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

Iberian acid peatlands: types, origin and general trends of development.

ABSTRACT: In the present study we reviewed the genesis, development and classification of peatlands in the Iberian 1. The region has a wide variety of peatlands which are classified according to their biogeochemical, geomorphological and ecological characteristics into different types of bogs and fens. 2. Most of the peatlands occur in the Atlantic region followed by the Mediterranean and Alpine regions. Fens are more widely distributed than bogs, and blanket and raised bogs are mainly found in the Eurosiberian biogeographical region. 3. In many of the fens, the last active peat-forming cycle occurred during the Late Holocene (43 %). In most of the bogs, the peat-forming cycle occurred in the Middle Holocene (70 %), although in a substantial proportion of blanket bogs these processes occurred in the Early Holocene (30 %). 4. The peat formed in the last active cycle is, on average, thicker in raised bogs (322 cm) than in blanket bogs (257 cm) and fens (156 cm). 5. Vertical peat accumulation rates varied between 16 and 30 yr cm-1 in more than 40 % of the peatlands. The accumulation rates differed significantly between the different types of peatlands and were highest in the raised bogs. The accumulation rates were very variable in the fens. 6. The genesis, evolution and types of Iberian peatlands are similar to those observed in peatlands in northern latitudes in Europe and North America.Our research has been made possible by the following project grants: INCITE09-200-019-PR (Xunta de Galicia Government); DESIRÈ-HAR2013-43701-P (Spanish Ministry of Economy and Competitiveness); and Relictflora-P11-RNM-7033 (Excellence Research Projects Program from the Andalusian Government)

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

Introducing global peat-specific temperature and pH calibrations based on brGDGT bacterial lipids

Glycerol dialkyl glycerol tetraethers (GDGTs) are membrane-spanning lipids from Bacteria and Archaea that are ubiquitous in a range of natural archives and especially abundant in peat. Previous work demonstrated that the distribution of bacterial branched GDGTs (brGDGTs) in mineral soils is correlated to environmental factors such as mean annual air temperature (MAAT) and soil pH. However, the influence of these parameters on brGDGT distributions in peat is largely unknown. Here we investigate the distribution of brGDGTs in 470 samples from 96 peatlands around the world with a broad mean annual air temperature (-8 to 27 degrees C) and pH (3-8) range and present the first peat-specific brGDGT-based temperature and pH calibrations. Our results demonstrate that the degree of cyclisation of brGDGTs in peat is positively correlated with pH, pH = 2.49 x CBTpeat + 8.07 (n = 51, R-2 = 0.58, RMSE = 0.8) and the degree of methylation of brGDGTs is positively correlated with MAAT, MAAT(peat) (degrees C) = 52.18 x MBT'(5me) - 23.05 (n = 96, R-2 = 0.76, RMSE = 4.7 degrees C). These peat-specific calibrations are distinct from the available mineral soil calibrations. In light of the error in the temperature calibration (similar to 4.7 degrees C), we urge caution in any application to reconstruct late Holocene climate variability, where the climatic signals are relatively small, and the duration of excursions could be brief. Instead, these proxies are well-suited to reconstruct large amplitude, longer-term shifts in climate such as deglacial transitions. Indeed, when applied to a peat deposit spanning the late glacial period (similar to 15.2 kyr), we demonstrate that MAAT(peat) yields absolute temperatures and relative temperature changes that are consistent with those from other proxies. In addition, the application of MAAT(peat) to fossil peat (i.e. lignites) has the potential to reconstruct terrestrial climate during the Cenozoic. We conclude that there is clear potential to use brGDGTs in peats and lignites to reconstruct past terrestrial climate. (C) 2017 The Authors. Published by Elsevier Ltd

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