Incorporation Of Organic Matter Research Articles

The effects of long-term management on patterns of carbon storage in a northern highbush blueberry production system.

Perennial crops potentially provide a sink for atmospheric carbon. However, there is a poor understanding of how perennial crops differ in their carbon allocation patterns, and few studies have tested how agronomic practices such as fertilization influence long-term patterns of carbon allocation in actual production systems. In this study, we report results of a long-term field experiment that tested the individual and combined effects of organic matter incorporation and nitrogen fertilization on carbon allocation. The mature (nine-year-old) blueberry plants in this study had an average standing carbon stock of 1147gCm-2 and average annual Net Primary Production (NPP) of 523gCm-2yr-1, values that are similar to those reported for other woody crops. Forty-four percent of blueberry annual NPP was sequestered in persistent biomass, 19% was exported as harvested fruit, and 37% entered the detrital pathway. Nitrogen applied at rates typical for blueberry production throughout the span of the study had no significant effect on total plant or soil C. However, pre-planting organic matter incorporation and periodic mulching with sawdust significantly increased both soil organic matter and soil C. Pre-planting organic matter incorporation also increased total standing plant C nine years later at maturity. At the field scale, we estimate that fields receiving pre-planting organic matter incorporation would have 4.8% (4.5Mgha-1) more standing C relative to non-amended fields, although the difference is within the range of uncertainty of the estimated values. These results suggest that blueberry production can provide a valuable medium-term carbon store that is comparable in magnitude to that of temperate tree crops, but overall carbon budgets are influenced by management practices over the first decade after planting.

Disentangling interactions between microbial communities and roots in deep subsoil

Soils, paleosols and terrestrial sediments serve as archives for studying climate change, and represent important terrestrial carbon pools. Archive functioning relies on the chronological integrity of the respective units. Incorporation of younger organic matter (OM) e.g. by plant roots and associated microorganisms into deep subsoil and underlying soil parent material may reduce reliability of paleoenvironmental records and stability of buried OM. Long-term effects of sedimentary characteristics and deep rooting on deep subsoil microbial communities remain largely unknown. We characterized fossil and living microbial communities based on molecular markers in a Central European Late Pleistocene loess-paleosol sequence containing recent and ancient roots with ages of several millenia. The molecular approach, comprising free and phospholipid fatty acids (FAs), core and intact polar glycerol dialkyl glycerol tetraethers (GDGTs), as well as 16S rRNA genes from bacterial DNA, revealed the presence of living microorganisms along the sequence, with bacterial community composition comparable to that of modern topsoils. Up to 88% redundancy between bacterial genetic fingerprint and molecular signature of fossil microorganisms suggested a time-integrated signal of the molecular markers accumulated over a time span potentially lasting from sedimentation over one or more rooting phases until today. Free FAs, core GDGTs and DNA, considered as remains of fossil microorganisms, corresponded with ancient and recent root quantities, whereas phospholipid FAs and intact polar GDGTs, presumably derived from living microorganisms, correlated only with living roots. The biogeochemical and ecological disequilibrium induced by postsedimentary rooting may entail long-term microbial processes like OM mineralization, which may continue even millenia after the lifetime of the root. Deep roots and their fossil remains have been observed in various terrestrial settings, and roots as well as associated microorganisms cause both, OM incorporation and mineralization. Therefore, these findings are crucial for improved understanding of OM dynamics and carbon sequestration potential in deep subsoils.

Light Regimes Shape Utilization of Extracellular Organic C and N in a Cyanobacterial Biofilm.

ABSTRACTAlthough it is becoming clear that many microbial primary producers can also play a role as organic consumers, we know very little about the metabolic regulation of photoautotroph organic matter consumption. Cyanobacteria in phototrophic biofilms can reuse extracellular organic carbon, but the metabolic drivers of extracellular processes are surprisingly complex. We investigated the metabolic foundations of organic matter reuse by comparing exoproteome composition and incorporation of 13C-labeled and 15N-labeled cyanobacterial extracellular organic matter (EOM) in a unicyanobacterial biofilm incubated using different light regimes. In the light and the dark, cyanobacterial direct organic C assimilation accounted for 32% and 43%, respectively, of all organic C assimilation in the community. Under photosynthesis conditions, we measured increased excretion of extracellular polymeric substances (EPS) and proteins involved in micronutrient transport, suggesting that requirements for micronutrients may drive EOM assimilation during daylight hours. This interpretation was supported by photosynthesis inhibition experiments, in which cyanobacteria incorporated N-rich EOM-derived material. In contrast, under dark, C-starved conditions, cyanobacteria incorporated C-rich EOM-derived organic matter, decreased excretion of EPS, and showed an increased abundance of degradative exoproteins, demonstrating the use of the extracellular domain for C storage. Sequence-structure modeling of one of these exoproteins predicted a specific hydrolytic activity that was subsequently detected, confirming increased EOM degradation in the dark. Associated heterotrophic bacteria increased in abundance and upregulated transport proteins under dark relative to light conditions. Taken together, our results indicate that biofilm cyanobacteria are successful competitors for organic C and N and that cyanobacterial nutrient and energy requirements control the use of EOM.

Application of leaves to induce earthworms to reduce phenolic compounds released by decomposing plants

The negative impacts (allelopathic effects) of phenolic compounds (PCs) in soil on plant growth and microbial communities have recently received considerable attention. Similarly, there have been several recent studies on the effects of microbes on the degradation of PCs. Because of the profound effects of their feeding and burrowing activity, earthworms should have significant effects on PCs degradation; however, few studies have examined this potential effect, and particularly, factors that may affect the course of degradation. We tested different earthworm species and density, different conditions (sterilization or not) of mixture of soil and plant residual, and different source of PCs to evaluate the capacity of earthworms to accelerate PCs degradation. In addition, earthworm behavior experiments were set up to test whether adding plant leaves can stimulate earthworm feeding activity. The results showed that native earthworms exhibited a higher capacity than compost earthworms for degrading PCs; furthermore, when the number of Metaphire guillemi reached 300 individuals m−2 in our experimental units, the PCs decreased most quickly, and the residual PCs concentration was 105 μg (p-coumaric acid)g−1 (dry soil) less than that of control group. The source of PCs also affected their degradation rate, as PCs derived from leaves seemed to degrade more quickly. The results of our experiment suggested that earthworms avoid feeding on phenolic acids, but can be induced to do so by adding leaves to the substrate. These results indicate that earthworm activity can accelerate the degradation of total PCs, and that this may be further facilitated by incorporation of organic matter, which may be used to alleviate allelopathic effects of PCs in soil.

Spatial patterns of plant litter in a tidal freshwater marsh and implications for marsh persistence

The maintenance of marsh platform elevation under conditions of sea level rise is dependent on mineral sediment supply to marsh surfaces and conversion of above- and belowground plant biomass to soil organic material. These physical and biological processes interact within the tidal zone, resulting in elevation-dependent processes contributing to marsh accretion. Here, we explore spatial pattern in a variable related to aboveground biomass, plant litter, to reveal its role in the maintenance of marsh surfaces. Plant litter persisting through the dormant season represents the more recalcitrant portion of plant biomass, and as such has an extended period of influence on ecosystem processes. We conducted a field and remote sensing analysis of plant litter height, aboveground biomass, vertical cover, and stem density (collectively termed plant litter structure) at a tidal freshwater marsh located within the Potomac River estuary, USA. LiDAR and field observations show that plant litter structure becomes more prominent with increasing elevation. Spatial patterns in litter structure exhibit stability from year to year and correlate with patterns in soil organic matter content, revealed by measuring the loss on ignition of surface sediments. The amount of mineral material embedded within plant litter decreases with increasing elevation, representing an important tradeoff with litter structure. Therefore, at low elevations where litter structure is short and sparse, the role of plant litter is to capture sediment; at high elevations where litter structure is tall and dense, aboveground litter contributes organic matter to soil development. This organic matter contribution has the potential to eclipse that of belowground biomass as the root:shoot ratio of dominant species at high elevations is low compared to that of dominant species at low elevations. Because of these tradeoffs in mineral and organic matter incorporation into soil across elevation gradients, the rate of marsh surface elevation change is remarkably consistent across elevation. Because of the role of plant litter in marsh ecosystem processes, monitoring and assessment of these dynamic geomorphic marsh landscapes might be streamlined through the measurement of plant litter structure, either via LiDAR technologies or field observation.

Assessment of soil organic matter mineralization under various management practices

ABSTRACTMineralization is the main organic matter conversion process, which leads not only to preservation of organic matter in the soil but also to its sequestration. Soil organic matter has equal value as mineral part if we want to improve soil quality or increase the yield. Because of intensive farming, irresponsible use of mineral fertilizers and natural factors, soil organic matter is decreasing. To counteract this process, different soil-friendly management practices and techniques, such as shallow tillage, no-tillage or direct drilling and application of additional organic matter are used. The objective of the present study was to assess the changes in the intensity of soil organic matter mineralization as influenced by primary soil tillage of different intensity in combination with organic matter incorporation. Long-term studies showed that land management practices differentiated the soil into two layers: upper (0–10 cm) layer containing more moisture and nutrients and lower (10–20 cm) layer comprising less moisture and nutrients. The conditions of aeration in the arable soil layer did not change under the effect of ploughing. In this soil, the rate of mineralization was lower than that in the ploughless tillage treatment. The most active mineralization of soil organic matter in the ploughless tillage treatment occurred in the autumn period, when high level of rainfall promoted the loss of nutrients from the topsoil layer.

Winery and distillery derived materials as phosphorus source in calcareous soils

The depletion of phosphate rock reserves makes necessary the finding and characterization of new phosphorus (P) sources to ensure a sustainable P fertilization. This research deals with the effect of the application of organic materials derived from the winery and distillery industries on P availability in two calcareous soils. Soils were treated with five organic materials providing different amounts of P: two raw wastes (exhausted grape marc and grape stalk) and three composts made with different proportions of these materials or including cake lees as well. The soils were incubated for 16weeks determining soil pH, dissolved organic carbon and Olsen P in five samplings with time. At the end of the incubation, inorganic P was fractionated to NaOH–NaCl–P, citrate-bicarbonate-dithionite–P (CBD–P), and HCl–P and the P sorption index (PSI) was also determined. The increment in Olsen P was firstly positively related to the amount of P applied, being higher in the composted materials, but along time the effect of other factors such as the organic matter incorporation influenced these changes. After 16weeks of incubation, the enhancement of Olsen P produced by the different materials equalized (8.9mgkg−1 on average), despite of the different amounts of P applied with each one. Increasing the P applied with the organic materials in these soils enhanced P retained in the sparingly soluble P fraction (HCl–P) whereas the addition of raw materials slightly released P from this fraction, recovering more P in the most labile pool (NaOH–NaCl–P). It can be concluded that the winery and distillery derived materials had a positive effect on soil P availability and that P in excess would be retained due to the calcareous nature of these soils, avoiding contamination risks.

Variability of Soil Micronutrients Concentration along the Slopes of Mount Kilimanjaro, Tanzania

Soil micronutrients are important elements for plant growth despite being required in small quantities. Deficiency of micronutrients can result in severe crop failure while excess levels can lead to health hazards; therefore, investigating their status in agricultural land is crucial. Fifty plots were established along an altitudinal gradient from 680 to 1696 m a.s.l. on the slopes of Mount Kilimanjaro, Tanzania. Soils were sampled at the top- (0–20 cm) and subsoils (21–50 cm) in four locations within each plot. Fourier Transform Mid-Infrared (FT-MIR) spectroscopy and wet chemistry were used for soil analysis. Results indicated that the mean concentrations of the micronutrients in the topsoil were Fe (130.4±6.9 mgkg−1), Mn (193.4±20.5 mgkg−1), Zn (2.8±0.2 mgkg−1), B (0.68±0.1 mgkg−1), and Cu (8.4±0.8 mgkg−1). Variations of the micronutrients were not statistically different by elevation (df = 41,p>0.05) and by soil depth (df = 49,p>0.05). Correlations among micronutrients were significant for FeversusMn (r=0.46,p<0.001), BversusZn (r=0.40,p=0.003), BversusCu (r=0.34,p=0.013), and CuversusZn (r=0.88,p<0.001). The correlated micronutrients implied that they were affected by similar factors. Soil pH correlated positively with B, Fe, and Mn and negatively with Cu and Zn, hence probably influencing their availability. Therefore, the need for sustaining micronutrient at sufficient levels is crucial. Management interventions may include moderating soil pH by reducing acidity through liming in the higher elevations and incorporation of organic matter in the lowlands.

Incorporation of iron and organic matter into young Antarctic sea ice during its initial growth stages

Abstract This study reports concentrations of iron (Fe) and organic matter in young Antarctic pack ice and during its initial growth stages in situ. Although the importance of sea ice as an Fe reservoir for oceanic waters of the Southern Ocean has been clearly established, the processes leading to the enrichment of Fe in sea ice have yet to be investigated and quantified. We conducted two in situ sea-ice growth experiments during a winter cruise in the Weddell Sea. Our aim was to improve the understanding of the processes responsible for the accumulation of dissolved Fe (DFe) and particulate Fe (PFe) in sea ice, and of particulate organic carbon and nitrogen, dissolved organic carbon, extracellular polymeric substances, inorganic macro-nutrients (silicic acid, nitrate and nitrite, phosphate and ammonium), chlorophyll a and bacteria. Enrichment indices, calculated for natural young ice and ice newly formed in situ, indicate that during Antarctic winter all of the measured forms of particulate matter were enriched in sea ice compared to underlying seawater, and that enrichment started from the initial stages of sea-ice formation. Some dissolved material (DFe and ammonium) was also enriched in the ice but at lower enrichment indices than the particulate phase, suggesting that size is a key factor for the incorporation of impurities in sea ice. Low chlorophyll a concentrations and the fit of the macro-nutrients (with the exception of ammonium) with their theoretical dilution lines indicated low biological activity in the ice. From these and additional results we conclude that physical processes are the dominant mechanisms leading to the enrichment of DFe, PFe, organic matter and bacteria in young sea ice, and that PFe and DFe are decoupled during sea-ice formation. Our study thus provides unique quantitative insight into the initial incorporation of impurities, in particular DFe and PFe, into Antarctic sea ice.

The importance of soil carbon and nitrogen for amelioration of acid sulphate soils

AbstractWhen exposed to air and adequate moisture, soils containing sulphides (sulphidic soils with pH > 4) become oxidized and generate sulphuric acid to form ‘sulphuric soils’ (pH < 4). Treatment of this acidity is undertaken by addition of lime. In this study, we investigated the effectiveness of adding plant organic matter, and simple carbon and nitrogen compounds, as alternatives to lime to sulphuric and sulphidic soils. In sulphuric soils under aerobic conditions, organic matter increased pH, the extent depending on the nitrogen content. Lucerne hay, which had the largest nitrogen content, increased the pH from 3.7 to 8.0, while pea straw and wheat straw effected smaller changes, in proportion to their respective nitrogen contents. Lucerne hay also caused the greatest reductions in soil redox potential and sulphate content, consistent with the action of sulphate‐reducing bacteria. Similarly, incorporation of organic matter under aerobic conditions effectively prevented sulphidic soil acidification and reduced the redox potential and sulphate content. The individual effects of carbon and nitrogen compounds were then examined and compared to plant organic material. Glucose was ineffective at both small and large concentrations, while molasses increased the pH slightly to 4.6 and acetate to 5.9. None of these carbon compounds was as effective as complex organic matter. Nitrogen added alone as nitrate or ammonia had little or no effect on pH, whereas organic nitrogen in the form of urea caused the pH to rise to 6.3 and reduced the redox to less than 0 mV but had no significant effect on sulphate content.

Nitrous oxide emissions during biological soil disinfestation with different organic matter and plastic mulch films in laboratory-scale tests

Nitrous oxide (N2O), which is a greenhouse gas, may be more emitted as an intermediate product of denitrification during biological soil disinfestation. The biological soil disinfestation is a method to suppress soil-borne pathogens under reductive soil conditions produced by the application of organic matter and water irrigation with plastic film. The objective of the study was to determine the effects of different organic matter and mulch films on N2O emissions during biological soil disinfestation. Grey lowland soil amended with cattle compost plus rice bran (0.2%), rice husk (0.2%) or dent corn (0.1%, 0.2% and 0.4%) was incubated at 100% water-holding capacity with or without plastic films made of polyvinyl chloride (PVC) and triple-layer polyolefin (3PO) for 72 h at 50°C. Permeation of the two films was also measured at 25°C and 50°C. Results showed that incorporation of organic matter increased N2O emissions compared with no organic matter addition at 50°C. Incorporation of rice bran and dent corn with easily decomposable C and low C:N ratios increased N2O emissions for the first 12 h, but thereafter, available C supply from these amendments suppressed N2O emissions. Permeability of mulch films increased at a higher temperature and was larger for PVC than for 3PO. Our study indicated that rice husk should not be used for soil disinfestation and that application rates of organic matter must be determined based on their decomposability. Moreover, mulch film covering would not suppress N2O emission in biological soil disinfestation because of high temperature.

Possible Biosphere-Lithosphere Interactions Preserved in Igneous Zircon and Implications for Hadean Earth.

Granitoids are silicic rocks that make up the majority of the continental crust, but different models arise for the origins of these rocks. One classification scheme defines different granitoid types on the basis of materials involved in the melting/crystallization process. In this end-member case, granitoids may be derived from melting of a preexisting igneous rock, while other granitoids, by contrast, are formed or influenced by melting of buried sedimentary material. In the latter case, assimilated sedimentary material altered by chemical processes occurring at the near surface of Earth-including biological activity-could influence magma chemical properties. Here, we apply a redox-sensitive calibration based on the incorporation of Ce into zircon crystals found in these two rock types, termed sedimentary-type (S-type) and igneous-type (I-type) granitoids. The ∼400 Ma Lachlan Fold Belt rocks of southeastern Australia were chosen for investigation here; these rocks have been a key target used to describe and explore granitoid genesis for close to 50 years. We observe that zircons found in S-type granitoids formed under more reducing conditions than those formed from I-type granitoids from the same terrain. This observation, while reflecting 9 granitoids and 289 analyses of zircons from a region where over 400 different plutons have been identified, is consistent with the incorporation of (reduced) organic matter in the former and highlights one possible manner in which life may modify the composition of igneous minerals. The chemical properties of rocks or igneous minerals may extend the search for ancient biological activity to the earliest period of known igneous activity, which dates back to ∼4.4 billion years ago. If organic matter was incorporated into Hadean sediments that were buried and melted, then these biological remnants could imprint a chemical signature within the subsequent melt and the resulting crystal assemblage, including zircon.

Soil Health and Related Ecosystem Services in Organic Agriculture

<p>Soil health is dependent upon complex bio-physical and bio-chemical processes which interact in space and time. Microrganisms and fauna in soil comprise highly diverse and dynamic communities that contribute, over either short or long time frames, to the transformation of geological minerals and release of essential nutrients for plant growth. Certified organic soil management practices generally restrict the use of chemically-processed highly soluble plant nutrients, leading to dependence on nutrient sources that require microbial transformation of poorly soluble geological minerals. Consequently, slow release of nutrients controls their rate of uptake by plants and associated plant physiological processes. Microbial and faunal interactions influence soil structure at various scales, within and between crystalline mineral grains, creating complex soil pore networks that further influence soil function, including the nutrient release and uptake by roots. The incorporation of organic matter into soil, as either manure or compost in organic farming systems is controlled to avoid excessive release of soluble nutrients such as nitrogen and phosphorus, while simultaneously contributing an essential source of carbon for growth and activity of soil organisms. The interdependence of many soil physical and chemical processes contributing to soil health is strongly linked to activities of the organisms living in soil as well as to root structure and function. Capitalizing on these contributions to soil health cannot be achieved without holistic, multiscale approaches to nutrient management, an understanding of interactions between carbon pools, mineral complexes and soil mineralogy, and detailed examination of farm nutrient budgets.</p>

Characteristics of man-made soils of greenhouse fields in urban areas, Osaka Prefecture, Japan

Fertility status of man-made greenhouse agricultural soils in Osaka prefecture, Japan, where is characterized as highly urbanized area, were investigated. From the plow layer of greenhouse fields, 31 ordinary soil samples and 36 man-made soil samples were collected and physico-chemical properties including labile organic N by chemical extraction method, nonexchangeable nutrients and water-soluble ions were measured. We clarified that the ordinary and man-made soils differed significantly in many properties; total C, total N, phosphate buffer extractable N, and P or K fertility were significantly higher in the ordinary soils than in the man-made soils. This tendency would be reflected the longer agricultural use and incorporation of organic matter and applied fertilizers in ordinary fields through paddy use before greenhouse use. In contrast, non-exchangeable K, and water-soluble Ca and SO4 were higher in the man-made soils. The PCA (principal component analysis) analysis revealed that man-made soils could be differentiated from ordinary soils, and man-made soils were characterized by low content in soluble or exchangeable magnesium, organic matter, available and hardly extractable phosphorus, and the fact that they remained the parent materials’ characteristics. Our results demonstrated that the soil properties were considerably different between the ordinary soils and the man-made soils. It is reasonable to separate man-made soils from ordinary soils for the planning the suitable agricultural soil management.

Fusarium-suppressive effects of green manure of turnip rape

Allelochemicals of Brassica can inhibit a wide range of soil-borne pathogenic fungi. In the present study, the effects of different turnip rape (Brassica rapa) cultivation treatments on the soil fungal community were investigated in two experiments in 2009 2010 and 2010 2011. The treatments used turnip rape as a green manure, as a mixed-crop with barley, or as a rotational crop after barley, with continuous barley as the reference. The composition of the soil fungal community was monitored with capillary-based length heterogeneity PCR using primers ITS1F/ITS4. The operational taxonomic units (OTUs) identified as the pathogens Botrytis cinerea, Rhizoctonia solani and Sclerotinia sclerotiorum did not respond to different treatments. Fungal diversity was the lowest and the relative abundance of Fusarium spp. the highest in barley monoculture. Incorporation of turnip rape plants into the soil as green manure was associated with a low relative abundance of Fusarium spp. Turnip rape as a mixed crop or rotational crop did not substantially decrease the relative abundance of Fusarium spp. Aqueous and non-polar extracts of allelochemicals from turnip rape had very little effect on the growth of Fusarium culmorum in vitro. We conclude that high fungal diversity, resulting from either application of fertilizer or incorporation of organic matter of turnip rape, was more important than allelochemicals in affecting the growth of Fusarium spp. in field soils.

The role of organic matter in ameliorating acid sulfate soils with sulfuric horizons

Acid sulfate soils with sulfuric horizons (pH<4) can exert a range of negative impacts on the ecology and productivity of soils. The primary treatment for these soils is to raise the pH of the sulfuric horizons using lime. Although often effective, this treatment can be expensive and not well suited to large areas. In this laboratory study, we have investigated the possible use of plant organic matter (OM) to ameliorate: (i) “sulfuric soils” [produced by the oxidization of clayey sulfidic material (pH>4) samples to form “sulfuric horizon material” (pH<4)] and (ii) “neutralized sulfuric soils” [produced by the neutralization of peaty sulfuric horizon material (pH<4) with alkaline sandy loam]. The advantage of this approach is that organic matter is readily available and inexpensive. The experimental treatments used leaf material from Phragmites australis as the source of organic matter, which was either incorporated into the two manufactured soils or applied to the surface. After 6months of incubation under either aerobic or anaerobic soil conditions, pH, Eh and sulfate content were measured. The results showed that incorporation of OM into the sulfuric soil significantly increased soil pH, the extent depending on the moisture level. Changes in pH and sulfate content were correlated with Eh. Application of OM to the “neutralized sulfuric soil” was only partially effective in preventing acidification. It was concluded that the decomposition of OM by aerobic bacteria results in oxygen depletion, which then favors metabolic conversion of sulfates to sulfides by anaerobic bacteria. The results of this study have important implications for the broad scale management of acid sulfate soils.

Reconstruction of environmental changes during the late glacial and Holocene reflected in a soil-sedimentary sequence from the lower Selenga River valley, Lake Baikal region, Siberia, assessed by lipid molecular proxies

Sediments of Lake Baikal and smaller lakes in its surroundings have been frequently used to trace paleoenvironmental changes. However, these sediments integrate environmental proxies over large areas and the processes leading to alteration of terrestrial signals are not fully understood. More specific information can be derived from terrestrial archives such as alternating soil-sediment sequences. Near the village of Burdukovo, southeast of Lake Baikal, such sequences are accessible along the ∼5 m high right terrace of the Selenga River. However, terrestrial archives can be associated with degradation of organic matter. Therefore, lipid molecular proxies were applied in the current study to trace environmental and vegetation shifts as well as incorporation and degradation of organic matter. Alkane and fatty acid molecular proxies as part of the lipid fraction are well known for their diagnostic character to trace sources of organic matter and its degradation. Several parameters including the carbon preference indices of alkanes and fatty acids indicated a well preservation of the organic matter in the investigated sequence. Furthermore, the organic matter in the C horizons of the terrestrial upper part of the sediments was most likely overprinted by rooting of the plants growing on respective overlaying soils as reflected by the average chain length of fatty acids and alkanes and the relative composition of long-chain n-alkanes (C25–33). The 3.5 m thick sequence enabled tracing of vegetation shifts. The alkane composition argued for changes in the grass dominated vegetation cover within the different phases of the Holocene until today, whereas a birch and willow dominated deciduous forest vegetation as traced in other archives of the larger Baikal area could not be determined in the Burdukovo sequence by lipid molecular proxies. The scatter in the alkane and fatty acid composition revealed only minor vegetation shifts throughout the Holocene. Nevertheless, some changes in the lipid composition indicated a change in the plant community. As coniferous trees have often similar alkane patterns to grass vegetation, it cannot be excluded that conifers also contributed to a certain degree to the molecular record in the Burdukovo sequence. The general decrease in the carbon preference index of alkanes since approximately 4 ka BP until recent times further argues for an increasing admixture of coniferous lipids to the record. Lipid molecular proxies of sediment that formed 2.8–2.6 ka BP revealed the incorporation of deciduous tree-derived organic matter most likely originating from birch that grew elsewhere in the catchment of the Selenga River. The proxies enabled an assessment of site-specific vegetation shifts and degradation of organic matter in the soil-sediment sequence of the Burdukovo area, and thus provide more specific information related to a certain area than lacustrine sediments integrating over larger catchments.

Predicting thermal performance of fired clay bricks lightened by adding organic matter: Improvement of brick geometry

Fired clay masonry bricks adapt to a variety of constraints during use. Through their mass, these products provide thermal inertia and thus a good indoor climate. Thanks to their thermal insulation properties, they help to minimize heating and cooling costs. The brick industry allows different by-products to be added into the clay mixture at the beginning of the industrial cycle, and the incorporation of organic matter improves thermal insulation while reducing the weight of the bricks. This article presents an experimental and numerical method for determining the thermal resistance of fired clay bricks containing residue of wheat straw. As their thermal conductivity reaches a value 35% lower than that of clay without organic matter, the thermal transmittance of such bricks can be improved by more than 20% relative to existing values.

Organic matter biomarker analysis as a potential chemostratigraphic tool for Late Pleistocene tills from the Hudson Bay Lowlands, Canada

During the Last Glacial Maximum approximately 22,000years ago, the Hudson Bay Lowlands (HBL) lay at the center of the 3km thick Laurentide Ice Sheet. During the course of the last glacial cycle HBL was crossed by ice from the west (the Keewatin sector) and from the east (Labrador sector) but the relative influence of the outflow centers is debateable because of continuing uncertainty surrounding the age and stratigraphic position of lithologically-similar tills in different areas. This study examines the use of organic matter (OM) biomarkers to analyze OM sources in HBL tills. These tills are believed to be of late Wisconsin age (Sachigo, Severn) and an older possibly early Wisconsin deposit (Rocksand Till) and biomarkers may provide insights into source materials and degree of diagenesis. Solvent extraction, base hydrolysis, and cupric oxide oxidation were performed to isolate and quantify free lipids, bound lipids, and lignin-derived phenols respectively. Lipid biomarker patterns indicate higher Sphagnum-derived OM to the Severn and Rocksand tills relative to the Sachigo Till consistent with subglacial reworking and incorporation of peat. OM within the Severn Till is dominated by OM derived from non-woody gymnosperms and non-woody angiosperms whereas Sachigo and Rocksand tills have both woody and non-woody gymnosperms and angiosperms derived OM. Furthermore, the Severn Till contained the most suberin-derived OM, while the Sachigo Till had the least. Acid-to-aldehyde ratios of lignin-derived phenols suggest that the Severn Till has undergone less diagenesis in comparison to Sachigo and Rocksand confirming that it is likely the youngest of the three tills. This study highlights that biomarker analysis is an important chemostratigraphic tool that may distinguish till deposits and provides insight into paleovegetation and paleoclimate in the HBL prior to glacial incorporation of OM into till. This information facilitates paleoenvironmental analyses to be extended into preglacial and interstadial episodes where no stratigraphic record exists.

Earthworm assemblages as affected by field margin strips and tillage intensity: An on-farm approach

Earthworm species contribute to soil ecosystem functions in varying ways. Important soil functions like structural maintenance and nutrient cycling are affected by earthworms, thus it is essential to understand how arable farm management influences earthworm species. One aim of arable field margin strips and non-inversion tillage is to enhance agrobiodiversity, however their influence on earthworm species assemblages remains unclear. In particular, on-farm studies conducted over multiple years that capture variability across the landscape are rare. The current study monitored earthworm species assemblages on 4 farms in Hoeksche Waard, The Netherlands, from 2010 to 2012. It was hypothesised that arable field margin strips (FM) and non-inversion tillage (NIT; a reduced tillage system that loosens subsoil at 30−35 cm depth) would have higher earthworm species abundances (epigeics and anecics in particular), soil organic matter, and soil moisture than adjacent mouldboard ploughing (MP) fields, and that earthworm numbers would decrease with distance away from FM into arable fields (MP only). FM contained a mean total earthworm abundance of 284 m−2 and biomass of 84 g m−2 whereas adjacent MP arable fields had only 164 earthworms m−2 and 31 g m−2. Aporrectodea rosea, Lumbricus rubellus, Lumbricus terrestris, and Lumbricus castaneus were significantly more abundant in FM than adjacent arable soil under MP. However, no decreasing trend with distance from FM was observed in earthworm species abundances. A tillage experiment initiated on the farms with FM showed that relative to MP, NIT significantly increased mean total earthworm abundance by 34% to 275 m−2 and mean total earthworm biomass by 15% to 51 g m−2 overall sampling dates and farms. L. rubellus, A. rosea, and L. terrestris were significantly more abundant overall in NIT than MP. FM and NIT positively affected earthworm species richness and abundances and it is noteworthy that these effects could be observed despite variation in environmental conditions and soil properties between samplings, farms, and crops. Higher top-soil organic matter and less physical disturbance in FM and NIT likely contributed to higher earthworm species richness and abundances. The anecic species L. terrestris (linked to water infiltration and organic matter incorporation) was more abundant in FM, but densities remained very low in arable soil, irrespective of tillage system.