Identificación, caracterización molecular y significado de los residuos de fuego en los suelos coluviales de Campo Lameiro (NO Peninsular)

The thick organic matter-rich colluvial soils of NW Spain (Atlantic rankers), which formed as a result of Holocene slope transport processes, might well contain large amounts of Black C from palaeofires, not only as large charcoal fragments (as was frequently reported) but also as finely divided and amorphous, largely NaOH-extractable material, as appeared to be the case for the soils of the study area. Therefore, Black C may be a major agent in the pedogenesis of these soils. Furthermore, the abundance of Black C may be responsible for the deep dark colour and explain the high resistance of the soil organic matter against biological degradation, in combination with occlusion and the traditional sorptive preservation mechanisms. The indirect evidence of human influence in the fire regime that created these soils implies that the Atlantic rankers have an anthropogenic character. Upon long-term burial, Black C becomes increasingly oxidised, depolymerised, depolyaromatised, fractionated (on a macrostructural scale) and incorporated in the fine fabric of the soils studied here. The results presented suggest significant alteration of Black C on the millennial scale. The difficulties in recognising amorphous and degraded Black C without application of advanced molecular characterisation techniques explains why fire (thermal modification) was hitherto ignored as a major cause of soil organic matter stability in Atlantic rankers. In the study area, local deforestation and shrubland expansion started already ca. 7000 cal BP and accelerated since ca. 6000–5500 cal BP. In all likelihood, past societies used fire to clear the land and facilitate animal grazing, but climate deterioration after the Holocene Thermal Maximum and Roman Warm Period may have catalysed human inpact on the vegetation patterns. Fabaceae and Ericaceae shrubland communities first colonised the upper slopes of the hill and then probably expanded into the lower areas. The deciduous forest never completely recovered after the phases of forest retreat (ca. 7000–6500 cal BP, 5700–5300 cal BP, 4000–3500 cal BP, 3000–2000 cal BP and 2000–1500 cal BP) because of the intense burning and grazing disturbance regime imposed. This process might reflect the formation of the traditional dual landscape that can still be observed nowadays: shrubland and pasture grounds at o monte and cultivated land and some fragmented remains of deciduous forest in the valleys. If this proves correct, the roots of the o monte land use, including slash-and-burn practices and extensive pastoralism, may date back to the Neolithic and perhaps even Late Epipalaeolithic/Mesolithic period

Potential of pyrolysis-GC–MS molecular fingerprint as a proxy of Modern Age Iberian shipwreck wood preservation

Even though pyrolysis in combination with gas chromatography and mass spectrometry (Py-GC–MS) is widely used for molecular characterization of wood, its abilities to determine the taxonomy (species), provenance and the nature and intensity of degradation of archaeological woods are hardly explored. We performed principal component analysis (PCA) on Py-GC–MS data of sound woods and shipwreck woods of Pinus sp. and Quercus sp., to identify the impact of diagenesis on pyrolysis fingerprints. It was found that the proportion of most polysaccharide products decreased significantly upon diagenesis with the exception of 3-hydroxy-2-methyl-2-cyclopenten-1-one, which remains relatively well preserved. Furthermore, the guaiacyl lignin products were generally well preserved with the exception of 4-propylguaiacol, the relative contribution of which decreased considerably. New indices are proposed to establish the preservation state of shipwreck wood (shipwreck wood preservation index; SWPI) on the basis of polysaccharides (SWPIPS) and guaiacyl lignin (SWPILG) and syringyl lignin (SWPILS) fingerprints. Stepwise multiple linear regressions analyses applied on FTIR data of the same samples are indicative of the consistency of both techniques and the potential to identify changes in wood chemistry as a result of degradation. Other factors that influence wood composition, such as the differences between soft- and hardwood lignin and sap- and heartwood were also recognizedThis study was developed within the framework of the ForSeaDiscovery project funded by the European Research Council through the Seventh Framework Programme under grant agreement number 607545. We thank the editor and the anonymous reviewer for their time and insightful commentsS

Composição da matéria orgânica em solos de seis zonas pedoclimáticas de Magdalena (Colômbia)

[ES] Los suelos al noreste del departamento del Magdalena (Colombia) afrontan una creciente degradación, principalmente por las bajas tasas de acumulación de materia orgánica del suelo (MOS) y su reducido período de transformación. Tradicionalmente se han realizado estudios tendentes a mitigar esta situación, pero todos se han centrado en aspectos cuantitativos analizando los contenidos totales de MOS. Por tanto, en el presente estudio se propuso determinar la composición molecular de la MOS en suelos de seis zonas con diferentes características edafoclimáticas en zonas de bosques húmedos y secos tropicales, con una altitud entre 5-956 msnm, temperatura media entre 24-30 °C, precipitación media entre 663-2000 mm y diferentes usos actuales (bosques y cultivos varios). Para ello se caracterizó por pirólisis (acoplada a cromatografía de gases y espectroscopía de masas) la MOS extraída con NaOH 0.1M de muestras superficiales en suelos cultivados y de bosques. Fueron cuantificados 110 productos de pirólisis en la siguiente proporción: compuestos con N (34,1% ± 5,1%), polisacáridos (21,1% ± 7.1%), aromáticos (20,0% ± 4.5%), alifáticos (7,7%± 1,4%), fenoles (7,0% ± 5,0%), poliaromáticos (3,6% ± 0,9%), ligninas (0,3% ± 0,3%) y otros compuestos (0,2% ± 0,1%). A través del análisis de varianza no se encontraron diferencias estadísticas entre los productos de pirólisis para usos del suelo (bosque y cultivados), pero sí para las zonas muestreadas. Por otro lado el análisis factorial por componentes principales permitió reducir el conjunto de compuestos productos de pirólisis en dos variables sintéticas que explicaron el 51% de la variabilidad total. Aunque en todas las zonas se evidenció una MOS con un grado importante de descomposición, el factor 1 permitió separar entre MOS de origen microbiano relativamente descompuesta y MOS fresca o de descomposición lenta y de origen vegetal. En términos generales, las zonas con mayor pluviosidad y menores promedios de temperatura mostraron una contribución relativamente alta de MOS microbiana y, en menor proporción, de MOS de origen vegetal tanto para suelos de bosques como para suelos de cultivo, en contraste con las zonas más secas que presentaron mayor proporción de MOS de origen vegetal.[EN] The soils in the NE of the Magdalena province (Colombia) are subject to intense degradation primarily because of the low accumulation rate of soil organic matter (SOM) and its fast turnover. Numerous traditional studies have aimed to mitigate this situation, focusing on the analysis of total SOM contents. The present study aimed to determine SOM quality from six areas under humid and dry tropical forest with different pedoclimatic conditions, using molecular characterization. For each area, sites with different current land use were studied, including forest and cultivated sites. We applied analytical pyrolysis (pyrolysis-GC/MS) to aqueous NaOH-extractable SOM from surface soil samples. One-hundred and ten pyrolysis products were identified and quantified, from the following chemical groups: N-containing compounds (34.1 ± 5.1%), carbohydrate markers (21.1% ± 7.1%), monocyclic aromatic compounds (20.0% ± 4.5%), aliphatic compounds (7.7% ± 1.4%), phenols (7.0% ± 5.0%), polycyclicaromatic compounds (3.6% ± 0.9 %), lignin products (0.3% ± 0.3%) and other compounds (0.2% ± 0.1%). SOM ofall studied areas showed a large proportion of N-containing products, indicating a high contribution from microbial material to the SOM. Multivariate statistics allowed for the differentiation between microbial-derived and plantderived SOM (Factor 1) and the relative proportion of burning residues (Factor 2), and indicated that pedoclimatic conditions exert more influence on SOM composition (cool and humid zones were enriched in microbial SOM while dry zones contained more plant-derived SOM) than land use for the studied soils.[PT] Os solos a nordeste da provincía de Magdalena (Colombia) estão submetidos a uma crescente degradação, devido principalmente às baixas taxas de acumulação de materia orgânica do solo (MOS) e ao seu reduzido período de transformação. Tradicionalmente têm sido realizados estudos tendentes a mitigar esta situação,mas todos eles focados em aspetos quantitativos analisando os teores totais de MOS. Por este motivo, no presente estudo propõe-se determinar a composição molecular da MOS em solos de seis zonas com diferentes características pedoclimáticas em áreas de floresta húmida e seca tropical, con uma altitude entre 5-956 msnm, temperatura media entre 24- 30 °C, precipitação media entre 663-2000 mm e diferentes usos atuais (floresta e zonas cultivadas). Para esse efeito, caraterizou-se por pirólise (associada a cromatografía gasosa e espetroscopía de massa) a MOS extraída con NaOH 0.1 M de amostras superficiais em solos cultivados e de floresta. Quantificaram-se 110 produtos de pirólise na seguinte proporção: compostos com N (34,1% ± 5,1%), polissacáridos (21,1% ± 7,1%), aromáticos (20,0% ± 4,5%), alifáticos (7,7% ± 1,4%), fenóis (7,0% ± 5,0%), poliaromáticos (3,6% ± 0,9%), lenhina (0,3% ± 0,3%) e outros compostos (0,2% ± 0,1%). Através de análise de variância não se encontraram diferenças estatísticas entre os produtos de pirólise para diferentes usos do solo (floresta e cultivados), mas sim para as zonas amostradas. Por outro lado a análise factorial por componentes principais permitiu reduzir o conjunto de compostos produto da pirólise em duas variáveis sintéticas que permitiram explicar 51% da variabilidade total. Ainda que em todas as zonas se tenha evidenciado uma MOS com um importante grau de descomposição, o factor 1 permitiu separar entre MOS de origem microbiana relativamente decomposta e MOS fresca ou de descomposição lenta e de origem vegetal. Em termos gerais, as zonas con maior pluviosidade e menores temperaturas médias apresentaram uma composição relativamente alta de MOS microbiana e, em menor proporção, de MOS de origem vegetal tanto para solos de floresta como para solos cultivados, contrastando com as zonas mais secas que apresentaram maior proporção de MOS de origem vegetal.Peer Reviewe

The configuration of the cultural landscape during the early Middle Ages (5th-11th centuries): Environmental changes and human activity in the northwest of the Iberian Peninsula

Este trabajo tiene por objetivo aportar algunos elementos para el debate sobre la reconstrucción paleoambien-tal, desde las disciplinas de las Ciencias de la Tierra, centrándose en el período cultural de la Alta Edad Media (siglos V-XI). El artículo se divide en tres apartados. El primero, introduce conceptos básicos sobre la evolu-ción ambiental: ideas generales sobre la reconstrucción paleoambiental y un breve comentario sobre la activi-dad humana en el contexto de los paleoambientes. El segundo, muestra una aproximación metodológica a la reconstrucción desde diferentes disciplinas de las Ciencias de la Tierra. En el tercero, se comentan algunos resultados recientes obtenidos en el noroeste peninsular utilizando ejemplos de archivos que, en este caso, están representados por suelos coluviales y sus señales geoquímicas, analizando los procesos naturales y otros inducidos por la actividad antrópica, con la finalidad de ilustrar los conceptos discutidos en la primera parte. A modo de conclusión, el artículo se cierra con unas pinceladas sobre el paisaje de la Alta Edad Media en el Noroeste Peninsular, a partir de la interpretación y reconstrucción de los datos obtenidosThis paper aims to promote the discussion of some elements relating to paleoenvironmental reconstruction, from the point of view of the Earth Sciences, focusing on the cultural period of the early Middle Ages (5th-11th centuries). The article is divided into three sections. In the first, the basic concepts of environmental evolution are introduced, such as the general ideas of paleoenvironmental reconstruction and a brief commentary on human activity in the context of paleoenvironments. The second section demonstrates a methodological ap-proach to reconstruction from the point of view of different disciplines of Earth Sciences. In the third section, recent results obtained in the northwest of the Iberian Peninsula are commented on, making use of samples of colluvial soils and their geochemical signals obtained from environmental archives. An analysis is made of both natural processes and those caused by human activity, in order to illustrate the concepts discussed in the first part. The article concludes with some comments on the landscape of the early Middle Ages in the north-west of the Peninsula, based on the interpretation and reconstruction of the data obtainedS

Differentiation between pine woods according to species and growing location using FTIR-ATR

Attenuated total reflectance-Fourier transform infrared (FTIR-ATR) spectroscopy was applied to 120 samples of heartwood rings from eight individual pine trees from different locations in Spain. Pinus sylvestris cores were collected at the Artikutza natural park (Ps-ART). Pinus nigra cores were collected in Sierra de Cazorla (Pn-LIN) and in La Sagra Mountain (Pn-LSA). Three discriminant analysis tests were performed using all bands (DFT), lignin bands only (DFL) and polysaccharides bands only (DFP), to explore the ability of FTIR-ATR to separate between species and growing location. The DFL model enabled a good separation between pine species, whereas the DFP model enabled differentiation for both species and growing location. The DFT model enabled virtually perfect separation, based on two functions involving twelve FTIR bands. Discrimination between species was related to bands at 860 and 1655 cm−1, which were more intense in P. sylvestris samples, and bands at 1425 and 1635 cm−1, more intense in P. nigra samples. These vibrations were related to differences in lignin structure and polysaccharide linear chains. Discrimination between growing locations was mainly related to polysaccharide absorptions: at 900, 1085 and 1335 cm−1 more representative of Pn-LIN samples, and at 1105 and 1315 cm−1 mostly associated to Pn-LSA samples. These absorptions are related to β-glycosidic linkages (900 cm−1), cellulose and hemicellulose (C–O bonds, 1085 and 1105 cm−1) and content in amorphous/crystalline cellulose (1315 and 1335 cm−1). These results show that FTIR-ATR in combination with multivariate statistics can be a useful tool for species identification and provenancing for pine wood samples of unknown originS

When is a terrace not a terrace? The importance of understanding landscape evolution in studies of terraced agriculture

Before the invention of modern, large-scale engineering projects, terrace systems were rarely built in single phases of construction, but instead developed gradually, and could even be said to have evolved. Understanding this process of landscape change is therefore important in order to fully appreciate how terrace systems were built and functioned, and is also pivotal to understanding how the communities that farmed these systems responded to changes; whether these are changes to the landscape brought about by the farming practices themselves, or changes to social, economic or climatic conditions. Combining archaeological stratigraphy, soil micromorphology and geochemistry, this paper presents a case-study from the historic and extensive terraced landscape at Konso, southwest Ethiopia, and demonstrates e in one important river valley at least e that the original topsoil and much of the subsoil was lost prior to the construction of hillside terraces. Moreover, the study shows that alluvial sediment traps that were built adjacent to rivers relied on widespread hillside soil erosion for their construction, and strongly suggests that these irrigated riverside fields were formerly a higher economic priority than the hillside terraces themselves; a possibility that was not recognised by numerous observational studies of farming in this landscape. Research that takes into account how terrace systems change through time can thus provide important details of whether the function of the system has changed, and can help assess how the legacies of former practices impact current or future cultivation

Deciphering the unique structure and acylation pattern of Posidonia oceanica lignin

Copyright © 2020 American Chemical Society. Lignins from different parts of the seagrass Posidonia oceanica-namely sheaths, rhizome, and roots-as well as from fibrous balls from P. oceanica detritus were isolated and thoroughly characterized by pyrolysis coupled with gas chromatography/mass spectrometry, derivatization followed by reductive cleavage, two-dimensional nuclear magnetic resonance spectroscopy, and gel permeation chromatography. The lignins of P. oceanica were enriched in guaiacyl (G) over syringyl (S) units, with S/G ratios ranging from 0.1 (fibrous balls) to 0.5 (rhizome). β-O-4′ ethers and phenylcoumarans were the most abundant lignin substructures, followed by resinols, and minor amounts of dibenzodioxocins and spirodienones. Moreover, all lignins were found to be highly I-Acylated (up to 44% of total units), mainly with p-hydroxybenzoates but also, to a lesser extent, with acetates. The data indicated that this acylation extensively occurred in both G-and S-lignin units, contrary to what happens in palms, poplar, and willow, where p-hydroxybenzoates overwhelmingly appear at the I-position of S-units

Shared technologies for pottery and acorns processing? Multidisciplinary and functional approach to modular kilns

This paper deals with the so-called modular kilns, ceramic structures characteristic of the Bronze and Iron Age periods in various regions of Europe. Despite the interest shown in these material forms in recent years, their exact function is still unclear. However, the dominant interpretation within archaeological research has tended to associate them with pottery production. While this hypothesis has been based mainly on macro-observations derived from settlement surveys and excavations, our aim is to go further by exploring through a material- analytical approach. A set of samples from the sites of A Fontela and Castromao, in northwestern Iberia, have been analysed using a set of methods (mineralogical, geochemical, archaeobotanical and organic chemical) to evaluate the hypotheses on production and use. Although the samples share a similar morphology and tech- nology, the analytical results reveal differences in the manufacturing processes between the two sites studied. Local clays, crop by-products and wild plants from the surrounding areas were used in the modelling, but with different purposes. In some cases, cereal chaff was added as a temper. Organic-chemical analysis revealed traces of oils of vegetal origin, with high levels of C18:1 fatty acid (probably mostly oleic acid) and its degradation products, together with phytosterols, such as β-sitosterol, stigmasterol, campesterol, and δ-5-avenasterol. The organic compounds are compatible with the processing or culinary transformation of acorns, that appeared persistently in hearths, pots, and storage structures during Late Prehistory in the regio

Post-disturbance vegetation dynamics during the Late Pleistocene and the Holocene: An example from NW Iberia

This is the post-print version of the final paper published in Global and Planetary Change. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2012 Elsevier B.V.There is a wealth of studies dealing with the reconstruction of past environmental changes and their effects on vegetation composition in NW Iberia, but none of them have focused specifically on the post-disturbance dynamics (i.e. the type of response) of the vegetation at different space and time scales. To fill this gap, we analysed the record of pollen and non-pollen palynomorphs (NPP) of a 235-cm thick colluvial sequence spanning the last ~ 13,900 years. The aims were to detect the changes in vegetation, identify the responsible drivers and determine the type of responses to disturbance. To extract this information we applied multivariate statistical techniques (constrained cluster analysis and principal components analysis on transposed matrices, PCAtr) to the local (hydro-hygrophytes and NPP) and regional (land pollen) datasets separately. In both cases the cluster analysis resulted in eight local and regional assemblage zones, while five (local types) and four (regional types) principal components were obtained by PCAtr to explain 94.1% and 96.6% of the total variance, respectively. The main drivers identified were climate change, grazing pressure, fire events and cultivation. The vegetation showed gradual, threshold and elastic responses to these drivers, at different space (local vs. regional) and time scales, revealing a complex ecological history. Regional responses to perturbations were sometimes delayed with respect to the local response. The results also showed an ecosystem resilience, such as the persistence of open Betula-dominated vegetation community for ~ 1700 years after the onset of the Holocene, and elastic responses, such as the oak woodland to the 8200 cal yr BP dry/cold event. Our results support the notion that palaeoecological research is a valuable tool to investigate ecosystem history, their responses to perturbations and their ability to buffer them. This knowledge is critical for modelling the impact of future environmental change and to help to manage the landscape more sustainably.The Spanish Governmen

Fingerprinting blue carbon: Rationale and tools to determine the source of organic carbon in marine depositional environments

Blue carbon is the organic carbon in oceanic and coastal ecosystems that is captured on centennial to millennial timescales. Maintaining and increasing blue carbon is an integral component of strategies to mitigate global warming. Marine vegetated ecosystems (especially seagrass meadows, mangrove forests, and tidal marshes) are blue carbon hotspots and their degradation and loss worldwide have reduced organic carbon stocks and increased CO2 emissions. Carbon markets, and conservation and restoration schemes aimed at enhancing blue carbon sequestration and avoiding greenhouse gas emissions, will be aided by knowing the provenance and fate of blue carbon. We review and critique current methods and the potential of nascent methods to track the provenance and fate of organic carbon, including: bulk isotopes, compound-specific isotopes, biomarkers, molecular properties, and environmental DNA (eDNA). We find that most studies to date have used bulk isotopes to determine provenance, but this approach often cannot distinguish the contribution of different primary producers to organic carbon in depositional marine environments. Based on our assessment, we recommend application of multiple complementary methods. In particular, the use of carbon and nitrogen isotopes of lipids along with eDNA have a great potential to identify the source and quantify the contribution of different primary producers to sedimentary organic carbon in marine ecosystems. Despite the promising potential of these new techniques, further research is needed to validate them. This critical overview can inform future research to help underpin methodologies for the implementation of blue carbon focused climate change mitigation schemes