Native Soil Organic Carbon Mineralization Research Articles

Effects of biochar addition on the mineralization of native soil organic carbon in Cunninghamia lanceolata plantation.

Effects of addition of different biochars on soil organic carbon (SOC) mineralization were studied by the 13C-labelling technique for a better understanding of biomass resource utilization and carbon sequestration in subtropical Chinese fir (Cunninghamia lanceolata) plantation. An incubation experiment under 25 ℃ was performed over a period of 112 days to address how different biochar addition would affect the mineralization of native SOC. Biochars were produced from Schimasuperba or C. lanceolata litter at 350, 550 and 750 ℃, respectively. Results showed that the mineralization of native SOC was significantly accelerated during the first three days and subsequently suppressed from 7 to 112 days of incubation after C. lanceolata biochar addition compared to the control. In the S. superba biochar addition treatment, there was a significant increase in mineralization of native SOC within the first 14 days of incubation and then a rapid decrease from days 28 to 112. After 112 days incubation, all the three C. lanceolata biochar (350, 550 and 750 ℃) additions significantly inhibited the mineralization of native SOC. A similar trend was observed for the two S. superba biochar (350 and 550 ℃) additions but not for the S. superba biochar (750 ℃) addition. The decomposition rates of S. superba biochar and C. lanceolata biochar were 0.8%-2.8% after 112 days incubation and decreased with the increases of pyrolysis temperature. Under the same pyrolysis temperature, the decomposition rate of the S. superba biochar was significantly higher than that of the C. lanceolata biochar. In conclusion, both the raw material and pyrolysis temperature of biochars would be important factors driving the mineralization of native SOC and biochar degradation.

Effect of in-situ aged and fresh biochar on soil hydraulic conditions and microbial C use under drought conditions

Biochar (BC) amendments may be suitable to increase the ecosystems resistance to drought due to their positive effects on soil water retention and availability. We investigated the effect of BC in situ ageing on water availability and microbial parameters of a grassland soil. We used soil containing 13C labeled BC and determined its water holding capacity, microbial biomass and activity during a 3 months incubation under optimum and drought conditions. Our incubation experiment comprised three treatments: soil without BC (Control), soil containing aged BC (BCaged) and soil containing fresh BC (BCfresh), under optimum soil water (pF 1.8) and drought conditions (pF 3.5). Under optimum water as well as drought conditions, soils containing BC showed higher soil organic carbon (SOC) mineralization as compared to control soil. Moreover, BC effects on the soil water regime increase upon in situ aging. Native SOC mineralization increased most for soils containing BCaged. The BCaged led to improved C use under drought as compared to the other treatments. We conclude that BC addition to soils can ameliorate their water regime, especially under drought conditions. This beneficial effect of BC increases upon its aging, which also improved native substrate availability.

Microbial mechanisms of carbon priming effects revealed during the interaction of crop residue and nutrient inputs in contrasting soils.

Agronomic practices such as crop residue return and additional nutrient supply are recommended to increase soil organic carbon (SOC) in arable farmlands. However, changes in the priming effect (PE) on native SOC mineralization in response to integrated inputs of residue and nutrients are not fully known. This knowledge gap along with a lack of understanding of microbial mechanisms hinders the ability to constrain models and to reduce the uncertainty to predict carbon (C) sequestration potential. Using a 13 C-labeled wheat residue, this 126-day incubation study examined the dominant microbial mechanisms that underpin the PE response to inputs of wheat residue and nutrients (nitrogen, phosphorus and sulfur) in two contrasting soils. The residue input caused positive PE through "co-metabolism," supported by increased microbial biomass, C and nitrogen (N) extracellular enzyme activities (EEAs), and gene abundance of certain microbial taxa (Eubacteria, β-Proteobacteria, Acidobacteria, and Fungi). The residue input could have induced nutrient limitation, causing an increase in the PE via "microbial nutrient mining" of native soil organic matter, as suggested by the low C-to-nutrient stoichiometry of EEAs. At the high residue, exogenous nutrient supply (cf. no-nutrient) initially decreased positive PE by alleviating nutrient mining, which was supported by the low gene abundance of Eubacteria and Fungi. However, after an initial decrease in PE at the high residue with nutrients, the PE increased to the same magnitude as without nutrients over time. This suggests the dominance of "microbial stoichiometry decomposition," supported by higher microbial biomass and EEAs, while Eubacteria and Fungi increased over time, at the high residue with nutrients cf. no-nutrient in both soils. Our study provides novel evidence that different microbial mechanisms operate simultaneously depending on organic C and nutrient availability in a residue-amended soil. Our results have consequences for SOC modeling and integrated nutrient management employed to increase SOC in arable farmlands.

Soil microbial biomass size and soil carbon influence the priming effect from carbon inputs depending on nitrogen availability

Microbial biomass plays a critical role in soil organic carbon (SOC) mineralization. However, the effects of microbial biomass size on SOC mineralization are poorly understood. We investigated how the priming effect (PE) of plant residue inputs on native SOC mineralization responds to changes in microbial biomass size and nitrogen (N) availability in the same soil with a 23 y history of crops and grass cover with contrasting SOC contents. The size of the soil microbial biomass was changed by pre-incubating soils with glucose. The pre-incubated soils were then treated with 13C-labeled ryegrass residue combined with or without N to determine the PE. In all soils, the addition of ryegrass residue significantly increased cumulative carbon dioxide (CO2) production, whereas the addition of N decreased it compared to the control (no ryegrass or N addition). After a 42-day incubation, only 9–16% of the ryegrass carbon (C) was mineralized to CO2, which contributed approximately 55 and 34% to the total CO2 production in crop and grass soils, respectively. The addition of N decreased CO2 production during the ryegrass decomposition by 9–45%, while the change in soil microbial biomass size had no impact. In addition, a positive PE was generally found in the soils amended with ryegrass alone, while the application of ryegrass residue combined with N decreased the PE. Moreover, the priming effect was independent of the size of the microbial biomass in crop soil. However, we observed a significant interaction of microbial biomass size and N availability on the priming effect in a grass soil but not in a crop soil. Our results indicate that soil microbial biomass size and soil C influence the magnitude and direction of the priming effect from C inputs depending on N availability.

Temperature sensitivity and priming of organic matter with different stabilities in a Vertisol with aged biochar

Understanding the temperature sensitivity (Q10) of carbon (C) mineralization and priming of organic matter with different stabilities in a soil with aged biochar is required to enable better forecasting of biochar C sequestration potential under a warming climate. Here, we quantified the Q10 and priming of C mineralization in a Vertisol from: (i) newly added labile organic matter (LOM) in the presence of “aged biochars”; and (ii) stable (“aged”) native soil organic matter in the presence of aged biochars or new LOM. We also quantified the Q10 of aged biochar-C (BC) or aged soil organic carbon (SOC)+BC mineralization. Leaf litter from Eucalyptus saligna (a source of LOM) was applied at 4% w/w (δ13C −38‰) to a Vertisol (δ13C −14‰), containing either wood, leaf or poultry litter biochar (δ13C −25 to −28‰), and nil biochar (control soil), previously incubated for 4 years. These biochar−soil mixtures and the control soil, with or without LOM, were re-incubated at 10, 20, 30 and 40 °C for 252 days. The results showed that 22–39% of LOM-C, 0.10–2.81% of aged BC and 2.4–77.0% of “aged SOC” mineralized across all temperatures over 252 days. The Q10 of C mineralization increased with decreasing quality of C substrates in the soil, that is, LOM (1.17–1.21) < SOC (1.23–1.66), SOC + BC (1.23–1.60) < aged BC (1.92–2.26). Positive priming of SOC mineralization was greater by LOM (cf. aged biochar), causing a significant decrease in the SOC Q10 at all temperatures. The aged biochars resulted in negative priming of LOM-C mineralization, mainly at 10 °C, with no impact on the LOM Q10. The results suggest that global warming and tropical climates may lower the C sequestration potential of biochar, by reducing its capacity to slow the mineralization of LOM-C, while increasing the mineralization of native SOC.

Biochar-induced negative carbon mineralization priming effects in a coastal wetland soil: Roles of soil aggregation and microbial modulation

Biochar can sequestrate carbon (C) in soils and affect native soil organic carbon (SOC) mineralization via priming effects. However, the roles of soil aggregation and microbial regulation in priming effects of biochars on SOC in coastal wetland soils are poorly understood. Thus, a coastal wetland soil (δ13C −22‰) was separated into macro-micro aggregates (53–2000μm, MA) and silt-clay fractions (<53μm, SF) to investigate the priming effect using two 13C enriched biochars produced from corn straw (δ13C −11.58‰) at 350 and 550°C. The two biochars induced negative priming effect on the native SOC mineralization in the both soil aggregate size fractions, attributed to the enhanced stability of the soil aggregates resulting from the intimate physico-chemical associations between the soil minerals and biochar particles. Additionally, biochar amendments increased soil microbial biomass C and resulted in a lower metabolic quotient, suggesting that microbes in biochar amended aggregates could likely incorporate biomass C rather than mineralize it. Moreover, the biochar amendments induced obvious shifts of the bacterial community towards low C turnover bacteria taxa (e.g., Actinobacteria and Deltaproteobacteria) and the bacteria taxa responsible for stabilizing soil aggregates (e.g., Actinobacteria and Acidobacteria), which also accounted for the negative priming effect. Overall, these results suggested that biochar had considerable merit for stabilizing SOC in the coastal soil and thus has potential to restore and/or enhance “blue C” sink in the degraded coastal wetland ecosystem.

Photooxidation of pyrogenic organic matter reduces its reactive, labile C pool and the apparent soil oxidative microbial enzyme response

The surface chemistry of pyrogenic organic matter (PyOM) is altered by a variety of abiotic and biotic oxidative and sorption/desorption processes in the environment. Exposure of PyOM to high energy light prior to addition to soil or sediment, or while entrained in the atmosphere, may induce significant surface photooxidation, i.e., photochemical weathering, altering its environmental reactivity. We report on a 30-day soil incubation experiment testing the effects of the photochemical weathering of a 13C-enriched ponderosa pine PyOM, produced by pyrolysis at 450°C, on PyOM and soil organic carbon (SOC) mineralization. PyOM C mineralization was measured for both the photochemically weathered (i.e. UV treated PyOM or PyOMUV) and PyOM not exposed to high-energy light (i.e. PyOMW serving as a dark control). PyOMW exhibited a 3.7 times faster C mineralization rate across the 30-d study, which was driven by a large early mineralization of accessible/labile C during the first 6d. In contrast, PyOMUV had faster C mineralization rates in the later part of the experiment (days 11–30). Overall, PyOMUV had a 13% lower net C mineralization than the untreated PyOMW where the MRT of accessible PyOMUV-C and PyOMW-C was calculated at 25.7±6.8d and 1.7±0.2d, respectively. Both forms of PyOM promoted a similar net reduction in native SOC mineralization (i.e., negative priming) of approximately 50% relative to the unamended, control soil. Addition of either PyOM form resulted in an equivalent minor decrease in the concentration of extractable soil lignin phenols and substituted fatty acids chemistry with respect to the unamended soil. At 30d, soil phenol oxidase and peroxidase enzyme activities were higher with additions of either form of PyOM compared with the unamended control soils with PyOMUV exhibiting lower activities than PyOMW. Our results indicate that PyOM photochemical weathering can impart important changes to short-term PyOM reactivity and soil microbial activity, which could have important implications for soil systems by ultimately lowering turnover rates for both NSC and PyOM-C.

亚热带几种典型稻田与旱作土壤中外源输入秸秆的分解与转化差异

PDF HTML阅读 XML下载 导出引用 引用提醒 亚热带几种典型稻田与旱作土壤中外源输入秸秆的分解与转化差异 DOI: 10.5846/stxb201607211481 作者: 作者单位: 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（41371252，41430860，41671242）；国家重点研发计划项目（2016YFD0300902）。 Decomposition and transformation of input straw in several typical paddy and upland soils in subtropical China Author: Affiliation: 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:选取亚热带四种典型母质（花岗岩风化物、第四纪红色粘土、板页岩风化物、近代河流沉积物）发育的稻田土壤，以毗邻的旱作土壤为对比，通过室内模拟培养试验研究45%田间持水量（WHC）条件下稻田和旱作土壤中外源输入秸秆矿化和转化的特征与差异。结果表明：在180 d的培养期内，所选4种稻田土壤中外源输入秸秆的累积矿化率（18%-21%）均显著低于对应的旱作土壤（21%-28%），外源秸秆的输入对土壤原有有机碳矿化的激发效应也是以稻田土壤（5%-30%）明显低于对应的旱作土壤（17%-65%）。外源秸秆在土壤中的分解产物主要向颗粒有机碳（POC）和铁铝结合态有机碳（Fe/Al-OC）分配，分配比例分别为9%-21%和12%-24%，其次为腐殖质碳（HMC）（11%-15%），而向微生物生物量碳（MBC）和溶解性有机碳（DOC）分配的比例极小，分别仅为2%-7%和0.1%-0.7%。与旱作土壤相比，稻田土壤中外源秸秆的分解产物向POC、Fe/Al-OC和MBC分配的比例较高，分别为15%-21%、17%-24%和6%-7%，而旱作土壤为9%-17%、13%-18%和2%-4%。此外，外源秸秆分解产物向2000-250 μm水稳性粗团聚体分配的比例也以稻田土壤（10%-13%）高于旱作土壤（6%-7%），其它粒径中稻田与对应的旱作土壤之间并无显著差异。本研究结果说明，稻田土壤中外源输入秸秆的矿化率低于旱作土壤的现象在不同母质类型的土壤中可能普遍存在，这可能与稻田土壤中外源秸秆分解产物受水稳性团聚体的物理保护、与氧化铁铝的化学键合以及向有机碳稳定组分的分配作用较强有关，从而贡献于稻田土壤较高的有机碳积累。 Abstract:Decomposition and transformation of input straw in four types of paddy soils were investigated under incubation at 25℃ and 45% water holding capacity (WHC) for 180 d. The soils were derived from different parent materials (weathered granite, quaternary red clay, weathered shale, and river alluvial) in subtropical China, and the adjacent upland soils were selected as a control. During the 180 d period, the mineralization ratios of input straw in the selected paddy soils (18%-21%) were lower than those in the corresponding upland soils (21%-28%). The priming effects of straw amendment on native soil organic carbon mineralization were also lower in the paddy (5%-37%) than in the corresponding upland soils (23%-65%). The decomposed products of input straw were mainly distributed in particulate organic carbon (POC, 9%-21%) and Fe/Al-bound organic carbon (Fe/Al-OC, 12%-24%), followed by humus carbon (HMC) (11%-15%), whereas only a small part was distributed as microbial biomass carbon (MBC, 2%-7%) and dissolved organic carbon (DOC, 0.1%-0.7%). In paddy soils, the conversion ratios of input straw in POC, Fe/Al-OC, and MBC (15%-21%, 17%-24%, and 6%-7%) were higher than those in upland soils (9%-17%, 13%-18%, and 2%-4%). In addition, the 2,000-250 μm coarse water-stable aggregates in paddy soils tended to receive more decomposed products of input straw than those in upland soils (10%-13% vs. 6%-7%), whereas no significant difference was observed between paddy and upland soils in other small sizes of aggregates. The results indicated that the mineralization of input straw may be lower in paddy than in upland soils derived from different parent materials, possibly owing to stronger physical protection in soil coarse aggregates, chemical protection by binding with Fe/Al oxyhydrates, and larger transformation to stable fractions of input straw during its decomposition in paddy soils. This fate of input straw decomposition may contribute to a higher organic carbon accumulation in paddy than in upland soils. 参考文献 相似文献 引证文献

Fate of rice shoot and root residues, rhizodeposits, and microbe-assimilated carbon in paddy soil – Part 1: Decomposition and priming effect

Abstract. The input of recently photosynthesized C has significant implications on soil organic C sequestration, and in paddy soils, both plants and soil microbes contribute to the overall C input. In the present study, we investigated the fate and priming effect of organic C from different sources by conducting a 300-day incubation study with four different 13C-labelled substrates: rice shoots (shoot-C), rice roots (root-C), rice rhizodeposits (rhizo-C), and microbe-assimilated C (micro-C). The efflux of both 13CO2 and 13CH4 indicated that the mineralization of C in shoot-C-, root-C-, rhizo-C-, and micro-C-treated soils rapidly increased at the beginning of the incubation and decreased gradually afterwards. The highest cumulative C mineralization was observed in root-C-treated soil (45.4 %), followed by shoot-C- (31.9 %), rhizo-C- (7.90 %), and micro-C-treated (7.70 %) soils, which corresponded with mean residence times of 39.5, 50.3, 66.2, and 195 days, respectively. Shoot and root addition increased C emission from native soil organic carbon (SOC), up to 11.4 and 2.3 times higher than that of the control soil by day 20, and decreased thereafter. Throughout the incubation period, the priming effect of shoot-C on CO2 and CH4 emission was strongly positive; however, root-C did not exhibit a significant positive priming effect. Although the total C contents of rhizo-C- (1.89 %) and micro-C-treated soils (1.90 %) were higher than those of untreated soil (1.81 %), no significant differences in cumulative C emissions were observed. Given that about 0.3 and 0.1 % of the cumulative C emission were derived from labelled rhizo-C and micro-C, we concluded that the soil organic C-derived emissions were lower in rhizo-C- and micro-C-treated soils than in untreated soil. This indicates that rhizodeposits and microbe-assimilated C could be used to reduce the mineralization of native SOC and to effectively improve soil C sequestration. The contrasting behaviour of the different photosynthesized C substrates suggests that recycling rice roots in paddies is more beneficial than recycling shoots and demonstrates the importance of increasing rhizodeposits and microbe-assimilated C in paddy soils via nutrient management.

The priming potential of environmentally weathered pyrogenic carbon during land‐use transition to biomass crop production

AbstractSince land‐use change (LUC) to lignocellulosic biomass crops often causes a loss of soil organic carbon (SOC), at least in the short term, this study investigated the potential for pyrogenic carbon (PyC) to ameliorate this effect. Although negative priming has been observed in many studies, most of these are long‐term incubation experiments which do not account for the interactions between environmentally weathered PyC and native SOC. Here, the aim was to assess the impact of environmentally weathered PyC on native SOC mineralization at different time points in LUC from arable crops to short rotation coppice (SRC) willow. At eight SRC willow plantations in England, with ages of 3–22 years, soil amended 18–22 months previously with PyC was compared with unamended control soil. Cumulative CO2 flux was measured weekly from incubated soil at 0–5 cm depth, and soil‐surface CO2 flux was also measured in the field. For the incubated soil, cumulative CO2 flux was significantly higher from soil containing weathered PyC than the control soil for seven of the eight sites. Across all sites, the mean cumulative CO2 flux was 21% higher from soil incubated with weathered PyC than the control soil. These results indicate the potential for positive priming in the surface 5 cm of soil independent of changes in soil properties following LUC to SRC willow production. However, no net effect on CO2 flux was observed in the field, suggesting this increase in CO2 is offset by a contrasting PyC‐induced effect at a different soil depth or that different effects were observed under laboratory and field conditions. Although the mechanisms for these contrasting effects remain unclear, results presented here suggest that PyC does not reduce LUC‐induced SOC losses through negative priming, at least for this PyC type and application rate.

Negative priming of native soil organic carbon mineralization by oilseed biochars of contrasting quality

SummaryOilseed‐derived biochar, a by‐product of pyrolysis for biodiesel production, is richer in aliphatic compounds than the commonly studied wood‐derived biochar, affecting both its mineralization in soil and its interaction with native soil organic carbon (nSOC). Here, we investigated the soil C sequestration potential of three different oilseed biochars derived from C3 plant material: soyabean, castor bean and jatropha cake. The chemical composition of these biochars was determined by elemental analysis (CHN) and 13C NMR spectroscopy. The cumulative CO2 efflux from 30‐day laboratory incubations of biochar mixed with a sandy soil containing nSOC from C4 plants was measured as a proxy for mineralization rate. The relative contribution of each source to CO2 production was calculated based on the 13C‐signatures of total CO2 efflux and the source materials (soil and biochars). Our results showed that: (i) castor bean biochar contained relatively large amounts of aliphatic compounds, resulting in a greater mineralization rate than soyabean and jatropha biochars; (ii) CO2 efflux from the soil‐biochar mixtures originated mostly from the biochars, suggesting that these biochars contain rapidly decomposable compounds; and (iii) all three oilseed biochars decelerated nSOC mineralization. This negative priming effect appeared to be caused by different factors. We conclude that oilseed biochars have the potential to increase soil C stocks directly and increase soil C sequestration indirectly in the short term through negative priming of nSOC mineralization.

Response of soil organic carbon mineralization in typical Karst soils following the addition of 14C‐labeled rice straw and CaCO3

Organic substrates and calcium are important factors controlling organic matter turnover in Karst soils. To understand their effects on soil organic carbon (SOC) mineralization, an incubation experiment was conducted involving a control treatment (CK), the addition of a (14)C-labeled rice straw (T1), CaCO(3) (T2), and both (14)C-labeled rice straw and CaCO(3) (T3) to two types of Karst soils (terra fusca and rendzina) and a red soil from southwestern China. Cumulative mineralization of the rice straw over 100 days in rendzina (22.96 mg kg(-1)) and terra fusca (23.19 mg kg(-1)) was higher than in the red soil (15.48 mg kg(-1); P < 0.05). Cumulative mineralization of native SOC decreased following addition of (14)C-labeled rice straw in the rendzina and terra fusca but increased in the red soil (negative and positive priming effects on native SOC). The turnover times of (14)C-labeled microbial biomass C (MBC) in the red soil, terra fusca and rendzina were 71 ± 2, 243 ± 20 and 254 ± 45 days, respectively. By adding CaCO(3), the accumulation of SOC was greater in the Karst soils than in the red soil. Although the interactions between rice straw decomposition and priming effects on native SOC are not yet understood, there was considerable variation between Karst and red soils. Soil calcium was a positive factor in maintaining SOC stability. MBC from rice straws was stable in terra fusca and rendzina, whereas it was active in the red soil. The Karst soils (terra fusca and rendzina) used in this study benefited SOC accumulation.