The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Yakov Kuzyakov - One of the best experts on this subject based on the ideXlab platform.
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comparing carbon and nitrogen stocks in paddy and Upland Soils accumulation stabilization mechanisms and environmental drivers
Geoderma, 2021Co-Authors: Liang Wei, Mouliang Xiao, Yakov Kuzyakov, Zhenke Zhu, Yu Luo, Yuanhe Yang, Zhifeng YanAbstract:Abstract Paddy Soils, a type of Hydragric Anthrosol, have much greater soil organic C (SOC) and total N (TN) contents than that in Upland Soils. However, this fact has never been generalized or mechanistically explained. We conducted a global meta-analysis on the organic C and total N contents and their stocks in continuous paddy Soils (578 sites) and compared them with those in adjacent Upland Soils. Average C stocks up to depths of 35 cm in Upland and paddy Soils were 31 and 47 Mg C ha−1, respectively. The N stocks in Upland and paddy Soils were 2.2 and 3.2 Mg N ha−1, respectively. The combined effects of mean annual temperature and precipitation showed that C and N stocks in paddy and Upland Soils are generally the largest under cool and humid conditions and the smallest in warm and dry climates. Quantitative analysis of climatic, and soil physical and chemical factors showed that 1) climate effects are weakened by management such as puddling and flooding, thereby increasing the importance of soil physico-chemical properties, which control soil organic matter (SOM) stabilization, and 2) climate (e.g., mean annual precipitation) mainly affects C and N stocks in Upland Soils; the chemical properties (such as pH), on the other hand, primarily affect C and N stocks in paddy Soils. Greater C and N stocks in paddy Soils are the result of 1) a larger input of organic C by rice than by most Upland cereals, 2) slower decomposition of plant residues and SOM under anoxic conditions, and 3) a greater importance of sesquioxides in the biochemical stabilization of SOM. We conclude that these man-made paddy Soils store more organic C and N than their Upland neighbors despite long-term and intensive management.
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organic matter stabilization in aggregates and density fractions in paddy soil depending on long term fertilization tracing of pathways by 13c natural abundance
Soil Biology & Biochemistry, 2020Co-Authors: Cornelius Talade Atere, Anna Gunina, Mouliang Xiao, Yakov Kuzyakov, Liang Chen, Yangwu Deng, Jinshui WuAbstract:Abstract Previous studies on Upland Soils showed that 13C natural abundance can successfully reveal C stabilization pathways between aggregates and soil organic matter (SOM) density fractions. The direction of C stabilization in paddies can, however, deviate from that in Upland Soils owing to i) periodic drying–rewetting cycles, with oxygen pulses under oxic conditions, and thus, shifts in microbial processing of organic residues, and ii) intensive organic and mineral fertilization. To trace C stabilization in paddies, soil was sampled from a long-term field experiment under an unfertilized Control and NPK, NPK + straw, and NPK + manure fertilizer regimes. Soil was analyzed for total C, microbial biomass (MB), and dissolved organic C, and separated into three classes based on aggregate size (>250 μm, 53–250 μm, and
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Fate of 14C-labeled dissolved organic matter in paddy and Upland Soils in responding to moisture
The Science of the total environment, 2014Co-Authors: Xiangbi Chen, Aihua Wang, Hua Zheng, Yakov KuzyakovAbstract:Soil organic matter (SOM) content in paddy Soils is higher than that in Upland Soils in tropical and subtropical China. The dissolved organic matter (DOM) concentration, however, is lower in paddy Soils. We hypothesize that soil moisture strongly controls the fate of DOM, and thereby leads to differences between the two agricultural Soils under contrasting management regimens. A 100-day incubation experiment was conducted to trace the fate and biodegradability of DOM in paddy and Upland Soils under three moisture levels: 45%, 75%, and 105% of the water holding capacity (WHC). (14)C labeled DOM, extracted from the (14)C labeled rice plant material, was incubated in paddy and Upland Soils, and the mineralization to (14)CO2 and incorporation into microbial biomass were analyzed. Labile and refractory components of the initial (14)C labeled DOM and their respective half-lives were calculated by a double exponential model. During incubation, the mineralization of the initial (14)C labeled DOM in the paddy Soils was more affected by moisture than in the Upland Soils. The amount of (14)C incorporated into the microbial biomass (2.4-11.0% of the initial DOM-(14)C activity) was less affected by moisture in the paddy Soils than in the Upland Soils. At any of the moisture levels, 1) the mineralization of DOM to (14)CO2 within 100 days was 1.2-2.1-fold higher in the paddy Soils (41.9-60.0% of the initial DOM-(14)C activity) than in the Upland Soils (28.7-35.7%), 2) (14)C activity remaining in solution was significantly lower in the paddy Soils than in the Upland Soils, and 3) (14)C activity remaining in the same agricultural soil solution was not significantly different among the three moisture levels after 20 days. Therefore, moisture strongly controls DOM fate, but moisture was not the key factor in determining the lower DOM in the paddy Soils than in the Upland Soils. The UV absorbance of DOM at 280 nm indicates less aromaticity of DOM from the paddy Soils than from the Upland Soils. At any of the moisture levels, much more labile DOM was found in paddy Soils (34.3-49.2% of the initial (14)C labeled DOM) compared with that in Upland Soils (19.4-23.9%). This demonstrates that the lower DOM content in the paddy soil compared with that in the Upland soil is probably determined by the less complex components and structure of the DOM.
Scott Fendorf - One of the best experts on this subject based on the ideXlab platform.
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Effects of moisture and physical disturbance on pore-scale oxygen content and anaerobic metabolisms in Upland Soils.
The Science of the total environment, 2021Co-Authors: E. M. Lacroix, R. Rossi, Deborah Bossio, Scott FendorfAbstract:Soils are the largest dynamic stock of carbon (C) on Earth, and microbial respiration of soil organic C accounts for over 25% of global carbon dioxide (CO2) emissions. Zones of oxygen depletion in Upland Soils (anaerobic microsites) are increasingly recognized as an important control on soil microbial respiration rates, but the factors governing the volume and distribution of anaerobic microsites are relatively unknown. We measured the dissolved oxygen (DO) content of porewater from incubated soil cores of varying moisture contents ( 80% water saturation) and degrees of disturbance (undisturbed, conventionally tilled, and physically disturbed). Porewater was extracted sequentially from pores constrained by three effective pore diameters, ≥3.0 μm, 3.0-1.0 μm, and 1.0-0.6 μm, from cores incubated for 7, 14, or 28 days, using a modified Tempe cell extraction system. We observed a parabolic pattern in mean dissolved oxygen (DO) concentrations across pore sizes, independent of soil moisture and degree of disturbance. Specifically, DO values within the largest and smallest pore domains were relatively depleted (155 ± 10 μM and 160 ± 11 μM, respectively), while DO values within medium pores were closer to saturation (214 ± 8 μM). The observed DO pattern provides insight into the balance of microbial oxygen demand versus oxygen supply across pore domains within Upland Soils. Additionally, we observed iron and manganese reduction in all Soils except samples subjected to disturbance and incubated at
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anoxic microsites in Upland Soils dominantly controlled by clay content
Soil Biology & Biochemistry, 2018Co-Authors: Marco Keiluweit, Kaitlyn Gee, Amanda Denney, Scott FendorfAbstract:Abstract Recent evidence suggests that oxygen limitations are a critical regulator of soil organic matter mineralization rates, even within seemingly well-drained Upland Soils. Oxygen limitations may arise in otherwise well-aerated Soils when oxygen consumption (via microbial respiration) in soil microsites outpaces oxygen supply (through diffusion). Due to analytical limitations, attempts to parameterize oxygen limitations in models have so far been limited to measures of bulk oxygen concentrations or cm-scale gradients within larger soil structural units (e.g., aggregates or peds). Smaller anoxic microsites may thus have gone undetected, limiting our ability to accurately model and predict anoxic pore volume. Here we quantify the extent of anoxic microsites in Soils held at moderate moisture and identify the soil properties that dictate their formation and persistence. Using a planar optode imaging system, we monitored oxygen dynamics during incubations of a range of Soils spanning natural and artificial gradients in texture and organic matter availability. While bulk oxygen concentrations ranged from 40 to 100% of saturation, we observed significant micro-scale variability resulting in the formation of anoxic microsites, here defined as soil spaces showing less than 5% saturation. Anoxic microsites comprised 2 and 9% of the total soil volume, or 14–85% of the total pore volume. Bulk oxygen concentrations showed a strong negative correlation with bioavailable organic matter, presumably due to its influence on microbial oxygen consumption. In contrast, the extent of anoxic microsites was negatively correlated to clay content, an effect attributed to limited oxygen supply in clay-rich microstructures. Our results demonstrate that texture-dependent diffusion limitations at moderate moisture conditions cause an abundance of anoxic domains, not only in cm-sized macro-aggregates as current modeling approaches assume, but also within micro-aggregates. Anoxic domain size within these microstructures is at least partially decoupled from bulk oxygen concentrations, challenging the use of bulk oxygen concentrations for predicting microbially available oxygen levels and resulting OM mineralization rates and pathways in Upland Soils.
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Are oxygen limitations under recognized regulators of organic carbon turnover in Upland Soils?
Biogeochemistry, 2016Co-Authors: Marco Keiluweit, Peter S. Nico, Markus Kleber, Scott FendorfAbstract:Understanding the processes controlling organic matter (OM) stocks in Upland Soils, and the ability to management them, is crucial for maintaining soil fertility and carbon (C) storage as well as projecting change with time. OM inputs are balanced by the mineralization (oxidation) rate, with the difference determining whether the system is aggrading, degrading or at equilibrium with reference to its C storage. In Upland Soils, it is well recognized that the rate and extent of OM mineralization is affected by climatic factors (particularly temperature and rainfall) in combination with OM chemistry, mineral–organic associations, and physical protection. Here we examine evidence for the existence of persistent anaerobic microsites in Upland Soils and their effect on microbially mediated OM mineralization rates. We corroborate long-standing assumptions that residence times of OM tend to be greater in soil domains with limited oxygen supply (aggregates or peds). Moreover, the particularly long residence times of reduced organic compounds (e.g., aliphatics) are consistent with thermodynamic constraints on their oxidation under anaerobic conditions. Incorporating (i) pore length and connectivity governing oxygen diffusion rates (and thus oxygen supply) with (ii) ‘hot spots’ of microbial OM decomposition (and thus oxygen consumption), and (iii) kinetic and thermodynamic constraints on OM metabolism under anaerobic conditions will thus improve conceptual and numerical models of C cycling in Upland Soils. We conclude that constraints on microbial metabolism induced by oxygen limitations act as a largely unrecognized and greatly underestimated control on overall rates of C oxidation in Upland Soils.
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Are oxygen limitations under recognized regulators of organic carbon turnover in Upland Soils?
Biogeochemistry, 2016Co-Authors: Marco Keiluweit, Peter S. Nico, Markus Kleber, Scott FendorfAbstract:To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Springer and can be found at: http://link.springer.com/journal/10533Understanding the processes controlling organic matter (OM) stocks in Upland Soils, and the ability to management them, is crucial for maintaining soil fertility and carbon (C) storage as well as projecting change with time. OM inputs are balanced by the mineralization (oxidation) rate, with the difference determining whether the system is aggrading, degrading or at equilibrium with reference to its C storage. In Upland Soils, it is well recognized that the rate and extent of OM mineralization is affected by climatic factors (particularly temperature and rainfall) in combination with OM chemistry, mineral–organic associations, and physical protection. Here we examine evidence for the existence of persistent anaerobic microsites in Upland Soils and their effect on microbially mediated OM mineralization rates. We corroborate long-standing assumptions that residence times of OM tend to be greater in soil domains with limited oxygen supply (aggregates or peds). Moreover, the particularly long residence times of reduced organic compounds (e.g., aliphatics) are consistent with thermodynamic constraints on their oxidation under anaerobic conditions. Incorporating (i) pore length and connectivity governing oxygen diffusion rates (and thus oxygen supply) with (ii) ‘hot spots’ of microbial OM decomposition (and thus oxygen consumption), and (iii) kinetic and thermodynamic constraints on OM metabolism under anaerobic conditions will thus improve conceptual and numerical models of C cycling in Upland Soils. We conclude that constraints on microbial metabolism induced by oxygen limitations act as a largely unrecognized and greatly underestimated control on overall rates of C oxidation in Upland Soils
Marco Keiluweit - One of the best experts on this subject based on the ideXlab platform.
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anoxic microsites in Upland Soils dominantly controlled by clay content
Soil Biology & Biochemistry, 2018Co-Authors: Marco Keiluweit, Kaitlyn Gee, Amanda Denney, Scott FendorfAbstract:Abstract Recent evidence suggests that oxygen limitations are a critical regulator of soil organic matter mineralization rates, even within seemingly well-drained Upland Soils. Oxygen limitations may arise in otherwise well-aerated Soils when oxygen consumption (via microbial respiration) in soil microsites outpaces oxygen supply (through diffusion). Due to analytical limitations, attempts to parameterize oxygen limitations in models have so far been limited to measures of bulk oxygen concentrations or cm-scale gradients within larger soil structural units (e.g., aggregates or peds). Smaller anoxic microsites may thus have gone undetected, limiting our ability to accurately model and predict anoxic pore volume. Here we quantify the extent of anoxic microsites in Soils held at moderate moisture and identify the soil properties that dictate their formation and persistence. Using a planar optode imaging system, we monitored oxygen dynamics during incubations of a range of Soils spanning natural and artificial gradients in texture and organic matter availability. While bulk oxygen concentrations ranged from 40 to 100% of saturation, we observed significant micro-scale variability resulting in the formation of anoxic microsites, here defined as soil spaces showing less than 5% saturation. Anoxic microsites comprised 2 and 9% of the total soil volume, or 14–85% of the total pore volume. Bulk oxygen concentrations showed a strong negative correlation with bioavailable organic matter, presumably due to its influence on microbial oxygen consumption. In contrast, the extent of anoxic microsites was negatively correlated to clay content, an effect attributed to limited oxygen supply in clay-rich microstructures. Our results demonstrate that texture-dependent diffusion limitations at moderate moisture conditions cause an abundance of anoxic domains, not only in cm-sized macro-aggregates as current modeling approaches assume, but also within micro-aggregates. Anoxic domain size within these microstructures is at least partially decoupled from bulk oxygen concentrations, challenging the use of bulk oxygen concentrations for predicting microbially available oxygen levels and resulting OM mineralization rates and pathways in Upland Soils.
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Are oxygen limitations under recognized regulators of organic carbon turnover in Upland Soils?
Biogeochemistry, 2016Co-Authors: Marco Keiluweit, Peter S. Nico, Markus Kleber, Scott FendorfAbstract:Understanding the processes controlling organic matter (OM) stocks in Upland Soils, and the ability to management them, is crucial for maintaining soil fertility and carbon (C) storage as well as projecting change with time. OM inputs are balanced by the mineralization (oxidation) rate, with the difference determining whether the system is aggrading, degrading or at equilibrium with reference to its C storage. In Upland Soils, it is well recognized that the rate and extent of OM mineralization is affected by climatic factors (particularly temperature and rainfall) in combination with OM chemistry, mineral–organic associations, and physical protection. Here we examine evidence for the existence of persistent anaerobic microsites in Upland Soils and their effect on microbially mediated OM mineralization rates. We corroborate long-standing assumptions that residence times of OM tend to be greater in soil domains with limited oxygen supply (aggregates or peds). Moreover, the particularly long residence times of reduced organic compounds (e.g., aliphatics) are consistent with thermodynamic constraints on their oxidation under anaerobic conditions. Incorporating (i) pore length and connectivity governing oxygen diffusion rates (and thus oxygen supply) with (ii) ‘hot spots’ of microbial OM decomposition (and thus oxygen consumption), and (iii) kinetic and thermodynamic constraints on OM metabolism under anaerobic conditions will thus improve conceptual and numerical models of C cycling in Upland Soils. We conclude that constraints on microbial metabolism induced by oxygen limitations act as a largely unrecognized and greatly underestimated control on overall rates of C oxidation in Upland Soils.
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Are oxygen limitations under recognized regulators of organic carbon turnover in Upland Soils?
Biogeochemistry, 2016Co-Authors: Marco Keiluweit, Peter S. Nico, Markus Kleber, Scott FendorfAbstract:To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Springer and can be found at: http://link.springer.com/journal/10533Understanding the processes controlling organic matter (OM) stocks in Upland Soils, and the ability to management them, is crucial for maintaining soil fertility and carbon (C) storage as well as projecting change with time. OM inputs are balanced by the mineralization (oxidation) rate, with the difference determining whether the system is aggrading, degrading or at equilibrium with reference to its C storage. In Upland Soils, it is well recognized that the rate and extent of OM mineralization is affected by climatic factors (particularly temperature and rainfall) in combination with OM chemistry, mineral–organic associations, and physical protection. Here we examine evidence for the existence of persistent anaerobic microsites in Upland Soils and their effect on microbially mediated OM mineralization rates. We corroborate long-standing assumptions that residence times of OM tend to be greater in soil domains with limited oxygen supply (aggregates or peds). Moreover, the particularly long residence times of reduced organic compounds (e.g., aliphatics) are consistent with thermodynamic constraints on their oxidation under anaerobic conditions. Incorporating (i) pore length and connectivity governing oxygen diffusion rates (and thus oxygen supply) with (ii) ‘hot spots’ of microbial OM decomposition (and thus oxygen consumption), and (iii) kinetic and thermodynamic constraints on OM metabolism under anaerobic conditions will thus improve conceptual and numerical models of C cycling in Upland Soils. We conclude that constraints on microbial metabolism induced by oxygen limitations act as a largely unrecognized and greatly underestimated control on overall rates of C oxidation in Upland Soils
Ralf Conrad - One of the best experts on this subject based on the ideXlab platform.
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Cold-temperate climate: a factor for selection of ammonia oxidizers in Upland soil?
Canadian Journal of Microbiology, 2005Co-Authors: Sharon Avrahami, Ralf ConradAbstract:Ammonia-oxidizing bacteria in various Upland Soils show a rather large diversity with respect to their amoA genes (coding for a subunit of the ammonium monooxygenase). It is known that the community structure of ammonia-oxidizing bacteria in Upland Soils is influenced by different selective factors, such as pH, gravimetric water content, fertilizer treatment, and temperature. The question, from an ecological point of view, is whether a particular ecophysiological factor, such as temperature, could select for a particular community structure of ammonia oxidizers in Upland Soils that would be represented by distinct clusters of the amoA gene (AmoA cluster). Studying the literature, including recent publications and our own unpublished results, we found that AmoA clusters 3a, 3b, and 9–12 apparently exhibited no preference for either subtropical/tropical Soils (i.e., warm regions) or temperate cold Soils. However, AmoA clusters 1 and 4 (and perhaps cluster 2) seem to occur predominantly in Soils from cold-te...
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cold temperate climate a factor for selection of ammonia oxidizers in Upland soil
Canadian Journal of Microbiology, 2005Co-Authors: Sharon Avrahami, Ralf ConradAbstract:Ammonia-oxidizing bacteria in various Upland Soils show a rather large diversity with respect to their amoA genes (coding for a subunit of the ammonium monooxygenase). It is known that the community structure of ammonia-oxidizing bacteria in Upland Soils is influenced by different selective factors, such as pH, gravimetric water content, fertilizer treatment, and temperature. The question, from an ecological point of view, is whether a particular ecophysiological factor, such as temperature, could select for a particular community structure of ammonia oxidizers in Upland Soils that would be represented by distinct clusters of the amoA gene (AmoA cluster). Studying the literature, including recent publications and our own unpublished results, we found that AmoA clusters 3a, 3b, and 9-12 apparently exhibited no preference for either subtropical/tropical Soils (i.e., warm regions) or temperate cold Soils. However, AmoA clusters 1 and 4 (and perhaps cluster 2) seem to occur predominantly in Soils from cold-temperate regions. Here we review the evidence for a temperature effect on the global distribution of amoA genes in warm- and cold-temperate Soils.
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Diversity of Methanotrophic Bacteria in Tropical Upland Soils under Different Land Uses
Applied and environmental microbiology, 2005Co-Authors: Claudia Knief, Ralf Conrad, Peter F. Dunfield, Supika Vanitchung, Narumon W. Harvey, Amnat ChidthaisongAbstract:Three Upland Soils from Thailand, a natural forest, a 16-year-old reforested site, and an agricultural field, were studied with regard to methane uptake and the community composition of methanotrophic bacteria (MB). The methane uptake rates were similar to rates described previously for forest and farmland Soils of the temperate zone. The rates were lower at the agricultural site than at the native forest and reforested sites. The sites also differed in the MB community composition, which was characterized by denaturing gradient gel electrophoresis (DGGE) of pmoA gene fragments (coding for a subunit of particulate methane monooxygenase) that were PCR amplified from total soil DNA extracts. Cluster analysis based on the DGGE banding patterns indicated that the MB communities at the forested and reforested sites were similar to each other but different from that at the farmland site. Sequence analysis of excised DGGE bands indicated that Methylobacter spp. and Methylocystis spp. were present. Sequences of the “forest soil cluster” or “Upland soil cluster α,” which is postulated to represent organisms involved in atmospheric methane consumption in diverse Soils, were detected only in samples from the native forest and reforested sites. Additional sequences that may represent uncultivated groups of MB in the Gammaproteobacteria were also detected.
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sequential reduction processes and initiation of ch4 production upon flooding of oxic Upland Soils
Soil Biology & Biochemistry, 1996Co-Authors: Verena Peters, Ralf ConradAbstract:Sequential reduction processes were studied in four oxic Upland Soils (cultivated, forest, savanna and desert soil) which were slurried and incubated under anoxic conditions. NO3−1 reduction began almost immediately and was followed by reduction of manganese(IV), sulfate and iron(III). The phases of reduction of Mn4+, SO42− and Fe3+ overlapped, with SO42− being depleted long before accumulation of Mn2+ and Fe2+ was finished. CH4 production and growth of methanogenic bacteria began when all the other reduction processes were finished. Radiotracer experiments showed that CH4 was produced from H2 (29–42%) and acetate. The respiratory index indicated that the acetate was predominantly degraded by methanogenic bacteria. The late onset of methanogenesis was not a consequence of limitation by the methanogenogenic precursors, since H2 and acetate were present long before the initiation of methanogenesis. Thermodynamic calculations showed that the concentrations of these substrates were always sufficient to allow exergonic production of CH4 at Gibbs free energies of ΔG + 400 mV to final values of < − 150 mV, except in the forest soil where the redox potential stayed at + 50 mV. The onset of methanogenesis and of growth of methanogenic bacteria coincided with redox potentials between +70 and 0 mV, which is much higher than claimed in literature. We speculate that the redox-active substances in soil were the signal for methanogenic bacteria to initiate activity.
Zhenke Zhu - One of the best experts on this subject based on the ideXlab platform.
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comparing carbon and nitrogen stocks in paddy and Upland Soils accumulation stabilization mechanisms and environmental drivers
Geoderma, 2021Co-Authors: Liang Wei, Mouliang Xiao, Yakov Kuzyakov, Zhenke Zhu, Yu Luo, Yuanhe Yang, Zhifeng YanAbstract:Abstract Paddy Soils, a type of Hydragric Anthrosol, have much greater soil organic C (SOC) and total N (TN) contents than that in Upland Soils. However, this fact has never been generalized or mechanistically explained. We conducted a global meta-analysis on the organic C and total N contents and their stocks in continuous paddy Soils (578 sites) and compared them with those in adjacent Upland Soils. Average C stocks up to depths of 35 cm in Upland and paddy Soils were 31 and 47 Mg C ha−1, respectively. The N stocks in Upland and paddy Soils were 2.2 and 3.2 Mg N ha−1, respectively. The combined effects of mean annual temperature and precipitation showed that C and N stocks in paddy and Upland Soils are generally the largest under cool and humid conditions and the smallest in warm and dry climates. Quantitative analysis of climatic, and soil physical and chemical factors showed that 1) climate effects are weakened by management such as puddling and flooding, thereby increasing the importance of soil physico-chemical properties, which control soil organic matter (SOM) stabilization, and 2) climate (e.g., mean annual precipitation) mainly affects C and N stocks in Upland Soils; the chemical properties (such as pH), on the other hand, primarily affect C and N stocks in paddy Soils. Greater C and N stocks in paddy Soils are the result of 1) a larger input of organic C by rice than by most Upland cereals, 2) slower decomposition of plant residues and SOM under anoxic conditions, and 3) a greater importance of sesquioxides in the biochemical stabilization of SOM. We conclude that these man-made paddy Soils store more organic C and N than their Upland neighbors despite long-term and intensive management.
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effect of simulated tillage on microbial autotrophic co2 fixation in paddy and Upland Soils
Scientific Reports, 2016Co-Authors: Qiong Liu, Zhenke Zhu, Hongzhao Yuan, Wei Wang, Andrew S WhiteleyAbstract:Tillage is a common agricultural practice affecting soil structure and biogeochemistry. To evaluate how tillage affects soil microbial CO2 fixation, we incubated and continuously labelled samples from two paddy Soils and two Upland Soils subjected to simulated conventional tillage (CT) and no-tillage (NT) treatments. Results showed that CO2 fixation ((14)C-SOC) in CT Soils was significantly higher than in NT Soils. We also observed a significant, soil type- and depth-dependent effect of tillage on the incorporation rates of labelled C to the labile carbon pool. Concentrations of labelled C in the carbon pool significantly decreased with soil depth, irrespective of tillage. Additionally, quantitative PCR assays revealed that for most Soils, total bacteria and cbbL-carrying bacteria were less abundant in CT versus NT treatments, and tended to decrease in abundance with increasing depth. However, specific CO2 fixation activity was significantly higher in CT than in NT Soils, suggesting that the abundance of cbbL-containing bacteria may not always reflect their functional activity. This study highlights the positive effect of tillage on soil microbial CO2 fixation, and the results can be readily applied to the development of sustainable agricultural management.
