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Chiquinquirá Hontoria Rodolfo Velásquez Marta Benito Javier Almorox Ana Moliner 《Soil biology & biochemistry》2009,41(7):1583-1585
Glomalin, a substance produced by arbuscular mycorrhizal fungi, is reported to play a role in soil aggregation, but this role has been questioned in soils rich in calcium carbonate. We studied the relationship between aggregation stability and glomalin in a Haplic Calcisol comparing abandoned and active cultivation of olive groves. Abandonment was associated with increases in soil organic carbon, the percentage of water stable aggregates (WSA1-2mm), and easily extractable and total Bradford-reactive soil protein. WSA1-2mm was strongly positively correlated with both easily extractable and total Bradford-reactive soil protein. While easily extractable Bradford-reactive soil protein measured in both stable and unstable aggregates did not show any significant differences, Bradford-reactive soil protein was twice as high in stable than in unstable aggregates under both tillage and abandonment. Our results suggest that Bradford-reactive soil protein influences aggregate stability, even in soils with low organic matter and high calcium carbonate contents. However, more research is needed to elucidate the role of easily extractable Bradford-reactive soil protein in soil aggregation. 相似文献
2.
Soil evolution over the Quaternary period in a semiarid climate (Segre river terraces,northeast Spain) 总被引：1，自引：0，他引：1
A macro- and micromorphologic study was done on the soils from a stepped sequence of seven dated fluvial terraces in the lower Segre river valley (Lleida, northeast Spain) under a present-day semiarid Mediterranean climate. The soils have evolved from the Holocene through the early Pleistocene, providing an excellent morphostratigraphic framework for evaluating time-dependent factors influencing soil formation in a dry and calcareous environment. Throughout the chronosequence, some properties are regularly age-related specially carbonatation in subsurface horizons. The carbonates occur mainly as micrite, and although microsparite and sparite also appear in the oldest soils, they are replaced by fine-grained calcite by dissolution–reprecipitation processes (micritization process), which is active at present. Some pedological paleofeatures as the presence of sparite and recarbonated argillans in oldest terrace can be interpreted as the reflex of climatic changes during the Quaternary. In spite of this climate variability, the soils display progressive and systematic patterns of carbonate accumulation: on the lowest terraces, the soils do not yet have secondary carbonates but in the beginning Late Pleistocene calcic horizons, with carbonate pendents, are developed; these pendents increase its thickness with age although pendent growth rates decreases from Late Pleistocene to Middle Pleistocene. In the middle of the Late Pleistocene, calcic horizons evolved to petrocalcic horizons, which increase its thickness in the Middle and specially in Early Pleistocene. The presence of calcic and petrocalcic horizons is the primary basis for soil classification. This criterion is applicable not only to the soils of the lower Segre river basin, but also to many soils throughout the semiarid Mediterranean region. 相似文献
3.
Short-term biochar-induced increase in soil CO2 release is both biotically and abiotically mediated 总被引：2，自引：0，他引：2
The application of biochar to soil has been shown to cause an apparent increase in soil respiration. In this study we investigated the mechanistic basis of this response. We hypothesized that increased CO2 efflux could occur by: (1) Biochar-induced changes in soil physical properties (bulk density, porosity, moisture content); (2) The biological breakdown of organic carbon (C) released from the biochar; (3) The abiotic release of inorganic C contained in the biochar; (4) A biochar-induced stimulation of decomposition of native soil organic matter (SOM) which could occur both biotically or abiotically; (5) The intrinsic biological activity of the biochar results in the liberation of CO2. Our results show that most of the extra CO2 produced after biochar addition to soil came from the equal breakdown of organic C and the release of inorganic C contained in the biochar. Using long-term 14C-labelled SOM, we show that biochar repressed native SOM breakdown, counteracting the release of CO2 from the biochar. A range of mechanisms to describe this negative priming response is presented. Although biochar-induced significant changes in the physical characteristics of the soil, overall this made no contribution to changes in soil respiration. Similarly, the evidence from our study suggests that changes in soluble polyphenols do not help explain the respiration response. In summary, biochar induced a net release of CO2 from the soil; however, this C loss was very small relative to the amount of C stored within the biochar itself (ca. 0.1%). This short-term C release should therefore not compromise its ability to contribute to long-term C sequestration in soil environments. 相似文献
4.
Soil inorganic carbon (C) represents a substantial C pool in arid ecosystems, yet little data exist on the contribution of this pool to ecosystem C fluxes. A closed jar incubation study was carried out to test the hypothesis that CO2-13C production and response to sterilization would differ in a calcareous (Mojave Desert) soil and a non-calcareous (Oklahoma Prairie) soil due to contributions of carbonate-derived CO2. In addition to non-sterilized controls, soils were subjected to sterilization treatments (unbuffered HgCl2 addition for Oklahoma soil and unbuffered HgCl2 addition, buffered HgCl2 addition, and autoclaving for Mojave Desert soil) to decrease biotic respiration and more readily measure abiotic CO2 flux. Temperature and moisture treatments were also included with sterilization treatments in a factorial design.The rate of CO2 production in both soils was significantly decreased (36-87%) by sterilization, but sterilization treatments differed in effectiveness. Sterilization had no significant effect on effluxed CO2-13C values in the non-calcareous Oklahoma Prairie soil and autoclaved Mojave Desert soil as compared to their respective non-sterilized controls. However, sterilization significantly altered CO2-13C values in Mojave Desert soil HgCl2 sterilization treatments (both buffered and non-buffered). Plots of 1/CO2 versus CO2-δ13C (similar to Keeling plots) indicated that the source CO2-δ13C value of the Oklahoma Prairie soil treatments was similar to the δ13C value of soil organic matter [(SOM); −17.76‰ VPDB] whereas the source for the (acidic) unbuffered-HgCl2 sterilized Mojave Desert soil was similar to the δ13C value of carbonates (−0.93‰ VPDB). The source CO2-δ13C value of non-sterilized and autoclaved (−18.4‰ VPDB) Mojave Desert soil treatments was intermediate between SOM (−21.43‰ VPDB) and carbonates and indicates up to 13% of total C efflux may be from abiotic sources in calcareous soils. 相似文献
5.
Deyvid Diego Carvalho Maranhão Ademir Fontana Vanessa Francieli Vital Gustavo Souza Valladares 《Communications in Soil Science and Plant Analysis》2017,48(14):1646-1658
The global cycle of carbon (C) has raised attention in recent decades due to the great increase in carbon dioxide levels (CO2) levels in the atmosphere and its influence on climate change. Calcareous soils represent a significant fraction of the areas with potential for agriculture and have differential attributes, such as high calcium contents, magnesium, carbonates, and pH values. These attributes have been ignored in analytical procedures despite these characteristics, resulting in an overestimation or underestimation of the soil carbon. Several methods have been proposed for determining the soil carbon contents, however, studies evaluating the analytical procedures of C quantification methods, considering the soil characteristics, such as the calcareous soils, are needed, in order to improve their accuracy. Therefore, the objective of this work was to evaluate and compare methods for C determination and to propose adjustments in the methodology for calcareous soil analysis. The Yeomans and Bremner (YB) was the most efficient method for quantification of organic C among the wet oxidation methods. On the other hand, the Donagemma (WB) method underestimated the organic carbon contents. The results showed that the samples must be macerated and pretreated with a hydrochloric acid solution for the use of CHNS-O, in order to eliminate carbonates in the form of nodules and concretions. 相似文献
6.
Glomalin is a recently discovered glypoproteinaceous substance produced by arbuscular mycorrhizal fungi (AMF) that plays an important role in structuring soil. We quantified soil fungal hyphal length and glomalin content at vegetated and open microsites in Stipa tenacissima steppes of SE Spain. Soils underneath the canopy of S. tenacissima had higher glomalin pools compared to open microsites. We also found significant differences between sites, suggesting the presence of landscape level heterogeneity in glomalin concentration. Soil fungal hyphal length also differed significantly among the sites, but there was no significant effect of microsite. Water-stable aggregates (1-2 mm diameter; WSA1-2 mm), however, while differing among sites, did not vary as a function of microsite. Furthermore, WSA1-2 mm was negatively correlated with glomalin fractions, as well as soil organic C. Carbonates were likely the major binding agents in these carbonate-rich (average carbonate content: 71%) soils, and not organic C (including glomalin). AMF-mediated stabilization of soil aggregates did not contribute to the formation and maintenance of fertile islands underneath the canopy of S. tenacissima. 相似文献
7.
Billon Gabriel Ouddane Baghdad Laureyns Jacky Boughriet Abdel 《Journal of Soils and Sediments》2003,3(3):180-187
Background, Aim and Scope The identification of certain minerals directly in the raw sediment has proved to be difficult, if not impossible, because
of their instability and/or low contents. This explains why the characterization/composition/crystalline nature of multiple
(co)precipitates and solid solutions often necessitate the combined use of density separation methods and macro and microanalytical
techniques, and in some cases the possible existence of certain mineral solids is only sustained from thermodynamic considerations.
In this context, the comparison of porewater concentration profiles with thermodynamic calculations recently proved to be
a convenient way of obtaining clues relative to the potential occurrence of natural minerals.
Methods Porewaters and sedimentary-solid phases were extracted from sliced sediment samples collected in the Seine estuary (northern
France), and studied as a function of sediment depth. Porewater concentration profiles were determined for Ca, Fe, Mg, Mn,
Na, P and Sr using inductively coupled plasma atomic emission spectroscopy, and for dissolved sulfur using square wave, cathodic
stripping voltammetry. To obtain information about sediment mineralogy, sedimentary solid phases were analysed directly and
after density separation with a heavy liquid (CHBr3) by means of several techniques: X-ray diffraction; electron spin resonance and micro-Raman spectroscopies. Furthermore,
using sequential extraction procedures, the chemical speciation versus depth of several elements (Al, Ca, Fe, Mg, Mn, P, Pb,
Sr, Ti, and Zn) and particularly sulfur [i.e. acid volatile sulfides (AVS) and chromium reducible sulfurs (CRS)] were undertaken.
Results and Discussion. From these analytical data, some thermodynamic calculations [using ion activity products (LAP)] were attempted for the anoxic
porewaters where most of the ionic complexing species were measured to support the involvement of relevant geochemical equilibria
between these ions and some metals and the existence of any discrete solid phases (calcite, dolomite, greigite and probably
vivianite, apatite and siderite), as well as coprecipitates and solid solutions in calcium carbonate.
Conclusions Thermodynamic equilibria in sedimentary media are rarely achieved because many chemical processes in these systems are established
in long periods. Nevertheless, these calculations remain useful to increase our insight into the considered system. They help
to support our view about the possible existence of certain minerals (iron sulfides, calcite, dolomite...). They also help
account for the real power of ESR for indicating the presence of hypothesised solid solutions, MnxCa1-xC03. The critical investigations of the authors, however, reveal some weaknesses of XRD and Raman microscopy for identifying
minor minerals/precipitates, which result from combinations between the inorganic anions P04
3-, C03
2- and S2- and the metallic cations Fe2+, Mn2+, Mg2+, and Sr2+. 相似文献
8.
Soil pH and calcium carbonate contents are often hypothesized to be important factors controlling organic matter turnover in agricultural soils. The aim of this study was to differentiate the effects of soil pH from those related to carbonate equilibrium on C and N dynamics. The relative contributions of organic and inorganic carbon in the CO2 produced during laboratory incubations were assessed. Five agricultural soils were compared: calcareous (74% CaCO3), loess (0.2% CaCO3) and an acidic soil which had received different rates of lime 20 years ago (0, 18 or 50 t ha−1). Soil aggregates were incubated with or without rape residues under aerobic conditions for 91 days at 15 °C. The C and N mineralized, soil pH, O2 consumption and respiratory quotient (RQ=ΔCO2/ΔO2) were monitored, as well as the δ13C composition of the evolved CO2 to determine its origin (mineral or organic). Results showed that in non-amended soils, the cumulative CO2 produced was significantly greater in the limed soil with a pH>7 than in the same soil with less or no lime added, whereas there was no difference in N mineralization or in O2 consumption kinetics. We found an exponential relationship between RQ values and soil pH, suggesting an excess production of CO2 in alkaline soils. This CO2 excess was not related to changes in substrate utilization by the microbial biomass but rather to carbonates equilibrium. The δ13C signatures confirmed that the CO2 produced in soils with pH>7 originated from both organic and mineral sources. The contribution of soil carbonates to CO2 production led to an overestimation of organic C mineralization (up to 35%), the extent of which depended on the nature of soil carbonates but not on the amount. The actual C mineralization (derived from organic C) was similar in limed and unlimed soil. The amount of C mineralized in the residue-amended soils was ten times greater than in the basal soil, thus masking the soil carbonate contribution. Residue decomposition resulted in a significant increase in soil pH in all soils. This increase is attributed to the alkalinity and/or decarboxylation of organic anions in the plant residue and/or to the immobilization of nitrate by the microbial biomass and the corresponding release of hydroxyl ions. A theoretical composition (C, O, H, N) of residue and soil organic matter is proposed to explain the RQ measured. It emphasizes the need to take microbial biomass metabolism, O2 consumption due to nitrification and carbon assimilation yield into account when interpreting RQ data. 相似文献
9.
《Communications in Soil Science and Plant Analysis》2012,43(6):509-519
Abstract Crystalline minerals in anaerobically digested sewage sludges were determined by x‐ray diffraction analysis. Sludge samples were prepared for x‐ray analysis by either washing with H2O to remove soluble salts or oxidizing organic matter with H2O. A limited number of minerals are present as crystalline materials in sludge. Even though the sludges contained appreciable concentrations of Cu, Zn, Cd, Pb and Ni, no crystalline metal sulfides, phosphates, hydroxides, oxides or carbonates were found with the exception of a possible Cu, Zn carbonate hydroxide. All other crystalline components detected are common minerals such as quartz, feldspar, montmorillonite, chlorite, mica, dolomite and calcite. 相似文献
10.
A. S. Sheta M. S. Al-Sewailem A. Sh. Sallam A. S. Al-Mashhady 《Arid Land Research and Management》2013,27(4):387-401
Chemical characteristics of groundwater and the composition of newly formed precipitates are critical in the management of modern irrigated agriculture in arid regions. Water samples representing the main aquifers in Riyadh region, Saudi Arabia, and solid samples fromthe newly formed precipitates were studied. Results showed that water temperature varied between 30.3-69°C, being higher in the deep aquifer and low in the relatively shallow aquifers. Initial water pH ranged from 6.39-7.92, increasing to 7.65-8.20 at atmospheric conditions. Shallowaquifer waters were categorized into sulfate-type and Cl- or no-dominant type waters, while the deep aquifers were characterized as Cl-type and no-dominant type. Soluble H 4 SiO 4 , soluble Fe and Mn ranged from 3.15 to 18.82, 0.10 to 17.30, and 0.01 to 4 0.32 mg L-¹, respectively. Calculation of saturation indices from water composition at initial, closed and equilibriumconditions indicated that changes in pH and water temperature cause major chemical changes in the water favoring the precipitation of carbonates and Fe-silicates. Data of total chemical analysis indicated that carbonates are present in all samples and constituted up to 976 g kg-¹ of the precipitates formed from the deep aquifer water in the irrigation tubes. Amorphous and/or crystalline Fe compounds were the dominant fractions in the surface crust precipitates, while crystalline Fe compounds was the dominant form in the precipitates in irrigation tubes and in the cooling reservoir. XRD data confirmed that aragonite was the dominant carbonate mineral in the precipitates formed fromthe deep aquifer water. Calcite and Mg-calcite were detected in considerably low quantities. Poorly crystalline Fe-oxide minerals were present in all the precipitate samples. Results suggested that formation of precipitates either in cooling reservoirs or in irrigation systems can be minimized by controlling the degassing through keeping the system closed, lowering the pH through the injection of inorganic acids in the system or both. 相似文献
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