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Peatlands are archives of environmental change that can be driven by climate and human activity. Proxies for peatland vegetation composition provide records of (local) environmental conditions that can be linked to both autogenic and allogenic factors. Analytical pyrolysis offers a molecular fingerprint of peat, and thereby a suite of environmental proxies. Here we investigate analytical pyrolysis as a method for biomarker analysis. Pyrolysates of 48 peatland plant species were compared, comprising seventeen lichens, three Sphagnum species, four non-Sphagnum mosses, eleven graminoids (Cyperaceae, Juncaceae, Poaceae), five Ericaceae and six species from other families. This resulted in twenty-one potential biomarkers, including new markers for lichens (3-methoxy-5-methylphenol) and graminoids (ferulic acid methyl ester). The potential of the identified biomarkers to reconstruct vegetation composition is discussed according to their depth records in cores from six peatlands from boreal, temperate and tropical biomes. The occurrence of markers for Sphagnum, graminoids and lichens in all six studied peat deposits indicates that they persist in peat of thousands of years old, in different vegetation types and under different conditions. In order to facilitate the quantification of biomarkers from pyrolysates, typically expressed as proportion (%) of the total quantified pyrolysis products, an internal standard (5-a-androstane) was introduced. Depth records of the Sphagnum marker 4-isopropenylphenol from the upper 3 m of a Sphagnum-dominated peat, from samples analysed with and without internal standard showed a strong positive correlation (r2 = 0.72, P

The occurrence of Umbric Ferralsols with thick umbric epipedons (> 100 cm thickness) in humid Tropical and Subtropical areas is a paradox since the processes of organic matter decomposition in these environments are very efficient. Nevertheless, this soil type has been reported in areas in the Southeast and South of Brazil, and at some places in the Northeast. Aspects of the genesis and paleoenvironmental significance of these Ferralsols still need a better understanding. The processes that made the umbric horizons so thick and dark and contributed to the preservation of organic carbon (OC) at considerable depths in these soils are of special interest. In this study, eight Ferralsols with a thick umbric horizon (UF) under different vegetation types were sampled (tropical rain forest, tropical seasonal forest and savanna woodland) and their macromorphological, physical, chemical and mineralogical properties studied to detect soil characteristics that could explain the preservation of high carbon amounts at considerable depths. The studied UF are clayey to very clayey, strongly acidic, dystrophic, and Al-saturated and charcoal fragments are often scattered in the soil matrix. Kaolinites are the main clay minerals in the A and B horizons, followed by abundant gibbsite and hydroxyl-interlayered vermiculite. The latter was only found in UFs derived from basalt rock in the South of the country. Total carbon (TC) ranged from 5 to 101 g kg-1 in the umbric epipedon. Dichromate-oxidizable organic carbon represented nearly 75 % of TC in the thick A horizons, while non-oxidizable C, which includes recalcitrant C (e.g., charcoal), contributed to the remaining 25 % of TC. Carbon contents were not related to most of the inorganic soil variables studied, except for oxalate-extractable Al, which individually explained 69 % (P < 0.001) of the variability of TC in the umbric epipedon. Clay content was not suited as predictor of TC or of the other studied C forms. Bulk density, exchangeable Al3+, Al saturation, ECEC and other parameters obtained by selective extraction were not suitable as predictors of TC and other C forms. Interactions between organic matter and poorly crystalline minerals, as indicated by oxalate-extractable Al, appear to be one of the possible organic matter protection mechanisms of these soils. A ocorrência de Latossolos com horizonte A húmico hiperdesenvolvido (> 100 cm de espessura) nos trópicos e subtrópicos úmidos é um paradoxo, pois os processos de decomposição da matéria orgânica nesses ambientes são bastante eficientes. Apesar disso, esses solos têm sido documentados nas regiões Sudeste e Sul do Brasil, com algumas ocorrências na região Nordeste. Aspectos da gênese e do significado paleoambiental desses Latossolos aguardam por melhor entendimento. Os processos que levaram o horizonte A a ser tão espesso e escuro e contribuíram para preservação de C orgânico (CO) em profundidades consideráveis nesses pedons são de especial interesse. Neste trabalho, oito Latossolos com horizonte A húmico hiperdesenvolvido (Lh) sob diferentes fitofisionomias (Floresta Ombrófila, Floresta Estacional e Savana Arborizada) foram amostrados e os seus atributos macromorfológicos, físicos, químicos e mineralógicos estudados, com o objetivo de relacioná-los com a preservação de CO em profundidade. Esses Lh são argilosos a muito argilosos, fortemente ácidos, distróficos, álicos e muitos possuem fragmentos de carvão vegetal dispersos na matriz do solo. Caulinita é o principal mineral da fração argila nos horizontes A e B, seguido em abundância por gibbsita e por vermiculita com hidroxi entrecamadas. Este último argilomineral é identificado apenas nos Lh derivados de rochas basálticas da região Sul. Os teores de C total (CT) variam de 5 a 101 g kg-1 no horizonte A húmico. Carbono oxidado por via úmida com dicromato de potássio constitui, em média, 75 % do CT dos horizontes A húmicos, enquanto o C não oxidável com dicromato (C-res), que inclui formas de C recalcitrantes (como carvões), contribui para os restantes 25 % do CT. Os conteúdos de C foram independentes da maioria das variáveis inorgânicas do solo, exceto do Al extraído com oxalato de amônio ácido (OAA), que individualmente explica 69 % (P < 0,001) da variabilidade de CT do horizonte A húmico. Os conteúdos de argila não foram estimadores eficazes do CT e de outras formas de C estudadas, como também não foram: densidade do solo, Al3+ trocável, saturação por Al, capacidade de troca de cátions efetiva e outros parâmetros obtidos por extrações seletivas com OAA e ditionito-citrato-bicarbonato. Interações entre materiais orgânicos e minerais pobremente cristalinos, como indicado pelo Al extraído com OAA, apresentam-se como um dos mecanismos possíveis para proteção da matéria orgânica nesses solos.

Soil organic matter (OM) stability plays an important role in the global carbon cycle. The molecular characterisation of soil OM may contribute to an understanding of the feedback mechanisms between soil OM and climate. Umbric Ferralsols with humic properties (humic Ferralsols) are characterised by a thick dark carbon-rich A horizon, and co-occur next to Umbric Ferralsols without humic characteristics. They are concentrated in south-eastern Brazil which suggests an environmental control. In order to understand OM stability in these soils, humic Ferralsols from three Brazilian biomes were studied, including Cerrado (savanna), subtropical forest and tropical forest. The studied soils were developed on several geological substrates, including basalt, gneiss, chamokites, phyllite and tertiary sediments. The molecular composition of the free light fraction (FLF), occluded light fraction (OLF) and 0.1 M NaOH extractable OM of samples from topsoil and subsoil from eight profiles was examined using analytical pyrolysis (pyrolysis-GC/MS). The light fraction reflects litter and charcoal, obtained by density fractionation before (FLF) and after (OLF) ultrasonic disruption; the NaOH extractable fraction (humic acid + fulvic acid) reflects more decomposed material. The chemical differences among soils from different Brazilian biomes were much smaller than the vertical gradient within each profile. The results showed that, within the light fractions, the content of which varied between 2% and 22% of the total carbon content (C t ), black carbon (BC) derived pyrolysis products showed a higher abundance in the topsoil. In the extractable OM, which varied between 46% and 88% of C t , BC derived pyrolysis products showed a higher abundance in the subsoil. This suggests a continuous input of BC and an increase in the degree of decomposition with depth. Pyrolysis products associated with BC contributed up to 10% to the extractable pyrolysable fraction in the subsoil. The results suggest that degradation of charcoal, which is translocated to the subsoil by macroscopic soil organisms, results in a relative high contribution from naphthalene, 2-ethenylnaphthalene, phenanthrene, benzene, dibenzofuran and benzonitrile (subsoil) compared to (other) polyaromatic hydrocarbons (PAHs; C 1 -, C 2 - and C 3 -naphthalenes and fluorene) in relatively fresh charcoal (topsoil). The results highlight the importance of the subsoil in studies of the long term effects of fire on soil OM and suggest that BC is an important factor that underlies carbon stability in humic Ferralsols.

In archaeology and nature conservation studies, knowledge about (pre)historical land-use is important. The molecular composition of soil organic matter (SOM) supplies information about its history, as its composition is controlled by input material and decay processes. In this study, the molecular composition of SOM of calcareous A-horizons from SE Spain was studied with pyrolysis gas chromatography/mass spectrometry (pyrolysis-GC/MS). The effect of vegetation type (Pinus halepensis forest and Stipa tenacissima grassland), land-use (cultivation with cereals and olive trees) and wildfire were examined. In addition, former grassland and agricultural soils that had been reforested with P. halepensis (35 yr) were selected. Three locations were sampled for each vegetation type, except for the olive tree (two) and cereal (six) fields, resulting in a total of 26 samples. Each sample was a composite of ten sub-samples taken from a plot of 1 ha. After removal of weakly or non-decomposed particulate OM, two OM fractions were obtained; (i) sodium hydroxide (NaOH) extractable OM and (ii) the OM that remained after extraction, which was isolated after dissolution of minerals by repeated hydrofluoric acid (HF) treatment. The NaOH-extractable fraction is generally used in soil chemistry (i.e. humic acid), but surprisingly little is known about the SOM that remains in the residue (i.e. humin plus minerals). Comparison of the two SOM fractions (by factor analyses applied to 82 quantified pyrolysis products) provided insight into soil OM dynamics. Polyaromatic pyrolysis products were more prominent in the extractable OM, while a relative enrichment of aliphatic compounds was found in the non-extractable OM. Although some pyrolysis products were associated with one vegetation type in both SOM fractions (C3-naphthalene, dimethylphenanthrene and 2,3,5-trimethylphenanthrene, retene, and monoterpenes for both burnt and unburnt P. halepensis forest; benzene, naphthalene and C1-naphthalene for burnt and unburnt S. tenacissima grassland), lignin content and composition highly differed between agricultural soils and soils under native vegetation in both SOM fractions. These differences were mainly decay characteristics, reinforced by cultivation. In reforested soils it was still possible to identify their former land-use, decades after the vegetation change. The probability of the sites to be correctly attributed to its present land-use was P > 0.7 for grassland and pine forest, while most of the cultivated sites had a P > 0.5 to be assigned correctly. The results obtained suggest that the molecular composition of SOM has a large potential for reconstructing land-use history, at least at the scale of decades/centuries.

This study on humic acids (HAs) of podzol horizons from the southeastern region of Brazil investigated the accumulation and degradation of soil organic matter (SOM) in warm-climate podzols. Humic acids from sandy coastal Spodosols (Histic Alaquod and Arenic Alorthod) from Cardoso Island in Sao Paulo State were characterized by pyrolysis in combination with gas chromatography and mass spectrometry (Py-GC/MS). The soils developed on quartziticsandynutrient-poor parent materials under restinga forest in a coastal area. The Py-GC/MS results show that the chemical composition of HAs in B horizons in one out of three profiles was influenced by both dissolved organic C (DOC) and C from in situ decaying roots. Carbon derived from DOC dominated in the deepest part of the B horizons. In the Arenic Alorthod (H9) profileSOM from the B horizon seemed to be largely derived from roots. The DOC-derived SOM was characterized by large contributions of phenolmethylphenolsand degraded polysaccharide productswhile root contributions were mainly characterized by lignin products. Aliphatics were most abundant in A horizons (E and EB horizons were not analyzed). Both DOC-derived and lignin-derived SOM showed distinct degradation patterns. The Py-GC/MS results corroborate those obtained by 13C variable amplitude cross polarization magic angle spinning nuclear magnetic resonance spectroscopy and Fourier-transform infrared spectroscopy. Molecular chemistry showed that podzol B horizons are variable in compositionand local influencessuch as drainage and vertical or lateral water transportand SOM decomposition play an important role in podzolization processes in warm climates.

There is little information on the effects of land use change on soil Carbon stocks in Colombian Amazonia. Such information would be needed to assess the impact of this area on the global C cycle and the sustainability of agricultural systems that are replacing native forest. The aim of this study was to evaluate soil carbon stocks and changes after the clearing of the native forest, the establishment of pastures and the reclamation of the degraded pasture, in Caqueta, Colombia. We compared the contents of Total C, Oxidizable C and Non-Oxidizable (stable) C in four different land use systems, namely Monoculture ( Brachiaria grassland), Association ( Brachiaria + Arachis pintoi ), Forage Bank (a mixture of forage tree species), and Natural Regeneration of the pasture in both a flat area and a sloping one. The Degraded Pasture was the reference. Results showed that in the sloping area all treatments have higher Total Carbon stocks than the Degraded Pasture, while three of the treatments significantly increased the stocks of Non-Oxidizable C. In the flat landscape, only the Association significantly increased Total C stocks. Plowing and fertilization cause significant increases in Oxidizable carbon and decreases in Non-Oxidizable carbon. This effect needs further research, as C stability will influence equilibrium stocks. In the sloping area, improved pastures and fodder bank rapidly increased Total Carbon contents and stocks, with increases as large as10 ton.ha −1 yr −1 . In the Traditional Fodder Bank, which showed the largest increase, this is partially due to the application of organic manure. Surprisingly, also C stocks under Natural Regeneration were significantly higher than under the original Degraded Grassland. This increase was fully due to Non-Oxidizable Carbon, which is difficult to explain. Stable isotope analysis indicated that under improved grassland, especially Brachiaria monoculture, up to 40% of the original C in the upper 10 cm was replaced in 3.3 years.

We identified the effects of vegetation changes, and aerobic and anaerobic decay on the lignin composition in the Penido Vello peat record (Galicia, Spain). The ombrotrophic part of this peat record was dominated by graminoids and has significant contributions of ericoids at some depths. The organic matter (OM) of different peat fractions (bulk, NaOH-extractable fraction, and non-extractable residues) of 15 samples from the upper meter was analysed with pyrolysis-gas chromatography/mass spectrometry (pyrolysis-GC/MS). In addition, the dominant plant species were analysed, including Carex durieui, Agrostis curtisii, Molinia caerulea, Deschampsia flexuosa, Festuca rubra, Eriophorum angustifolium, Erica mackaiana and Calluna vulgaris, and their lignin composition compared to that of the peat OM. The high abundance of guaiacol and 4-formylguaiacol in fresh plant tissue compared to peat OM suggests that in addition to p-coumaric and ferulic acid (which are abundant in graminoids), other non-lignin phenolic monomers are contributed by graminoid species. For the non-lignin phenolics, graminoids differed from ericoids in the high abundance of ferulic acid (4-vinylguaiacol), while p-coumaric acid (4-vinylphenol) showed high and similar abundances in ericoids and graminoids. This result suggests that ratios between p-hydroxyphenyl (or p-coumaric acid) and other lignin moieties in (pyrolysates of) peat cannot be used as source indicator. Comparison of plant and peat fractions using factor analysis allowed a distinction between the effects of source (plant identity) and decay on the lignin composition of the Penido Vello peat, and different stages of decomposition were identified. Preferential decay of guaiacyl over syringyl moieties was found for the first stage of decay. This preferential decay is probably related to the large abundance of guaiacyl moieties in easily degradable non-lignin phenolics. Preferential decay of syringyl moieties occurred during subsequent aerobic decay.

Knowledge of the spatial distribution of total carbon is important for understanding the impact of regional land use change on the global carbon cycle. We studied spatial total carbon variability using transect sampling in an Imperata grassland area. Spatial variability was modeled following an isotropic stationary process with spherical and exponential variogram functions. Range and sill were estimated at 100 m and 82.29 ton2 ha-2, respectively. For nugget, sill ratio was estimated at 24%, implying a rather strong spatial dependence. In a subsequent total carbon stock inventory based on the sampling design mentioned above, we applied three types of estimators, namely, “naive average procedure,” “spatial average procedure,” and “spatial optimal procedure.” Estimation of total carbon stock (in ton ha-1) following naive average procedure (which erroneously ignores the spatial dependence) resulted in a considerably too narrow 95% confidence interval of 37.52 to 39.75, whereas the outcomes using spatial average procedure and spatial optimal procedure were 36.54 to 40.73 and 37.14 to 40.78), respectively, using the spherical model, and 36.63 to 40.64 and 37.07 to 40.64, respectively, using the exponential model. Our research indicated that, when total carbon stock estimation is the main goal, random sampling is optimal, whereas wide design sampling (i.e., shortest distance between sampling locations not less than the range) can be preferred in some cases

Between 30 and 63% of the soil organic matter (SOM) is stored below 30 cm, making subsoil-SOM an important source and sink in the global carbon cycle. Nevertheless, detailed information on the composition of subsoil-SOM remains scarce. This study aims to evaluate the chemical composition of SOM in topsoil and subsoil horizons in broadleaved forests on acid loamy soils. Six sites were chosen in Northern Belgium under beech, oak and hybrid poplar, on Gleysols, Umbrisols, Cambisols and Albeluvisols on loamy Quaternary deposits. Analytical pyrolysis–gas chromatography/mass spectrometry (pyrolysis–GC/MS) was performed on the dialyzed alkaline extract, which represents between 41 and 90% of the total organic carbon for the selected sites. All extracts show a significant shift in chemical composition between the topsoil and the subsoil. While topsoil-SOM mainly differs according to input and nutrient status, subsoil-SOM shows high relative amounts of alkanes and alkenes or polysaccharides for coarse and fine textured soils respectively. Lignins, lignin-derived phenols or aromatics were not major contributors to subsoil-SOM, regardless of soil type. Furthermore, results show that very labile plant-derived molecules are present in the subsoil, i.e. long-chain aliphatics and (cellulose-derived) anhydrosugars. The organic matter signature of the subsoil samples was evaluated for typical indications of fresh material, decay, podzolisation and anaerobic processes, and indicates root input and stabilization of certain labile plant-derived compounds against microbial decay to be important in the subsoil.

Soil organic matter (SOM) in Alu-andic Andosols and Alu-humic Umbrisols is believed to accumulate because of the protection caused by binding to aluminium (Al). We investigated soils that differed in the abundance of organo-Al complexes to determine the effect of such binding on SOM chemistry. For this, the surface horizons of three types of acid soils in the Basque Country (northern Spain) under forest stands were studied: (i) Alu-andic Andosols (AND soils) on basalts and trachytes, (ii) Umbrisols or so-called 'aluminic'(ALU) soils also on basalts and trachytes and (iii) soils with a podzolizing trend (POD), on quartzites. Values of Al extractable with sodium pyrophosphate (Alp) in the surface horizons of these soils ranged between 8.5 and 13.1, 1.9 and 9.3, and 0.8 and 3.7 g kg-1 dry weight, for the AND, ALU and POD soils respectively. For POD and ALU soils, surface horizons were sampled at two depths, 0-5 and 5-20 cm, whereas the AND soils were sampled at different depths down to the B horizon. NaOH-extractable SOM from three AND soils, 12 ALU soils and 12 POD soils was studied by pyrolysis-gas chromatography/mass spectrometry. The POD soils had the largest loads of plant-derived markers (lignin, long-chain alkanes and alkenes, methyl ketones, fatty acids); SOM of the AND soils had the smallest amounts of plant-derived SOM and the largest amounts of microbial products (microbial sugars and N-compounds) of the soils studied. ALU soils had an intermediate pattern, as expected. The results indicate that the SOM of Alu-andic Andosols, developed from basalt and trachyte rocks, is essentially dissimilar to that of soils derived from quartz-rich parent material, under the same climate conditions and similar forest stands. The dominance of secondary (microbial-derived) SOM in Alu-andic Andosols, also observed in previous research on Sil-andic Andosols (these are dominated by short-range ordered Si compounds in contrast to the dominance of organo-Al complexes in Alu-andic Andosols), reveals the small contribution of primary (plant-derived) material to SOM in soils with andic properties. © 2011 The Authors. Journal compilation © 2011 British Society of Soil Science., M.S.A.’s period at Wageningen University was funded by INIA, Instituto Nacional de Investigación y Tecnología Agraria y Alimentación (proyecto SUM2006-0013.00.00). N.G.B. was funded by the same Project.

n-Alkane distributions are frequently used as palaeoclimate proxies in ombrotrophic peat deposits. Although n-alkane distributions differ strongly between plant species, n-alkanes are not species-specific molecules. For a proper interpretation, it is important to understand the different abundances of n-alkanes in various plant species as well as the changes that occur when plant litter is transformed to peat. In particular because molecular markers are especially valuable in highly decomposed peat where plant remains are no longer recognizable, it is important to understand the effects of decomposition on n-alkane distributions. The organic matter (OM) of a high-resolution sampled, 9 m thick, ombrotrophic peat deposit from Tierra del Fuego was analysed with pyrolysis-gas chromatography/mass spectrometry (pyrolysis-GC/MS). The same samples were analysed for carbon (C) and nitrogen (N) content. Depth profiles of C:N ratio, the summed lignin and summed polysaccharide pyrolysis products, and markers specific for Sphagnum spp., Empetrum rubrum and Nothofagus antarctica, enabled a reconstruction of changes in vegetation composition to be made. This reconstruction was used to examine the validity of the n-C23 alkane to indicate Sphagnum and the summed long chain n-alkanes (C29 and C31) to reflect leaf input of the woody species E. rubrum and N. antarctica. Our results show that even in Sphagnum-dominated peat, the n-alkane distribution is not determined by Sphagnum but by leaf input of E. rubrum and N. antarctica. However, good correlations between the n-C23 alkane and the Sphagnum marker 4-isopropenylphenol, and between the summed n-C29 and n-C31 alkanes and the marker of N. antarctica support that their relative change with depth can be used to indicate the abundance of these species in Sphagnum-dominated peat. In peat with relatively low contributions of Sphagnum, both n-alkane proxies (C23 and C29 + C31) reflect the degree of decomposition. We evaluated the influence of Sphagnum dominance, decomposition, and pyrolysis on the n-alkane distributions in peat OM.

In the comparison of treatments in soil science experiments, a well-chosen experimental design is of crucial importance for making appropriate (optimal) statistical inference at low (lowest) costs. In the very common case that several observations from each plot are obtained, one should be aware that measurement units are not equivalent to so-called statistical experimental units. We illustrate the severe consequences of misinterpretations in some very commonly used experimental designs. Appropriate methodology is developed, which entails the aggregation of observations at the plot level based on the tools of spatial statistics, followed by a classical statistical analysis on the plot aggregated data. The model-based approach, in contrast to the design-based approach, appears to be a natural setting for comparison of treatments in soil-based experiments. Consequences for the planning of the experimental design are discussed, and recommendations are given

While the influence of climate, vegetation, management and abiotic site factors on total carbon budgets and turn-over is intensively assessed, the influences of these ecosystem properties on the chemical complexity of soil organic matter (SOM) remains poorly understood. This study addresses the chemical composition of NaOH-extracted SOM from maritime temperate forest sites in Flanders (Belgium) by pyrolysis-GC/MS. The studied forests were chosen based on dominant tree species (Pinus sylvestris, Fagus sylvatica, Quercus robur and Populus spp.), soil texture and soil-moisture conditions. Differences in extractable-SOM pyrolysis products were correlated to site variables including dominant tree species, management of the woody biomass, site history, soil properties, total carbon stocks and indicators for microbial activity. Despite of a typical high intercorrelation between these site variables, the influence of the dominant tree species is prominent. The extractable-SOM composition is strongly correlated to litter quality and available nutrients. In nutrient-poor forests with low litter quality, the decomposition of relatively recalcitrant compounds (i.e. short and mid-chain alkanes/alkenes and aromatic compounds) appears hampered, causing a relative accumulation of these compounds in the soil. However, if substrate quality is favorable, no accumulations of recalcitrant compounds were observed, not even under high soil-moisture conditions. Former heathland vegetation still had a profound influence on extractable-SOM chemistry of young pine forests after a minimum of 60 years.

Humic acids have been widely investigated by spectroscopic methods, especially NMR and FTIR, and they are known to show significant differences according to their origin. Low resolution methods such as NMR and FTIR, however cannot easily distinguish different input sources or establish relations between SOM chemistry and vegetation or land use in general. High resolution methods, such as analytical pyrolysis and pyrolysis combined with methylation do offer such possibilities. Therefore, HAs from five reference soils called the Eurosoils, including a Vertic Cambisol (E1, Italy), a Rendzina (E2, Greece), a Dystic Cambisol (E3, Great Britain), an Orthic Luvisol (E4, France) and an Orthic Podzol (E5, Germany), that were previously characterized a.o. by NMR, FTIR and ESR, were also analyzed by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and thermally assisted hydrolysis and methylation (THM) and subsequent analysis by GC/MS. The Orthic Podzol sample showed the largest aliphaticity, and the strongest degradation of aliphatics and lignin. The Dystric Cambisol featured the least decomposed HA, which was reflected by a large content of long-chain alkanes, and little lignin degradation. Both the Dystric Cambisol and the Orthic Luvisol HAs contained a significant amount of microbial organic matter. Polyaromatics, which indicate the presence of charred material, were most abundant in the Vertic Cambisol and the Podzol HAs and lowest in the Dystric Cambisol and the Rendzina HAs. THM was able to distinguish between the various vegetations/land uses. Although quantifications by NMR and py-GC/MS are essentially different, the general results largely coincided. NMR appears to underestimate aromaticity and overestimate aliphaticity, but a molecular mixing model yielded reasonable correlations between NMR and pyrolysis data. Classification by ‘degradation state’ based on py-GC/MS largely coincided with acidity determined by titration, but FTIR data did not coincide. Py-GC/MS, with its much larger resolution, is a better tool to distinguish effects of vegetation, microbial input, and degradation. HA's produce the same variety of compounds upon pyrolysis as total SOM extracts and are therefore chemically not more simple than SOM. HA chemistry, however can be understood in the light of land use history and SOM dynamics.

Soil organic matter (SOM) is a key factor in ecosystem dynamics. A better understanding of the global relationship between environmental characteristics, ecosystems and SOM chemistry is vital in order to assess its specific influence on carbon cycles. This study compared the composition of extracted SOM in 18 topsoil samples taken under tundra, taiga, steppe, temperate forest and tropical forest using pyrolysis–GC/MS. Results indicate that SOM from cold climates (tundra, taiga) still resembles the composition of litter, evidenced by high quantities of levosugars and long alkanes relative to N-compounds and a clear odd-over-even dominance of the longer alkanes. Under temperate conditions, increased microbial degradation generally results in a more altered SOM chemistry. SOM formed under temperate coniferous forests shows an accumulation of aromatic and aliphatic moieties, probably induced by substrate limitations. Tropical SOM was characterized by an SOM composition rich in N-compounds and low in lignins, without any accumulation of recalcitrant fractions (i.e. aliphatic and aromatic compounds). Lignin composition moreover varies according to vegetation type. Results were validated against 13 new samples. The humic signature of topsoil organic matter formed under different biomes indicates a dominating effect of (i) SOM input composition related to vegetation, and (ii) SOM breakdown reflecting both climate and input quality. No evidence was found for a chemically stabilized SOM fraction under favorable decomposition conditions (temperate or warm climate with broadleaved vegetation).

Soil characteristics in palaeosols are an important source of information on past climate and vegetation. Fingerprinting of soil organic matter (SOM) by pyrolysis-GC/MS is assessed as a proxy for palaeo-reconstruction in the complex of humic layers on top of the Rocourt pedosequence in the Veldwezelt-Hezerwater outcrop (Belgian loess belt). The fingerprints of the extractable SOM of different soil units are related to total organic carbon content, δ13C and grain-size analysis. Combined results indicate that the lower unit of the humic complex reflects a stable soil surface, allowing SOM build-up, intensive microbial activity and high decomposition. Higher in the profile, decomposition and microbial activity decrease. This is supported by a shift in the isotopic signal, an increasedUratio and evidence of wildfires. Although the chemical composition of the extracted SOM differed greatly from recent SOM, fingerprinting yielded detailed new information on SOM degree of decomposition and microbial contribution, allowing the reconstruction of palaeo-environmental conditions during pedogenesis.

The soil memory recorded in paleosols of loess-paleosol sequences is an important contributor to our understanding of past climatic conditions. Molecular proxies based on the organic matter preserved in paleosols form an essential part of this record, but the long-term preservation of SOM is poorly understood, especially for sediment traps and slope profiles. This paper addresses the composition of organic material from the Early Weichselian A-horizons of the Rocourt paleosol, a major paleostratigraphic marker for the Eemian and Early Weichselian in Western Europe. NaOH-extractable organic matter from an exceptionally thick Rocourt profile in the Kesselt Quarry (Belgian Loess Belt) was analyzed by pyrolysis-Gas Chromatography/Mass Spectrometry (pyrolysis-GC/MS) and the results evaluated against paleopedological data. The molecular composition of the organic matter at Kesselt was compared with reference samples from two nearby quarries (including the type locality at Veldwezelt-Hezerwater), and to a sample from the contemporary Nussloch sequence in Germany. The SOM composition found at the four sites indicated a large content of microbial matter and was dominated by carbohydrates and N compounds, many of which were not reported before from SOM pyrolysates. Differences in the molecular composition between samples, both within profiles and between sites, coincided with differences in landscape position (slope-shoulder-plateau) and fossil redox conditions (surface gleys). Samples form drier and more upland situations contained more burnt material, while samples from slope profiles and surface gleys contained even more microbial material, in particular chitin. Results therefore suggest that the admixture of microbial SOM is considerable in loess-paleosols and that differences in edaphic conditions (in particular slope position and soil moisture) and occurrence of wildfires are important for the long-term preservation of SOM. These should therefore be considered when interpreting biogeochemical proxies.

We performed solid state 13C cross-polarization magic angle spinning (CPMAS) nuclear magnetic resonance (NMR) spectroscopy and pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS) on the Penido Vello peat deposit located in Galicia, NW Spain. Often regarded as complementary techniques, solid state 13C NMR and Py–GC/MS are widely used for the characterisation of organic matter. Recently, a molecular mixing model (MMM) was proposed to predict the distribution of C in biochemical components (carbohydrate, protein, lignin, lipid, char) from the 13C NMR spectral distribution, thereby allowing a quantitative comparison with Py–GC/MS product abundances. We discuss the application of this model to a peat core, by comparing NMR-MMM results with Py–GC/MS data. The core represents ∼5000 yr accumulation and ranges from fibric (at the surface) to hemic (bottom). The amounts of carbohydrates and lipids predicted by the MMM and calculated from the quantified Py–GC/MS chromatograms are in close agreement. However, the well known low capability of the conventional Py–GC/MS method to provide structural information on proteins from bulk soils, the poor GC amenability of polar compounds and many other possible sources of inaccuracy in Py–GC/MS and NMR-MMM caused discrepancies with predictions made with the MMM. Also, the MMM failed to give good prediction of the C/N ratio of the peat material. Although the NMR-MMM approach does not account for molecular transitions during decomposition, this oversimplification proved to be acceptable. The MMM seems to be a useful tool for the interpretation of NMR spectral distributions in peat material.

Kauri is known to cause low soil pH and loss of Al from the Al-hydroxy-interlayers from interlayered vermiculite. Kauri is also associated with intense podzolisation and therefore we studied the Al and Fe phases in soil under kauri and under adjacent broadleaf/treefern vegetation for comparison. Kauri accumulates significantly higher amounts of organic matter, which cause a significantly lower soil pH. This lower soil pH under kauri results in increased breakdown of alumino-silicates relative to broadleaf/treefern vegetation. At the same time, the larger amount of organic carbon in soils under kauri causes higher amounts of bound Al and Fe. In Ah-horizons under kauri, sesquioxides appear to be protected by organic matter, which renders them inaccessible to oxalate extraction. The distribution of pyrophosphate-extractable Fe and Al suggests podzolisation, but is due to a combination of transport and local weathering and complexation. The effect of kauri on the soil, as compared to adjacent tree species, appears to be generated by its longevity: large amounts of litter and leachates on one site, rather than its litter quality.

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 Rodmossamyran 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.

Changes in soil organic carbon (SOC) contents with soil cultivation have been investigated extensively, but information on the influence of land use changes on the chemistry of soil organic matter (SOM) and SOM fractions is scarce. To make a contribution in this context, we sampled silty soils under different land use (spruce forest (Ah horizon, 0–7 cm), continuous maize cropping (Ap horizon, 0–30 cm), and grassland (Ah horizon, 0–10 cm)) as well as the organic layer (L, Of, and Oh) of the forest floor and collected plant materials from the three sites. Separation of SOM density fractions (free particulate organic matter, occluded particulate organic matter, and mineral-associated organic matter) and water-stable aggregate size fractions of the surface soils was performed in order to follow changes in the chemical composition of SOM in physical soil fractions using CPMAS 13C NMR spectroscopy and to determine land use effects on the chemistry of SOM fractions. The CPMAS 13C NMR spectra showed that maize litter had the highest content of O-alkyl-C and the lowest content of alkyl-C, aryl-C and carbonyl-C compared with the plant material from the spruce stand and the grassland. The forest litter had the largest content of aromatic and alkyl-C. Decomposition of spruce litter in the humus layer resulted in a decreasing O-alkyl-C content and an increasing alkyl-C content. The SOM of the acid forest soil consisted mainly of particulate organic matter (POM) with a high content of spruce litter-derived alkyl-C. The SOC stocks in the grassland and maize soil were dominated by mineral-associated SOM which contained relatively larger proportions of aryl and carbonyl-C. The decrease of the SOC concentration induced by cultivation resulted in a relative accumulation of aromatic C structures in the mineral-bound SOM. In all soils, the free POM had a smaller proportion of alkyl-C and a larger proportion of O-alkyl-C than the POM occluded in aggregates. The mean age of the SOM in the density fractions of the maize soil increased with increasing aromaticity in the order free POM

Peat domes in Kalimantan (Indonesia) are reported to loose their dome shape as a result of disturbance such as logging and artificial drainage. The loss of the dome shape can be caused by (a combination of) two major processes: compaction and oxidation. Because natural, undisturbed peat is a major sink for atmospheric CO2, the distinction between the two processes is of utmost importance with regard to carbon storage. In case of compaction, no CO2 need to be lost to the atmosphere. In case of oxidation, either as a result of increased decomposition upon improved drainage or by burning, all CO produced goes to the atmosphere. To estimate the contribution of oxidation and compaction to the loss of peat dome shape, research was conducted in the Mawas area in Central Kalimantan. Physical and chemical parameters of an intact and collapsed dome were compared. Increased bulk densities in the collapsed peat dome showed that considerable compaction has occurred. Depending on the initial bulk density, compaction has probably caused a subsidence from 2.2 to 4.0 in. According to ash content measurements, no significant oxidation has taken place, but increased EC found at the collapsed dome can be due to oxidation of at least 2.3 cur to 46.9 cm peat, which implies an emission of respectively 4.2 to 85.9 kg CO2 m(-2) over the 6 years since collapse. Compaction appeared to be a more important factor in the loss of dome structure than oxidation based on the estimated possible ranges in peat loss. Collapse of the dome had only minor influence on its chemical parameters. Regrowth did not seem to be hindered by the collapse and its consequences, but it was less at sites that had suffered recent fires. If peat growth resumes, collapse need not be detrimental to carbon storage. (c) 2006 Elsevier B.V. All rights reserved.

Kauri (Agathis australis) is generally associated with intense podzolisation, but little research has been carried out to substantiate this. We studied soil profiles, grain size distribution patterns and clay mineralogy under kauri and broadleaf/tree fern vegetation in the Waitakere Ranges, North Island, New Zealand. Kauri appears to cause increased breakdown of fines (0–10 μm) in the top of the profiles due to lower soil pH, relative to broadleaf/tree fern forest. The low soil pH under kauri apparently causes the loss of Al-hydroxy-interlayers from interlayered vermiculite and possibly the conversion of vermiculite to smectite. The effect of microtopographic differences in the landscape on the grain size distribution within the topmost horizons can be observed using laser grain size diffraction. Kauri does not cause podzolisation on andesitic material, and although similar weathering of clay minerals was observed, there was no evidence for transport of clay particles.

Present models of podzolisation emphasize the mobilization and precipitation of dissolved organic matter. together with Al(-silicates) and Fe. Such models cannot explain the dominance of pellet-like organic matter in most boreal podzols and in well-drained podzols outside the boreal zone, and the discrepancy between the chemistry of percolating organic matter (DOC) and the organic matter accumulated in well-drained podzol-B horizons. The present paper offers an amended podzolisation theory, in which relative contribution of illuviated organic matter and root litter together with organic matter dynamics provide an explanation for the large variation in podzol morphology, It is suggested that fast organic matter dynamics as occurs on nutrient-rich parent materials in the boreal zone causes small accumulation of organic matter, mainly derived from roots. In such soils. the colors of Fe components dominate in the B horizon. Slow organic matter dynamics, as occurs on nutrient-poor parent materials and under hydromorphic circumstances, favors large organic matter accumulations in the B horizon. and a larger abundance of DOC-derived organic matter coatings. The latter group includes tropical podzols. (C) 2004 Elsevier B.V. All rights reserved.

Tropical America (TA) holds 8% of the world's population, 11% of the world's continental area, 23% and 22%, respectively, of the world's forest and water resources, and 13% of the world's pasture and agro-pastoral land, this representing 77% of TA's agricultural land. Recent interest in carbon sequestration and preliminary research suggest that well-managed pasture systems in TA could provide a good combination of economic production, poverty reduction, recovery of degraded areas and delivery of environmental services, particularly, carbon sequestration. This paper presents 3-year research results generated by the "Carbon Sequestration Project, The Netherlands Cooperation CO-01002" on soil carbon stocks (SCS) for a range of pasture and silvo-pastoral systems prevalent in agro-ecosystems of TA compared to native forest and degraded land. In the tropical Andean hillsides, Colombia (1350-1900 m.a.s.l., 1800 mm rainfall/yr, 14-18°C mean annual temperature, medium to high slopes, medium fertility soils), SCS from Brachiaria decumbens pastures were statistically lower than those from native forest, but higher than those from natural regeneration of a degraded pasture (fallow land), degraded pasture and mixed-forage bank. In contrast, in the humid tropical forest of the Atlantic Coast, Costa Rica (200 m.a.s.l., 28-35°C, 3500 mm/year, poor acid soils), pasture or silvo-pastoral systems with native or planted pasture species such as Ischaemum ciliare, Brachiaria brizantha + Arachis pintoi and Acacia mangium + Arachis pintoi showed statistically higher SCS than native forest. Similar rankings were found in the humid tropical forest of Amazonia, Colombia (800 m.a.s.l., 30-42°C, 4200 mm/yr, flat, very poor acid soils) where improved Brachiaria pastures (monoculture and legume-associated) showed statistically higher SCS than native forest. In the sub-humid tropical forest of the Pacific Coast, Costa Rica (200 m.a.s.l., 6-month dry season, 2200 mm/year, poor acid soils) no statistical differences in SCS were found between land-use systems. In tropical ecosystems, improved pasture and silvo-pastoral systems show comparable or even higher SCS than those from native forests, depending on climatic and environmental conditions (altitude, temperature, precipitation, topography and soil), and represent attractive alternatives as C-improved systems.

A well-developed podzol hydrosequence that has been partially covered with drift sand, and partially subjected to improved drainage, provides new insights into the causes of variation in soil organic matter chemistry in such soils. While E horizons invariably move towards a dominance of aliphatic components reflecting residual accumulation, the chemistry of organic matter in well-drained B horizons is determined mainly by decaying roots, which are transformed by microorganisms to humus aggregates. In poorly drained, stratified B horizons, humus coatings dominate and the chemistry is very close to that of dissolved organic carbon. When a sand cover inhibits the supply of fresh litter, microbial decomposition in the A horizon causes a shift in chemistry towards that of the E horizon. Similarly, upon improved drainage and removal of complexed metals from the top of the B horizon, microbial decomposition of all palatable organic matter in the top of the B horizon causes a shift towards E-horizon chemistry. This is probably the mechanism by which most E horizons in podzols are formed, and not by re-solution. Marked chemical changes upon improved drainage may take only decades. During microbial decay, small polysaccharide-derived pyrolysis products (mainly furans, furaldehydes and acetic acid) remain abundant due to the contribution of microbial sugars. Both micromorphology and factor analysis on quantified results of pyrolysis-gas chromatography/mass spectrometry contribute significantly to the interpretation of the humus chemistry of these profiles and thus to our understanding of soil genesis. Organic chemistry of the investigated podzols can be understood only in the context of their genesis

Most knowledge about the degradation of lignocellulose in natural environments is based on woody tissue and aerobic systems; however, in peatlands the contribution of graminoids to organic matter (OM) is often significant and anaerobic conditions prevail. In order to reconstruct past environmental conditions from peatlands and predict possible feedback mechanism between peatlands and climate change, a better understanding of the decomposition of graminoid tissue and the effects of anaerobic conditions on decomposition are needed. Samples (51) from the upper 1 m of the graminoid-dominated Penido Vello peatland (Xistral Mountains, Galicia, NW Spain) were analysed with pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS) and 13C cross polarisation magic angle spinning nuclear magnetic resonance spectroscopy (13C CPMAS NMR). Carbon and nitrogen contents were also determined. Depth profiles of molecular groups identified using 13C CPMAS NMR were consistent with those of depth-related distributions of quantified pyrolysis products (aliphatics, polysaccharides and aromatics). Molecular proxies were selected from peat pyrolysates to reflect the state of decay of 1) lignocellulose (the summed lignin and polysaccharide pyrolysis products, Lg and Ps, respectively), 2) lignified cellulose (levoglucosan/Ps) and hemicellulose (4-hydroxy-5,6-dihydro-(2H)-pyran-2-one/Ps), 3) macromolecular lignin including syringyl (S), guaiacyl (G) and p-hydroxyphenyl (H) ratios (S/G; H/(S + G), and side chain oxidation and shortening (vanillic acid/G, syringic acid/S, 4-acetylguaiacol/G, 4-acetylsyringol/S, C3-guaicols/G and C3-syringols/S) and 4) non-lignin phenolic acids (4-vinylphenol/H, 4-vinylguaiacol/G). Factor analysis was applied to these proxies and 120 quantified pyrolysis products to examine the influence of possible underlying factors that could explain the observed variation. Botanical changes and several degradation stages including surface decay (both aerobic and anaerobic), aerobic sub-surface decay and depth related decay (long-term anaerobic) were identified with factor analysis and all affected the variance of lignin-based decomposition proxies. The net effect of these environmental factors on the lignin proxies was examined using their depth records. This revealed that some lignin decomposition proxies were not in agreement with the literature: 1) G and S moieties with a C3 alkyl side chain showed no correlation with bog hydrology at the time of peat formation; 2) G and S moieties with acetyl side chains were related to both relatively dry (secondary aerobic decay) and wet (first stage of decay) conditions; 3) vanillic acid and syringic acid were related partly to ericoids (indicating dry conditions) and partly to free phenolic acids (less depleted under wet conditions); and 4) preferential decay of G over S moieties was found during the first stage of decay (both aerobic and anaerobic) and long-term anaerobic decay. These contradictions can be explained by the dominance of non-woody lignin sources (graminoids) and the prominence of anaerobic decay in peatlands. Our findings indicate that the effect of anaerobic decay and source vegetation should be considered when using lignin proxies to deduce aerobic decay in peat records.

Tropical climate dynamics play a major role in the global climate system. Precipitation patterns in the Serra do Espinhaco Meridional (Minas Gerais, Brazil) are influenced by both the South Atlantic Convergence Zone (SACZ) and the Inter Tropical Convergence Zone (ITCZ). This makes the area important for the interpretation of climate dynamics. The composition of the Holocene Pau de Fruta peat deposit was analysed using pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS). Molecular records agreed well with δ13C and δ15N stable isotopes, C content and mineral content, and pollen records. Changes in peatland plant species composition and fire occurrence indicated several wet and dry periods for the Pau de Fruta peatland during the Holocene; from the beginning of the Holocene to 7400 cal yr BP (phase I; dry and cold), from 7400 to 4200 cal yr BP (phase II; wet and warm), from 4200 to 1000 cal yr BP (phase III; dry and warm), from 1000 to 400 cal yrBP (phase IV; wet and warm) and from 400 cal yr BP to the present (V). The hydrological shifts showed a chronology comparable with that described in other palaeoclimatic studies for central-eastern Brazil, indicating that local conditions agree with regional ones. Analytical Py of the peat deposit provided a multi-proxy record via the identification of specific markers for both peatland plants (vegetation) and charred material (fire), whereas the general chemistry provided information on the degree of decomposition of the organic matter. Molecular chemistry of the peat core sampled at high resolution provided insight into peatland C dynamics, which is important for the interpretation of C sequestration in tropical peatlands. Molecular aspects accurately reflected local environmental change. The general agreement of Py data with pollen and inorganic chemistry supports the use of the molecular approach, because it provides local proxy indicators for peatlands, avoiding a mixture of local and regional signals.

As the environment influences soil formation, Quaternary loess-paleosols provide an important, yet complex source on former climate and vegetation conditions. This study revises the paleopedological record of the Rocourt-complex, the pedostratigraphic marker for the Eemian and early Weichselian in the Belgian loess belt. Depth functions were established from an exceptionally well-preserved, in-situ sequence. Based on soil micromorphological features, total element contents, iron fractions and carbon content a reconstruction was made of the polygenetic formation of the Rocourt soil. Results indicate that only by combining multiple soil features, consistent information could be obtained. Furthermore, this study shows that cryogenic processes, transport of colloids, iron dynamics, redox-conditions, organic matter formation and biological activity were major soil forming processes. The hypothesis of six major stages of soil formation under varying climatic conditions was most supported by the data. During the warm to temperate oceanic climate of the Eemian, a strongly weathered argic horizon was formed. This horizon was later disrupted by reticulate ice segregation and stagnogley during the severe and prolonged cold conditions of the first cold stadial following the Eemian. Weak soil formation, during the relatively short continental St. Germain I interstadial, subsequently formed cambic soil properties and a humiferous horizon in a mixture of local and new sediments. These soils were disrupted by fragipan Formation, with its associated cryogenic structure, banded eluviation and redoxfront, during the succeeding stadial with periglacial conditions. During the St. Germain II, another A horizon formed in new, calcareous material during more stable climatic conditions, allowing organic matter build-up, eluviation of smectite and formation of pedogenetic iron. During the evolution from this warmer climate with forest or forested steppe to eventually periglacial open tundra, an accretionary humiferous soil concluded the last episode of soil formation before the onset of pleniglacial Weichselian conditions. (c) 2013 Elsevier B.V. All rights reserved.

A selection of plant species that may have been relevant for the Neolithic in the SW Mediterranean have been characterised with pyrolysis gas chromatography mass spectrometry (pyrolysis–GC/MS) in search for molecular vegetation markers. Roots and aerial parts were analysed separately for the following species: Anthyllis cytisoides, Asphodelus cerasiferus, Brachypodium retusum, Cistus albidus, Cistus clusii, Dorycnium pentaphyllum, Ephedra fragilis, Juniperus oxycedrus, Juniperus phoenicea, Olea europaea, Phillyrea angustifolia, Pinus halepensis, Pistacia lentiscus, Quercus coccifera, Rhamnus lycioides, Rosmarinus officinalis, Smilax aspera and Stipa tenacissima; furthermore domesticated plants were analysed, including wheat (Triticum aestivum, Triticum dicoccum, Triticum monococcum, Triticum timopheevi and Triticum turgidum), barley (Hordeum vulgare and H. vulgare Hulled) and legumes (Lathyrus cicera, Lathyrus sativus, Lens culinaris, Pisum sativa, Vicia ervilia, Vicia faba and Vicia sativa). This resulted in 290 potential markers. In addition, the organic matter of surface soils under different vegetation cover has been analysed to test the presence of the potential markers in the soil. Forty-six of the potential markers were detected in the soil organic matter, of which part have not been reported before. The results may be useful for interpretation of the organic matter composition of soils and plant remains, which can be valuable in archaeology.

A continuous section of hydromorphic to well-drained podzols in a Late Pleistocene marine terrace of southeastern Brazil offers a unique opportunity for a detailed interpretation of podzol morphology. The soils show very deep and homogeneously colored B horizons in the most hydromorphic members, where the predominant water movement in the B horizon appears to be lateral. Upon improving drainage, the effect of roots becomes evident by the increase in root-related E-horizon tongues, while the B horizon becomes shallower and shows a more pronounced accumulation of organic matter at its top. Only where the groundwater does not periodically reach into the B horizon, a homogeneous distribution of Fe is found in the Bs horizon. The sequence shows clear effects of decomposition of the B horizon through growth of the E horizon, sometimes leading to isolated remnants of the B horizon, on the fringes of which organic matter may accumulate. Especially the hydromorphic profiles show large mottles with roughly concentric structures in the B horizon where organic matter has been depleted. In the poorly drained members of the sequence, the effect of improved drainage by erosion of the cliff is visible in black instead of brown colors of the upper B horizon. In all profiles, the conversion of the former B horizon into an E horizon is accompanied by strong biological activity in the form of burrows.

The chemical composition of soil organic matter (SOM) following secondary succession in Imperata grassland was investigated by Pyrolysis-Gas Chromatography/Mass Spectrometry (GC/MS). We studied 46 samples from different stages of succession using plots that last burned 3 and 9 years previously, secondary forest (≥ 15 years), primary forest and Acacia mangium plantation (9 years). During regeneration of Imperata grasslands the chemical composition of SOM changes considerably. Differences between litters and SOM were larger than within SOM, which is mainly due to a rapid degradation of lignin in the soil. Both litter and SOM under Imperata contain larger amounts of carbohydrates and fewer lignin moieties, aliphatics and N-compounds than those under secondary and primary forest. Nevertheless, SOM degradation under grassland is less efficient because of scarcity of N-compounds. SOM decomposition is most advanced under forest, as indicated by lower amounts of plant derived compounds and higher contribution of microbial matter. Decomposition efficiency appears to be related to SOM chemistry, but more to abundance of N-compounds than to that of potentially recalcitrant compounds. C stocks were linked to decomposition efficiency and litter production.

Peat molecular chemistry reflects a combination of plant input and decomposition. Both vegetation community and the degree of decomposition of plant remains are highly dependent on depth and fluctuation of the water table and thus peat organic matter (OM) chemistry reflects past hydrological conditions. Changes in hydrology according to the OM composition (by pyrolysis-gas chromatography/mass spectrometry, pyrolysis-GC/MS) in a high-resolution sampled monolith of an 8000 years old peat deposit are presented. Analysis of 18 modern vegetation species resulted in molecular markers for Erica spp., Deschampsia flexuosa, Juncus bulbosus and Carex binervis, in addition to more general markers which enabled differentiation between woody, grass and moss vegetation. Factor analysis of 106 pyrolysis products quantified for all peat samples enabled identification of mineral (Factor 1) and hydrological (Factor 2) conditions of the bog. Depth profiles of vegetation markers showed good agreement with those of the scores of both factors and enabled the identification of 14 relatively wet periods, dating to 1430–1865 AD, 930–1045 AD, 640 AD, 270–385 AD, 190–215 AD, 135 AD, 45 BC–15 AD, 260–140 BC, 640–440 BC, 1055–960 BC, 1505–1260 BC, 2300 BC, 4190–2945 BC and 5700–5205 BC, which show excellent agreement with other palaeoclimatic studies in Europe. The results emphasize the importance of high-resolution sampling, in combination with the use of multiple vegetation markers and other peat OM characteristics for a proper interpretation of a peat record.

To investigate both the effect of land-use systems on SOM characteristics and the effect of occlusion in aggregates on chemical composition of the occluded fraction, SOM fractions of soils under Cerrado, no-tillage and conventional tillage, were investigated. Free light, occluded light and extractable organic matter from native Cerrado and from tilled and untilled fields under maize and bean rotation were separated and chemically analysed by pyrolysis-GC/MS. Ploughing incorporated more fresh OM into the soil than natural biological activity. Degradation of the occluded light fraction was not fully halted, but was different from that of SOM in the extractable fraction. Recalcitrant compounds had low abundances in the free light and extracted fractions, but were more abundant in the occluded light fraction, where the more accessible compounds were depleted by microbial decomposition. Because of intense decomposition, the extracted fractions did not differentiate between land uses, but differences in the light fractions were significant. The results indicate that the decay of the occluded fraction is different from that of the free light fraction: non-ideal circumstances of decay caused a relative accumulation of potentially recalcitrant compounds. When considering the rapid turnover of all components in the soil extracts, disruption of aggregates will probably cause rapid decay of the occluded fraction. The distribution of pyrolysis products that can be ascribed to charred wood (polyaromatics) indicates that this fraction is readily decayed if not occluded. Selective decomposition in the occluded fraction may cause a shift in d13C that should not be misinterpreted

Regeneration of grassland areas is becoming increasingly important, not only to create new secondary forest and recover the original biodiversity, but also recover for agriculture. We studied an early succession in Imperata grasslands in East Kalimantan, Indonesia, using plots that last burned 3 years, 4 years and 9 years previously on, secondary and primary forest. The species coverage data were analyzed using CANOCO. While Imperata decreases, the average percentage of shrubs and young trees clearly increases with time. In the burned plots, Melastoma malabathricum, Eupatorium inulaefolium, Ficus sp., and Vitex pinnata L. strongly increase with the age of regeneration, but these species were rare in the secondary forest. Texture strongly influenced regeneration: soils with more than 50% sand had a slower development towards secondary forest. The number of species was lower in the more sandy soils. The latter showed a stronger increase with time of Pteridium aquilinum L., which appears to slow down the subsequent vegetation development. Canonical correspondence analysis (CCA) of the environmental gradient and vegetation showed that pH, bulk density, sand and clay are the factors influencing the distribution of species. CCA showed also that soil properties had a strong influence on vegetation composition. M. malabathricum, V. pinnata L., Lycopodium cernum, Vernonia arborea Buch.-Ham., Dicranopteris linearis are all species associated with high levels of exchangeable Al and low pH. Imperata grasslands are not a final and stable stage of land degradation, but, when not maintained by frequent fires and human disturbances, regenerate spontaneously and rapidly to secondary forest. The introduction of native shrubs and trees will speed up this process. Recovery for agriculture has not been studied but should not pose major problems under management system without fire.

Soil carbon changes upon secondary succession in Imperata grasslands are important both for their effect on potential production and for possible implications of forest degradation and regeneration on global climate change. We studied the effect of forest regeneration after fire in Imperata (speargrass) grasslands of East Kalimantan on soil properties, using 47 plots that last burned in 2004, 94 plots that last burned in 2003, 126 plots last burned before 2003, 43 plots of secondary forest, and 28 plots of primary forest. Although soil carbon stocks increase upon natural regeneration from grassland to secondary forest, highest carbon stocks are found in the later regeneration phases and lowest under primary forest. This is contrary to the situation in other forest systems. Low C stocks under primary forests may be due to extremely low fertility, combined with shallow soils and low root mass in the topsoil. Root density—as observed in the field—is much higher under the grass vegetation. The effects of regeneration on soil are strongest in the A-horizon, where soil carbon content increases with 14%, from 14.5 g kg− 1 in Imperata grassland to 16.5 g kg− 1 in secondary forest, while carbon stocks in the A-horizon increase from 16.51 ton C ha− 1 to 18.70 ton C ha− 1. This is accompanied by a decrease in pH and an increase in bulk density. The total soil carbon stocks in Kalimantan (fixed mass, approximate depth section 40 cm) are 36.19 ton ha− 1 in Imperata grassland, 38.98 ton ha− 1 in secondary forest and 33.19 ton ha− 1 in primary forest, which is considerably lower than in Sumatra. Above-ground C/below-ground C ratios are higher in Kalimantan primary forest but lower in Kalimantan secondary forest than in Sumatra. Soil carbon stocks in Imperata grassland could be lower than previously thought. This has important consequences for carbon sequestration projects in East Kalimantan, because carbon storage potentials could be higher.

The soil organic matter (SOM) extracted under different vegetation types from a Brazilian mangrove (Pai Matos Island, São Paulo State) and from three Spanish salt marshes (Betanzos Ría and Corrubedo Natural Parks, Galícia, and the Albufera Natural Park, Valencia) was investigated by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The chemical variation was larger in SOM from the Spanish marshes than in the SOM of the Brazilian mangroves, possibly because the marshes included sites with both tidal and nontidal variation, whereas the mangrove forest underwent just tidal variation. Thus, plant-derived organic matter was better preserved under permanently anoxic environments. Moreover, given the low number of studied profiles and sedimentary¿vegetation sequences in both areas, depth trends remain unclear. The chemical data also allow distinction between the contributions of woody and nonwoody vegetation inputs. Soil organic matter decomposition was found to cause: (i) a decrease in lignin contents and a relative increase in aliphatics; (ii) an increase in short-chain aliphatics at the expense of longer ones; (iii) a loss of odd-over-even dominance in alkanes and alkenes; and (iv) an increase in microbial products, including proteins, sterols, short-chain fatty acids, and alkanes. Pyrolysis-gas chromatography/mass spectrometry is a useful tool to study the behavior and composition of SOM in wetland environments such as mangroves and salt marshes. Additional profiles need to be studied for each vegetation type, however, to improve the interpretability of the chemical data

Despite the potentially large contribution of black carbon (BC) to the recalcitrant soil organic matter pool, the molecular-level composition of aged BC has hardly been investigated. Pyrolysis-GC/MS, which provides structural information on complex mixtures of organic matter, was applied to the NaOH-extractable organic matter of an acidic colluvial soil (Atlantic ranker) sampled with high resolution (5 cm) that harbours a fire record of at least 8.5 ka. Additionally, 5 charcoal samples from selected soil layers were characterised using pyrolysis-GC/MS for comparison. Pyrolysis-GC/MS allowed distinguishing between BC and non-charred organic matter. It is argued that a large proportion of the polycyclic aromatic hydrocarbons (PAHs), benzenes and benzonitrile in the pyrolysates of the extractable organic matter, together accounting for 21–54% of total identified peak area, derived from BC. In charcoal samples, these compounds accounted for 60–98% of the pyrolysis products. The large quantity of BC in almost all samples suggested a key role of fire in Holocene soil evolution. The high C content of the soil (up to 136 g C kg−1 soil) may be attributed to the presence of recalcitrant organic C as BC, in addition to the sorptive preservation processes traditionally held responsible for long-term C storage in acid soils. Interactions between reactive Al hydroxides and BC could explain the longevity of BC in the soil. This work is the first thorough pyrolysis-GC/MS based study on ancient fire-affected organic matter.

Analytical pyrolysis-GC/MS and solid-state 13C NMR (nuclear magnetic resonance) were applied to the NaOH-extractable organic matter fraction of a colluvial soil from Galicia (NW Spain) that represents more than 8500 yr of accumulation. While molecular indicators of vegetation change were looked for, it seemed likely that any such signal was disturbed by the intense fire regime of the area. This conclusion was drawn from (1) the presence of three charcoal layers, (2) the high proportion of aryl C in NMR spectra (non-quantitative) and (3) the prevalence of benzenes and polycyclic aromatic hydrocarbons (PAHs) in the chromatograms (38 ± 6% of total identified peak area), also in charcoal-poor samples. If this conclusion is accurate, the area has been subjected to burning episodes for at least 8000 yr. Additionally, the results indicate that biomass burning residues (black carbon; BC) may become NaOH extractable after long periods of degradation in mineral soil. These results add to our knowledge of the long-term fate of BC in soil, which is a potential agent in the global C cycle., Project supported by the "Plan Nacional: Paleopaisaje y prehistoria del Futuro Parque de Arte Rupestre de Campo Lameiro, Pontevedra" (PGIDT02CCP60601).

Soil organic matter (SOM) in allophanic soils is supposed to accumulate due to protection caused by binding to allophane, aluminium and iron. We investigated a catena of allophanic and non-allophanic soils in Costa Rica to determine the effect of such binding mechanisms on SOM chemistry. These soils contain no contribution of black carbon. Molecular characterization of litter, extractable and dispersed organic matter was done by Curie-point pyrolysis-GC/MS. The molecular chemistry of the organic fractions indicates a strong decomposition of plant-derived organic matter and a strong contribution of microbial sugars and N-compounds to SOM. Both the decomposition of plant-derived SOM ¿ including that of relatively recalcitrant compounds ¿ and the relative contribution of microbial SOM were greater in allophanic samples than in non-allophanic ones. This suggests that chemical protection does not act on primary OM, although it may influence the accumulation of secondary OM in these soils. The effect of allophane on SOM contents in such perhumid soils is probably through incorporation of decomposition products and microbial SOM in very fine aggregates that ¿ in a perhumid environment ¿ remain saturated with water during much of the year. Greater concentrations of aliphatics are found in allophanic residues, but there is no evidence of any specific mineral-organic binding. The results do not support the existing theory of chemical protection of plant-derived components through binding to allophane, iron and aluminium.

Soils of volcanic areas often exhibit unique properties differentiating them from other soils on Earth. This book compiles information gained by an EU research network over six years of research on European volcanic soils. It gives comprehensive coverage of soils in volcanic regions within Europe, dealing with most aspects of modern day soil science. New methodology is introduced and the synthesis of the research casts a new light on soils with andic soil properties. It covers a range of issues such as mineralogy, chemistry, physics, biology, soil genesis, classification, land use and pollution. © Springer-Verlag Berlin Heidelberg 2007. All rights are reserved.

Some well-drained podzols on quartz sands in the Netherlands and neighbouring Belgium and Germany show mottling in all horizons due to selective removal of organic matter. Phospholipid analysis and morphology of the mottles suggests that this removal is due to a combination of bacteria, fungi, and actinomycetes. Investigation by pyrolysis-GC/MS of organic matter in the depleted zones as compared to their surroundings indicates (1) selective decay of relatively palatable components, (2) residual accumulation of aliphatic biopolymers such as cutan and suberan that produce alkanes, alkenes and methylketones upon pyrolysis, and (3) accumulation of microbial polysaccharides and N-containing compounds. Although the selective organic matter decay in the depleted mottles is similar to the process that causes degradation of organic matter at the top of the B-horizon and its conversion to an E-horizon, the essential difference is that, while decay at the E–B-horizon transition in podzols is governed by the presence or absence of aluminium and iron, the micro flora that is responsible for the decay mottles acts independently from metal concentrations.

Within the framework of EU-COST action 622 twenty soils developed on volcanic materials from Italy (IT: EUR01 to EUR04), Azores Islands (AI: EUR05, EUR06), Iceland (IC: EUR07 to EUR09), Canary Islands (CI: EUR10 to EUR12), Greece (GR: EUR13 to EUR15), France (FR: EUR16 and EUR17) and Hungary (HG: EUR18 to EUR20) were described, sampled and analyzed for a large number of physico-chemical soil properties by different research groups. This database provides a good opportunity for the application of multivariate statistical methods, although the number of samples is moderate (94 horizons). In this chapter we applied two different approaches for the explanation of the variance structure of the chemical properties of the European volcanic soils: (1) an exploratory analysis using principal component analysis (PCA) aimed to identify the major trends and processes in these soils, and (2) a confirmatory analysis based on PCA separation and knowledge on andic properties using discriminant analysis (DA) to identify the minimum set of properties that enable a good separation of the different types of horizons (non-andic, vitric, andic).

In geologically stable areas in the tropics, climatic changes and geomorphic cycles give origin to polygenetic soils. Polygenesis involves new soil formation phases taking place on preweathered materials from previous phases, resulting in soils with rather similar chemical and mineralogical properties. Polygenetic soils from Minas Gerais, Brazil, were investigated with the purpose of distinguishing mineralogical aspects in relation to polygenesis. The soil materials were studied by micromorphology and electron microscope and analyzed by XRD. All soils are strongly weathered and even show weathered grains of ilmenite and quartz. The soils show two phases of kaolinite formation (pseudomorphs after mica and precipitation from solution) and of accumulation of iron compounds. Desilication causes gibbsite formation from kaolinite, occasionally even in the deep saprolite. Superposed processes can be due to progressively deeper weathering or to changes of the external environment.

Previous studies on laser diffraction granulometry of volcanic soils indicate that (1) allophane causes the formation of fine-silt size aggregates that appear to increase in size with increasing allophane content, and (2) detailed grain-size data are equally effective as chemical analyses in detecting stratification of volcanic deposits (Buurman et al. 1997b, 2004). The second publication was based on the profiles EUR01–12. The purpose of the present study is fourfold: 1. To judge the effect of organic matter and amorphous silicates on aggregation; 2. To judge the stability of aggregates

Soils developed from volcanic materials are characterized by mixture of short range order components such as allophane, imogolite, ferrihydrite, opaline silica, Al(Fe)-humus complexes and volcanic glass, in addition to the crystalline minerals halloysite, gibbsite, goethite, and aluminised 2:1 phyllosilicates. The accumulation of highly reactive components formed upon rapid weathering of volcanic rocks is the main cause for the unique physical and chemical properties of Andosols (Shoji and Fujiwara 1984, Dahlgren and Saigusa 1994). Depending on the dominant forms of Al, two kinds of Andosols are distinguished: 'allophanic' (Al in allophane and/or imogolite predominates) and 'non allophanic' (Al mainly in complexes with humus) (Shoji and Fujiwara 1984). When these components are less abundant, in the presence of volcanic glass, soils on volcanic materials are called 'vitric' (FAO 1998). Allophane and imogolite are formed preferentially at pH about 5. In more acid conditions, Al-humus complexes tend to be dominant (Shoji and Fujiwara 1984, Nanzyo et al. 1993). At pH

NaOH and Na4P2O7 extractable organic matter fractions of two volcanic ash profiles (Azores Islands) were studied by pyrolysis gas chromatography/mass spectrometry (Py-GC/MS). The soils did not have melanic horizons and were not affected by burning. The pyrolysates of all samples were dominated by polysaccharide-derived compounds. The Na4P2O7 extractable fractions were relatively enriched by markers of lignin, proteins, and lipids. Only in the topsoils (A horizons) did lignin appear to be present in significant amounts and, although present with a high degree of side-chain oxidation, the distribution of lignin-derived products could be related to the overlying vegetation. A similar trend was observed for lipids, in particular the high abundance of C26 alkanol in profile EUR05 clearly reflecting grass. Below the topsoils, lignin and lipids were hardly detectable. With depth, markers of intact polysaccharides decreased relatively to smaller polysaccharide pyrolysis products. The same is true for chitin. Compared with other soils, the relative abundance of lignin and lipids was remarkably low. The occurrence of large amounts of polysaccharides including chitin points to an important in situ production of soil organic matter by fungi and/or arthropods. There is no indication of preservation of plant-derived organic matter by allophane or Al3+, but the presence of large amounts of (microbial) polysaccharides and chitin suggests that these secondary organic matter products are indeed stabilized.