Uncovering Ubiquitin and Ubiquitin-like Signaling Networks

Microscopic imaging and technolog

Restoration of ecosystem function in an abandoned sandpit: plant and soil responses to paper de-inking sludge

1. In minesoil reclamation, the establishment of a sustainable plant cover requires the improvement of limiting conditions and the re-initiation of carbon (C) and nutrient cycling. 2. The approach used in this study for reclaiming an abandoned sandpit in Quebec, Canada, was based on a heavy organic amendment as an attempt to accelerate the reconstruction of a functional ecosystem. 3. The one-time intervention consisted of incorporating paper de-inking sludge into soil at two rates (0 and 105 dry t ha–1), supplemented with nitrogen (N) at three rates (3, 6 and 9 g kg–1 sludge) and phosphorus (P) at two rates (0·5 and 1·0 g kg–1 sludge) followed by seeding (mid-summer) of Agropyron elongatum (Host) Beauv. (tall wheatgrass). 4. Standing biomass increased in the presence of sludge after both the first and second full growing seasons. High N application rates further increased yield, more importantly in the second season. The high P rate improved grass establishment in all cases. Ground cover increased with time and doubled in the presence of sludge whereas it declined in the absence of sludge. Phosphorus and N uptake was improved consistently in the presence of sludge. 5. Sludge application resulted in improved water retention and cation exchange capacities, and an increase in pH and bulk density of sandpit minesoil, all of which may have accounted for the significant improvement in plant responses. Levels of soil C and N suggest that this reconstructed system is approaching sustainability. 6. Adequate N and P supplements will accentuate the positive influence of sludge on revegetation

Co-accumulation of microbial residues and particulate organic matter in the surface layer of a no-till Oxisol under different crops

In the absence of significant mechanical disturbance such as under permanent no-till (NT), crop type should be a prominent factor controlling soil organic C (SOC) pools. Microbial cell residues have been shown to be influenced by plant species and are believed to contribute significantly to soil organic matter formation. We performed a study to investigate the co-accumulation of microbial cell wall residues (glucosamine, GlcN and muramic acid, MurN) and organic C (total and particle-size fractions) in the surface layer (0- to 5-cm depth) of an Oxisol after 7 yr under NT, as affected by different crop types. SOC content associated with pigeon pea [Cajanus cajan (L) Millsp.] was 20% and 18% higher than that with corn (Zea mays L) or sunflower (Helianthus annuus L.), respectively. The highest particulate organic C (POC) content in soil was also found under pigeon pea, which showed values 54, 46, and 48% higher than under corn, sunflower, and oilseed radish (Raphanus sativus L var. oleiformis Pers.), respectively. Changes in POC explained most of the variation in SOC. The positive impact of pigeon pea on POC and SOC was attributed to rapid decomposition of its residues, due to their low C/N ratio, followed by selective preservation of lignin-rich particulate organic matter. The accrual of POC was closely associated with the accumulation of fungal and bacterial cell wall residues. This may be due to preferential feeding of fungi and bacteria on recently deposited plant-derived C sources present in the form of particulate organic matter. This observation is consistent with a recent model suggesting that microbial residues play a greater role in the formation of SOC than previously considered. We emphasize that this effect was mediated by the accumulation of POC and influenced by crop type. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Non-labile plant C contributes to long-lasting macroaggregation of an Oxisol

Decomposition of plant material influences soil aggregation dynamics in ways that are still poorly understood, especially for Oxisols, in which oxides are believed to play a dominant role. In an incubation experiment, we investigated (i) the effect of plant material addition from selected monocot and dicot species on soil organic C (SOC), carbohydrate composition, fungal and total microbial biomass, and aggregation of an Oxisol; and (ii) the relationship among these properties and C mineralization patterns. The experiment was carried out at 25 °C for 180 d after addition of 11 plant materials (4 g C kg-1 soil) and a control (no plant material added). Mineralization of C during the incubation was described considering two pools of C (labile and non-labile) using a first-order plus linear fitting. Compared to the control, corn materials showed larger pentose input, greater mineralization rates for the non-labile C pool (k), greater soil pentose content (xylose + arabinose) and larger mean weight diameter of soil water-stable aggregates at 180 d of incubation. These effects were independent of changes in SOC content, suggesting that total C accrual and macroaggregation may be decoupled processes in this Oxisol. Our results support the hypothesis that the non-labile plant C pool contributes to the long-lasting stability of macroaggregates of this Oxisol and that this effect is mediated by plant and soil pentoses. We propose that plant pentose content and the decomposition rate of the slow pool (k) are useful parameters for the prediction of plant effects on aggregation dynamics of Oxisols and the selection of soil conservation practices. © 2012

Carbohydrate Composition and Water-Stable Aggregation of an Oxisol as Affected by Crop Sequence under No-Till

In no-till systems, plants play a substantial role in soil physical conditioning because physical management is otherwise confined to sowing operations. We performed a study to determine the effect of 28 different crop sequences on soil water-stable aggregation, soil organic C (SOC), and the neutral carbohydrate composition of the surface layer (0-5-cm depth) of an Oxisol under no-till. Summer crop sequences with corn (Zea mays L.) on a continuous basis or in rotation with soybean [Glycine max (L.) Merr.] showed a higher mean weight diameter (MWD) of water-stable aggregates than those with a rice (Oryza sativa L.)-bean (Phaseolus vulgaris L.)-cotton (Gossypium hirsutum L.) rotation. Among winter crops, pearl millet [Pennisetum americanum (L.) Leeke] or grain sorghum [Sorghum bicolor (L.) Moench] were associated with a higher MWD than oilseed radish (Raphanus sativus L. var. oleiformis Pers.). Plant tissues of Poaceae species (corn, pearl millet, and sorghum) were enriched in pentoses relative to other plant species. A principal component analysis showed a close positive relationship of the soil aggregate MWD with the soil xylose content, but not with other soil monosaccharide and SOC contents, and a positive relationship with the amount of pentose input to the soil, notably from aboveground plant materials. A possible explanation is that pentosans are used as an energy source by filamentous microorganisms, which play a well-known role in stabilizing soil aggregates. Our results suggest that plant-derived carbohydrates mediate crop species effects on soil structure under no-till conditions, and this effect appears to be independent of changes in total SOC.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Soil carbon stocks under different land uses and the applicability of the soil carbon saturation concept

International audienceIncreasing soil organic carbon (SOC) stocks via land management has been proposed as a temporary climate change mitigation measure. An upper limit of soil stable SOC storage, which refers to the concepts of SOC saturation has been proposed. Using systematic grid sampling of topsoil in mainland France and an equation that predicts this SOC saturation, we derived estimates of the SOC sequestration potential density (SOCspd) for various land uses. First, using French database and data from the literature we estimated the proportions of the SOC stored in the fine fraction (SOCfine) in total SOC for grassland (69%), cropland (85%) and forest (66%). Then, SOCspd was calculated as the difference between the theoretical SOC saturation value and SOCfine. The SOCspd stocks for French topsoil were estimated at about 1.1 Pg, in which cropland, forest and grassland accounted for 66%, 17% and 17%, respectively. Varying the proportions of SOCfine in the calculations by assuming a possible range of 0.8-0.9 for cropland and 0.6-0.9 for grassland and forest soils led to variations of total SOCspd stocks of about 0.1 Pg for each land use. Most importantly, we demonstrate that the distribution of SOCspd in forest soils is exactly centred at zero, which suggests that on average, forest topsoils are saturated in SOCfine, and thus Hassink’s equation provides a valid estimate for the SOC sequestration potential for French topsoil

Black Spruce Soils Accumulate More Uncomplexed Organic Matter than Aspen Soils

Improving knowledge on the dynamics and maintenance of the boreal soil’s C pool is of particular importance in response to climate change concerns. We hypothesized that different forest types (black spruce, trembling aspen, and mixedwood) found on a similar site type differentially affect soil organic carbon (SOC) distribution among physical fractions. The surface mineral soil (0–15 cm) of 24 plots differing in forest composition was sampled in forested Hapludalfs of the Abitibi-James Bay region, Canada. The soil was first separated into three water-stable aggregate size fractions (\u3e1000, 1000–250, and \u3c250 μm) by wet sieving, followed by a density flotation (NaI: 1.7 g cm−3) and a dispersion (with glass beads) to isolate the free light fraction (LF), the intraaggregate particulate organic matter (iPOM) and the silt plus clay fraction (S&C). According to mixed linear models, whole SOC contents (in Mg C ha−1) decreased in the following order: black spruce (46.3) \u3e mixedwood (41.9) \u3e trembling aspen (34.7). While similar amounts of SOC (~30 Mg C ha−1) were found in the S&C, more SOC was found in the less protected fractions (i.e., uncomplexed organic matter, UOM: LF and iPOM) under black spruce than under trembling aspen, the mixedwood being intermediate. This higher accumulation of UOM under black spruce suggests a slower C turnover that is probably induced by the low-quality C inputs and environmental constraints to decomposition found in these forests. These differences in the amounts of SOC stored within soil physical fractions might have strong repercussions on the SOC budget of the boreal forest of eastern Canada under climate change

Soil-quality indicators in LCA: method presentation with a case study

Soil-quality indicators in LCA: method presentation with a case study. 8eme International Conference on LCA in the Agri-Food Secto

Tillage practices of a clay loam soil affect soil aggregation and associated C and P concentrations

International audienceUnder long-term cultivation, greater accumulations of soil organic matter (SOM) and phosphorus (P) are found in the surface soil layer under no-till (NT) versus mouldboard ploughing (MP) practices. Our objective was to evaluate the effects of NT and MP practices on concomitant SOM and P distribution and sorption characteristics among water-stable aggregates and non-aggregated particles. The study was conducted in Quebec, Canada, as part of a long-term corn and soybean rotation experiment (established since 1992) on a clay loam soil of the St-Blaise series (Dark Grey Gleysol). Soil samples were collected in the fall of 2007 in the 0–5 cm layer from plots under NT and MP receiving 35 kg P ha–1 and 160 kg N ha–1. Samples were separated into three water-stable aggregate-sized classes (macro, 2000–250 μm; meso, 250–180 μm; micro, 180–53 μm) and (silt + clay)-sized particles (< 53 μm) using wet-sieving. Macro aggregates made up 60.2 and 48.5% of total soil weight under NT and MP, respectively. In wet-sieved soils from NT plots, water-extractable P (Pw) concentration increased in the order (silt + clay)-sized particles < micro- < meso- < macro-aggregates; under MP, micro-, meso-, and macro-aggregate fractions had the same Pw concentration, while the (silt + clay)-sized particles showed the lowest Pw concentration. The hierarchy observed among aggregate-sized classes under NT in relation to Pw concentration was also observed for carbon content, indicating that Pw is influenced by soil aggregation as driven by SOM accumulation. The lower Pw concentration in (silt + clay)-sized particles could be explained by a greater retention of P by reactive oxides and highly disordered alumino-silicates present on (silt + clay)-sized particles, thereby reducing the soluble P released from these particles. One important aspect of this study is the contrasting P sorption characteristics of solid particles under NT and MP. The P sorption maxima (Smax value) of the (silt + clay)-sized particles was twice that of the water-stable aggregates. Sorption characteristics reflect the hierarchy observed under NT for organic C and Pw, indicating a closer link between SOM and P dynamics within soil aggregates in contrast with MP