Bruno Glaser - Academia.edu (original) (raw)

Papers by Bruno Glaser

Tree Physiology, 2015

Plants allocate carbon (C) to sink tissues depending on phenological, physiological or environmen... more Plants allocate carbon (C) to sink tissues depending on phenological, physiological or environmental factors. We still have little knowledge on C partitioning into various cellular compounds and metabolic pathways at various ecophysiological stages. We used compound-specific stable isotope analysis to investigate C partitioning of freshly assimilated C into tree compartments (needles, branches and stem) as well as into needle water-soluble organic C (WSOC), non-hydrolysable structural organic C (stOC) and individual chemical compound classes (amino acids, hemicellulose sugars, fatty acids and alkanes) of Norway spruce (Picea abies) following in situ 13 C pulse labelling 15 days after bud break. The 13 C allocation within the above-ground tree biomass demonstrated needles as a major C sink, accounting for 86% of the freshly assimilated C 6 h after labelling. In needles, the highest allocation occurred not only into the WSOC pool (44.1% of recovered needle 13 C) but also into stOC (33.9%). Needle growth, however, also caused high 13 C allocation into pathways not involved in the formation of structural compounds: (i) pathways in secondary metabolism, (ii) C-1 metabolism and (iii) amino acid synthesis from photorespiration. These pathways could be identified by a high 13 C enrichment of their key amino acids. In addition, 13 C was strongly allocated into the n-alkyl lipid fraction (0.3% of recovered 13 C), whereby 13 C allocation into cellular and cuticular exceeded that of epicuticular fatty acids. 13 C allocation decreased along the lipid transformation and translocation pathways: the allocation was highest for precursor fatty acids, lower for elongated fatty acids and lowest for the decarbonylated n-alkanes. The combination of 13 C pulse labelling with compoundspecific 13 C analysis of key metabolites enabled tracing relevant C allocation pathways under field conditions. Besides the primary metabolism synthesizing structural cell compounds, a complex network of pathways consumed the assimilated 13 C and kept most of the assimilated C in the growing needles.

irst described over 120 years ago in Brazil, Amazonian Dark Earths (ADEs) are expanses of dark so... more irst described over 120 years ago in Brazil, Amazonian Dark Earths (ADEs) are expanses of dark soil that are exceptionally fertile and contain large quantities of archaeological artefacts. The elevated fertility of the dark and often deep A horizon of ADEs is widely regarded as an outcome of pre-Columbian human influence 1. Archaeological research provides clear evidence that their widespread formation in lowland South America was concentrated in the Late Holocene, an outcome of sharp human population growth that peaked towards 1000 BP 2-4. In their recent paper Silva et al. 5 argue that the higher fertility of ADEs is principally a result of fluvial deposition and, as a corollary, that pre-Columbian peoples just made use of these locales, contributing little to their enhanced nutrient status. Soil formation is inherently complex and often difficult to interpret, requiring a combination of geochemical data, stratigraphy, and dating. Although Silva et al. use this combination of methods to make their case 5 , their hypothesis, based on the analysis of a single ADE site and its immediate surroundings (Caldeirão, see maps in Silva et al. 5), is too limited to distinguish among the multiple possible mechanisms for ADE formation. Moreover, it disregards or misreads a wealth of evidence produced by archaeologists, soil scientists, geographers and anthropologists, showing that ADEs are anthropic soils formed on land surfaces enriched by inputs associated with pre-Columbian sedentary settlement 6-9. To be accepted, and be pertinent at a regional level, Silva et al.'s hypothesis 5 would need to be supported by solid evidence (from numerous ADE sites), which we demonstrate is lacking. Geomorphological and pedological considerations There are several problems with reviving the argument 10 that ADE fertility originates from deposited alluvium. First, the Caldeirão ADE site is located on a Miocene plateau~20 m above the Solimões River floodplain (~40 m asl), which in itself precludes significant flooding during the Holocene 11. Second,

Geochimica et Cosmochimica Acta, 2012

Tropical rainforests are highly important for the global climate regulation and for global biodiv... more Tropical rainforests are highly important for the global climate regulation and for global biodiversity. However, these ecosystems are characterized by nutrient-poor and highly weathered soils and by high turnover rates of organic matter. Thus, they are fragile ecosystems prone to loss of ecosystem services when anthropogenically disturbed. Currently, the major threat to these ecosystems is deforestation leading to irreversible destruction of rainforests. Surprising and not expected is that within these ecosystems small patches of highly fertile soils occur which are known as Anthropogenic Dark Earths or terra preta de Índio (terra preta). These soils exhibit high nutrient and soil organic matter stocks and allow sustainable agriculture. Frequent occurrence of pot-sherds of pre-Columbian origin and further evidence for settlement activities clearly demonstrate that terra preta is of anthropogenic origin. In recent years, the terra preta phenomenon has gained increasing interest because it is assumed that terra preta could act as a model for promoting sustainable agricultural practices in the humid tropics and because terra preta is an example for long-term CO 2 sequestration into terrestrial ecosystems with additional positive benefits for ecosystem services. These potentials of terra preta initiated a great number of studies but also stimulated fantasy about their genesis. Therefore, the aim of this review is to summarize the scientific knowledge about terra preta properties and to discuss their genesis. From our own and literature data it is evident that terra preta is the product of inorganic [e.g. ash, bones (esp. fish)] and organic (e.g. biomass wastes, manure, excrements, urine, and biochar) amendments to infertile Ferralsols. These ingredients were microbially metabolized and stabilized by humification in soil, fungi playing a bigger role in this process compared to bacteria in surrounding ecosystems. Biochar is a key component for this process due to its stability and its enrichment in terra preta. It is still unclear if terra preta was produced intentionally or unintentionally. In addition, it is unclear how much time was needed after the disposal of the materials mentioned above to develop a terra preta. Further research is highly desired to investigate these latter two issues.

Ecological Engineering, 2012

The need to reconcile food production, ecosystem services and biodiversity conservation has spurr... more The need to reconcile food production, ecosystem services and biodiversity conservation has spurred the search for more sustainable ways of farming. Archaeology offers examples of prehistoric pathways to agricultural intensification that could be rich sources of inspiration for applying ecological engineering in agriculture today. We examine one set of techniques, pre-Columbian raised-field agriculture in wetlands of Mesoamerica and South America. We point to gaps in knowledge at three levels. First, raised-field agriculture was conducted in a wide range of soils and climates. How different systems functioned was likely to have been correspondingly diverse, but this variation is under-appreciated. At the scale of single farms, nutrient dynamics in raised-field systems likely included complexities quite unusual in 'modern' agriculture, owing to the mixture of aerobic and waterlogged compartments, but data are scarce. Second, at the landscape level there is disagreement about whether fallow periods were necessary, and their eventual roles are poorly understood. Current evidence suggests that self-organizing processes in fallows may have increased the sustainability of some raised-field farming systems in unusual ways. Third, the labor-intensive nature of raised-field farming is held to limit its pertinence to today's global problems, but its real labor costs are unknown. Furthermore, achieving sustainable intensive agriculture will require compensating farmers for ecosystem services they provide. Under a socioeconomic regime that does this, raised-field agriculture could have considerable practical application.

Isotopes in Environmental and Health Studies

the layout of a figure by drawing a set of rectangles on the page using a standard SVG editor suc... more the layout of a figure by drawing a set of rectangles on the page using a standard SVG editor such as Inkscape [Altert13]. In Python, FigureFirst uses this layout file to generate Matplotlib figures and axes in which the user can plot the data. Additionally, FigureFirst saves the populated figures back into the original SVG layout file. This functionality allows the user to adjust the layout in Inkscape, then run the script again, updating the data layers to match the new layout. Building on this architecture, we have implemented a number of features that make complex tasks remarkably easy including axis templates; changing attributes of standard SVG items such as their size, shape, color, and text; and an API for adding JessyInk [Jagannathan12] extensions to Matplotlib objects for automatically generating animated slide presentations. We have used FigureFirst to generate figures for publications [Lindsay17] and provide code

Applied Geochemistry, 2010

The long chain n-alkane composition of plant material can significantly differ between plant grou... more The long chain n-alkane composition of plant material can significantly differ between plant groups e.g. trees and grasses. Due to their relative recalcitrance, they have been employed in paleoecological research as molecular proxies for different types of vegetation. Most of those paleoenvironmental studies rely on the assumption that characteristic molecular fingerprints of plant material are preserved in the fossil organic material without significant alteration. However, there exists evidence that n-alkane distributions may change in the course of plant litter degradation. Here, the authors propose and discuss a conceptual approach to the correction of n-alkane patterns in paleosols and terrestrial sediments for postsedimentary alteration effects. This might have potential to improve paleoenvironmental reconstructions derived from these molecular fossils. In soil depth profiles typically a correlation between the OEP (odd over even predominance) and paleoecological valuable long-chain n-alkane ratios (LARs) can be found. Similar relationships have been also obtained from n-alkane records in paleosols. With the OEP serving as a proxy of microbial reworking, the correction procedure applies OEP vs. LAR regression functions to correct fossil LARs for degradation effects. The regression functions have been derived from modern soils. The application of the procedure and its significance for paleoecological interpretations is demonstrated on a case study of a loess-paleosol sequence ($400-700 ka) in Romania. It is shown that changes in the C27/C31 n-alkane ratio at this site are closely related to degradation effects rather than to changes in the paleovegetation (e.g. tree vs. grass abundance). However, it was found that the C29/ C31 ratio is a more suitable paleoenvironmental proxy at the Mircea Voda site. The results indicate that there is a future potential to correct fossil n-alkane ratios via the OEP/LAR relationship, however at the moment a general straight forward application of this approach might be critical due to lack of extended and diverse n-alkane records from modern soils. The need of more systematic n-alkane studies on soil profiles is highlighted to improve knowledge concerning dynamics and actual mechanisms of postsedimentary LAR and OEP changes.

Proceedings of the …, 2010

The scale and nature of pre-Columbian human impacts in Amazonia are currently hotly debated. Wher... more The scale and nature of pre-Columbian human impacts in Amazonia are currently hotly debated. Whereas pre-Columbian people dramatically changed the distribution and abundance of species and habitats in some parts of Amazonia, their impact in other parts is less clear. Pioneer research asked whether their effects reached even further, changing how ecosystems function, but few in-depth studies have examined mechanisms underpinning the resilience of these modifications. Combining archeology, archeobotany, paleoecology, soil science, ecology, and aerial imagery, we show that pre-Columbian farmers of the Guianas coast constructed large raised-field complexes, growing on them crops including maize, manioc, and squash. Farmers created physical and biogeochemical heterogeneity in flat, marshy environments by constructing raised fields. When these fields were later abandoned, the mosaic of welldrained islands in the flooded matrix set in motion self-organizing processes driven by ecosystem engineers (ants, termites, earthworms, and woody plants) that occur preferentially on abandoned raised fields. Today, feedbacks generated by these ecosystem engineers maintain the human-initiated concentration of resources in these structures. Engineer organisms transport materials to abandoned raised fields and modify the structure and composition of their soils, reducing erodibility. The profound alteration of ecosystem functioning in these landscapes coconstructed by humans and nature has important implications for understanding Amazonian history and biodiversity. Furthermore, these landscapes show how sustainability of food-production systems can be enhanced by engineering into them fallows that maintain ecosystem services and biodiversity. Like anthropogenic dark earths in forested Amazonia, these self-organizing ecosystems illustrate the ecological complexity of the legacy of pre-Columbian land use.

European Journal of Forest Research, 2010

In the last century, many calcareous soils in Castilla León (northwestern Spain) have been transf... more In the last century, many calcareous soils in Castilla León (northwestern Spain) have been transformed from natural Quercus ilex forest to cropped land. Reforestation with Pinus halepensis has been taking place during the past 40 years. In order to obtain a better understanding of how these disturbances affect ecosystem functioning, we studied the quantity and quality of soil organic matter (SOM) in natural forest ecosystems, cropland and Pinus plantations. Density fractionation combined with ultrasonic dispersion enables separation and study of SOM fractions: free organic matter (OM), OM occluded into aggregates and OM stabilized in organo-mineral complexes, considered on the basis of the type of physical protection provided. We separated SOM density fractions and determined the concentrations of C and N, C/N ratios and the natural isotopic abundance (d 13 C and d 15 N values). Transformation of Quercus forest to cropland resulted in major losses of SOC and N, as expected. However, subsequent reforestation with Pinus resulted in good recovery of the original SOC and soil N pools. This indicates the potential for enhanced C storage in agricultural soils by their reversion to a forested state. Study of the density fractions and their 13 C and 15 N signatures enabled better understanding of the high stability of OM in calcareous soils, and analysis of d 13 C variations throughout the profile also enabled identification of past C3/C4 vegetation change. Despite the different OC contents of soils under different land use, OM stabilization mechanisms were not significantly different. In calcareous soils, accumulation of SOC and N is mainly due to organo-mineral associations, resulting in physicochemical stabilization against further decomposition.

Soil Biology and Biochemistry, 2005

Black carbon (BC) or charcoal is thought to represent an important component of the carbon cycle,... more Black carbon (BC) or charcoal is thought to represent an important component of the carbon cycle, but has seldom been quantified in soils. We quantified soil BC in a temperate mixed-grass savanna in the southern Great Plains using benzenecarboxylic acids as molecular markers for BC. Soils were collected from four fire treatments (repeated summer fires in 1992 and 1994; repeated winter fires in 1991, 1993 and 1995; alternate-season fires in winter 1991, summer 1992, and winter 1994; and unburned control) at 0-10 and 10-20 cm depth in 1996. Black carbon concentrations ranged from 50 to 130 g BC kg K1 of soil organic carbon (SOC), or from 0.55 to 1.07 g BC kg K1 of whole soil in this mixed grass savanna. The BC contribution to SOC increased significantly with soil depth (P!0.05). Repeated fires increased BC slightly compared to the unburned controls; however, the effects of repeated fires on BC were not statistically significant in this mixed-grass savanna. Results of this study provide estimates of BC concentrations for native, uncultivated mixed-grass savanna, and indicate that 2-3 fires have little effect on the size of the soil BC pool in this region. q

Water, Air, & Soil Pollution, 1994

For a one year period intact Spodosol soil columns were percolated weekly with H2Odeion, 1.58 mmo... more For a one year period intact Spodosol soil columns were percolated weekly with H2Odeion, 1.58 mmol H2SO 4 L -~, and 0.79 mmol H2SO 4 L -1 + 0.64 mmol HNO3 L -1, respectively, Decomposition rates, soil organic carbon (OC) solubilization, dissolved organic carbon (DOC) fractions, and Cr-, Cu-, and Cd-binding by dissolved hydrophobic and hydrophilic acids were studied. Acid treatment reduced significantly OC respiration as well as OC solubilization in the humic layers. The reduced OC solubility at acid addition was more pronounced for the less polar hydrophobic compounds, resulting in a decrease of the hydrophobie acids (from ca. 65 to 40-45% of DOC), and in an increase of the hydrophilic acids (from ca. 25 to 40-45% of DOC). For B horizon leachates, DOC increased at acid treatment. Generally, hydrophobic acids were retained preferentially in the B horizon. Also in the B horizon output there was an increase of the hydrophilic acids as acidity increased (from ca. 40 to 50% of DOC). Differences between the two acid treatments were negligible. The degree of metal-organic complexes decreased in the order Cr > Cu > Cd, from A to B horizon leachates, and with increasing acidity. Hydrophilic acids were found to be the dominating ligands in complexing Cr and Cu. Actual Cr-and Cu-binding by hydrophilic acids exceeded that by hydrophobic acids 2-8 times. As the hydrophilic acids represented the most mobile DOC components in the soil columns, in particular with increasing acidity, significant amounts of Cr and Cu in the B horizon leachates were organically complexed, although a great proportion of the hydrophobic acids was retained in the B horizon.

Organic Geochemistry, 2005

We present both conventional proxies (total organic carbon and N, 14C, δ13C, δ15N) and compound-s... more We present both conventional proxies (total organic carbon and N, 14C, δ13C, δ15N) and compound-specific stable isotope data for terrestrial, aquatic and microbial biomarkers combined with an in-depth interpretation of their environmental meaning for a sediment core from Lake Rukche at 3500m a.s.l. in the Gorkha Himal, Nepal, a region with a paucity of palaeoclimate data. Compound-specific δ13C values of

Amazonian Dark Earths, 2004

Soils serve as natural archives and store valuable information on site and climate conditions und... more Soils serve as natural archives and store valuable information on site and climate conditions under which they were formed (Zech et al., 2000). It has also been shown that landuse influences amounts and composition of soil organic matter (eg Srivastava and Singh, 1991; ...

Quaternary Science Reviews, 2003

Late Quaternary glacier fluctuations in the Macha Khola valley (Gorkha Himal, Nepal) were reconst... more Late Quaternary glacier fluctuations in the Macha Khola valley (Gorkha Himal, Nepal) were reconstructed using relative and absolute dating techniques. Our results indicate that younger moraine complexes were left by Late Holocene (o1.7 cal. ka BP), mid-Holocene (ca 3 cal. ka BP), and Lateglacial (ca 13 cal. ka BP) ice advances. Older Late Quaternary glacier advances occurred during Marine Oxygen Isotope Stages (MIS) 2 and 3-4. No relics of Middle or Early Pleistocene glaciations could be found. During MIS 3-4, glaciers advanced down to an altitude of at least 2150 m a.s.l., corresponding to an ELA depression of approximately 1300 m. At about 3500 m a.s.l., the MIS 2 Macha Khola glacier reached almost the thickness of the former MIS 3-4 glacier and retreated some time before 17.9 cal. ka BP. The Lateglacial glacier advanced again several times to altitudes between 2450 and 3400 m a.s.l. The mid-Holocene glaciers extended much farther down-valley than the Late Holocene ones. Dendrochronological data of Abies spectabilis suggested several periods of unfavourable growth conditions especially at the beginning of the 19th (1820) and 20th (1905) centuries. r

Quaternary International, 2011

Amazonian Dark Earths, 2004

Accelerated soil degradation is one of the most severe problems of landuse in the tropics (Zech e... more Accelerated soil degradation is one of the most severe problems of landuse in the tropics (Zech et al., 1997). This is to a large part due to the fact that soil organic matter (SOM) rapidly declines in tropical soils under arable cultivation (Tiessen et al., 1994). Soil organic matter is of ...

Amazonian Dark Earths, 2004

To secure food supply for the increasing population there is an urgent need to intensify the agri... more To secure food supply for the increasing population there is an urgent need to intensify the agricultural production especially in less developed countries of the tropics. There, soils are frequently poor and not suitable for intensive sustainable agriculture because low organic matter contents and minerals with low cation exchange capacity favor nutrient leaching. Under such circumstances, mineral fertilizers such as

Water, Air, & Soil Pollution, 2011

Due to long-lasting historic fly-ash deposition from lignite-fired power plants, soils of forest ... more Due to long-lasting historic fly-ash deposition from lignite-fired power plants, soils of forest ecosystems in Central Germany have been affected by a variety of contaminants. In addition to heavy metals and oxides, another fly-ash compound is Black carbon (BC) which supposedly has been accumulated as well. BC as a generic term describing different forms of pyrogenetic carbon is considered as a very stable fraction of the C cycle. In this study, BC content of organic layers of 38 sites from two adjacent forested areas was determined using a simplified benzenepolycarboxylic acid (BPCA) method. Considerable amounts of BC were detected in both areas. It accounted for up to 11.2 and 15.6% of total organic carbon (TOC) in the Oe and Oa horizons, respectively. On average, slightly higher BC contents were found in the Oe (23.0 g BC kg −1 ), whereas BC/TOC ratios were higher in the Oa. The BC/TOC ratio of the Oe horizon tended to decrease with increasing distance from the former main emitters. In contrast to expectations, BC contents of the Oa horizon tended to increase with increasing distance. The deposition gradient, in previous research found for other fly-ash compounds, could not be observed for BC. Higher values in more remote forests might be taken as an indicator for the influence of additional emission sources. Further research is needed to confirm the results and to elucidate the potential impact of (soot-) BC on humus dynamics in the study area.

Rapid Communications in Mass Spectrometry, 2003

The performance of a gas chromatography-combustion-isotope ratio mass spectrometry system (GC-C-I... more The performance of a gas chromatography-combustion-isotope ratio mass spectrometry system (GC-C-IRMS) with respect to the dependence of d 13 C values on the amount of sample is presented. Particular attention is paid to the localization of the amount-dependent isotopic fractionation within the system. Injection experiments with varying amounts of gases (CO 2 , n-hexane, and toluene) revealed that neither the detector unit nor the combustion reactor, but rather the conditions in the split/splitless injector, contributed to this effect. Although optimization of injector parameters was performed and a reduction of this adverse effect from 3 to 1% was achieved, it was not possible to eliminate isotopic fractionation completely. Consequently, additional injector parameters have to be considered and adjusted to achieve injection conditions free of fractionation. For routine analysis of the compound-specific d 13 C analysis of different biomarkers in many environmental samples, perfect optimization may not always be reached. Therefore, in order to prevent systematic errors in the measured d 13 C values due to different sample concentrations, it is suggested that correction for the remaining unknown amount-dependent fractionation can be made by means of co-analyzing standards of varying analyte concentrations and known d 13 C values. Residual overall amountdependent isotope-fractionation can thus be corrected mathematically.

Tree Physiology, 2015

Plants allocate carbon (C) to sink tissues depending on phenological, physiological or environmen... more Plants allocate carbon (C) to sink tissues depending on phenological, physiological or environmental factors. We still have little knowledge on C partitioning into various cellular compounds and metabolic pathways at various ecophysiological stages. We used compound-specific stable isotope analysis to investigate C partitioning of freshly assimilated C into tree compartments (needles, branches and stem) as well as into needle water-soluble organic C (WSOC), non-hydrolysable structural organic C (stOC) and individual chemical compound classes (amino acids, hemicellulose sugars, fatty acids and alkanes) of Norway spruce (Picea abies) following in situ 13 C pulse labelling 15 days after bud break. The 13 C allocation within the above-ground tree biomass demonstrated needles as a major C sink, accounting for 86% of the freshly assimilated C 6 h after labelling. In needles, the highest allocation occurred not only into the WSOC pool (44.1% of recovered needle 13 C) but also into stOC (33.9%). Needle growth, however, also caused high 13 C allocation into pathways not involved in the formation of structural compounds: (i) pathways in secondary metabolism, (ii) C-1 metabolism and (iii) amino acid synthesis from photorespiration. These pathways could be identified by a high 13 C enrichment of their key amino acids. In addition, 13 C was strongly allocated into the n-alkyl lipid fraction (0.3% of recovered 13 C), whereby 13 C allocation into cellular and cuticular exceeded that of epicuticular fatty acids. 13 C allocation decreased along the lipid transformation and translocation pathways: the allocation was highest for precursor fatty acids, lower for elongated fatty acids and lowest for the decarbonylated n-alkanes. The combination of 13 C pulse labelling with compoundspecific 13 C analysis of key metabolites enabled tracing relevant C allocation pathways under field conditions. Besides the primary metabolism synthesizing structural cell compounds, a complex network of pathways consumed the assimilated 13 C and kept most of the assimilated C in the growing needles.

irst described over 120 years ago in Brazil, Amazonian Dark Earths (ADEs) are expanses of dark so... more irst described over 120 years ago in Brazil, Amazonian Dark Earths (ADEs) are expanses of dark soil that are exceptionally fertile and contain large quantities of archaeological artefacts. The elevated fertility of the dark and often deep A horizon of ADEs is widely regarded as an outcome of pre-Columbian human influence 1. Archaeological research provides clear evidence that their widespread formation in lowland South America was concentrated in the Late Holocene, an outcome of sharp human population growth that peaked towards 1000 BP 2-4. In their recent paper Silva et al. 5 argue that the higher fertility of ADEs is principally a result of fluvial deposition and, as a corollary, that pre-Columbian peoples just made use of these locales, contributing little to their enhanced nutrient status. Soil formation is inherently complex and often difficult to interpret, requiring a combination of geochemical data, stratigraphy, and dating. Although Silva et al. use this combination of methods to make their case 5 , their hypothesis, based on the analysis of a single ADE site and its immediate surroundings (Caldeirão, see maps in Silva et al. 5), is too limited to distinguish among the multiple possible mechanisms for ADE formation. Moreover, it disregards or misreads a wealth of evidence produced by archaeologists, soil scientists, geographers and anthropologists, showing that ADEs are anthropic soils formed on land surfaces enriched by inputs associated with pre-Columbian sedentary settlement 6-9. To be accepted, and be pertinent at a regional level, Silva et al.'s hypothesis 5 would need to be supported by solid evidence (from numerous ADE sites), which we demonstrate is lacking. Geomorphological and pedological considerations There are several problems with reviving the argument 10 that ADE fertility originates from deposited alluvium. First, the Caldeirão ADE site is located on a Miocene plateau~20 m above the Solimões River floodplain (~40 m asl), which in itself precludes significant flooding during the Holocene 11. Second,

Geochimica et Cosmochimica Acta, 2012

Tropical rainforests are highly important for the global climate regulation and for global biodiv... more Tropical rainforests are highly important for the global climate regulation and for global biodiversity. However, these ecosystems are characterized by nutrient-poor and highly weathered soils and by high turnover rates of organic matter. Thus, they are fragile ecosystems prone to loss of ecosystem services when anthropogenically disturbed. Currently, the major threat to these ecosystems is deforestation leading to irreversible destruction of rainforests. Surprising and not expected is that within these ecosystems small patches of highly fertile soils occur which are known as Anthropogenic Dark Earths or terra preta de Índio (terra preta). These soils exhibit high nutrient and soil organic matter stocks and allow sustainable agriculture. Frequent occurrence of pot-sherds of pre-Columbian origin and further evidence for settlement activities clearly demonstrate that terra preta is of anthropogenic origin. In recent years, the terra preta phenomenon has gained increasing interest because it is assumed that terra preta could act as a model for promoting sustainable agricultural practices in the humid tropics and because terra preta is an example for long-term CO 2 sequestration into terrestrial ecosystems with additional positive benefits for ecosystem services. These potentials of terra preta initiated a great number of studies but also stimulated fantasy about their genesis. Therefore, the aim of this review is to summarize the scientific knowledge about terra preta properties and to discuss their genesis. From our own and literature data it is evident that terra preta is the product of inorganic [e.g. ash, bones (esp. fish)] and organic (e.g. biomass wastes, manure, excrements, urine, and biochar) amendments to infertile Ferralsols. These ingredients were microbially metabolized and stabilized by humification in soil, fungi playing a bigger role in this process compared to bacteria in surrounding ecosystems. Biochar is a key component for this process due to its stability and its enrichment in terra preta. It is still unclear if terra preta was produced intentionally or unintentionally. In addition, it is unclear how much time was needed after the disposal of the materials mentioned above to develop a terra preta. Further research is highly desired to investigate these latter two issues.

Ecological Engineering, 2012

The need to reconcile food production, ecosystem services and biodiversity conservation has spurr... more The need to reconcile food production, ecosystem services and biodiversity conservation has spurred the search for more sustainable ways of farming. Archaeology offers examples of prehistoric pathways to agricultural intensification that could be rich sources of inspiration for applying ecological engineering in agriculture today. We examine one set of techniques, pre-Columbian raised-field agriculture in wetlands of Mesoamerica and South America. We point to gaps in knowledge at three levels. First, raised-field agriculture was conducted in a wide range of soils and climates. How different systems functioned was likely to have been correspondingly diverse, but this variation is under-appreciated. At the scale of single farms, nutrient dynamics in raised-field systems likely included complexities quite unusual in 'modern' agriculture, owing to the mixture of aerobic and waterlogged compartments, but data are scarce. Second, at the landscape level there is disagreement about whether fallow periods were necessary, and their eventual roles are poorly understood. Current evidence suggests that self-organizing processes in fallows may have increased the sustainability of some raised-field farming systems in unusual ways. Third, the labor-intensive nature of raised-field farming is held to limit its pertinence to today's global problems, but its real labor costs are unknown. Furthermore, achieving sustainable intensive agriculture will require compensating farmers for ecosystem services they provide. Under a socioeconomic regime that does this, raised-field agriculture could have considerable practical application.

Isotopes in Environmental and Health Studies

the layout of a figure by drawing a set of rectangles on the page using a standard SVG editor suc... more the layout of a figure by drawing a set of rectangles on the page using a standard SVG editor such as Inkscape [Altert13]. In Python, FigureFirst uses this layout file to generate Matplotlib figures and axes in which the user can plot the data. Additionally, FigureFirst saves the populated figures back into the original SVG layout file. This functionality allows the user to adjust the layout in Inkscape, then run the script again, updating the data layers to match the new layout. Building on this architecture, we have implemented a number of features that make complex tasks remarkably easy including axis templates; changing attributes of standard SVG items such as their size, shape, color, and text; and an API for adding JessyInk [Jagannathan12] extensions to Matplotlib objects for automatically generating animated slide presentations. We have used FigureFirst to generate figures for publications [Lindsay17] and provide code

Applied Geochemistry, 2010

The long chain n-alkane composition of plant material can significantly differ between plant grou... more The long chain n-alkane composition of plant material can significantly differ between plant groups e.g. trees and grasses. Due to their relative recalcitrance, they have been employed in paleoecological research as molecular proxies for different types of vegetation. Most of those paleoenvironmental studies rely on the assumption that characteristic molecular fingerprints of plant material are preserved in the fossil organic material without significant alteration. However, there exists evidence that n-alkane distributions may change in the course of plant litter degradation. Here, the authors propose and discuss a conceptual approach to the correction of n-alkane patterns in paleosols and terrestrial sediments for postsedimentary alteration effects. This might have potential to improve paleoenvironmental reconstructions derived from these molecular fossils. In soil depth profiles typically a correlation between the OEP (odd over even predominance) and paleoecological valuable long-chain n-alkane ratios (LARs) can be found. Similar relationships have been also obtained from n-alkane records in paleosols. With the OEP serving as a proxy of microbial reworking, the correction procedure applies OEP vs. LAR regression functions to correct fossil LARs for degradation effects. The regression functions have been derived from modern soils. The application of the procedure and its significance for paleoecological interpretations is demonstrated on a case study of a loess-paleosol sequence ($400-700 ka) in Romania. It is shown that changes in the C27/C31 n-alkane ratio at this site are closely related to degradation effects rather than to changes in the paleovegetation (e.g. tree vs. grass abundance). However, it was found that the C29/ C31 ratio is a more suitable paleoenvironmental proxy at the Mircea Voda site. The results indicate that there is a future potential to correct fossil n-alkane ratios via the OEP/LAR relationship, however at the moment a general straight forward application of this approach might be critical due to lack of extended and diverse n-alkane records from modern soils. The need of more systematic n-alkane studies on soil profiles is highlighted to improve knowledge concerning dynamics and actual mechanisms of postsedimentary LAR and OEP changes.

Proceedings of the …, 2010

The scale and nature of pre-Columbian human impacts in Amazonia are currently hotly debated. Wher... more The scale and nature of pre-Columbian human impacts in Amazonia are currently hotly debated. Whereas pre-Columbian people dramatically changed the distribution and abundance of species and habitats in some parts of Amazonia, their impact in other parts is less clear. Pioneer research asked whether their effects reached even further, changing how ecosystems function, but few in-depth studies have examined mechanisms underpinning the resilience of these modifications. Combining archeology, archeobotany, paleoecology, soil science, ecology, and aerial imagery, we show that pre-Columbian farmers of the Guianas coast constructed large raised-field complexes, growing on them crops including maize, manioc, and squash. Farmers created physical and biogeochemical heterogeneity in flat, marshy environments by constructing raised fields. When these fields were later abandoned, the mosaic of welldrained islands in the flooded matrix set in motion self-organizing processes driven by ecosystem engineers (ants, termites, earthworms, and woody plants) that occur preferentially on abandoned raised fields. Today, feedbacks generated by these ecosystem engineers maintain the human-initiated concentration of resources in these structures. Engineer organisms transport materials to abandoned raised fields and modify the structure and composition of their soils, reducing erodibility. The profound alteration of ecosystem functioning in these landscapes coconstructed by humans and nature has important implications for understanding Amazonian history and biodiversity. Furthermore, these landscapes show how sustainability of food-production systems can be enhanced by engineering into them fallows that maintain ecosystem services and biodiversity. Like anthropogenic dark earths in forested Amazonia, these self-organizing ecosystems illustrate the ecological complexity of the legacy of pre-Columbian land use.

European Journal of Forest Research, 2010

In the last century, many calcareous soils in Castilla León (northwestern Spain) have been transf... more In the last century, many calcareous soils in Castilla León (northwestern Spain) have been transformed from natural Quercus ilex forest to cropped land. Reforestation with Pinus halepensis has been taking place during the past 40 years. In order to obtain a better understanding of how these disturbances affect ecosystem functioning, we studied the quantity and quality of soil organic matter (SOM) in natural forest ecosystems, cropland and Pinus plantations. Density fractionation combined with ultrasonic dispersion enables separation and study of SOM fractions: free organic matter (OM), OM occluded into aggregates and OM stabilized in organo-mineral complexes, considered on the basis of the type of physical protection provided. We separated SOM density fractions and determined the concentrations of C and N, C/N ratios and the natural isotopic abundance (d 13 C and d 15 N values). Transformation of Quercus forest to cropland resulted in major losses of SOC and N, as expected. However, subsequent reforestation with Pinus resulted in good recovery of the original SOC and soil N pools. This indicates the potential for enhanced C storage in agricultural soils by their reversion to a forested state. Study of the density fractions and their 13 C and 15 N signatures enabled better understanding of the high stability of OM in calcareous soils, and analysis of d 13 C variations throughout the profile also enabled identification of past C3/C4 vegetation change. Despite the different OC contents of soils under different land use, OM stabilization mechanisms were not significantly different. In calcareous soils, accumulation of SOC and N is mainly due to organo-mineral associations, resulting in physicochemical stabilization against further decomposition.

Soil Biology and Biochemistry, 2005

Black carbon (BC) or charcoal is thought to represent an important component of the carbon cycle,... more Black carbon (BC) or charcoal is thought to represent an important component of the carbon cycle, but has seldom been quantified in soils. We quantified soil BC in a temperate mixed-grass savanna in the southern Great Plains using benzenecarboxylic acids as molecular markers for BC. Soils were collected from four fire treatments (repeated summer fires in 1992 and 1994; repeated winter fires in 1991, 1993 and 1995; alternate-season fires in winter 1991, summer 1992, and winter 1994; and unburned control) at 0-10 and 10-20 cm depth in 1996. Black carbon concentrations ranged from 50 to 130 g BC kg K1 of soil organic carbon (SOC), or from 0.55 to 1.07 g BC kg K1 of whole soil in this mixed grass savanna. The BC contribution to SOC increased significantly with soil depth (P!0.05). Repeated fires increased BC slightly compared to the unburned controls; however, the effects of repeated fires on BC were not statistically significant in this mixed-grass savanna. Results of this study provide estimates of BC concentrations for native, uncultivated mixed-grass savanna, and indicate that 2-3 fires have little effect on the size of the soil BC pool in this region. q

Water, Air, & Soil Pollution, 1994

For a one year period intact Spodosol soil columns were percolated weekly with H2Odeion, 1.58 mmo... more For a one year period intact Spodosol soil columns were percolated weekly with H2Odeion, 1.58 mmol H2SO 4 L -~, and 0.79 mmol H2SO 4 L -1 + 0.64 mmol HNO3 L -1, respectively, Decomposition rates, soil organic carbon (OC) solubilization, dissolved organic carbon (DOC) fractions, and Cr-, Cu-, and Cd-binding by dissolved hydrophobic and hydrophilic acids were studied. Acid treatment reduced significantly OC respiration as well as OC solubilization in the humic layers. The reduced OC solubility at acid addition was more pronounced for the less polar hydrophobic compounds, resulting in a decrease of the hydrophobie acids (from ca. 65 to 40-45% of DOC), and in an increase of the hydrophilic acids (from ca. 25 to 40-45% of DOC). For B horizon leachates, DOC increased at acid treatment. Generally, hydrophobic acids were retained preferentially in the B horizon. Also in the B horizon output there was an increase of the hydrophilic acids as acidity increased (from ca. 40 to 50% of DOC). Differences between the two acid treatments were negligible. The degree of metal-organic complexes decreased in the order Cr > Cu > Cd, from A to B horizon leachates, and with increasing acidity. Hydrophilic acids were found to be the dominating ligands in complexing Cr and Cu. Actual Cr-and Cu-binding by hydrophilic acids exceeded that by hydrophobic acids 2-8 times. As the hydrophilic acids represented the most mobile DOC components in the soil columns, in particular with increasing acidity, significant amounts of Cr and Cu in the B horizon leachates were organically complexed, although a great proportion of the hydrophobic acids was retained in the B horizon.

Organic Geochemistry, 2005

We present both conventional proxies (total organic carbon and N, 14C, δ13C, δ15N) and compound-s... more We present both conventional proxies (total organic carbon and N, 14C, δ13C, δ15N) and compound-specific stable isotope data for terrestrial, aquatic and microbial biomarkers combined with an in-depth interpretation of their environmental meaning for a sediment core from Lake Rukche at 3500m a.s.l. in the Gorkha Himal, Nepal, a region with a paucity of palaeoclimate data. Compound-specific δ13C values of

Amazonian Dark Earths, 2004

Soils serve as natural archives and store valuable information on site and climate conditions und... more Soils serve as natural archives and store valuable information on site and climate conditions under which they were formed (Zech et al., 2000). It has also been shown that landuse influences amounts and composition of soil organic matter (eg Srivastava and Singh, 1991; ...

Quaternary Science Reviews, 2003

Late Quaternary glacier fluctuations in the Macha Khola valley (Gorkha Himal, Nepal) were reconst... more Late Quaternary glacier fluctuations in the Macha Khola valley (Gorkha Himal, Nepal) were reconstructed using relative and absolute dating techniques. Our results indicate that younger moraine complexes were left by Late Holocene (o1.7 cal. ka BP), mid-Holocene (ca 3 cal. ka BP), and Lateglacial (ca 13 cal. ka BP) ice advances. Older Late Quaternary glacier advances occurred during Marine Oxygen Isotope Stages (MIS) 2 and 3-4. No relics of Middle or Early Pleistocene glaciations could be found. During MIS 3-4, glaciers advanced down to an altitude of at least 2150 m a.s.l., corresponding to an ELA depression of approximately 1300 m. At about 3500 m a.s.l., the MIS 2 Macha Khola glacier reached almost the thickness of the former MIS 3-4 glacier and retreated some time before 17.9 cal. ka BP. The Lateglacial glacier advanced again several times to altitudes between 2450 and 3400 m a.s.l. The mid-Holocene glaciers extended much farther down-valley than the Late Holocene ones. Dendrochronological data of Abies spectabilis suggested several periods of unfavourable growth conditions especially at the beginning of the 19th (1820) and 20th (1905) centuries. r

Quaternary International, 2011

Amazonian Dark Earths, 2004

Accelerated soil degradation is one of the most severe problems of landuse in the tropics (Zech e... more Accelerated soil degradation is one of the most severe problems of landuse in the tropics (Zech et al., 1997). This is to a large part due to the fact that soil organic matter (SOM) rapidly declines in tropical soils under arable cultivation (Tiessen et al., 1994). Soil organic matter is of ...

Amazonian Dark Earths, 2004

To secure food supply for the increasing population there is an urgent need to intensify the agri... more To secure food supply for the increasing population there is an urgent need to intensify the agricultural production especially in less developed countries of the tropics. There, soils are frequently poor and not suitable for intensive sustainable agriculture because low organic matter contents and minerals with low cation exchange capacity favor nutrient leaching. Under such circumstances, mineral fertilizers such as

Water, Air, & Soil Pollution, 2011

Due to long-lasting historic fly-ash deposition from lignite-fired power plants, soils of forest ... more Due to long-lasting historic fly-ash deposition from lignite-fired power plants, soils of forest ecosystems in Central Germany have been affected by a variety of contaminants. In addition to heavy metals and oxides, another fly-ash compound is Black carbon (BC) which supposedly has been accumulated as well. BC as a generic term describing different forms of pyrogenetic carbon is considered as a very stable fraction of the C cycle. In this study, BC content of organic layers of 38 sites from two adjacent forested areas was determined using a simplified benzenepolycarboxylic acid (BPCA) method. Considerable amounts of BC were detected in both areas. It accounted for up to 11.2 and 15.6% of total organic carbon (TOC) in the Oe and Oa horizons, respectively. On average, slightly higher BC contents were found in the Oe (23.0 g BC kg −1 ), whereas BC/TOC ratios were higher in the Oa. The BC/TOC ratio of the Oe horizon tended to decrease with increasing distance from the former main emitters. In contrast to expectations, BC contents of the Oa horizon tended to increase with increasing distance. The deposition gradient, in previous research found for other fly-ash compounds, could not be observed for BC. Higher values in more remote forests might be taken as an indicator for the influence of additional emission sources. Further research is needed to confirm the results and to elucidate the potential impact of (soot-) BC on humus dynamics in the study area.

Rapid Communications in Mass Spectrometry, 2003

The performance of a gas chromatography-combustion-isotope ratio mass spectrometry system (GC-C-I... more The performance of a gas chromatography-combustion-isotope ratio mass spectrometry system (GC-C-IRMS) with respect to the dependence of d 13 C values on the amount of sample is presented. Particular attention is paid to the localization of the amount-dependent isotopic fractionation within the system. Injection experiments with varying amounts of gases (CO 2 , n-hexane, and toluene) revealed that neither the detector unit nor the combustion reactor, but rather the conditions in the split/splitless injector, contributed to this effect. Although optimization of injector parameters was performed and a reduction of this adverse effect from 3 to 1% was achieved, it was not possible to eliminate isotopic fractionation completely. Consequently, additional injector parameters have to be considered and adjusted to achieve injection conditions free of fractionation. For routine analysis of the compound-specific d 13 C analysis of different biomarkers in many environmental samples, perfect optimization may not always be reached. Therefore, in order to prevent systematic errors in the measured d 13 C values due to different sample concentrations, it is suggested that correction for the remaining unknown amount-dependent fractionation can be made by means of co-analyzing standards of varying analyte concentrations and known d 13 C values. Residual overall amountdependent isotope-fractionation can thus be corrected mathematically.