Preferential degradation of polyphenols from Sphagnum - 4-isopropenylphenol as a proxy for past hydrological conditions in Sphagnum-dominated peat

The net accumulation of remains of Sphagnum spp. is fundamental to the development of many peatlands. The effect of polyphenols from Sphagnum on decomposition processes is frequently cited but has barely been studied. The central area of the Rödmossamyran peatland (Sweden) is an open lawn that consists mostly of Sphagnum spp. with a very low contribution from vascular plants. In order to determine the effects of decay on sphagnum phenols, 53 samples of a 2.7 m deep core from this lawn were analysed with pyrolysis gas chromatography-mass spectrometry (pyrolysis-GC/MS) and compared with more traditional decomposition proxies such as C/N ratio, UV light transmission of alkaline peat extracts, and bulk density. Factor Analysis of 72 quantified pyrolysis products suggested that the variation in 4-isopropenylphenol was largely determined by aerobic decomposition instead of Sphagnum abundance. In order to evaluate the effects of aerobic decay in Sphagnum peat, down-core records from different climatic regions were compared using molecular markers for plant biopolymers and C/N ratio. These included markers for lignin from vascular plants ((di)methoxyphenols), polyphenols from Sphagnum spp. (4-isopropenylphenol), and cellulose (levoglucosan). Our results indicate that polyphenols from Sphagnum are preferentially degraded over polysaccharides; consequently the variability of the marker for sphagnum acid, 4-isopropenylphenol, was found indicative of decomposition instead of reflecting the abundance of Sphagnum remains. The fact that 4-isopropenylphenol is aerobically degraded in combination with its specificity for Sphagnum spp. makes it a consistent indicator of past hydrological conditions in Sphagnum-dominated peat. In contrast, the variability of C/N records in Sphagnum-dominated peat was influenced by both vegetation shifts and decomposition, and the dominant effect differed between the studied peatlands. Our results provide direction for modelling studies that try to predict possible feedback mechanisms between peatlands and future climate change, and indicate that the focus in Sphagnum decay studies should be on carbohydrates rather than on phenolic compounds

Patterning total mercury distribution in coastal podzolic soils from an Atlantic area: influence of pedogenetic processes and soil components

Soils are the main Hg reservoir in the terrestrial ecosystems where it is deposited via wet or dry deposition and litterfall. Once on the soil surface, different biogeochemical routes will determine the fate of Hg and the role of terrestrial ecosystems as a Hg source or sink. The specific chemical and physical characteristics of Podzols and podzolic soils contribute to the accumulation of Hg in their illuvial horizons, avoiding its leaching to groundwater. The geographical location, state of pedogenesis, soil age, abundance of carrier phases and physical properties can affect the presence and distribution of Hg in soils. Therefore, understand and relate these factors with the behavior of Hg in Podzols and podzolic soils is key to define the role of this type of soil in the terrestrial Hg cycle. In this work, ten podzolic soil profiles were collected in an Atlantic coastal forest area of Portugal and analyzed for the main physico-chemical properties and Hg content to assess the influence of the intensity of podzolization in the Hg depth distribution. Three different patterns of Hg distribution in the studied Podzols, depending on the predominance of atmospheric deposition or the intensity of podzolization, have been defined. The pattern I showed the maximum Hg contents in the surface A horizons (12.9–23.5 μg kg 1), pattern II exhibited the highest peaks in the subsurface illuvial horizons (2.3–17.3 μg kg 1) and pattern III presented an even distribution of Hg through the soil profile. We found that dissolved organic matter (DOM) is the main carrier of Hg in the A and E horizons, whereas metal(Al, Fe)-humus complexes and/or oxyhydroxides contribute to immobilizing Hg in the illuvial horizons (Bh, Bs and Bhs). The principal component regression (PCR) analysis predicted satisfactorily the Hg distribution through soil organic matter and Al and Fe oxyhydroxides. The Hg immobilized in the subsurface layers of Podzols is retained in the long term, avoiding its migration to other components of terrestrial ecosystems where it could cause serious environmental damage such as groundwater and superficial watersinfo:eu-repo/semantics/publishedVersio

Influencia del tipo de vegetación en la cantidad de Hg acumulado en horizontes orgânicos de suelos forestales del NE de Portugal

El papel de los suelos forestales como reservorio de Hg es clave en su ciclo biogeoquímico en los ecosistemas terrestres, función que puede verse influenciada por el tipo de especie forestal en base a la diferente capacidad de estas para capturar el Hg atmosférico y de transferirlo hacia los horizontes superficiales mediante la caída de material senescente. El principal objetivo de este estudio es evaluar el efecto del tipo de especie forestal en la presencia y acumulación (reservorio) de Hg en los horizontes orgánicos de suelos forestales. En el NE de Portugal se seleccionaron nueve parcelas forestales, tres dominadas por Pseudotsugamenziesii (PM), otras tres por Pinusnigra (PN) y tres más por Quercuspyrenaica (QP). En todas ellas se tomaron muestras de los horizontes orgánicos (Oi, Oe y Oa) en 5 localizaciones diferentes, analizando los niveles de Hg total (HgT) en cada una de las muestras (n= 134). Los niveles medios de HgT en los suelos de las parcelas de PM fueron 112, 170 y 142 ng g‐1 en los subhorizontes Oi, Oe y Oa, respectivamente. Estos valores fueron significativamente mayores que sus equivalentes en los suelos de PN (65, 92 y 108 ng g‐1 en Oi, Oe y Oa) y en los de QP (75, 106 y 122 ng g‐1 en Oi, Oe y Oa), mientras que no hubo diferencias entre los subhorizontes O de PN y QP. El HgT acumulado en los horizontes orgánicos (reservorio) fue también significativamente mayor en las parcelas de PM cuyos valores (83, 162 y 226 μg m‐2 para subhorizontes Oi, Oe y Oa, respectivamente) son el doble del que presentan las parcelas de PN (47, 74 y 108 μg m‐2 para Oi, Oe y Oa) y de QP (45, 40 y 105 μg m‐2 para Oi, Oe y Oa). Estos resultados indican que el tipo de especie ejerce una notable influencia en la presencia y acumulación de HgT en las capas más superficiales de los suelos forestales, especialmente cuando se trata de coníferas.info:eu-repo/semantics/publishedVersio

Climate Impacts of the Common Era on Aquatic Systems in NW Spain: preliminary results

Poster.-- Clivar 2023, Towards an integrated view of climate, 24-26 January, MadridEcological resistance and resilience of freshwater ecosystems is intimately linked to climate variability. To the extent of our knowledge, this issue has never been addressed using a long-term paleoecological perspective in Galicia (NW Spain). Project IMPACOM (Climate Impacts of the Common Era on Aquatic Systems in NW Spain, Spanish Ministry of Science and innovation, PID2019-107424RB-I00) is intended to study the impacts of changes in the precipitation regime and storm conditions, among other climate forcing factors, on coastal lakes and their enclosing barriers, as well as on bogs and mountain lakes in the region during the Common Era (CE, last 2,000 yr). To identify and precisely date the major ecological transitions of the CE we use a multidisciplinary approach which includes sedimentological facies analysis, inorganic bulk geochemical analyses (from X-ray fluorescence analysis, core scanning, Fourier-transform infrared spectroscopy, estimation of humification indexes, elemental and isotopic analyses of organic matter, biogenic silica), biological proxies (diatoms, pollen, plant macrofossils, testate amoeba and chironomids), as well as a set of geochronological techniques (AMS radiocarbon dating, concentrations of fallout 137Cs, 210Pb, 214Pb and 241Am, OSL dating)The study of the lacustrine sedimentary record of the coastal Lake Doniños, as well as of the sand barrier which encloses this lake and that of the wetland of Pantín, both in A Coruña province, shows a history of breaching and overwashing linked to the intensification of storms and enhanced precipitation over the last 4,500-4,000 yr. For the case of the last 2,000 yr, catastrophic emptying of Lake Doniños took place during the Dark Ages (DA, 350-750 CE) and the Little Ice Age (LIA, 1500-1930 CE). The transition from the Medieval Climate Anomaly (MCA) to the LIA involved in this lake a gradual 200 yr long transformation from an isolated lake to an intermittent tidal lagoon until the LIA breaching episode. Lake Ocelo, an oligotrophic mountain lake located in the Trevinca Massif (Ourense province) shows a net eutrophication trend since the termination of the Subatlantic period. This trend was however interrupted by oligotrophication events in the warm/cold transitions of the Roman Warm Period to the DA, lasting 500 years, and the MCA to LIA, which lasted 600 years. Extended ice cover during the LIA, as suggested by the preliminary diatom data, involved stronger denitrification processes associated to longer periods of anoxia, indicated by the nitrogen isotopic record. Anticipation of the oligotrophication events to the known chronologies for the onset of the DA and the LIA suggests that these two phases occurred approximately 100 and 200 years earlier than expected, according to other mountain lake record of the W Iberian Peninsula. Our preliminary data also show significant discrepancies in the timing of the ecological impacts of Recent Climate Changes (RCCs) taking place in the last 2,000 yr in coastal and mountain areas over a short longitudinal gradient which needs further explorationN

Geo‐Hydromorphological Assessment of Europe’s Southernmost Blanket Bogs

Blanket bogs are a globally rare type of ombrotrophic peatland internationally recognised for long‐term terrestrial carbon storage, the potential to serve as carbon sinks, habitat provision and for their palaeoenvironmental archive. This habitat is protected in the European Union under the Habitats Directive (92/43/EEC), but a number of blanket bogs located in the Cantabrian Mountains (northern Spain), representing the southernmost known edge‐of‐range for this habitat in Europe, are currently not recognised and are at increased threat of loss. Using climatic data, topography, aerial photography and peat depth surveys, this study has identified ten new areas of blanket bog located between the administrative regions of Cantabria and Castilla y León. Peat depth data and topography were used to provide a detailed geomorphological description and hydromorphological classification (mesotope units) of these currently unrecognised areas of blanket bog. Maximum peat depth measured across the ten sites ranged from 1.61 m to 3.78 m covering a total area of 18.6 ha of blanket bog (> 40 cm peat depth). The volume of peat accumulated across the sites was determined to be more than 216,000 m3 and is estimated to hold 19.89 ± 3.51kt C. Twenty‐four individual hydrological mesotope units were described indicating a diverse assemblage of blanket bogs in this region. The peatlands identified in this research extend the known limit of blanket bogs in Europe farther south than previously recorded and combined with four other unprotected blanket bogs recently identified in the Cantabrian Mountains, these peatlands represent 10.5% of blanket bog currently recognised and protected in Spain. The range of anthropogenic pressures currently acting on peatlands in the Cantabrian Mountains indicates that without protection these important landforms and carbon stored may be lost. An urgent update of European peatland inventories is thus required to preserve these valuable carbon stores and potential carbon sinks

The peatland map of Europe

Based on the ‘European Mires Book’ of the International Mire Conservation Group (IMCG), this article provides a composite map of national datasets as the first comprehensive peatland map for the whole of Europe. We also present estimates of the extent of peatlands and mires in each European country individually and for the entire continent. A minimum peat thickness criterion has not been strictly applied, to allow for (often historically determined) country-specific definitions. Our ‘peatland’ concept includes all ‘mires’, which are peatlands where peat is being formed. The map was constructed by merging national datasets in GIS while maintaining the mapping scales of the original input data. This ‘bottom-up’ approach indicates that the overall area of peatland in Europe is 593,727 km². Mires were found to cover more than 320,000 km² (around 54 % of the total peatland area). If shallow-peat lands (< 30 cm peat) in European Russia are also taken into account, the total peatland area in Europe is more than 1,000,000 km2, which is almost 10 % of the total surface area. Composite inventories of national peatland information, as presented here for Europe, may serve to identify gaps and priority areas for field survey, and help to cross-check and calibrate remote sensing based mapping approaches

Selecting parameters for the environmental interpretation of peat molecular chemistry - A pyrolysis-GC-MS study

A number of samples from a deep peat bog in Tierra del Fuego were analyzed using pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) in order to extract parameters that might be used to interpret the peat chemistry in terms of vegetation change, anaerobic and aerobic decomposition, and fire incidence. The choice of parameters was based on factor analysis of 177 pyrolysis products, quantified for 13 samples, separated into extract and residue, as well as the total samples. Factor analysis of extracts, residues and total samples yielded similar classifications in terms of vegetation and decomposition. Pyrolysis products and ratios that most clearly differentiated samples were used to interpret the depth profile. Although interpretation was not always straightforward, indications of parameters to describe vegetation shifts, aerobic and anaerobic decomposition, and fire largely coincided. These parameters will be used in a forthcoming study for a more complete interpretation of the peat profile