Decomposing Plant Material Research Articles

Elemental composition and fungal colonisation of decomposing Phragmites australis (Cav.) Trin. ex Steud. litter at different water regimes

Plant litter decomposition in intermittent dry and wet habitats share decomposition mechanisms of both dry land and submerged habitats. The aims of the present study were therefore to compare fungi communities on the decomposing plant material regarding the water regime of the location. Furthermore we wanted to evaluate the effects of the water regime on the decomposition in combination with fungal decomposers. Litter decomposition was followed on selected sites of Lake Cerknica with different hydrological regimes, using the litterbag method. The elemental composition of the decomposing plant tissues of Phragmites australis and fungal communities developing on the decomposing plant material were analysed. The hydrological regime has an important role in defining the fungal community of P. australis leaf litter. Water regime affected the fungal communities, which exhibited higher diversity under more stable dry or submerged conditions (in contrast to intermittent). Decomposition rates were more affected by the environment as by the fungal community diversity or composition. But, despite differences in the fungal communities the elemental composition showed similar patterns of enrichment due to decreases in the organic fraction of the plant tissue.

Characterizing Livestock Production in Portuguese Sown Rainfed Grasslands: Applying the Inverse Approach to a Process-Based Model

Grasslands are a crucial resource that supports animal grazing and provides other ecosystem services. We estimated the main properties of Portuguese sown biodiverse permanent pastures rich in legumes (SBP) starting from measured data for soil organic carbon (SOC) and using the Rothamsted Carbon Model. Starting from a dataset of SOC, aboveground production (AGP) and stocking rates (SR) in SBP, we used an inverse approach to estimate root to shoot (RS) ratios, livestock dung (LD), livestock intake (LI) and the ratio between easily decomposable and resistant plant material. Results for the best fit show that AGP and belowground productivity is approximately the same (RS is equal to 0.96). Animals consume 61% of the AGP, which is within the acceptable range of protein and energy intake. Carbon inputs from dung are also within the range found in the literature (1.53 t C/livestock unit). Inputs from litter are equally distributed between decomposable and resistant material. We applied these parameters in RothC for a dataset from different sites that only comprises SOC to calculate AGP and SR. AGP and SR were consistently lower in this case, because these pastures did not receive adequate technical support. These results highlight the mechanisms for carbon sequestration in SBP.

Stormwater runoff driven phosphorus transport in an urban residential catchment: Implications for protecting water quality in urban watersheds

Increased stormwater runoff in urban watersheds is a leading cause of nonpoint phosphorus (P) pollution. We investigated the concentrations, forms, and temporal trends of P in stormwater runoff from a residential catchment (31 low-density residential homes; 0.11 km2 drainage area) in Florida. Unfiltered runoff samples were collected at 5 min intervals over 29 storm events with an autosampler installed at the stormwater outflow pipe. Mean concentrations of orthophosphate (PO4–P) were 0.18 ± 0.065 mg/L and total P (TP) were 0.28 ± 0.062 mg/L in all runoff samples. The PO4–P was the dominant form in >90% of storm events and other–P (combination of organic P and particulate P) was dominant after a longer antecedent dry period. We hypothesize that in the stormwater runoff, PO4–P likely originated from soluble and desorbed pool of eroded soil and other–P likely originated from decomposing plant materials i.e. leaves and grass clippings and eroded soil. We found that the runoff was co-limited with nitrogen (N) and P in 34% of storm events and only N limited in 66% of storm events, implicating that management strategies focusing on curtailing both P and N transport would be more effective than focussing on only N or P in protecting water quality in residential catchments.

First record of Parasitus americanus (Berlese, 1905) and Cornigamasus ocliferius Skorupski & Witaliński, 1997 (Acari: Mesostigmata: Parasitidae) from Slovakia

Two species of Parasitidae, Parasitus americanus (Berlese, 1905) and Cornigamasus ocliferius Skorupski & Witaliński, 1997 were found for the first time in Slovakia. Parasitus americanus is a cosmopolitan species, which was found in several cemeteries and in a botanic garden in Bratislava. Almost all records of C. ocliferius are from Poland except for one record from Egypt. Cornigamasus ocliferius was found in decomposed plant material in Western and Central Slovakia and in bird nests in Western and Eastern Slovakia; part of the material was previously published as Cornigamasus lunaris (Berlese, 1882) and is revised here.

Horizontal natural product transfer: A potential source of alkaloidal contaminants in phytopharmaceuticals

BackgroundIt was recently shown that nicotine and pyrrolizidine alkaloids that leach out from decomposing plant material (donor plants) are subsequently taken up by the roots of acceptor plants and translocated into their leaves. Furthermore, it is well established that plant roots take up xenobiotics, generally by simple diffusion, and that this passive import depends on the physico-chemical properties of the substances. HypothesisBased on the well-known uptake of xenobiotics, we assumed that in analogy, the uptake of alkaloids, which are leached out from plant material (donor plants) represents a quite general feature of plant biology. MethodsUsing barley as a model plant, we analyzed the uptake of alkaloids by applying them to Hordeum vulgare seedlings. Based on HPLC analyses, the presence of the particular alkaloids in the acceptor plants was determined. ResultsWe demonstrated that numerous alkaloids of different structural types are able to diffuse through biomembranes and are taken up by acceptor plants. In contrast, an uptake of quaternary alkaloids, with a permanent positive charge, could not be detected. ConclusionAs most alkaloidal plants generally die back afield, and the corresponding natural products are leached out into the soil. Our findings have substantial relevance for all plant-derived commodities, especially for the production of phytopharmaceuticals and the related safety issues. Moreover, the evidence that plants are inherently able to take up alkaloids from the soil, which are derived from other plants, will alter our appraisal of plant–plant interactions. In this context, the classical definition of xenobiotics, which are considered as “non-natural” substances, might be also extended by including natural products leached out into the soil.

Soil particulate organic matter increases under perennial bioenergy crop agriculture

Annual row crop agriculture contributes to carbon (C) losses from Midwest soils, while the establishment of perennial crops for food and fuel has the potential to increase soil C stocks. Perennial grasses eliminate the need for tillage and increase belowground biomass, both critical to the accumulation and conservation of soil organic matter and to soil C sequestration. The effect of C4 perennial grasses on particulate organic matter carbon (POM-C), consisting primarily of partially decomposed plant material, was evaluated in Illinois, where native switchgrass (Panicum virgatum L.) and a sterile hybrid of the Asian grass Miscanthus (Miscanthus x giganteus) were planted as bioenergy feedstocks at the University of Illinois Energy Farm in 2008. Six years after establishment of perennial crops, POM-C was compared with a maize-maize-soybean (Zea mays L., Glycine max L.) rotation typical of the area and a 28-species restored prairie. POM-C concentrations increased for all crops between 31 and 71% over 6 years, with the greatest increases in prairie and M. x giganteus soils. POM-C concentrations were highest at the 0–10 cm depth. Isotopic analyses showed 23–44% of POM-C was new C4 material under perennial bioenergy crops after 6 years. As soil organic matter is primarily plant-derived, increases in POM-C reflect increased organic matter inputs or decreases in the rate of decomposition from the cessation of tillage. Increases in POM-C under annual row crops may result from the incorporation of aboveground organic matter by tillage, while POM-C increases in untilled perennial crops mirror increases in belowground biomass. As soil aggregation protects POM-C from microbial degradation, untilled soils under long-term perennial crop production increase the residence time for soil C.

Diagnosing phosphorus limitations in natural terrestrial ecosystems in carbon cycle models.

Most of the Earth System Models (ESMs) project increases in net primary productivity (NPP) and terrestrial carbon (C) storage during the 21st century. Despite empirical evidence that limited availability of phosphorus (P) may limit the response of NPP to increasing atmospheric CO2, none of the ESMs used in the previous Intergovernmental Panel on Climate Change assessment accounted for P limitation. We diagnosed from ESM simulations the amount of P need to support increases in carbon uptake by natural ecosystems using two approaches: the demand derived from (1) changes in C stocks and (2) changes in NPP. The C stock‐based additional P demand was estimated to range between −31 and 193 Tg P and between −89 and 262 Tg P for Representative Concentration Pathway (RCP) 2.6 and RCP8.5, respectively, with negative values indicating a P surplus. The NPP‐based demand, which takes ecosystem P recycling into account, results in a significantly higher P demand of 648–1606 Tg P for RCP2.6 and 924–2110 Tg P for RCP8.5. We found that the P demand is sensitive to the turnover of P in decomposing plant material, explaining the large differences between the NPP‐based demand and C stock‐based demand. The discrepancy between diagnosed P demand and actual P availability (potential P deficit) depends mainly on the assumptions about availability of the different soil P forms. Overall, future P limitation strongly depends on both soil P availability and P recycling on ecosystem scale.

Caenorhabditis elegans as a Model for Microbiome Research.

The nematode Caenorhabditis elegans is used as a central model system across biological disciplines. Surprisingly, almost all research with this worm is performed in the absence of its native microbiome, possibly affecting generality of the obtained results. In fact, the C. elegans microbiome had been unknown until recently. This review brings together results from the first three studies on C. elegans microbiomes, all published in 2016. Meta-analysis of the data demonstrates a considerable conservation in the composition of the microbial communities, despite the distinct geographical sample origins, study approaches, labs involved and perturbations during worm processing. The C. elegans microbiome is enriched and in some cases selective for distinct phylotypes compared to corresponding substrate samples (e.g., rotting fruits, decomposing plant matter, and compost soil). The dominant bacterial groups include several Gammaproteobacteria (Enterobacteriaceae, Pseudomonaceae, and Xanthomonodaceae) and Bacteroidetes (Sphingobacteriaceae, Weeksellaceae, Flavobacteriaceae). They are consistently joined by several rare putative keystone taxa like Acetobacteriaceae. The bacteria are able to enhance growth of nematode populations, as well as resistance to biotic and abiotic stressors, including high/low temperatures, osmotic stress, and pathogenic bacteria and fungi. The associated microbes thus appear to display a variety of effects beneficial for the worm. The characteristics of these effects, their relevance for C. elegans fitness, the presence of specific co-adaptations between microbiome members and the worm, and the molecular underpinnings of microbiome-host interactions represent promising areas of future research, for which the advantages of C. elegans as an experimental system should prove of particular value.

Effect of ecosystem type and fire on chemistry of WEOM as measured by LDI-TOF-MS and NMR

Soil organic matter (SOM) and its water-soluble components play an important role in terrestrial carbon cycling and associated ecosystem functions. Chemically, they are complex mixtures of organic compounds derived from decomposing plant material, microbial residues, as well as root exudates, and soil biota. To test the effect of the ecosystem type (forest and grassland) and fires events on the chemistry of dissolved organic matter (DOM), we applied a combination of laser-desorption/ionization time-of-flight mass spectrometry (LDI-TOF-MS) and 2D (1H and 13C) nuclear magnetic resonance (NMR) spectroscopy to water-extractable organic matter (WEOM) from a range of top soil samples. The aim was to assess the suitability of LDI-TOF-MS for the rapid characterization of WEOM. Therefore, we evaluated the effects of sample (pH and dilution) conditions and use of positive or negative reflector mode to identify the conditions under which LDI-TOF-MS best distinguished between WEOM from different sources. Thirty-six samples were measured with both analytical techniques and their chemical patterns were statistically evaluated to distinguish firstly the effect of the type of ecosystem (forest versus grassland) on WEOM characteristics, and secondly the impact of fire on the chemical composition of WEOM. The nonmetric multidimensional scaling (NMDS) analysis of the most suitable experimental LDI-TOF-MS conditions showed a clear separation between the type of vegetation and fire-induced changes, mostly reflecting the presence of poly(ethylene glycol) in grassland soils. Discrimination among WEOM from different vegetation types was preserved in the fire treated samples. The calculation of the relative abundance of certain functional structures in the WEOM samples revealed a common composition of forest and grassland WEOM, with polysaccharides and proteins making up to 60%. The compositional impact of forest fire on WEOM was more pronounced compared to the one of grassland, leading to a decline in the main components, and an increase in amino-sugars, fatty acids, and sterols. The recorded 1H NMR and heteronuclear single quantum coherence (HSQC) spectra showed a decrease of the carbohydrate signal in WEOM from fire-treated samples, which was more pronounced in forest than in grassland soils.

The roles of environment, site position, and seasonality in taxonomic and functional organization of chironomid assemblages in a heterogeneous wetland, Kis-Balaton (Hungary)

Environmental heterogeneity plays a determinant role in structuring taxonomic and functional composition of local assemblages via various interacting processes as synthesized in the metacommunity theory. In this study, we evaluate the relative roles of local environmental and landscape filters, spatial constraints and seasonality in organization of assemblages of Chironomidae (Diptera), a diverse aquatic insect group with winged adults, in an extremely heterogeneous wetland system, Kis-Balaton, Hungary. As expected, local environmental variables explained a substantial proportion of assemblage variance mainly along sediment structure, macrophyte coverage, and decomposing plant matter gradients. Considering the narrow spatial range of the study area, pure spatial influence was unexpectedly strong, likely because of the dispersal limitation related to tall terrestrial vegetation patches and mass effect related to the uneven distribution and area of certain microhabitats and their species pools. However, landscape- and season-related variability proved to be low or negligible. Taxonomic and functional feeding guild (FFG)-based approaches revealed the same main trends in assemblage data; however, FFGs seemed to track environmental changes more tightly. We argue for the common use of taxonomic and functional-based approaches and advise the improvement of species optima and tolerance spectra databases to expand bioassessment power.

Sources of organic ice nucleating particles in soils

Abstract. Soil organic matter (SOM) may be a significant source of atmospheric ice nucleating particles (INPs), especially of those active > −15 °C. However, due to both a lack of investigations and the complexity of the SOM itself, the identities of these INPs remain unknown. To more comprehensively characterize organic INPs we tested locally representative soils in Wyoming and Colorado for total organic INPs, INPs in the heat-labile fraction, ice nucleating (IN) bacteria, IN fungi, IN fulvic and humic acids, IN plant tissue, and ice nucleation by monolayers of aliphatic alcohols. All soils contained ≈ 106 to ≈ 5 × 107 INPs g−1 dry soil active at −10 °C. Removal of SOM with H2O2 removed ≥ 99 % of INPs active > −18 °C (the limit of testing), while heating of soil suspensions to 105 °C showed that labile INPs increasingly predominated > −12 °C and comprised ≥ 90 % of INPs active > −9 °C. Papain protease, which inactivates IN proteins produced by the fungus Mortierella alpina, common in the region's soils, lowered INPs active at ≥ −11 °C by ≥ 75 % in two arable soils and in sagebrush shrubland soil. By contrast, lysozyme, which digests bacterial cell walls, only reduced INPs active at ≥ −7.5 or ≥ −6 °C, depending on the soil. The known IN bacteria were not detected in any soil, using PCR for the ina gene that codes for the active protein. We directly isolated and photographed two INPs from soil, using repeated cycles of freeze testing and subdivision of droplets of dilute soil suspensions; they were complex and apparently organic entities. Ice nucleation activity was not affected by digestion of Proteinase K-susceptible proteins or the removal of entities composed of fulvic and humic acids, sterols, or aliphatic alcohol monolayers. Organic INPs active colder than −10 to −12 °C were resistant to all investigations other than heat, oxidation with H2O2, and, for some, digestion with papain. They may originate from decomposing plant material, microbial biomass, and/or the humin component of the SOM. In the case of the latter then they are most likely to be a carbohydrate. Reflecting the diversity of the SOM itself, soil INPs have a range of sources which occur with differing relative abundances.

Organellar phylogenomics of an emerging model system: Sphagnum (peatmoss).

Sphagnum-dominated peatlands contain approx. 30 % of the terrestrial carbon pool in the form of partially decomposed plant material (peat), and, as a consequence, Sphagnum is currently a focus of studies on biogeochemistry and control of global climate. Sphagnum species differ in ecologically important traits that scale up to impact ecosystem function, and sequencing of the genome from selected Sphagnum species is currently underway. As an emerging model system, these resources for Sphagnum will facilitate linking nucleotide variation to plant functional traits, and through those traits to ecosystem processes. A solid phylogenetic framework for Sphagnum is crucial to comparative analyses of species-specific traits, but relationships among major clades within Sphagnum have been recalcitrant to resolution because the genus underwent a rapid radiation. Herein a well-supported hypothesis for phylogenetic relationships among major clades within Sphagnum based on organellar genome sequences (plastid, mitochondrial) is provided. We obtained nucleotide sequences (273 753 nucleotides in total) from the two organellar genomes from 38 species (including three outgroups). Phylogenetic analyses were conducted using a variety of methods applied to nucleotide and amino acid sequences. The Sphagnum phylogeny was rooted with sequences from the related Sphagnopsida genera, Eosphagnum and Flatbergium Phylogenetic analyses of the data converge on the following subgeneric relationships: (Rigida (((Subsecunda) (Cuspidata)) ((Sphagnum) (Acutifolia))). All relationships were strongly supported. Species in the two major clades (i.e. Subsecunda + Cuspidata and Sphagnum + Acutifolia), which include >90 % of all Sphagnum species, differ in ecological niches and these differences correlate with other functional traits that impact biogeochemical cycling. Mitochondrial intron presence/absence are variable among species and genera of the Sphagnopsida. Two new nomenclatural combinations are made, in the genera Eosphagnum and Flatbergium Newly resolved relationships now permit phylogenetic analyses of morphological, biochemical and ecological traits among Sphagnum species. The results clarify long-standing disagreements about subgeneric relationships and intrageneric classification.

FleA Expression in Aspergillus fumigatus Is Recognized by Fucosylated Structures on Mucins and Macrophages to Prevent Lung Infection.

The immune mechanisms that recognize inhaled Aspergillus fumigatus conidia to promote their elimination from the lungs are incompletely understood. FleA is a lectin expressed by Aspergillus fumigatus that has twelve binding sites for fucosylated structures that are abundant in the glycan coats of multiple plant and animal proteins. The role of FleA is unknown: it could bind fucose in decomposed plant matter to allow Aspergillus fumigatus to thrive in soil, or it may be a virulence factor that binds fucose in lung glycoproteins to cause Aspergillus fumigatus pneumonia. Our studies show that FleA protein and Aspergillus fumigatus conidia bind avidly to purified lung mucin glycoproteins in a fucose-dependent manner. In addition, FleA binds strongly to macrophage cell surface proteins, and macrophages bind and phagocytose fleA-deficient (∆fleA) conidia much less efficiently than wild type (WT) conidia. Furthermore, a potent fucopyranoside glycomimetic inhibitor of FleA inhibits binding and phagocytosis of WT conidia by macrophages, confirming the specific role of fucose binding in macrophage recognition of WT conidia. Finally, mice infected with ΔfleA conidia had more severe pneumonia and invasive aspergillosis than mice infected with WT conidia. These findings demonstrate that FleA is not a virulence factor for Aspergillus fumigatus. Instead, host recognition of FleA is a critical step in mechanisms of mucin binding, mucociliary clearance, and macrophage killing that prevent Aspergillus fumigatus pneumonia.

Uptake and decomposition of the herbicide propanil in the plant Bidens pilosa L. dominating in the Yangtze Three Gorges Reservoir (TGR), China.

Propanil (3',4'-dichloropropionanilide) is a selective post emergence herbicide for controlling broad leaf and grass weeds in rice (Oryza sativa L.). After being taken up by plants, the fate of propanil in decomposing plant material is of particular importance to the phytoremediation of the environment. Therefore, we investigated the biotransformation of propanil in the plant Bidens pilosa under conditions close to those present in the Three Gorges Reservoir (TGR), China. Plants pre-treated with 14C-ring-labeled propanil were either (treatment a) directly submerged in TGR water for 90days or (treatment b) pre-extracted with organic solvents, and subsequently only insoluble materials and non-extractable residues (NER) of the pesticide fractions were similarly incubated. After incubation in TGR water (treatment a), 30% of applied radioactivity was released into water and simultaneously, amounts of NER in the plant debris appeared to increase with time finally amounting to 40% of applied 14C. The radioactivity contained in the extractable fractions were identified as propanil, 3,4-dichloroaniline (DCA), and N-β-D-glucopyranosyl-3,4-dichloroaniline (DCA-Glu). In treatment b, significant 14C amounts were released to the water (6% of applied 14C) and the solubilized radioactivity fractions were demonstrated to agree with those found in the extractable fractions. Therefore, if residues of the pesticide propanil are taken up by plants, it may enter again the aquatic environment after plant death and submergence. This phenomenon may have a potential impact on aquatic organisms, which to our knowledge has not been reported before. As plant uptake and degradation of xenobiotics are recognized as detoxification, we consider B. pilosa with its high uptake potential, at least for propanil, as suitable species for phytoremediation.

Changes in soil organic matter composition after afforestation of arable farmland in northeast China

ABSTRACTSince the 1970s, a substantial area of arable farmland in a semi-humid area of northeast China has been planted as deciduous forests (Populus tomentosa Carr.). This study investigates the effects of afforestation on soil organic carbon (SOC) content and the chemical composition of the soil. Soil samples (Calcic chernozem) were collected from the upper 10 cm of paired arable land and secondary forests established 5 and 25 years previously. Carbon isotope analysis and pyrolysis–gas chromatography/mass spectrometry were used to determine SOC composition. The results show that (i) compared to the arable land, five years of afforestation caused a decrease in SOC and N concentration, while 25 years of afforestation resulted in an increase in SOC content; (ii) stable isotope δ13C analyses of the forest soils show gradual loss of crop-derived C and an accumulation of forest-derived C; and (iii) afforestation increased lignin abundance and decreased decompositional activity in the 25-year-old forest topsoil. Higher amounts of short-/mid-chain aliphatic compounds were observed in the 5-year-old forest (5–10 cm); and (iv) the arable soil contained substantially higher amounts of decomposed plant material and microbially derived substances. The results obtained suggest that long-term afforestation increases the SOC concentration, and alters the chemical composition of SOC.

Hydrological controls on productivity of regenerating Sphagnum in a cutover peatland

AbstractRecent research into the production of Sphagnum biomass in extracted peatlands, an alternative to ecological restoration as a post‐industrial use of peatlands, has highlighted the need for an improved understanding of the ecohydrology of Sphagnum regenerating in these environments. Previous work suggested that limited connectivity between surficial layers and the underlying partially decomposed plant matter and peat would result in water stress and inhibited growth. This study links the soil water dynamics of regenerated layers ranging in age from 3 to 43 years and from 3 to 40 cm in thickness to the productivity of Sphagnum in order to determine the hydrological controls on productivity and the optimal range of water content for producing Sphagnum biomass. Productivity was never observed to be limited by insufficient supply of water, including during periods where water table was >40 cm below the surface and periods of 16 days without measured precipitation. While layers of different ages and thicknesses were able to sustain adequate water supply to remain productive under a range of conditions, the ability of layers to transmit water upwards differed greatly. Water content in the near‐surface inhibited productivity during wetter periods, especially at newly regenerating sites where the layer was <5 cm thick. This has important implications for biomass production using the Sphagnum species studied here. Using a mixed linear modelling approach to isolate the effects of water content on variance in productivity from those of other measured variables, a volumetric water content of 0.10 is identified as optimal. Copyright © 2015 John Wiley & Sons, Ltd.

Nanoscale evidence of contrasted processes for root-derived organic matter stabilization by mineral interactions depending on soil depth

Up to now stabilization of organic matter (OM) in soils due to mineral interactions has been assessed mainly by correlations between carbon and iron and/or aluminum oxides evidencing that metal oxides may be principal stabilization agents. The nature and morphology of stabilized OM are poorly known. Taking advantage of a field experiment, the aim of our study was to analyze the fate of 13C and 15N labeled root material at 30 and 90 cm depths after three years of incubation and to characterize the nature of OM stabilized by interactions with metal oxides. Our methodological approach included isolation of metal oxides by physical fractionation and visualization of their interaction with OM using NanoSIMS. We concentrated metal oxides in a fraction corresponding to our objectives: the heavy fraction (>3 g cm−3) of fine silt. NanoSIMS analyses of this fraction allowed us to locate unlabeled OM and OM either double labeled or carrying one single label in association with metal oxides. Our results suggest that decoupling of C and N may have happened during OM stabilization within the timeframe of the 3 year field experiment. Scanning electron microscopy (SEM) after NanoSIMS analyzes, indicated that 15N labeled OM at 90 cm were well-defined ovoid OM particles resembling to microbial cells in interaction with Fe, Al and Ti oxides. At 30 cm depth, OM associated with metal oxides was 13C and 15N labeled unstructured material, possibly derived from plant debris. We suggest that at the two soil depths under investigation different processes might be at work, leading to association of OM with mineral compounds of the isolated fraction: in upper soil layers, decomposed plant material may directly interact with metal oxides, whereas in deep mineral soil, OM could mainly interact with metal oxides after microbial turnover. Both types of interactions may be fairly stable as they persisted after ultrasonication and salt extraction.

A new conceptual model on the fate and controls of fresh and pyrolized plant litter decomposition

In recent years, litter decomposition stud- ies have begun to move beyond the concept of mass loss to consider the fate of fresh and pyrolized decomposing plant material in the ecosystem. How- ever, these concepts have yet to be incorporated into conceptual models of litter decomposition. Under- standing how fresh and pyrolized plant litter chemical traits control the partitioning of mass loss to dissolved organic carbon (DOC) leaching and respiration to CO2 would help to inform models of litter-soil-atmosphere carbon (C) cycling. To test these controls, we incu- bated five fresh and one pyrolized leaf litters with differing chemistry and measured DOC and CO2 fluxes as well as changes in substrate and dissolved organic matter (DOM) chemistry over time using Fourier transformed infrared spectroscopy and wet chemistry. We found that the amount of hot water extractable C was a strong predictor of initial DOC leaching, while the lignocellulose index (Lignin/ (Lignin ? a-Cellulose)) was a strong inverse predic- tor of later stage DOC:CO2 partitioning. Changes in substrate and DOM chemistry indicated a progression of substrate availability for leaching: from soluble plant components, to partially decomposed cellulose and lignin, to microbial products. Based on these results we developed a new conceptual model that demonstrates how chemical traits of fresh and py- rolyzed plant litter can be used to predict the fate of aboveground organic matter decomposition and form a better linkage between aboveground decomposition and terrestrial ecosystem C cycling.

Computational fluid dynamics simulation of Lafia–Obi bituminous coal in a fluidized-bed chamber for air- and oxy-fuel combustion technologies

Coal still remains the most plentiful and dominant fossil fuel. Coal is an inhomogeneous organic fuel formed mainly from decomposed plant matter consisting of aromatic and hydroaromatic structures joined by short aliphatic chains whereby aromaticity increases with coalification rank. The use of coal, particularly for electricity generation, is expected to continue for the foreseeable future. In this research study, computational fluid dynamics (CFD) is applied to simulate air–coal and oxy-coal flow, combustion, and emission characteristics in a fluidized-bed combustion chamber. This work investigates Lafia–Obi coal, which is found in the Middle Benue Trough (MBT) of Nigeria. As far as the authors are aware, this research presentation represents the first CFD-based assessment and analysis for any Nigerian coal. Realistic primary objectives of fluidized-bed combustion research in Nigeria would be the following: (1) establishing an understanding of the physics and emission characteristics of various fuels (coal, waste, etc.) in the country with a view to future scale-up; and (2) developing and establishing measures to curb pollutant emissions in such future power plants for electricity generation. The pertinent combustion parameters of this research were validated with existing experimental data; good agreement was achieved. This work furthers the understanding of the Lafia–Obi coal combustion mechanism and its potential utilization as fuel for future coal-power plants for electricity generation in Nigeria.

Description of adult and third instar larva of Trichostetha curlei sp. n. (Coleoptera, Scarabaeidae, Cetoniinae) from the Cape region of South Africa.

A new high altitude montane species of Trichostetha Burmeister, 1842 is described from the Elandsberg range of the Western Cape interior. This represents the 14th species of the genus and the first to be reported with a description of its larva. It is a significant addition to the growing number of species that exhibit no adult feeding behaviour and a short period of activity restricted to the onset of summer. Larvae dwell in rock crevices, feeding on decomposing plant matter. The genus Trichostetha is heterogeneous and the complex variability observed in some species, especially T. capensis (Linnaeus, 1767), requires the re-instatement of taxa that were recently synonymised. Thus, T. bicolor Péringuey, 1907 is here re-proposed as a separate species and T. capensis hottentotta (Gory & Percheron, 1833) as a separate subspecies. Conversely, T. alutacea Allard, 1994 is recognised as a dark variety of T. signata (Fabricius, 1775) and is, consequently, synonymised with this species.