeste de la Península Ibérica. Se identificaron cuatro fases principales: 7000-5000, 5000-3000, 3000-1500 y 1500-500 cal a. C. Cada fase está determinada por un conjunto de condiciones ambientales, una combinación de cambios en el clima, la vegetación, los suelos y el impacto humano. Las actividades humanas parecen haber estado involucradas en los cambios de paisaje en el noroeste de la Península Ibérica, al menos desde 5000 cal. a. C., con un creciente grado de antropización a través del tiempo, que se aceleró en 1500 cal. a. C. La interacción entre las actividades humanas y los cambios naturales expresados como modificaciones en la cubierta vegetal, la eliminación de los recursos del suelo en muchas zonas y su concentración en sectores más localizados demandados en cuanto a su control, así como una progresiva acidificación y la contaminación de los ecosistemas continentales. En gran medida, el paisaje actual en el noroeste de la Península Ibérica es el producto final de estas interacciones complejas, un paisaje cultural.

[EN] The colluvial soils of Galicia (NW Spain) are records of Holocene environmental change. In spite of the omnipresence of charcoal fragments in these soils, the effect of fires on the development of the Galician landscape and the potential role of past societies are poorly understood. We isolated macroscopic charcoal (>2 mm) and NaOH-extractable soil organic matter (SOM) from two Galician soils. Molecular characterisation of the extractable SOM using pyrolysis-GC/MS showed that fire residues (black carbon; BC) were abundant in the extractable SOM, even in the horizons containing few macroscopic charcoals. This indicates that the macroscopic charcoal record often used in geoarchaeological studies gives an incomplete image of the fire history. Polycyclic aromatic hydrocarbons and other presumably BC-derived pyrolysis products in samples from 8500 to 7000 cal years BP are evidence of Mesolithic fires. Molecular indicators of BC are abundant also in the Neolithic (c. 6000 BP), but the degree of thermal modification to the organic matter decreases, which could mirror a change in fuel type. This change coincides with the beginning of accelerated soil erosion in the area, and is followed by accumulation of relatively homogeneous BC-rich material up to at least the beginning of the Iron Age. This pattern is interpreted as deforestation around 6000 BP followed by periodic and presumably human-induced burning of poorly-developed vegetation (slash-and-burn). The open landscape of present-day Galicia would therefore be the outcome of prolonged anthropogenic burning, analogous to the open cultural landscapes of central Europe., [ES] Los suelos coluviales de Galicia (noroeste de España) son los registros de los cambios ambientales del Holoceno. A pesar de la omnipresencia de los fragmentos de carbón vegetal en estos suelos, el efecto de los incendios en el desarrollo del paisaje gallego y el papel potencial de las sociedades del pasado, son poco conocidos. Se aislaron de carbón macroscópica (> 2 mm) y NaOH extraíble la materia orgánica (MOS) de dos suelos de Galicia. La caracterización molecular de los extraíbles utilizando pirólisis-GC/MS SOM mostró que los residuos de fuego (negro de humo; aC) fueron abundantes en la materia orgánica del suelo extraíble, incluso en los horizontes que contienen pocos carbones macroscópicos. Esto indica que el registro de carbón macroscópico a menudo utilizado en estudios geoarqueológicos da una imagen incompleta de la historia de incendios. Hidrocarburos aromáticos policíclicos y otros, presumiblemente a. de C. -productos derivados de la pirólisis de muestras desde 8500 a 7000 años a. C. son una prueba de incendios Mesolíticos. Indicadores moleculares de antes de Cristo son abundantes también en el Neolítico (c. 6000 BP), pero disminuye el grado de modificación térmica de de la materia orgánica, lo que podría reflejan un cambio en el tipo de combustible. Este cambio coincide con el comienzo de la erosión acelerada del suelo en la zona, y es seguido por la acumulación de relativamente homogénea antes de Crito de material rico hasta al menos el comienzo de la Edad de Hierro. Este patrón se interpreta como la deforestación alrededor de 6000 BP seguido de la quema periódica y, presumiblemente provocadas por el hombre de la vegetación poco desarrollada (roza y quema). El paisaje abierto de la actual Galicia, por lo tanto, sería el resultado de la quema antropogénica prolongada, análogo a los paisajes abiertos culturales de Europa central.

[EN] The Schmidt Rock Test Hammer was used to study the effect of abrasion on shore platforms in Galicia, northwestern Spain. On platforms where tidally-induced weathering (salt, wetting and drying, etc.) is dominant, rock strength is significantly lower than in areas where abrasion is, or has been active in the recent past. This suggests that abrasion removes weathered surface material, exposing the stronger, less weathered rock below. Abrasion downwearing, measured with a transverse micro-erosion meter, ranged between 0.13 and 1.8 mm yr−1 over the last year. Most active abrasion occurs in the upper part of the intertidal zone, but weathering is slowly destroying formerly abraded surfaces at lower elevations. These abandoned surfaces were abraded bymaterials supplied by erosion of fluvio-nival and periglacial slope deposits that covered, or partially covered, parts of the Galician coast during the middle and late Weichselian. During the Holocene, rising sea level and erosion of the slope deposits caused the abrasion zone to gradually migrate up to its present position near the high tidal level. The spatial and temporal role of abrasion on this coast is, therefore, closely associated with the exhumation and inheritance of ancient platform surfaces from beneath Weichselian deposits., [ES] La prueba en rocas con el martillo de Schmidt fue utilizada para estudiar el efecto de la abrasión en plataformas marinas en Galicia, noroeste de España. En las plataformas, donde por las mareas inducidas la intemperie (sal, mojado y secado, etc) es dominante, la resistencia de la roca es significativamente menor que en las zonas donde la abrasión es, o ha estado activa en el pasado reciente. Esto sugiere que la abrasión elimina material de la superficie erosionada, exponiendo lo más sólido, menos erosionada debajo. Esta abrasión, medida con un medidor transversal de micro-erosión, osciló entre 0,13 y 1,8 mm año-1 en el último año. La abrasión más activa se presenta en la parte superior de la zona intermareal, pero la intemperie está destruyendo lentamente las superficies erosionadas antes en las elevaciones más bajas. Estas superficies abandonadas fueron desgastadas por el material suministrado por la erosión de los depósitos de pendiente fluvio-nivales y periglaciales que cubrían total o parcialmente, partes de la costa gallega durante la Weichseliense media y tardía. Durante el Holoceno, el nivel del mar y la erosión de los depósitos de pendiente de la zona incrementaron la abrasión causada hasta la gradual migración hasta su posición actual, cerca del nivel de la marea alta. La función espacial y temporal de la abrasión en esta costa es, por tanto, estrechamente relacionado con la exhumación y la herencia de antiguas superficies de las plataformas de debajo de los depósitos Weichseliense.