首页期刊导航|Geoderma: An International Journal of Soil Science
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Geoderma: An International Journal of Soil Science
Elsevier Science Publishers
Geoderma: An International Journal of Soil Science

Elsevier Science Publishers

0016-7061

Geoderma: An International Journal of Soil Science/Journal Geoderma: An International Journal of Soil Science
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    Consistent mineral-associated organic carbon chemistry with variable erosion rates in a mountainous landscape

    Wang, XiangWackett, Adrian A.Toner, Brandy M.Yoo, Kyungsoo...
    4页
    查看更多>>摘要：Interactions between organic carbon (OC) and minerals represent a critical mechanism for stabilizing organic matter in soils. Because both mineral weathering and plant productivity are negatively affected by soil erosion, mineral-associated organic carbon (MOC) chemistry is also expected to vary with erosion intensity. Here we show that MOC chemistry, determined by carbon X-ray absorption near-edge fine structure spectroscopy (XANES), exhibits little difference across a large (10-fold) gradient in erosion-derived soil turnover times. Mineral-associated OC chemistry further fails to explain the variation in radiocarbon-based MOC turnover times. Our results suggest that soil OC longevity is largely independent of organic matter chemistry in steep mountainous landscapes where soil development is constrained by erosion.
      原文链接:
    • NSTL
    • Elsevier

    Variations in soil aggregation, microbial community structure and soil organic matter cycling associated to long-term afforestation and woody encroachment in a Mediterranean alpine ecotone

    Ortiz, CarlosJose Fernandez-Alonso, MariaKitzler, BarbaraDiaz-Pines, Eugenio...
    12页
    查看更多>>摘要：Afforestation and subsequent expansion of trees on former grasslands may significantly impact the structure and activity of the soil microbial community, altering soil aggregation and affect its potential to store and cycle organic matter (OM). We investigated OM dynamics in aggregate-size topsoil samples collected along a Mediterranean alpine ecotone consisting of three vegetation types (grassland/shrubland, mixed shrubland-pine, and pine forest) in central Spain. Analytical determinations of soil organic carbon (SOC), total nitrogen (TN), particulate OM (POM), mineral-associated OM (MaOM), and the stable isotopic composition of carbon were conducted in each of the four aggregate-size fractions considered. Additionally, the structure of the microbial community (assessed as PLFA abundance), and the beta-glucosidase and beta-glucosaminidase activities were determined in bulk soil samples. More than half of the soil mass was contained within small macroaggregates regardless of vegetation type. SOC and TN values increased with decreasing aggregate-size classes across all vegetation types. The stability of microaggregates was negatively affected by the expansion of woody vegetation, which resulted in tree-dominated stands showing comparatively lower SOC and TN values in the smaller aggregate-size classes. On the other hand, these vegetation dynamics promoted soil macro-aggregation. While SOC contents did not show significant differences between land covers, vegetation shifts induced changes in the soil microbial community. Soil delta C-13 values, the abundance of gram-positive bacteria and beta-glucosidase activity were significantly higher in grasslands/shrublands than in forests, while significantly higher fungi/bacteria ratio was observed in forests. Small macroaggregates appear to play a key role in the stabilisation of relatively unprocessed OM across all vegetation types, as suggested by their significantly higher concentrations of POM. However, this fraction represents the most labile pool of OM, and as such, it is the most exposed to mineralisation. We conclude that the afforestation and potential vegetation shifts experienced in Mediterranean alpine grasslands lead to distinct changes in soil microbial communities, aggregation and soil OM dynamics, which given the strong temperature sensitivity to decomposition commonly reported in cold environments, suggests that soil OM in these high-elevation ecosystems may become highly vulnerable to environmental change.
      原文链接:
    • NSTL
    • Elsevier

    An integrated approach for the evaluation of quantitative soil maps through Taylor and solar diagrams

    Wadoux, Alexandre M. J-CWalvoort, Dennis J. J.Brus, Dick J.
    11页
    查看更多>>摘要：For many decades, soil scientists have produced spatial estimates of soil properties using statistical and non-statistical mapping models. Commonly in soil mapping studies the map quality is assessed through pairwise comparison of observed and predicted values of a soil property, from which statistical indices summarizing the quality of the entire map are computed. Often these indices are based on average error and correlation statistics. In this study, we recommend a more appropriate and effective method of map evaluation by means of Taylor and solar diagrams. Taylor and solar diagrams are summary diagrams exploiting the relationship between statistical indices to visualize differentiable aspects of map quality into a single plot. An important advantage over current map quality evaluation is that map quality can be assessed from the combined effect of a few statistical quantities, not just on the basis of a single index or list of indices. We illustrate the use of common statistical indices and their combination into summary diagrams with a simulation study and two applications on soil data. In the simulation study nine maps with known statistical properties are produced and evaluated with tables and summary diagrams. In the first case study with soil data, change in the quality of a large-scale topsoil organic carbon map is tracked for a number of permutations in the mapping model parameters, whereas in the second case study several maps of topsoil organic carbon content for the same area, made by various statistical and non-statistical models, are compared and evaluated. We consider that in all cases better insights in map quality are obtained with summary diagrams, instead of using a single index or an extensive list of indices. This underpins the importance of using integrated summary graphics to communicate on quantitative map quality so as to avoid excessive trust that a single map quality index may suggest.
      原文链接:
    • NSTL
    • Elsevier

    Microbial communities are associated with indicators of soil surface condition across a continental gradient

    Ding, JingyiTravers, Samantha KayEldridge, David John
    11页
    查看更多>>摘要：Soil microbes support multiple ecosystem functions in woody biomes and are regulated by both plant communities and soil properties. While most microbes reside in the uppermost soil layer, we have a poor understanding of how the condition of the soil surface affects soil microbes across different woody biomes. This knowledge is important because it could provide a cost-effective means of predicting the extent to which different soil surface types could be useful predictors of microbial communities in soil health monitoring programs. We collected data on soil bacterial and fungal communities, and 13 soil surface indicators and grazing intensity at 173 sites in eastern Australia along a climatic gradient (humid to arid) varying in tree cover. Our aim was to investigate potential relationships among the condition of the soil surface and soil microbes in forests and non-forests using linear regressions, correlations and structural equation modelling. We found that both bacterial and fungal richness were closely associated with measures of soil surface condition, particularly in forests. Greater microbial diversity was related to enhanced plant structure and richness, and lower litter characteristics in both ecosystems. In forests, these relationships were enhanced by higher temperatures or suppressed by greater tree richness. Bacterial and fungal communities responded differently to changes in soil surface attributes in forests, with winners (e.g., Proteobacteria) and losers (e.g., Cyanobacteria) among bacterial phyla, but consistent responses across fungal phyla. Our study provides empirical evidence of significant relationships among microbes and indicators of soil surface condition. This finding advances our understanding of plant-soil interactions, and indicates the possibility of using field-based soil surface attributes as potential cost-effective, practical, yet informative indicators to monitor changes in microbial richness and composition in forests and non-forests (open woodlands, shrublands).
      原文链接:
    • NSTL
    • Elsevier

    Monitoring soil organic matter on grassland farms: An exploratory analysis

    Hoogsteen, Martine J. J.Breure, Anton M.van Ittersum, Martin K.
    13页
    查看更多>>摘要：To meet the goals of the Climate Agreement, policy makers consider incentivizing soil carbon sequestration by carbon credits to offset greenhouse gas emissions from agriculture, industry and other sectors. Therefore, the interest in monitoring soil organic matter dynamics is growing rapidly, yet factors affecting the precision of the monitoring results are rarely quantified. We used the rhetorical scheme "The seven circumstances" to structure the methodological aspects of setting up a soil organic matter (SOM) monitoring program. The rhetorical scheme was applied during four years on two grass-based dairy farms in the Netherlands to assess in detail: conversion of SOM weight concentrations to SOM stocks (HOW), the effect of soil depth and the integration of scales field vs. farm (WHERE), and the effect of sampling date and sampling frequency on SOM estimates (WHEN). We found that all three circumstances affect conclusions on SOM stocks or SOM dynamics strongly. Considerable variation was found in the relationship between soil bulk density and SOM weight concentration (i.e. pedotransfer curves) among fields, depth and literature reference equations. Therefore, preferably a site specific pedotransfer curve should be used when comparing SOM stocks based on SOM weight concentrations across sites. Large differences in trends of SOM stock changes over time were found between fields and sampling depths. We conclude that a sampling depth in grassland soils up to 60 cm may be relevant to capture the dynamics in deeper layers. Furthermore, for quantitative underpinning of carbon payment schemes, the whole farm should be monitored rather than a few fields as trends between fields are highly variable.
      原文链接:
    • NSTL
    • Elsevier

    Soil biocrusts affect metabolic response to hydration on dunes in west Queensland, Australia

    Thomas, Andrew D.Elliott, David R.Hardcastle, DavidStrong, Craig L....
    10页
    查看更多>>摘要：Soil biocrusts, formed from communities of microbes and their extracellular products are a common feature of dryland soil surfaces. Biocrust organisms are only intermittently metabolically active, but due to their ubiquity they make a significant contribution to the carbon cycle. Quantification of the controls and insights into the interlinked process of photosynthesis and respiration are essential to enhancing our understanding of the carbon cycle in the world's drylands. Yet, there have been relatively few field studies investigating controls on both biocrust photosynthesis and respiration. We undertook field-based experiments at two dune sites during the dry season in Diamantina National Park in Queensland, Australia to determine how biocrust hydration and illumination affect soil CO2 flux and photosynthesis. Static chambers and an infra-red gas analyser were used to quantify soil CO2 flux, and a fluorometer and a CFlmager were used to determine a range of photosynthetic parameters in the field and laboratory respectively. When dry, biocrust photosynthetic activity was not detected and soil CO2 flux was very low irrespective of biocrust cover. Hydration led to a large and immediate increase in CO2 flux, which was more pronounced in the presence of biocrusts and on the dune with thinner biocrusts. Hydration also initiated the onset of photosynthesis in some biocrusts, which was greatest under low light conditions and sustained with further hydration. There were only infrequent periods of net CO2 uptake to the soil, occurring when CO2 uptake due to photosynthetic activity was less than background soil CO2 flux. Chlorophyll fluorescence imaging indicated biocrust spatial heterogeneity was evident at the cm scale where microtopography creates a myriad of environments for different crust organisms. Our findings demonstrate that biocrusts are highly spatially heterogenetic at both landscape and small scale, which suggests the maintenance of biocrust spatial diversity is likely to be key to imparting resilience to changing climate and disturbance. As well as reaffirming the importance of biocrusts for the carbon cycle in dryland dune soils the study demonstrates that biocrust respiration and photosynthesis respond differently to hydration and shading. This adds an unpredictability to the distribution of soil carbon stocks and the gaseous exchanges of CO2 between the surface and atmosphere. Future changes to precipitation and increased temperatures are likely to reduce soil moisture across much of the Australian interior and consequently biocrusts may experience a decline in biomass, structure, and function which could have significant repercussions beyond carbon stocks.
      原文链接:
    • NSTL
    • Elsevier

    Drought legacies on soil respiration and microbial community in a Mediterranean forest soil under different soil moisture and carbon inputs

    Liu, LeiEstiarte, MarcBengtson, PerLi, Jian...
    11页
    查看更多>>摘要：Soil moisture can strongly affect the fate of soil organic carbon (C) during microbial decomposition, but the characterisation and prediction of the effects remain challenging, especially the long-term effects of drought history and its interaction with current levels of soil moisture. We investigated the legacy effects of drought on soil activity and microbial community composition and its interaction with actual soil moisture and C addition. Soils from a long-term drought field experiment in a forest were incubated for 80 days under two levels of soil moisture after the addition of C-13-labelled glucose or cellulose. The drought legacy manifested as significantly higher soil CO2 efflux in wet soils from the long-term drought plots than in soils from all other treatments, including the historical control plots, as well as by a higher respiration in the dry treatment, but not in the wet one when cellulose was added. The supply of glucose primed the decomposition of SOM during the whole incubation whereas the supply of cellulose caused a negative priming at the very early stage but had an overall positive priming effect. The composition of the bacterial community varied with soil moisture, but the fungal community was more resistant to water stress and acquired labile C more efficiently under low moisture levels. Fungi dominated cellulose decomposition and bacteria dominated glucose decomposition. These results suggest a key role of fungi in SOM decomposition in the often water-stressed Mediterranean ecosystems. The legacy effects of long-term drought may increase soil respiration during the periods when soils are wet, although the effect may vary with the type of the C inputs.
      原文链接:
    • NSTL
    • Elsevier

    Bayesian approach for sample size determination, illustrated with Soil Health Card data of Andhra Pradesh (India)

    Brus, D. J.Kempen, B.Rossiter, D.Balwinder-Singh...
    11页
    查看更多>>摘要：A crucial decision in designing a spatial sample for soil survey is the number of sampling locations required to answer, with sufficient accuracy and precision, the questions posed by decision makers at different levels of geographic aggregation. In the Indian Soil Health Card (SHC) scheme, many thousands of locations are sampled per district. In this paper the SHC data are used to estimate the mean of a soil property within a defined study area, e.g., a district, or the areal fraction of the study area where some condition is satisfied, e.g., exceedence of a critical level. The central question is whether this large sample size is needed for this aim. The sample size required for a given maximum length of a confidence interval can be computed with formulas from classical sampling theory, using a prior estimate of the variance of the property of interest within the study area. Similarly, for the areal fraction a prior estimate of this fraction is required. In practice we are uncertain about these prior estimates, and our uncertainty is not accounted for in classical sample size determination (SSD). This deficiency can be overcome with a Bayesian approach, in which the prior estimate of the variance or areal fraction is replaced by a prior distribution. Once new data from the sample are available, this prior distribution is updated to a posterior distribution using Bayes' rule. The apparent problem with a Bayesian approach prior to a sampling campaign is that the data are not yet available. This dilemma can be solved by computing, for a given sample size, the predictive distribution of the data, given a prior distribution on the population and design parameter. Thus we do not have a single vector with data values, but a finite or infinite set of possible data vectors. As a consequence, we have as many posterior distribution functions as we have data vectors. This leads to a probability distribution of lengths or coverages of Bayesian credible intervals, from which various criteria for SSD can be derived. Besides the fully Bayesian approach, a mixed Bayesian-likelihood approach for SSD is available. This is of interest when, after the data have been collected, we prefer to estimate the mean from these data only, using the frequentist approach, ignoring the prior distribution. The fully Bayesian and mixed Bayesian-likelihood approach are illustrated for estimating the mean of log-transformed Zn and the areal fraction with Zn-deficiency, defined as Zn concentration <0.9 mg kg(-1), in the thirteen districts of Andhra Pradesh state. The SHC data from 2015-2017 are used to derive prior distributions. For all districts the Bayesian and mixed Bayesian-likelihood sample sizes are much smaller than the current sample sizes. The hyperparameters of the prior distributions have a strong effect on the sample sizes. We discuss methods to deal with this. Even at the mandal (sub-district) level the sample size can almost always be reduced substantially. Clearly SHC over-sampled, and here we show how to reduce the effort while still providing information required for decision-making. R scripts for SSD are provided as supplementary material.
      原文链接:
    • NSTL
    • Elsevier

    Zeolite increases grain yield and potassium balance in paddy fields

    Li, YinghaoXia, GuiminWu, QiChen, Wei...
    8页
    查看更多>>摘要：Most paddy fields in China are potassium (K) insufficient, while soil inorganic amendments such as zeolite are good strategies to increase soil K content. There is limited information on the interactive effects of zeolite and K applications on rice (Oryza sativa L.) productivity, apparent K balance, and soil K balance. This two-year field study using a split-plot design with three replicates investigated the effects of zeolite and K applications on grain yield, soil available K dynamics, apparent K balance, and soil K balance in a paddy rice system. The main plots were three zeolite application rates (0, 5, and 10 t ha (-1); Z(0), Z(5), and Z(10)). Within each main plot were subplots subjected to three K application rates (0, 30, and 60 kg ha(-1); K-0, K-30, and K-60). Zeolite was only applied in the first year while K was applied in both years. Results revealed that zeolite and K application, alone or in combination, significantly increased rice grain yield and economic benefit (based on resource inputs and grain value). In both years, the combination of 5 t ha(-1)- zeolite with 30 kg ha(-1) K fertilizer (i.e., Z(5)K(30)) increased grain yield by up to 6.4% and economic benefit by up to 6.6%, relative to the most commonly used practice (i.e., Z(0)K(60)). With 5 and 10 t ha(-1) zeolite amended, the highest K application rate (K-60) did not further increase grain yield, but it decreased economic benefit, relative to the lower K application rate (K-30). Zeolite and K application, alone or in combination, significantly increased topsoil (0-30 cm) average available K content, post-harvest aboveground K uptake, and apparent K balance in the paddy rice system. Zeolite and K application alone significantly increased soil K balance. The results of this study demonstrated that zeolite amendments increased topsoil available K, enhanced rice K uptake, alleviated negative K balance, and improved productivity and agricultural profitability of paddy cultivation. The recommended treatment Z(5)K(30) is suitable for rice cultivation due to its higher economic and environmental benefit as compared with the commonly used farmer practices.
      原文链接:
    • NSTL
    • Elsevier

    Differences in the flow of spruce-derived needle leachates and root exudates through a temperate coniferous forest mineral topsoil

    Jilkova, VeronikaJandova, KaterinaCajthaml, TomasKukla, Jaroslav...
    11页
    查看更多>>摘要：Coniferous forest ecosystems are important pools of soil organic carbon (SOC) in the Northern temperate zone. Needle leachates and root exudates represent a significant input of C to these soils and can differently affect soil C cycling because of their differences in chemistry and stoichiometry. This is the first study to investigate the differences in the flow of dissolved organic C (DOC) in the form of needle leachates, root exudates, and their combination through a forest mineral topsoil. We conducted a 5-month microcosm experiment with ecologically relevant additions of C-13-labelled spruce-derived substrates. The proportion of DOC lost from or incorporated into the mineral soil as microbial biomass or soil fractions (free, occluded by or adsorbed onto mineral particles) as well as differences in the priming effect (PE) caused by the two substrates were assessed.
      原文链接:
    • NSTL
    • Elsevier