CO2-C Emissions Research Articles

Dynamics of CO2 Emission and Biochemical Properties of a Sandy Calcareous Soil Amended with Conocarpus Waste and Biochar

ABSTRACT Biochar is a carbon-rich product obtained by biomass pyrolysis and considered a mean of carbon sequestration. In this research, a sandy calcareous soil from the Farm of the College of Food & Agriculture Sciences, King Saud University, Saudi Arabia, was amended with either woody waste of Conocarpus erectus L. (CW) or the biochar (BC) produced from CW at rates of 0 (control), 10, 30 and 50 g kg−1. The effects of the amendments on soil pH, dissolved organic carbon (DOC), microbial biomass carbon (MBC), CO2 emission and metabolic quotient (qCO2) of the sandy calcareous soil were studied in a 60-d incubation experiment. The results showed that the addition of CW led to a significant decrease in soil pH compared to the control and the addition of BC. The CO2-C emission rate was higher in the first few days of incubation than when the incubation time progressed. The cumulative CO2-C emission from the soil amended with CW, especially at higher rates, was higher (approximately 3- to 6-fold) than that from the control and the soil amended with BC. The BC-amended soil showed significant increases in CO2-C emission rate during the first days of incubation as compared to the non-amended soil, but the increase in cumulative CO2-C emission was not significant after 60 d of incubation. On the other hand, CW applications resulted in considerably higher cumulative CO2-C emission, MBC and DOC than the control and BC applications. With the exception of 0 day (after 1 h of incubation), both CW and BC applications led to lower values of qCO2 as compared to the control. The power function kinetic model satisfactorily described the cumulative CO2-C emission. Generally, the lowest values of CO2 emission were observed in the soil with BC, suggesting that the contribution of BC to CO2 emission was very small as compared to that of CW.

Impact of organic no-till vegetables systems on soil organic matter in the Atlantic Forest biome

Soil organic matter is widely recognized as a strategy used to improve soil quality and reduce carbon emissions to the atmosphere. A field study was carried out to investigate the effects of cover crops in organic no-till vegetables systems on changes in soil organic matter and CO2C emissions, in dry and rainy seasons. We hypothesized that CO2C emissions are higher in conventional till as compared with no-till, and that no-till increases soil C sink. The crop rotation comprised a 3-year cropping sequence involving two crops per year—cabbage (Brassica oleracea L.) in winter and eggplant (Solanum melongena L.) in summer time. Treatments were no-till on dead mulch of grass (Avena strigosa Schreb. and Zea mays L.), leguminous (Lupinus albus L. and Crotalaria juncea L.), intercrop (grass and leguminous) and conventional till (no dead mulch) with rotary hoe arranged in a randomized block design on a clayey Oxisol (Typic Haplustox) at Domingos Martins-ES, Brazil. On 2012 and 2013, disturbed soil samples at three different layers (0–5, 5–15 and 15–30cm) and undisturbed samples at 0–10, 10–20 and 20–30cm, for chemical and organic matter characterization were taken. CO2C emissions and soil temperature were measured in situ on March, May, August and October 2012 and February 2013 (after 3 years of experiment). Conventional till site showed the lowest microporosity values and the highest macroporosity, followed by lower soil bulk density at 0–10cm layer. Total organic C ranged from 34.94 to 50.48gkg−1 in intercrop and 27.11 to 43.74gkg−1 in conventional till. Total N ranged from 2.81 to 5.34gkg−1 in grass and 2.54 to 4.51gkg−1 in conventional till. Highest C stock was recorded in intercrop. Conventional till showed lower labile C values while recalcitrant C was higher in the intercrop treatment. The annual average of CO2C emissions (μmolCO2m−2s−1) followed the order: grass (15.89)>intercrop (13.77)>leguminous (13.09)>conventional till (11.20). Highest annual average of soil temperature was recorded in conventional till (23.95°C). Lowest annual mean of soil water content, microbial biomass C, and highest metabolic quotient were recorded in conventional till. These results suggest that the use of cover crops and organic compost in pre-planting promote C increments. The contribution of organic residues increases the water holding capacity and reduces soil temperature. No-till reduces soil disturbance and promotes a positive balance of C. Organic no-till vegetable systems is a strategy to increase soil C and should be encouraged in order to increase soil quality in the Atlantic Forest Biome in Brazil.

The Effects of Three Mineral Nitrogen Sources and Zinc on Maize and Wheat Straw Decomposition and Soil Organic Carbon

The incorporation of straw in cultivated fields can potentially improve soil quality and crop yield. However, the presence of recalcitrant carbon compounds in straw slow its decomposition rate. The objective of this study was to determine the effects of different nitrogen sources, with and without the application of zinc, on straw decomposition and soil quality. Soils were treated with three different nitrogen sources, with and without zinc: urea (CO(NH2)2), ammonium sulfate ((NH4)2SO4), and ammonium chloride (NH4Cl). The combined treatments were as follows: maize (M) and wheat (W) straw incorporated into urea-, ammonium sulfate-, or ammonium chloride-treated soil (U, S, and C, respectively) with and without zinc (Z) (MU, MUZ, WU, WUZ; MS, MSZ, WS, WSZ; MC, MCZ, WC, WCZ, respectively); straw with zinc only (MZ, WZ); straw with untreated soil (MS, WS); and soil-only or control conditions (NT). The experiment consisted of 17 treatments with four replications. Each pot contained 150 g soil and 1.125 g straw, had a moisture content of 80% of the field capacity, and was incubated for 53 days at 25°C. The rates of CO2-C emission, cumulative CO2-C evolution, total CO2 production in the soils of different treatments were measured to infer decomposition rates. The total organic carbon (TOC), labile organic carbon (LOC), and soil microbial biomass in the soils of different treatments were measured to infer soil quality. All results were significantly different (P<0.05) with the exception of the labile organic carbon (LOC). The maize and wheat straw showed different patterns in CO2 evolution rates. For both straw types, Zn had a synergic effect with U, but an antagonistic effect with the other N sources as determined by the total CO2 produced. The MUZ treatment showed the highest decomposition rate and cumulative CO2 concentration (1120.29 mg/pot), whereas the WACZ treatment had the lowest cumulative CO2 concentration (1040.57 mg/pot). The addition of NH4Cl resulted in the highest total organic carbon (TOC) concentration (11.59 mg kg−1). The incorporation of wheat straw resulted in higher microbial biomass accumulation in soils relative to that of the maize straw application. The results demonstrate that mineral N sources can affect the ability of microorganisms to decompose straw, as well as the soil carbon concentrations.

Short-term carbon dioxide emission under contrasting soil disturbance levels and organic amendments

Agriculture can be either a source or sink of atmospheric CO2 depending on soil management. The application of swine slurry in conventional tilled soils could enhance soil CO2 emission depleting soil organic C stocks. However, the use of recalcitrant C-rich organic fertilizers in no-till soils can offset soil CO2 emission promoting soil C sequestration. This hypothesis was tested by evaluating short-term CO2-C emissions from a Rhodic Nitisol under contrasting soil disturbance levels (disturbed (DS) and undisturbed soil (US)) top-dressed with mineral or organic fertilizers (urea (UR), raw swine slurry (RS), anaerobically digested swine slurry (ADS), and composted swine slurry (CS)). Soil CO2 emission was evaluated for 64 days using static chambers where gas samples were collected and analysed by photoacoustic infrared spectroscopy. Soil water-filled pore space (WFPS), temperature and meteorological data were concomitantly registered and a first-order exponential decay model was used to assess the decomposition of organic fertilizers and CO2 emissions induced by soil disturbance. Soil CO2-C emission was correlated with soil temperature, while limiting soil aeration impaired CO2-C efflux when WFPS >0.6cm3cm−3. Disturbance increased soil CO2-C efflux (36.3±2.2kg CO2-Cha−1 day−1) in relation to US (33.3±1.6kg CO2-Cha−1 day−1). Extra labile C input through RS amendment induced an increased soil CO2-C efflux for a longer period (t1/2=16.9 and 9.6 days in DS and US treatments, respectively), resulting in higher CO2-C emissions than soil amended with other fertilizers. The recalcitrant C input by ADS and CS had limited effect on soil CO2-C emissions. CS presented a genuine potential for substantial soil organic C accumulation while offsetting increased CO2-C emissions in comparison to RS amended soils.

Long Term Effect of Land Reclamation from Lake on Chemical Composition of Soil Organic Matter and Its Mineralization

Since the late 1950s, land reclamation from lakes has been a common human disturbance to ecosystems in China. It has greatly diminished the lake area, and altered natural ecological succession. However, little is known about its impact on the carbon (C) cycle. We conducted an experiment to examine the variations of chemical properties of dissolved organic matter (DOM) and C mineralization under four land uses, i.e. coniferous forest (CF), evergreen broadleaf forest (EBF), bamboo forest (BF) and cropland (CL) in a reclaimed land area from Taihu Lake. Soils and lake sediments (LS) were incubated for 360 days in the laboratory and the CO2 evolution from each soil during the incubation was fit to a double exponential model. The DOM was analyzed at the beginning and end of the incubation using UV and fluorescence spectroscopy to understand the relationships between DOM chemistry and C mineralization. The C mineralization in our study was influenced by the land use with different vegetation and management. The greatest cumulative CO2-C emission was observed in BF soil at 0–10 cm depth. The active C pool in EBF at 10–25 cm had longer (62 days) mean residence time (MRT). LS showed the highest cumulative CO2-C and shortest MRT comparing with the terrestrial soils. The carbohydrates in DOM were positively correlated with CO2-C evolution and negatively correlated to phenols in the forest soils. Cropland was consistently an outlier in relationships between DOM chemistry and CO2-evolution, highlighting the unique effects that this land use on soil C cycling, which may be attributed the tillage practices. Our results suggest that C mineralization is closely related to the chemical composition of DOM and sensitive to its variation. Conversion of an aquatic ecosystem into a terrestrial ecosystem may alter the chemical structure of DOM, and then influences soil C mineralization.

Artificial root exudates and soil organic carbon mineralization in a degraded sandy grassland in northern China

Plant root exudates contain various organic and inorganic components that include glucose, citric and oxalic acid. These components affect rhizosphere microbial and microfaunal activities, but the mechanisms are not fully known. Studies concerned from degraded grassland ecosystems with low soil carbon (C) contents are rare, in spite of the global distribution of grasslands in need of restoration. All these have a high potential for carbon sequestration, with a reduced carbon content due to overutilization. An exudate component that rapidly decomposes will increase soil respiration and CO2 emission, while a component that reduces decomposition of native soil carbon can reduce CO2 emission and actually help sequestering carbon in soil. Therefore, to investigate root exudate effects on rhizosphere activity, citric acid, glucose and oxalic acid (0.6 g C/kg dry soil) were added to soils from three biotopes (grassland, fixed dune and mobile dune) located in Naiman, Horqin Sandy Land, Inner Mongolia, China) and subjected to a 24-day incubation experiment together with a control. The soils were also analyzed for general soil properties. The results show that total respiration without exudate addition was highest in grassland soil, intermediate in fixed dune and lowest in mobile dune soil. However, the proportion of native soil carbon mineralized was highest in mobile dune soil, reflecting the low C/N ratio found there. The exudate effects on CO2-C emissions and other variables differed somewhat between biotopes, but total respiration (including that from the added substrates) was significantly increased in all combinations compared with the control, except for oxalic acid addition to mobile dune soil, which reduced CO2-C emissions from native soil carbon. A small but statistically significant increase in pH by the exudate additions in grassland and fixed dune soil was observed, but there was a major decrease from acid additions to mobile dune soil. In contrast, electrical conductivity decreased in grassland and fixed dune soil and increased in mobile dune. Thus, discrete components of root exudates affected soil environmental conditions differently, and responses to root exudates in soils with low carbon contents can differ from those in normal soils. The results indicate a potential for, e.g., acid root exudates to decrease decomposition rate of soil organic matter in low carbon soils, which is of interest for both soil restoration and carbon sequestration.

Soil respiration, labile carbon pools, and enzyme activities as affected by tillage practices in a tropical rice–maize–cowpea cropping system

In order to identify the viable option of tillage practices in rice-maize-cowpea cropping system that could cut down soil carbon dioxide (CO2) emission, sustain grain yield, and maintain better soil quality in tropical low land rice ecology soil respiration in terms of CO2 emission, labile carbon (C) pools, water-stable aggregate C fractions, and enzymatic activities were investigated in a sandy clay loam soil. Soil respiration is the major pathway of gaseous C efflux from terrestrial systems and acts as an important index of ecosystem functioning. The CO2-C emissions were quantified in between plants and rows throughout the year in rice-maize-cowpea cropping sequence both under conventional tillage (CT) and minimum tillage (MT) practices along with soil moisture and temperature. The CO2-C emissions, as a whole, were 24% higher in between plants than in rows, and were in the range of 23.4-78.1, 37.1-128.1, and 28.6-101.2mgm(-2)h(-1) under CT and 10.7-60.3, 17.3-99.1, and 17.2-79.1mgm(-2)h(-1) under MT in rice, maize, and cowpea, respectively. The CO2-C emission was found highest under maize (44%) followed by rice (33%) and cowpea (23%) irrespective of CT and MT practices. In CT system, the CO2-C emission increased significantly by 37.1% with respect to MT on cumulative annual basis including fallow. The CO2-C emission per unit yield was at par in rice and cowpea signifying the beneficial effect of MT in maintaining soil quality and reduction of CO2 emission. The microbial biomass C (MBC), readily mineralizable C (RMC), water-soluble C (WSC), and permanganate-oxidizable C (PMOC) were 19.4, 20.4, 39.5, and 15.1% higher under MT than CT. The C contents in soil aggregate fraction were significantly higher in MT than CT. Soil enzymatic activities like, dehydrogenase, fluorescein diacetate, and β-glucosidase were significantly higher by 13.8, 15.4, and 27.4% under MT compared to CT. The soil labile C pools, enzymatic activities, and heterotrophic microbial populations were in the order of maize > cowpea > rice, irrespective of the tillage treatments. Environmental sustainability point of view, minimum tillage practices in rice-maize-cowpea cropping system in tropical low land soil could be adopted to minimize CO2-C emission, sustain yield, and maintain soil health.

Carbon dioxide emissions from horizontal sub-surface constructed wetlands in the Mediterranean Basin

Constructed wetlands (CWs) are widely used natural-like systems for wastewater treatment where organic matter is removed through carbon dioxide (CO2) emissions. Several studies have been conducted regarding emissions and the sequestration of CO2 in CWs in the Northern Hemisphere; however, to the best of our knowledge, no studies have been performed in the Mediterranean Basin. This work quantified daily and cumulative CO2 emissions from a full-scale CW horizontal subsurface flow (HSSF) bed during semiarid Mediterranean spring climate conditions. The average daily CO2-C that was released in the atmosphere during the first 50 days ranged from approximately 17.5% to 32.6% of the C that was removed from wastewater. Considering both the Phragmites australis aerial part dry matter production (0.83kgm−2) and the average CO2-C emissions, after 50 days of vegetative regrowth, the HSSF bed was demonstrated to act as a CO2 sink. The cumulative CO2 efflux was 452.15±50.40CO2gm−2 and 276.02±12.07CO2gm−2 for vegetated and unvegetated sites, respectively.

Greenhouse gas emission in constructed wetlands for wastewater treatment: A review

A literature analysis of 158 papers published in international peer-reviewed journals indexed by the Thomson Reuters Web of Knowledge from 1994 to 2013 showed that CO2C emission was significantly lower in free water surface (FWS) constructed wetlands (CW) than in subsurface flow (SF) CWs (median values from 95.8 to 137.0mgm−2h−1, respectively). In vertical subsurface flow (VSSF) CWs the CH4C emission was significantly lower than in horizontal subsurface flow (HSSF) CWs (median values 3.0, 6.4, and 4.0mgm−2h−1, respectively). There were no significant differences in N2ON emission in various CW types (median for FWS, VSSF and HSSF CWs: 0.09, 0.12, and 0.13mgm−2h−1 correspondingly).The highest value of emission factor (EF) of CH4 ((CH4C/inflow TOCin)*100%) was found for FWS CWs (median 18.0%), followed by HSSF CWs (3.8%), and VSSF CWs (1.28%). Median values of N2O EFs ((N2ON/inflow TNin)*100%) differed significantly in all three CW types: 0.34% for HSSF, 0.11% for FWS, and 0.018% for VSSF CWs.We found a significant correlation between TOCin and CH4C emission and between the TNin and N2ON emission values for all of the types of CWs we studied.Hybrid CWs (e.g., the subsequent combination of VSSF, HSSF and FWS CWs) are beneficial from the point of view of both water purification and minimization of greenhouse gas (GHG) emissions. Likewise, intermittent loading in VSSF CWs and macrophyte harvesting in HSSF and FWS CWs can mitigate GHG emissions.

Effect of mono- and divalent cations on sorption of water-extractable organic carbon and microbial activity

Sorption is an important process for retention of organic carbon (C) in soils. The effect of Na+ and Ca2+ on sorption of organic C has been studied in salt-affected soils, but little is known about the effect of K+ and Mg2+ ions on sorption of water-extractable organic C (WEOC). The effect of Na+, K+, Ca2+ and Mg2+ ions on sorption of WEOC and its decomposition were investigated in a loamy sand (7.5 % clay) and a sandy clay loam (34.4 % clay). Salinity was developed with NaCl, KCl, MgCl2 or CaCl2 to obtain different concentrations of exchangeable Na+, K+, Ca2+ and Mg2+ at an electrical conductivity in a 1:5 soil/water extract (EC1:5) of 1 dS m−1. Water-extractable organic C was derived from wheat straw, and microbial activity after sorption was quantified by measuring CO2 emission from the soils for 27 days. The concentration of sorbed C was higher in the sandy clay loam than in the loamy sand and decreased in the treatment order Ca2+ > Mg2+ > K+ > Na+, but cumulative CO2-C emission after sorption was highest from the Na+ and lowest from the Ca2+ treatments. The strong binding in the Ca2+ and Mg2+ treatments can be explained by the low zeta potential and the high covalency index of cation binding with C, whereas zeta potential was high and the covalency index was low in the Na+ treatments. Although K+ is also monovalent, WEOC was more strongly bound in the K+ than in the Na+ treatment. The weak binding with Na increased the accessibility of the sorbed C to soil microbes and, thus, microbial activity. Our results suggest that monovalent cations may enhance decomposition and leaching of WEOC in saline soils with Na+ having a greater effect than K+. Divalent cations, particularly Ca2+, enhance the binding of organic matter and thus organic C stabilization, whereas Mg2+ ions have a smaller effect.

Soil and crop residue CO2-C emission under tillage systems in sugarcane-producing areas of southern Brazil

Appropriate management of agricultural crop residues could result in increases on soil organic carbon (SOC) and help to mitigate gas effect. To distinguish the contributions of SOC and sugarcane (Saccharum spp.) residues to the short-term CO2-C loss, we studied the influence of several tillage systems: heavy offset disk harrow (HO), chisel plow (CP), rotary tiller (RT), and sugarcane mill tiller (SM) in 2008, and CP, RT, SM, moldboard (MP), and subsoiler (SUB) in 2009, with and without sugarcane residues relative to no-till (NT) in the sugarcane producing region of Brazil. Soil CO2-C emissions were measured daily for two weeks after tillage using portable soil respiration systems. Daily CO2-C emissions declined after tillage regardless of tillage system. In 2008, total CO2-C from SOC and/or residue decomposition was greater for RT and lowest for CP. In 2009, emission was greatest for MP and CP with residues, and smallest for NT. SOC and residue contributed 47 % and 41 %, respectively, to total CO2-C emissions. Regarding the estimated emissions from sugarcane residue and SOC decomposition within the measurement period, CO2-C factor was similar to sugarcane residue and soil organic carbon decomposition, depending on the tillage system applied. Our approach may define new emission factors that are associated to tillage operations on bare or sugarcane-residue-covered soils to estimate the total carbon loss.

Litter species traits, but not richness, contribute to carbon and nitrogen dynamics in an alpine meadow on the Tibetan Plateau

Litter, as afterlife of plants, plays an important role in driving belowground decomposition processes. Here we tested effects of litter species identity and diversity on carbon (C) and nitrogen (N) dynamics during litter decomposition in N-limited alpine meadow soil from the Qinghai-Tibet Plateau. We incubated litters of four meadow species, a sedge ("S", Kobresia humilis), a grass ("G", Elymus nutans), a herb ("H", Saussurea superba), and a legume ("L", Oxytropis falcata), in monoculture and in mixture with meadow soil. CO2 release was measured 21 times during the incubation, and soil available N and microbial biomass C and N were measured before and after the experiment. The organic C decay rate did not differ much among soils amended with monocultures or mixtures of litter, except in the H, S, L, and S+H treatments, which had much higher decay rates. Potential decomposable C pools were lowest in the control, highest in the L treatment, and intermediate in the S treatment. Mineralized N was completely immobilized by soil microbes in all treatments except the control, S+L, and S+G+L treatments. Litter mixtures had both additive and non-additive effects on CO2-C emission (mainly antagonistic effects), net N mineralization (mainly synergistic), and microbial biomass C and N (both). Overall, these parameters were not significantly correlated with litter species richness. Similarly, microbial C or N was not significantly correlated with litter N content or C/N. However, cumulative CO2-C emission and net N mineralization were positively correlated with litter N content and negatively correlated with litter C/N. Litter N content and C/N rather than litter species richness drove the release of CO2-C and net available N in this ecosystem. The antagonistic effects of litter mixtures contributed to a modest release of CO2-C, but their synergistic effects enhanced net available N. We suggest that in alpine meadow communities, balancing species with high and low N contents will benefit soil carbon sequestration and plant competition for available N with soil microbes.

Nitrous oxide emissions from black soils with different pH

N2O fluxes as a function of incubation time from soil with different available N contents and pH were determined. Cumulative carbon dioxide (CO2) emissions were measured to indicate soil respiration. A 144-hr incubation experiment was conducted in a slightly acidic agricultural soil (pHH2O 5.33) after the pH was adjusted to four different values (3.65, 5.00, 6.90 and 8.55). The experiments consisted of a control without added N, and with NH+4-N and NO−3-N fertilization. The results showed that soil pH contributed significantly to N2O flux from the soils. There were higher N2O emissions in the period 0–12 hr in the four pH treatments, especially those enhanced with N-fertilization. The cumulative N2O-N emission reached a maximum at pH 8.55 and was stimulated by NO−3-N fertilization (70.4 μg/kg). The minimum emissions appeared at pH 3.65 and were not stimulated by NO−3-N or NH+4-N fertilization. Soil respiration increased significantly due to N-fertilization. Soil respiration increased positively with soil pH (R2 = 0.98, P < 0.01). The lowest CO2-C emission (30.2 mg/kg) was presented in pH 3.65 soils without N-fertilization. The highest CO2-C emissions appeared in the pH 8.55 soils for NH+4-N fertilization (199 mg/kg). These findings suggested that N2O emissions and soil respiration were significantly influenced by low pH, which strongly inhibits soil microbial nitrification and denitrification activities. The content of NO−3-N in soil significantly and positively affected the N2O emissions through denitrification.

Emission of Carbon Dioxide Influenced by Different Water Levels from Soil Incubated Organic Residues

We studied the influence of different organic residues and water levels on decomposition rate and carbon sequestration in soil. Organic residues (rice straw, rice root, cow dung, and poultry litter) including control were tested under moistened and flooding systems. An experiment was laid out as a complete randomized design at 25°C for 120 days. Higher CO2-C (265.45 mg) emission was observed in moistened condition than in flooding condition from 7 to 120 days. Among the organic residues, poultry litter produced the highest CO2-C emission. Poultry litter with soil mixture increased 121% cumulative CO2-C compared to control. On average, about 38% of added poultry litter C was mineralized to CO2-C. Maximum CO2-C was found in 7 days after incubation and thereafter CO2-C emission was decreased with the increase of time. Control produced the lowest CO2-C (158.23 mg). Poultry litter produced maximum cumulative CO2-C (349.91 mg). Maximum organic carbon was obtained in cow dung which followed by other organic residues. Organic residues along with flooding condition decreased cumulative CO2-C, k value and increased organic C in soil. Maximum k value was found in poultry litter and control. Incorpored rice straw increased organic carbon and decreased k value (0.003 g d−1) in soil. In conclusion, rice straw and poultry litter were suitable for improving soil carbon.

盐分和底物对黄河三角洲区土壤有机碳分解与转化的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 盐分和底物对黄河三角洲区土壤有机碳分解与转化的影响 DOI: 10.5846/stxb201206290914 作者: 作者单位: 滨州学院山东省黄河三角洲生态环境重点实验室 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（41101220，41101277）；山东省优秀中青年科学家奖励基金项目（BS2011HZ001）；山东省高校科研发展计划项目（J13LE58）；滨州学院国家级大学生创新训练计划项目（201210449127）；滨州学院博士基金项目（2008Y05） Effects of salinity and exogenous substrates on the decomposition and transformation of soil organic carbon in the Yellow River Delta Author: Affiliation: Shangdong Key laboratory of Eco-enviromental Science for Yellow River Delta, Binzhou University, Binzhou 256603, Shandong, China 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:土壤盐碱化能抑制微生物活性，影响土壤有机碳的分解与转化。以黄河三角洲盐碱耕地为研究对象，采用室内恒温培养法，设置3个NaCl盐分梯度（S1：0.1%；S2：0.5%；S3：0.9%），通过在土壤中添加不同底物（CK：不添加底物；N：添加氮；C：添加碳；C+N：添加碳+氮），研究该土壤释放CO2-C量、土壤微生物生物量碳（SMBC）、土壤微生物呼吸商（qCO2）及溶解性有机碳（DOC）对盐分和底物的响应。结果表明：在45 d的培养期内，CK、N处理中S1盐分土壤释放CO2-C量最高，S2和S3明显低于S1，降低幅度分别为18.3%-23.7%和24.3%-39.8%。C、C+N处理中3个盐分土壤释放CO2-C量差异较小，特别是在C+N处理中，3个盐分土壤释放CO2-C差异不显著。4个底物处理中，SMBC均在S1和S2盐分中含量较高，S3盐分最低。与CK相比，N处理并不能提高SMBC含量，C、C+N处理可明显提高SMBC，但S1和S2盐分土壤提高的幅度（80.4%-80.5%、58.0%-58.7%）明显高于S3（68.9%、49.7%）。4个底物处理中，qCO2均在S1盐分土壤中最高，C、C+N处理可明显提高qCO2。CK、N处理中3个盐分土壤DOC差异不显著，C、C+N处理中S3盐分土壤DOC较高。说明在无碳源输入条件下，增加盐分含量能明显抑制土壤释放CO2量。添加碳源后，盐分含量对土壤释放CO2的影响变小。微生物对碳源和盐分胁迫的响应较快，添加碳源能明显提高微生物数量及其活性。但较高盐分（含盐量 > 0.5%）可明显降低土壤微生物活性及对外源碳的利用率，导致较高盐分SMBC及qCO2较低而DOC较高。 Abstract:In the Yellow River Delta, nearly 50 percent of soils are saline and alkaline. Soil salinization can suppress microbial activity and thus affect the decomposition and transformation of soil organic carbon, while little information was found about the effects of salinity and exogenous C and N amendment on the decomposition and transformation of soil organic carbon in this area. A laboratory experiment was conducted to investigate the effects of soil salinity and exogenous substances on the turnover of organic carbon under conditions with 25℃ and 60% water holding capacity over 45 days. Three levels of salinity (S1: 0.1%; S2: 0.5%; S3: 0.9%) using NaCl (w/w) were imposed in the saline-alkaline cultivated soil in Yellow River Delta. Soil was amended with or without C (750 mg/kg) or inorganic N (30 mg/kg) as glucose or NH4Cl, and 4 treatments were established, including (Control: no substrates addition, N: NH4Cl addition, C: glucose addition, C+N: glucose and NH4Cl addition). The CO2-C emission, soil microbial biomass carbon (SMBC), dissolved organic carbon (DOC) and calculation of the respiratory quotient(qCO2)were determined. Without glucose addition, the cumulative amount of CO2-C emission was highest in S1 during the incubation, and it was decreased by 18.3%-23.7% and 24.3%-39.8% in S2 and S3 compared with S1, respectively. After glucose addition, the cumulative amount of CO2-C emission little changed among the three salinity soils, and especially it was no significant difference between the three salinity soils in C+N treatment. SMBC was higher in S1 and S2 than that in S3 under the four treatments with substrates addition. Addition of NH4Cl had no significant effect, but addition of glucose significantly increased SMBC, and SMBC increased by 80.4%-80.5% or 58.0%-58.7% in S1 and S2 in C or C+N treatment, and only 68.9% or 49.7% in S3. The qCO2 was significant higher in S1 than that in S2 and S3, and it was significantly improved with glucose addition. Compare with the control, DOC reminded unchanged in the N treatment, but it increased in S3 with glucose addition. It was suggested that the CO2 emission could be depressed with the increase of soil salinity without C addition, and soil salinity had little influence on CO2 emission after C addition. Microorganism was more sensitive to exogenous carbon and soil salinity. The size and the activity of microbial biomass would be improved with C addition, but higher salinity (>0.5%) could depress the microbial activity and the utilization of exogenous carbon, resulting in higher SMBC and qCO2 and lower DOC in higher salinity soil. 参考文献 相似文献 引证文献

Effect of cover plants on soil C and N dynamics in different soil management systems in dwarf cashew culture

Inappropriate soil management practices are one of most important constraints on cashew production in Northeast Brazil. This work aimed to evaluate the changes in soil C and N dynamics caused by different management of cover plants (spontaneous or leguminous) in dwarf cashew culture in Northeast Brazil. The evaluated management systems for control of spontaneous vegetation included: disc harrowing (DH), mechanical mowing (MeM), manual mowing (MaM), leguminous cover crop (LEG), leguminous cover crop+mulch of Carnaúba palm (LEG+m), and application of herbicide (HERB). The floristic composition, plant density, biomass production, and the nutrient content of the spontaneous plants that grew between cashew rows were evaluated. Total soil C and N, mineral- and organic-N, light organic matter fraction, microbial biomass, CO2-C emission rates and humic substances were determined. HERB treatment promoted a substantial change in the floristic composition of spontaneous species. Richness index was highest in the LEG treatment in the fifth year of the experiment. Dry matter amount of spontaneous plants was quite similar in MeM, MaM, LEG, and LEG+m treatments, with average values of 2245kgha−1. DH and HERB treatments reduced dry matter by 69 and 80%, respectively. The MeM system resulted in the highest soil C stock, whereas the DH treatment tended to intensify the mineralization process of soil organic matter due to soil disturbance. LEG treatment resulted in the highest mineral-N contents. Our results suggest that the maintenance of soil organic C levels in DH and MeM treatments is strongly dependent on maintenance of light organic matter levels. Soil from treatments which favored input of organic matter (e.g., LEG, LEG+m and HERB) presented greater C-humic/C-fulvic acids ratio, indicating the predominance of humic acids. Our findings reinforce that cover plants (e.g., spontaneous vegetation and leguminous species) play an important environmental role, contributing to organic matter and nutrient cycling in the soil. Management systems that promote soil covering and the use of leguminous species increased soil organic matter stocks.

Carbon balance and crop residue management in dynamic equilibrium under a no-till system in Campos Gerais

The adoption of no-tillage systems (NT) and the maintenance of crop residues on the soil surface result in the long-term increase of carbon (C) in the system, promoting C sequestration and reducing C-CO2 emissions to the atmosphere. The purpose of this study was to evaluate the C sequestration rate and the minimum amount of crop residues required to maintain the dynamic C equilibrium (dC/dt = 0) of two soils (Typic Hapludox) with different textural classes. The experiment was arranged in a 2 x 2 x 2 randomized block factorial design. The following factors were analyzed: (a) two soil types: Typic Hapludox (Oxisol) with medium texture (LVTM) and Oxisol with clay texture (LVTA), (b) two sampling layers (0-5 and 5-20 cm), and (c) two sampling periods (P1 - October 2007; P2 - September 2008). Samples were collected from fields under a long-term (20 years) NT system with the following crop rotations: wheat/soybean/black oat + vetch/maize (LVTM) and wheat/maize/black oat + vetch/soybean (LVTA). The annual C sequestration rates were 0.83 and 0.76 Mg ha-1 for LVTM and LVTA, respectively. The estimates of the minimum amount of crop residues required to maintain a dynamic equilibrium (dC/dt = 0) were 7.13 and 6.53 Mg ha-1 year-1 for LVTM and LVTA, respectively. The C conversion rate in both studied soils was lower than that reported in other studies in the region, resulting in a greater amount of crop residues left on the soil surface.

CO2-C losses and carbon quality of selected Maritime Antarctic soils

AbstractPolar Regions are the most important soil carbon reservoirs on Earth. Monitoring soil carbon storage in a changing global climate context may indicate possible effects of climate change on terrestrial environments. In this regard, we need to understand the dynamics of soil organic matter in relation to its chemical characteristics. We evaluated the influence of chemical characteristics of humic substances on the process of soil organic matter mineralization in selected Maritime Antarctic soils. A laboratory assay was carried out with soils from five locations from King George Island. We determined the contents of total organic carbon, oxidizable carbon fractions of soil organic matter, and humic substances. Two in situ field experiments were carried out during two summers, in order to evaluate the CO2-C emissions in relation to soil temperature variations. The overall low amounts of soil organic matter in Maritime Antarctic soils have a low humification degree and reduced microbial activity. CO2-C emissions showed significant exponential relationship with temperature, suggesting a sharp increase in CO2-C emissions with a warming scenario, and Q10 values (the percentage increase in emission for a 10°C increase in soil temperature) were higher than values reported from elsewhere. The sensitivity of the CO2-C emission in relation to temperature was significantly correlated with the humification degree of soil organic matter and microbial activity for Antarctic soils.

Biochar from swine manure solids: influence on carbon sequestration and Olsen phosphorus and mineral nitrogen dynamics in soil with and without digestate incorporation

Interest in biochar (BC) has grown dramatically in recent years, due mainly to the fact that its incorporation into soil reportedly enhances carbon sequestration and fertility. Currently, BC types most under investigation are those obtained from organic matter (OM) of plant origin. As great amounts of manure solids are expected to become available in the near future, thanks to the development of technologies for the separation of the solid fraction of animal effluents, processing of manure solids for BC production seems an interesting possibility for the recycling of OM of high nutrient value. The aim of this study was to investigate carbon (C) sequestration and nutrient dynamics in soil amended with BC from dried swine manure solids. The experiment was carried out in laboratory microcosms on a silty clay soil. The effect on nutrient dynamics of interaction between BC and fresh digestate obtained from a biogas plant was also investigated to test the hypothesis that BC can retain nutrients. A comparison was made of the following treatments: soil amended with swine manure solids (LC), soil amended with charred swine manure solids (LT), soil amended with wood chip (CC), soil amended with charred wood chip (CT), soil with no amendment as control (Cs), each one of them with and without incorporation of digestate (D) for a total of 10 treatments. Biochar was obtained by treating OM (wood chip or swine manure) with moisture content of less than 10% at 420°C in anoxic conditions. The CO2-C release and organic C, available phosphorus (P) (Olsen P, POls) and inorganic (ammonium+nitrate) nitrogen (N) (Nmin) contents at the start and three months after the start of the experiment were measured in the amended and control soils. After three months of incubation at 30°C, the CO2-C emissions from soil with BC (CT and LT, ±D) were the same as those in the control soil (Cs) and were lower than those in the soils with untreated amendments (CC and LC, ±D). The organic C content decreased in CT and LT to a lesser extent than in CC and LC. In soils with D (+D), the CO2-C emissions were equal to or higher than those in soils without (-D). The Nmin content increased in all treatments; the POls content decreased in the +D treatments. The incorporation of BC into soil, by reducing CO2 emissions, actually contributes to C sequestration without modifying N availability for crops. For a given N content, the BC from swine manure solids supplies much more P than the non-treated OM and, therefore, represents an interesting source of P for crops.

Future vegetation changes in thawing subarctic mires and implications for greenhouse gas exchange—a regional assessment

One of the major concerns regarding climate change in high latitudes is the potential feedback from greenhouse gases (GHG) being released from thawing peat soils. In this paper we show how vegetational patterns and associated GHG fluxes in subarctic palsa (peat mounds with a permanently frozen core) mires can be linked to climate, based on field observations from fifteen palsa sites distributed in northern Fennoscandia. Fine resolution (100 m) land cover data are combined with projections of future climate for the 21st century in order to model the potential future distribution of palsa vegetation in northern Fennoscandia. Site scale climate-vegetational relationships for two vegetation types are described by a climate suitability index computed from the field observations. Our results indicate drastic changes in the palsa vegetational patterns over the coming decades with a 97 % reduction in dry hummock areas by 2041–2060 compared to the 1961–1990 areal coverage. The impact of these changes on the carbon balance is a decrease in the efflux of CO2 from 130 kilotonnes C y−1 to a net uptake of 11 kilotonnes C y−1 and a threefold increase in the efflux of CH4 from 6 to 18 kilotonnes C y−1 over the same period and over the 5,520 km2 area of palsa mires. The combined effect is equivalent to a slight decrease in CO2-C emissions, from 182 to 152 kilotonnes C y−1. Main uncertainties involve the ability of the vegetation community to adapt to new conditions, and long-term changes in hydrology due to absence of ice and frost heaving.