Soil Organic Components Research Articles

Interaction of pesticides with natural and synthetic solids. Evaluation in dynamic and equilibrium conditions.

Interactions between pesticides (paraquat, glyphosate, 2,4-D, atrazine, and metsulfuron methyl) and soil organic and inorganic components have been studied in batch experiments by performing adsorption, dissolution, and chemical and photochemical degradation under different conditions. The obtained results confirm that the affinity of a pesticide to the solid surface depends on the nature of both and shows that each reactant strongly affects the mobility of the other one, e.g., anionic pesticides promote the dissolution of the solid humic acid but if this last is retained into the inorganic matrix enhances the adsorption of a cationic pesticide. Adsorption also seems to protect the bonded specie to be chemical degraded, such as shown in two pesticide/clay systems at constant pH. The use of mesoporous silicas could result in a good alternative for pesticide remediation. In fact, the solid shows high adsorption capacity towards paraquat and its modification with TiO2 nanoparticles increases not only the pesticide adsorption but also seems to catalyze its degradation under UV light to less-toxic metabolites. UV-VIS spectroscopy was relevant and novel in such sense. Electrostatic interactions, hydrogen and coordinative bonds formations, surface complexations and hydrophobic associations play a key role in the fate of mentioned pesticides on soil and ground/surface water environments.

Differential soil microbial community responses to the linkage of soil organic carbon fractions with respiration across land-use changes

Abstract Land-use change can modify terrestrial ecosystem processes with potentially important effects on below-ground carbon dynamics. Soil microbes are considered the rate-limiting factor in carbon decomposition. However, the effect of land-use change on soil microbial community and the mechanism of soil carbon dynamics remain unclear. In this study, soil samples were collected during four periods (April, June, August, and October) at sites in the Loess Plateau in China with different land- use types: Robinia pseudoacacia L. (RP) and abandoned land (AL); these areas were converted 40 years ago from similar farmlands, while the millet (Setaria italica) farmlands (FL) were selected as a control in our study. Quantitative PCR and Illumina sequencing of the 16S rRNA and ITS genes were performed to analyze the abundance, diversity, and compositions of the soil microbes (bacteria and fungi). Additionally, soil organic carbon fractions (soil organic carbon: SOC, dissolved organic carbon: DOC, microbial biomass carbon: MBC) and soil respiration components (soil respiration: SR, heterotrophic respiration: HR, autotrophic respiration: AR) were evaluated. The results showed that SOC fractions and soil respiration increased after land-use change, with significant correlation being observed. In particular, DOC was more related to SR and HR than to the other fractions. Moreover, the abundance and diversity of the microbes (bacteria and fungi) were greatly affected by the land- use change; both of them were significantly and positively correlated with soil organic carbon fractions and soil respiration components. For dominant bacterial phyla, both Proteobacteria and Bacteroidetes were significantly more abundant in the afforested soil than in the FL, while the abundances of Actinobacteria and Chloroflexi ranked as FL > AL > RP. For dominant fungal phyla, Ascomycota responded positively to land- use changes, whereas Basidiomycota responded negatively. Such changes in the abundances of microbial phyla were significantly correlated with the linkage of soil organic carbon fractions and respiration components. Altogether, these results suggest that the changes in components of soil respiration may be highly susceptible to soil organic carbon fractions, especially to DOC, and this linkage is largely modulated by microbial community across land-use changes.

Identification of Distinct Functional Microstructural Domains Controlling C Storage in Soil.

The physical, chemical, and biological processes forming the backbone of important soil functions (e.g., carbon sequestration, nutrient and contaminant storage, and water transport) take place at reactive interfaces of soil particles and pores. The accessibility of these interfaces is determined by the spatial arrangement of the solid mineral and organic soil components, and the resulting pore system. Despite the development and application of novel imaging techniques operating at the micrometer and even nanometer scale, the microstructure of soils is still considered as a random arrangement of mineral and organic components. Using nanoscale secondary ion mass spectroscopy (NanoSIMS) and a novel digital image processing routine adapted from remote sensing (consisting of image preprocessing, endmember extraction, and a supervised classification), we extensively analyzed the spatial distribution of secondary ions that are characteristic of mineral and organic soil components on the submicrometer scale in an intact soil aggregate (40 measurements, each covering an area of 30 μm × 30 μm with a lateral resolution of 100 nm × 100 nm). We were surprised that the 40 spatially independent measurements clustered in just two complementary types of micrometer-sized domains. Each domain is characterized by a microarchitecture built of a definite mineral assemblage with various organic matter forms and a specific pore system, each fulfilling different functions in soil. Our results demonstrate that these microarchitectures form due to self-organization of the manifold mineral and organic soil components to distinct mineral assemblages, which are in turn stabilized by biophysical feedback mechanisms acting through pore characteristics and microbial accessibility. These microdomains are the smallest units in soil that fulfill specific functionalities.

Wildfire effects on lipid composition and hydrophobicity of bulk soil and soil size fractions under Quercus suber cover (SW-Spain)

Soil water repellency (hydrophobicity) prevents water from wetting or infiltrating soils, triggering changes in the ecosystems. Fire may develop, enhance or destroy hydrophobicity in previously wettable or water-repellent soils. Soil water repellency is mostly influenced by the quality and quantity of soil organic matter, particularly the lipid fraction. Here we report the results of a study on the effect of fire on the distribution of soil lipids and their role in the hydrophobicity grade of six particle size fractions (2–1, 1–0.5, 0.5–0.25, 0.25–0.1, 0.1–0.05 and <0.05mm) of an Arenosol under Quercus suber canopy at the Doñana National Park (SW-Spain). Hydrophobicity was determined using water drop penetration time test. Field emission scanning electron microscopy (FESEM) was used to assess the presence and morphology of the inorganic and organic soil components in the particle size fractions. Soil lipids were Soxhlet extracted with a dichloromethane-methanol mixture. Fatty acids (FAs) and neutral lipids were separated, derivatized, identified and quantified by gas chromatography/mass spectrometry and gas chromatography/flame ionization detection. The hydrophobicity values of soil samples and fractions were statistically different (P < 0.05), for both, the unburnt and burnt soils, and particle size fractions. All samples displayed a similar distribution of FAs, straight-chain saturated acids in the C14–C32 range, and neutral lipids (n-alkan-1-ols, n-alkanes), only differing in their relative abundances. Among possible biogeochemical mechanisms responsible for the changes in soil lipids, the observed depletion of long chain FAs (C≥24) in the coarse fraction is best explained by thermal cracking caused by the heat of the fire. The enrichment of long chain FAs observed in other fractions suggests possible exogenous additions of charred, lipid-rich, material, like cork suberin or other plant-derived macromolecules (cutins). Principal component analysis was used to study the relationships between hydrophobicity with soil organic matter and its different components. Extractable organic matter (EOM) and specifically long chain FAs content were positively correlated to soil hydrophobicity. Therefore, the latter could be used as biomarkers surrogated to hydrophobicity in sandy soils.

Fecal sludge management in developing urban centers: a review on the collection, treatment, and composting.

The problems posed by fecal sludge (FS) are multidimensional because most cities rapidly urbanize, which results in the increase in population, urban settlement, and waste generation. Issues concerning health and waste treatment have continued to create alarming situations. These issues had indeed interfered with the proper steps in managing FS, which contaminates the environment. FS can be used in agriculture as fertilizer because it is an excellent source of nutrients. The recent decline in crop production due to loss of soil organic component, erosion, and nutrient runoff has generated interest in the recycling of FS into soil nutrients through stabilization and composting. However, human feces are considerably liable to spread microorganisms to other persons. Thus, sanitation, stabilization, and composting should be the main objectives of FS treatment to minimize the risk to public and environmental health. This review presents an improved FS management (FSM) and technology option for soil amendment that is grouped into three headings, namely, (1) collection, (2) treatment, and (3) composting. On the basis of the literature review, the main problems associated with the collection and treatment of FS, such as inadequate tools and improper treatment processes, are summarized, and the trends and challenges that concern the applicability of each of the technologies in developing urban centers are critically reviewed. Stabilization during pretreatment before composting is suggested as the best method to reduce pathogens in FS. Results are precisely intended to be used as a support for decisions on policies and strategies for FSM and investments for improved treatment facilities.

Effects of long-term fertilization on organic nitrogen fractions in aquic brown soil

The purpose of present research was to investigate how different fertilization regimes altered soil organic nitrogen fractions and their inter-annual dynamics based on a series of long-term experiment (initiated at 1990), including: CK (non-fertilization); M (recycled pig manure); NPK (chemical fertilizer NPK); NPK + M (recycled pig manure with chemical fertilizer NPK). The results showed that soil organic nitrogen components under the different fertilization treatments presented contrastive patterns from the establishment the experiments to 2015. Generally, acid hydrolysable organic nitrogen content increased year by year. The amino acid nitrogen content under CK and NPK treatments consistently declined, although amino acid nitrogen for M and NPK+M treatments showed a increasing trend. These phenomena were probably ascribed to the utilization of soil amino acids by microbes. From 1990 to 2015, NPK treatment substantially elevated the content of acid-released ammonium nitrogen by 31.1% compared with CK (mean value across the experiment), and for the treatments using organic manure (M and NPK+M), the contents of all fractions of soil organic nitrogen increased. Notably, the increase magnitudes for NPK+M were more dramatic than those of M. These results demonstrated that combined use of organic and inorganic fertilizers could more effectively elevate soil organic nitrogen, subsequently helping to improve the capacity of soil nitrogen supply and enhance the soil fertility.

Using new hetero-spectral two-dimensional correlation analyses and synchrotron-radiation-based spectromicroscopy to characterize binding of Cu to soil dissolved organic matter

Understanding the binding characteristics of copper (Cu) to different functional groups in soil dissolved organic matter (DOM) is important to explore Cu toxicity, bioavailability and ultimate fate in the environment. However, the methods used to explore such binding characteristics are still limited. Here, two-dimensional correlation spectroscopy (2DCOS) integrated with Fourier transform infrared (FTIR), 29Si nuclear magnetic resonance (NMR), 27Al NMR, and synchrotron-radiation-based FTIR spectromicroscopy were used to explore the binding characteristics of Cu to soil DOM as part of a long-term (23 years) fertilization experiment. Compared with no fertilization and inorganic fertilization (NPK), long-term pig manure fertilization (M) treatment significantly increased the concentration of total and bioavailable Cu in soils. Furthermore, hetero-spectral 2DCOS analyses demonstrated that the binding characteristics of Cu onto functional groups in soil DOM were modified by fertilization regimes. In the NPK treatment, Cu was bound to aliphatic C, whereas in the manure treatment SiO groups had higher affinity toward Cu than aliphatic C. Also, the sequence of binding of functional groups to Cu was modified by the fertilization treatments. Moreover, synchrotron-radiation-based FTIR spectromicroscopy showed that Cu, clay minerals and sesquioxides, and C functional groups were heterogeneously distributed at the micro-scale. Specifically, clay-OH as well as mineral elements had a distribution pattern similar to Cu, but certain (but not all) C forms showed a distribution pattern inconsistent with that of Cu. The combination of synchrotron radiation spectromicroscopy and 2DCOS is a useful tool in exploring the interactions among heavy metals, minerals and organic components in soils.

Exploring the interactions and binding sites between Cd and functional groups in soil using two-dimensional correlation spectroscopy and synchrotron radiation based spectromicroscopies

Understanding how heavy metals bind and interact in soils is essential for predicting their distributions, reactions and fates in the environment. Here we propose a novel strategy, i.e., combining two-dimensional correlation spectroscopy (2D COS) and synchrotron radiation based spectromicroscopies, for identifying heavy metal binding to functional groups in soils. The results showed that although long-term (23 yrs) organic fertilization treatment caused the accumulation of Cd (over 3 times) in soils when compared to no fertilization and chemical fertilization treatments, it significantly (p<0.05) reduced the Cd concentration in wheat grain. The 2D COS analyses demonstrated that soil functional groups controlling Cd binding were modified by fertilization treatments, providing implications for the reduced bioavailability of heavy metals in organic fertilized soils. Furthermore, correlative micro X-ray fluorescence spectromicroscopy, electron probe micro-analyzer mapping, and synchrotron-radiation-based FTIR spectromicroscopy analysis showed that Cd, minerals, and organic functional groups were heterogeneously distributed at the micro-scale in soil colloids. Only minerals, rather than organic groups, had a similar distribution pattern with Cd. Together, this strategy has a potential to explore the interactions and binding sites among heavy metals, minerals and organic components in soil.

English

A good soil structure is indicated by the abundance of soil aggregates which has an important role in sustainable agricultural management and soil productivity. As it affects hydraulic conductivity, gases transport within the soil and seed germination, root respiration and eventually plant growth. The different sized fractions of soil aggregates are influenced significantly by both the amount and the composition of organic matter present in the soil (Piccolo, 1996). The degree of soil aggregation and aggregate stability is the result of the interaction between organic and inorganic soil components. Soil structure degradation occurs mostly due to the decrease in soil organic carbon caused by excessive soil cultivation and soil erosion. Eroded soils have consistently shown lower soil organic carbon and nutrient concentrations in upper profiles than cultivated soils, this is also true for other physical properties such as soil texture and saturated hydraulic conductivity (Heckrath et al., 2005). Soil organic carbon (SOC), includes soil organisms (e.g. microbial biomass), simple organic compounds (e.g. polysaccharides), large and complex humic substances, as well as relatively fresh residue at various stages of decomposition (Weil and Magdoff, 2004). The effect of different composted and un composted products on soil aggregate stability across time scales vary from weeks, months to years after the incorporation (Monnier, 1965). The various components of organic carbon such as microbial biomass carbon, polysaccharides and humic substances play very important role in the aggregate formation mechanism. The polysaccharides are highly complex polymers, consisting of many structural units, and are naturally resistant to decomposition or become resistant through reaction with other soil constituents and serve as binding agents. Microbial biomass carbon is an active form of carbon and it influences aggregate formation and stability. Humic substances account for the largest and most decomposed proportion of soil organic matter (SOM) with chemically complex and ill-defined structure, and act as persistent binding agent for stabilization of aggregates. Stabilization of aggregates by organic matter (Six et al., 2004) and interactions between aggregative factors and aggregate structures is well documented. In most studies, the organic matter additions were characterized by their elemental composition but additional information such as contents of humic and non-humic substances were seldom provided. In this study we hypothesized that addition of organic sources on equivalent carbon level basis affect the soil aggregate formation differently as composition of materials vary. The objectives of the present study were, to examine the quality (fundamental characteristics) of the traditional organic manures and their direct effect upon formation, Pak. J. Agri. Sci., Vol. 53(4), xxx-xxx; 2016 ISSN (Print) 0552-9034, ISSN (Online) 2076-0906 DOI: 10.21162/PAKJAS/16.4205 http://www.pakjas.com.pk

An assessment of model averaging to improve predictive power of portable vis-NIR and XRF for the determination of agronomic soil properties

Many soil science laboratories are now equipped with technology platforms in portable visible near infrared (vis-NIR) and X-ray fluorescence (XRF) spectrometers. These technologies have complementary capabilities, where XRF is known to accurately measure the soil's inorganic element concentration, and vis-NIR has the ability to estimate the soil's organic component and mineralogy suites. In this study data mining was used to estimate soil properties from the vis-NIR spectra, and in a novel way from the XRF spectral data. The prediction outcomes were combined into a single prediction outcome, using formal methods called model averaging procedures. Combining model outcomes derived from spectra using model averaging techniques improves or maintains the prediction status (as ratio of performance to inter-quartile distance) of vis-NIR and XRF models for a wide range of soil properties of agronomic importance. Overall, the relative improvement in %RMSE ranged from 4 to 44%. Weight preference in model averaging was related to the inference of soil chemical and physical properties from vis-NIR and XRF spectra. For example, the weights preference the vis-NIR predictions for soil pH, soil carbon (C), clay, and XRF predictions for most of the elemental soil properties. Based on both the relative improvement in RMSE and RPIQ status, model averaging was found to be suitable for soil pH, soil C (soil organic C (SOC) and total C (TC)), soil texture (sand and clay), CEC and total elements K, Mg, Co, Cr and Mn. Optimum prediction performance for total elements Cu and Zn is achieved by XRF alone. The unreliable RPIQ status for total elements P, S, Mo, Se and exchangeable Ca, Mg, K, and Na derived from vis-NIR and XRF predictions in this study did not improve with model averaging. Overall, Granger-Ramanathan averaging produced similar or better outcomes compared to variance weighted averaging. This model averaging approach is more simple to compute requiring only to fit a simple multiple linear regression model, unlike the VWA approach in which the weighting is estimated for each soil property, and thus in the interests of parsimony is recommended as the model averaging technique to be adopted as protocol. More conventional use of portable XRF in soil analysis is to employ the elemental concentrations measured by the XRF device to predict other soil properties, generally applying multiple linear regression models. When XRF is used in a conventional way to determine elemental concentrations it was demonstrated to be highly reliable for elemental concentrations present in high concentrations, but predictions of elemental content derived from XRF spectra was more effective for elements present in low concentrations. This in turn reduces the capacity of XRF elemental concentrations to be used in the prediction of other soil properties by inference.

Decomposition of Arboreal Legume Fractions in a Silvopastoral System

Deposition and decomposition of arboreal vegetation represent crucial but poorly understood soil nutrient and organic matter cycling components of warm climate silvopastoral systems. Biomass loss and nutrient release from decomposition bags with leaves (Exp. 1) or branches (Exp. 2) of the arboreal legumes gliricidia [Gliricidia sepium (Jacq.) Kunth] and sabiá (Mimosa caesalpiniifolia Benth.) in a signal grass [Brachiaria decumbens (Stapf) R.D. Webster] silvopastoral system were measured in 2011 and 2012. In Exp. 2, branches were divided into 0‐ to 3‐, &gt;3‐ to 9‐, and &gt;9‐ to 20‐cm circumference classes. The incubated nylon bags were collected 0, 4, 8, 16, 32, 64, 128, and 256 d after placement on the soil surface. Gliricidia leaves and branches, in general, had higher N and lower acid detergent lignin (ADL) concentrations and ADL/N ratios than those of sabiá. Gliricidia leaf biomass loss rates were greater (P &lt; 0.001; k = 0.0038 g g−1 d−1) than those of sabiá (k = 0.0012 g g−1 d−1), as were the branch biomass loss rates (gliricidia, k = 0.0018 g g−1 d−1; sabiá, k = 0.0005 g g−1 d−1). Leaf N release from the fixed amounts incorporated as annual litterfall corresponded to 47 and 14 kg N ha−1 from gliricidia and sabiá, respectively. The differences in concentrations and decomposition rates of the various fractions indicate that the two legume species differ in their nutrient recycling capacities.

Temporal and spatial changes in soil micronutrients in managed Nothofagus pumilio forest of Tierra del Fuego, Argentina

Soil organic components are important factors in the quality and productivity of forest ecosystems. Timber harvesting reduces plant cover and the amount of organic matter in forest floor layer, increases surface runoff, soil erosion and alters microclimatic conditions over large areas. These changes can have important implications for nutrient cycling dynamics and soil organic matter mineralization. Fueguian temperate forests of Nothofagus pumilio (lenga) have been intensely harvested for the last decades, mainly by shelterwood-cut silvicultural system. Harvesting removes nutrients contained in logs from the site, modifies light, temperature and soil humidity, constraining nutrient cycling process. In this study, we evaluate available copper (Cua), zinc (Zna), iron (Fea), and manganese (Mna) concentrations and reservoirs in stands that represent a chronosequence and their respective primary forests (controls): stands cut 1 year ago, stands cut 5–10 years ago, and stands harvested more than 50 years ago. Concentrations of Zna and Cua in primary forest were 39.9 and 2.6 mg/kg, and increased in harvested sites to 60.5 and 3.2 mg/kg, respectively. Fea and Mna concentrations showed similar ranges in both harvested and control sites. Recent harvested sites showed the highest Cua concentrations. Micronutrient reservoirs showed similar ranges in both harvested and primary forests. We concluded that micronutrient availability changes at short term after forest harvesting; thus, the inclusion of soil fertility assessment in forest management plans should be incorporated to preserve the fertility of lenga forests soils and ensure sustainability.

Bituminous substances and polycyclic aromatic hydrocarbons in soils under lenses of oil and oil products in underground karst cavities (Polaznenskii Peninsula, Perm region)

Bituminous substances and polycyclic aromatic hydrocarbons in soils under karst rocks have been studied for revealing fluxes of oil and oil products in karst cavities near the earth’s surface (with the Polaznenskii Peninsula in Perm region as an example). It has been found that the hydrocarbon fluxes from underground oil lenses to the surface can be directly detected from the nonspecific organic components of soils and the composition of free gases circulating in soils. Changes in the soil-geochemical parameters indicative of the presence of an underground oil lens have been revealed. It has been shown that the hydrocarbon fluxes from underground oil lenses to the surface can be mapped from nonspecific organic soil components: composition and amount of bituminous substances, polycyclic aromatic hydrocarbons, and gaseous hydrocarbons.

Short communication: Predicting cation exchange capacity from hygroscopic moisture in agricultural soils of Western Europe

Soil cation exchange capacity (CEC) depends on the extent and negative charge density of surfaces of soil mineral and organic components. Soil water sorption also depends on the extent of such surfaces, giving thus way to significant relationships between CEC and hygroscopic moisture (HM) in many soils. In this work, we explored whether CEC could be accurately predicted from HM in agricultural soils of Mediterranean and humid temperate areas in Western Europe. For this purpose, we examined 243 soils across a wide variation range of their intrinsic properties. Soil CEC was determined using 1 M ammonium acetate at pH 7 and HM at an equilibrium air relative humidity (RH) of 43% (HM43). Most of the variation of soil CEC was explained by HM43 through a linear function (CEC = 1.4 + 0.78HM43; R2 = 0.962; standard deviation = 2.30 cmolc/kg). Coefficients of the regression equation were similar for subgroups of soils differing in moisture regime, clay mineralogy, carbonate content and organic carbon content. Therefore, soil hygroscopic moisture measurements at a fixed RH level provided a simple, robust, inexpensive method for predicting soil CEC.

From Spill to Sequestration: The Molecular Journey of Contamination via Comprehensive Multiphase NMR.

Comprehensive multiphase NMR is a novel NMR technique that permits all components (solutions, gels, and solids) to be studied in unaltered natural samples. In this study a wide range of CMP-NMR interaction and editing-based experiments are combined to follow contaminants (pentafluorophenol (PFP) and perfluorooctanoic acid (PFOA)) from the solution state (after a spill) through the gel-state and finally into the true solid-state (sequestered) in an intact water-swollen soil. Kinetics experiments monitoring each phase illustrate PFOA rapidly transfers from solution to the solid phase while for PFP the process is slower with longer residence times in the solution and gel phase. Interaction-based experiments reveal that PFOA enters the soil via its hydrophobic tails and selectively binds to soil microbial protein. PFP sorption shows less specificity exhibiting interactions with a range of gel and solid soil components with a preference toward aromatics (mainly lignin). The results indicate that in addition to more traditional measurements such as Koc, other factors including the influence of the contaminant on the soil-water interface, specific biological interactions, soil composition (content of lignin, protein, etc.) and physical accessibility/swellability of soil organic components will likely be central to better explaining and predicting the true behavior of contaminants in soil.

New Indices Determining Heavy Metals Migration in a Sewage Sludge

Abstract The four step procedure developed by the European Community Bureau of Reference (BCR) is the optimum means of identifying heavy metal fractions in sewage sludge samples. Using the BCR procedure enables to get the date basing on which one can calculate metal stability index which supplies information on the strength of metal bonds with mineral organic soil components. Unfortunately, very popular formulae describing this index do not possess any theoretical justification and do not generate all values in the range of [0; 1]. Hence, in this paper one has presented new formulae describing not only the stability index but also a strictly connected with it the mobility index. In addition, one has suggested that these new formulae depend on the Equivalent Population (EP) indicator.

Speciation of plutonium and americium in the soils affected by Kraton-3 accidental underground nuclear explosion in Yakutia (Russia)

In calcareous soils from Yakutia only 0.1 % or less 239Pu and 241Am exist in water-soluble form, i.e., the mobility of these radionuclides is relatively low. In the top humus-containing layer (0–4 cm) 239Pu and 241Am are distributed uniformly between organic and inorganic soil components. In the bottom soil layer (20–30 cm) the radionuclides are present mainly in inorganic soil components. The estimation of the radionuclide mobility demonstrates that 241Am is potentially a more mobile element than 239Pu. In the considered calcareous soils collected from the top layer 239Pu and 241Am exist both in humic and fulvic acids (FA). 241Am is much stronger bound to the group of mobile FA than 239Pu. In the bottom soil layer 239Pu and 241Am have been found mainly in FA.

Soil organic carbon, nitrogen, and phosphorus distribution in stable aggregates of an Ultisol under contrasting land use and management history

AbstractDifferent land‐use affects the organization of mineral soil particles and soil organic components into aggregates and the consequent arrangement of the aggregates will influence essential ecosystem functions. We investigated a continuous rubber plantation (forested), land fallowed for 10 y (fallow), 10‐y continuous arable cropping land and cropped land with top soil removed (TSR) for concentrations of C, N, and P in bulk soil and dry aggregates. Results showed that a high level of soil disturbance decreased the proportion of surface (0–15 cm) soil aggregate stability (low mean weight diameter) in TSR by 149% and arable cropping by 125% compared with the forested. Aggregate associated SOC was higher in aggregate‐size fractions of forested land‐use when compared with that in 10‐y fallow, continuous arable cropping, and TSR. For aggregate associated N, fallow and forested land‐use types concentrated higher proportion across aggregate sizes than the arable cropping and TSR. Macro aggregate fractions generally contained higher concentrations of C, N, and P compared with the micro‐aggregates. Water transmission indicators like total porosity and saturated hydraulic conductivity recorded higher values with forested and fallow land‐use than the others. We can thus conclude that long‐term soil disturbance due to cultivation and removal of top soil reduces the accumulation of soil C, N, and P in bulk soil and decreases water transmission properties. On the other hand, aggregate‐associated C, N and P accumulations are dependent on the level of soil surface disturbance and aggregate sizes.

Mid-infrared spectra predict nuclear magnetic resonance spectra of soil carbon

Nuclear magnetic resonance (NMR) spectroscopy is a powerful technique for characterising the complex chemistry of soil organic carbon (SOC), but is prohibitively expensive, time-consuming and technically-demanding. Diffuse reflectance mid-infrared (MIR) spectroscopy is an attractive alternative because it is a high-throughput, cost-effective and easy-to-use technique that provides information on the amount and nature of soil mineral and organic components. However, interpretation of complex MIR spectra can be challenging due to difficulties with distinguishing SOC peaks from overlapping mineral-related peaks. We present a novel approach to predict the entire NMR spectra of SOC from corresponding MIR spectra using partial least-squares regression (PLSR) in an R environment. We developed a multi-response MIR–PLSR prediction model by regressing corresponding NMR and MIR spectra of 99 HF-treated <50μm fractions of soils using the pls package. The model was validated using (set-aside) test sets in four model iterations. The model provided accurate predictions of the entire average NMR spectra. Average Euclidean distance values between spectra in the training set were at least 3.5 fold greater than those between average reference and predicted NMR spectra, indicating that prediction errors were small relative to between-soil variation. Our approach accurately predicted intricate NMR spectra, demonstrating new potential for routine analysis of complex SOC chemistry.

瓦屋山扁刺栲-中华木荷常绿阔叶次生林土壤有机碳组分特征

PDF HTML阅读 XML下载 导出引用 引用提醒 瓦屋山扁刺栲-中华木荷常绿阔叶次生林土壤有机碳组分特征 DOI: 10.5846/stxb201401010005 作者: 作者单位: 四川农业大学,四川农业大学,四川农业大学,重庆金佛山国家级自然保护区管理局,四川农业大学,四川农业大学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目(31300522);教育部高等学校博士学科点专项科研基金项目(20125103120018);四川省教育厅重点项目(12ZA118,13ZA0246) Characteristics of soil organic carbon components in a secondary Castanopsis platyacantha-Schima sinensis evergreen broad-leaved forest, Wawushan Mountain Author: Affiliation: Sichuan Agricultural University,Sichuan Agricultural University,Sichuan Agricultural University,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:次生林在全球碳循环中占有重要地位,为了研究中国中亚热带次生林土壤有机碳组分特征,以四川瓦屋山中山段扁刺栲-中华木荷常绿阔叶次生林为对象,通过挖取土壤剖面分层(0-10、10-40、40-70 cm和70-100 cm)取样方式,研究土壤各有机碳组分特征。结果表明:土壤有机碳、微生物生物量碳、可浸提溶解性有机碳和易氧化碳含量均随土层深度增加而减小,0-10 cm土层有机碳含量为121.89 g/kg,高于已报道的亚热带其他常绿阔叶林和四川各类森林;0-10 cm层微生物生物量碳含量为1931.82 mg/kg,可浸提溶解性有机碳含量为697.42 mg/kg,易氧化碳含量为20.98 g/kg,高于已报道的许多相似天然林和人工林活性碳含量。土壤有机碳储量为154.87 t/hm2,在四川省各类森林中处于中等水平。研究表明瓦屋山扁刺栲-中华木荷常绿阔叶次生林活性碳含量较大,微生物活动和养分流动较为活跃,凋落物层转化为土壤碳的潜力较大,这类生态系统可能会在区域碳循环过程中扮演更为重要的角色。 Abstract:Secondary forests are one of the most important fast-growth forest types, with a large distribution area and high potential carbon sequestration capacity. In order to investigate the component characteristics of soil organic carbon in a subtropical secondary evergreen broad-leaved forest, an experiment was conducted in a typical evergreen broad-leaved secondary forest (Castanopsis platyacantha-Schima sinensis) in the middle section of Wawushan Mountain, southwest China. The physical soil properties and soil carbon fractions were studied, with the soil profile divided (0-10, 10-40, 40-70 cm and 70-100 cm) and sampled. Results showed that the soil at each level was acidic. Soil potential acidity was between 3.2 and 4.0, field moisture capacity was 63%-190%, and total porosity and bulk density were 63.0%-83.3% and 0.41-0.99 g/cm3 respectively. Soil pH value and bulk density increased with increased soil depth, while the field moisture capacity and total porosity showed the opposite trend. The organic carbon content of litter was 443 g/kg, and the litter stock and litter carbon stock were 10.4 t/hm2 and 4.5 t/hm2, respectively. Litter organic C stock in the studied forest was higher than in the majority of the plantations and natural forests in Sichuan Province. Soil organic carbon, microbial biomass carbon, extractable dissolved organic carbon, and readily oxidizable carbon decreased with an increase in soil depth. The soil organic carbon content in the 0-10 cm layer was 121.9 g/kg, which was higher than reported in other subtropical evergreen broad-leaved forests and in all types of forests in Sichuan (3.6, 8.6, and 14.6 times the soil organic content of the soil layers at 10-40 cm, 40-70 cm, and 70-100 cm respectively). The content of microbial biomass carbon in the 0-10 cm layer was 1931.82 mg/kg, which was 2.6, 5.7, and 7.8 times that in the following three layers. The contents of extractable dissolved organic carbon and readily oxidizable carbon in the 0-10 cm layer were 697.42 mg/kg and 20.98 g/kg, respectively. The contents of labile organic carbon in the 0-10 cm layer were higher than in many other reported similar natural forests and plantations. The density of soil organic carbon, microbial biomass carbon, extractable dissolved organic carbon, and readily oxidizable carbon were 7.5-48, 0.20-0.81, 0.25-0.37, and 0.8-8.4 kg/m3, respectively. The density of soil organic carbon, extractable dissolved carbon, and readily oxidizable carbon decreased with an increase in soil depth, while the microbial biomass carbon first increased and then decreased and peaked at the horizon, 10-40 cm. Soil organic carbon stock was 154.9 t/hm2, which was at the mid-level in Sichuan Province. The stocks of microbial biomass carbon, extractable dissolved organic carbon, and readily oxidizable carbon were 3.1, 3.0 and 21.0 t/hm2, respectively. This study suggests that (1) the content of the soil labile organic carbon was relatively high, (2) the activity of microorganisms and the flow of nutrients were relatively active, and (3) there is a huge amount of forest litter in the C. platyacantha-S. sinensis evergreen broad-leaved secondary forest that can be transformed into soil carbon in the future. These ecosystems will play a more important role in regional carbon cycles in the future. 参考文献 相似文献 引证文献