Carbon accumulation in Umbrisols under Quercus pyrenaica forests: Effects of bedrock and annual precipitation     

María-Belén Turrión  Knut Schneider  Juan F. Gallardo 《CATENA》2009

The objective of this study was to determine the effect of bedrock, mean annual precipitation and slope orientation on soil organic carbon (SOC) accumulation of Quercus pyrenaica Willd forests. Twelve different oak stands, along a rainfall gradient over two bedrock types (granites and schists), were selected for this study. Properties of the diagnostic soil horizons were determined. Bedrock type was the principal factor affecting soil development and fertility. Accumulated SOC varied between 33 and 185 Mg C ha^− 1, the amounts of C accumulated over schists being significantly higher than over granites because of higher soil acidity, ‘silt + clay’ content and metal complexation. The SOC content in the entire profile was over 125 times higher than the C accumulated in the stand forest litter at the schist sites and 50 times higher at the granite sites. Soil acidity and metal complexation hampered microbial decomposition of soil organic matter, producing SOC accumulation and forming thick umbric Ah/AB-horizons, being thicker at sites with high values of mean annual precipitation than at sites with low ones. Mineral N release was low in these soils.  相似文献   

Distribution and dynamics of soil organic matter in an Antarctic dry valley     

B. Elberling  E.G. Gregorich  A.D. Sparrow  L.G. Greenfield 《Soil biology & biochemistry》2006,38(10):3095-3106

Terrestrial ecosystems in the Antarctic dry valleys function under extremely cold and dry climatic conditions that severely constrain C and N cycling and, like other polar regions, are likely to be sensitive to environmental change. To characterize the distribution and dynamics of soil organic C (SOC) and N in the various landscape elements of an Antarctic dry valley, we measured soil profile organic C and organic N stocks, inorganic N (NH₄-N and NO₃-N), soil CO₂ effluxes, water contents and soil temperatures in the Garwood Valley, a relatively small valley in southern Victoria Land. We also conducted laboratory measurements of basal respiration on soils collected from the Valley. SOC and respiration rates were low and SOC was highly stratified in the soil profile, with the largest values observed near the surface. Significant variations of SOC stocks and soil CO₂ effluxes were observed between landscape elements and spatial variability was closely related to the distance from the lake, the major site of primary production. The fastest rate of SOC turnover (residence time c. 30 years) was found in the soils at the lake edge, slower rates were found in landscape elements close to the lake (c. 52-67 years), and the slowest rates in other landscape elements (c. 84-123 years) further away. A mass balance of organic C indicates that the quantity of C fixed in the lake, accumulated on the lake edge, exposed and subsequently displaced on a 14-year basis can explain the near-surface SOC turnover within the entire valley. We conclude that the displacement of organic matter derived from the lake is an important external source for the microbial processes in these soils at a landscape scale. However, further investigations are needed in order to evaluate the importance of displaced C compared to other nutrients (e.g. N) on the spatial control of observed soil respiration rates.  相似文献   

Long-term impact of reduced tillage and residue management on soil carbon stabilization: Implications for conservation agriculture on contrasting soils   总被引：1，自引：0，他引：1  

P.P. Chivenge  H.K. Murwira  K.E. Giller  P. Mapfumo  J. Six 《Soil & Tillage Research》2007,94(2):328-337

Residue retention and reduced tillage are both conservation agricultural management options that may enhance soil organic carbon (SOC) stabilization in tropical soils. Therefore, we evaluated the effects of long-term tillage and residue management on SOC dynamics in a Chromic Luvisol (red clay soil) and Areni-Gleyic Luvisol (sandy soil) in Zimbabwe. At the time of sampling the soils had been under conventional tillage (CT), mulch ripping (MR), clean ripping (CR) and tied ridging (TR) for 9 years. Soil was fully dispersed and separated into 212–2000 μm (coarse sand), 53–212 μm (fine sand), 20–53 μm (coarse silt), 5–20 μm (fine silt) and 0–5 μm (clay) size fractions. The whole soil and size fractions were analyzed for C content. Conventional tillage treatments had the least amount of SOC, with 14.9 mg C g⁻¹ soil and 4.2 mg C g⁻¹ soil for the red clay and sandy soils, respectively. The highest SOC content was 6.8 mg C g⁻¹ soil in the sandy soil under MR, whereas for the red clay soil, TR had the highest SOC content of 20.4 mg C g⁻¹ soil. Organic C in the size fractions increased with decreasing size of the fractions. In both soils, the smallest response to management was observed in the clay size fractions, confirming that this size fraction is the most stable. The coarse sand-size fraction was most responsive to management in the sandy soil where MR had 42% more organic C than CR, suggesting that SOC contents of this fraction are predominantly controlled by amounts of C input. In contrast, the fine sand fraction was the most responsive fraction in the red clay soil with a 66% greater C content in the TR than CT. This result suggests that tillage disturbance is the dominant factor reducing C stabilization in a clayey soil, probably by reducing C stabilization within microaggregates. In conclusion, developing viable conservation agriculture practices to optimize SOC contents and long-term agroecosystem sustainability should prioritize the maintenance of C inputs (e.g. residue retention) to coarse textured soils, but should focus on the reduction of SOC decomposition (e.g. through reduced tillage) in fine textured soils.  相似文献   

城郊土壤不透水表面有土壤机碳转化及其相关性质的研究   总被引：2，自引：0，他引：2  

WEI Zong-Qiang  WU Shao-Hu  ZHOU Sheng-Lu  LI Jing-Tao  ZHAO Qi-Guo 《土壤圈》2014,24(1):56-64

Installation of impervious surface in urban area prevents the exchange of material and energy between soil and other environmental counterparts, thereby resulting in negative effects on soil function and urban environment. Soil samples were collected at 0-20 cm depth in Nanjing City, China, in which seven sites were selected for urban open soils, and fourteen sites with similar parent material were selected for the impervious-covered soils, to examine the effect of impervious surface on soil properties and microbial activities, and to determine the most important soil properties associated with soil organic carbon （SOC） transformation in the urban soils covered by impervious surfaces. Soil organic carbon and water-soluble organic carbon （WSOC） concentrations, potential carbon （C） and nitrogen （N） mineralization rates, basal respiration, and physicochemical properties with respect to C transformation were measured. Installation of impervious surface severely affected soil physicochemical properties and microbial activities, e.g., it significantly decreased total N contents, potential C mineralization and basal respiration rate （P 〈 0.01）, while increased pH, clay and Olsen-P concentrations. Soil organic carbon in the sealed soils at 0-20 cm was 2.35 kg m-2, which was significantly lower than the value of 4.52 kg m-2 in the open soils （P 〈 0.05）. Canonical correlation analysis showed WSOC played a major role in determining SOC transformation in the impervious-covered soil, and it was highly correlated with total N content and potential C mineralization rate. These findings demonstrate that installation of impervious surface in urban area, which will result in decreases of SOC and total N concentrations and soil microbial activities, has certain negative consequences for soil fertility and long-term storage of SOC.  相似文献   

Soil carbon responses to past and future CO2 in three Texas prairie soils     

《Soil biology & biochemistry》2015

Changes in soil carbon storage could affect and be affected by rising atmospheric CO₂. However, it is unlikely that soils will respond uniformly, as some soils are more sensitive to changes in the amount and chemistry of plant tissue inputs whereas others are less sensitive because of mineralogical, textural, or microbial processes. We studied soil carbon and microbial responses to a preindustrial-to-future CO₂ gradient (250–500 ppm) in a grassland ecosystem in the field. The ecosystem contains three soil types with clay fractions of 15%–55%: a sandy loam Alfisol, a silty clay Mollisol, and a black clay Vertisol. Soil and microbial responses to atmospheric CO₂ are plant-mediated; and aboveground plant productivity in this ecosystem increased linearly with CO₂ in the sandy loam and silty clay. Although total soil organic carbon (SOC) did not change with CO₂ treatment after four growing seasons, fast-cycling SOC pools increased with CO₂ in the two clay soils. Microbial biomass increased 18% and microbial activity increased 30% across the CO₂ gradient in the black clay (55% clay), but neither factor changed with CO₂ in the sandy loam (15% clay). Similarly, size fractionation of SOC showed that coarse POM-C, the youngest and most labile fraction, increased four-fold across the CO₂ gradient in the black clay, but increased by only 50% across the gradient in the sandy loam. Interestingly, mineral-associated C, the oldest and most recalcitrant fraction, declined 23% across the gradient in the third soil type, a silty clay (45% clay). Our results provide evidence for priming in this soil type, as labile C availability and decomposition rate (measured as soil respiration and soil C mineralization) also increased across the CO₂ gradient in the silty clay soil. In summary, CO₂ enrichment in this grassland increased the fast-cycling SOC pool as in other CO₂ studies, but only in the two high-clay soils. Priming in the silty clay could limit SOC accumulation after prolonged CO₂ exposure. Because soil texture varies geographically, including data on soil types could enhance predictions of soil carbon and microbial responses to future CO₂ levels.  相似文献   

Soil properties influencing erodibility of soils in the Ntabelanga area,Eastern Cape Province,South Africa     

Cosmas Parwada  Johan Van Tol 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2017,67(1):67-76

Soil erosion has serious off-site impacts caused by increased mobilization of sediment and delivery to water bodies causing siltation and pollution. To evaluate factors influencing soil erodibility at a proposed dam site, 21 soil samples collected were characterized. The soils were analyzed for soil organic carbon (SOC), exchangeable bases, exchangeable acidity, pH, electrical conductivities, mean weight diameter and soil particles’ size distribution. Cation exchange capacity, exchangeable sodium percentage, sodium adsorption ratio, dispersion ratio (DR), clay flocculation index (CFI), clay dispersion ratio (CDR) and Ca:Mg ratio were then calculated. Soil erodibility (K-factor) estimates were determined using SOC content and surface soil properties. Soil loss rates by splashing were determined under rainfall simulations at 360?mmh^?1 rainfall intensity. Soil loss was correlated to the measured chemical and physical soil properties. There were variations in soil form properties and erodibility indices showing influence on soil loss. The average soil erodibility and SOC values were 0.0734?t?MJ^?1?mm^?1 and 0.81%, respectively. SOC decreased with depth and soil loss increased with a decrease in SOC content. SOC significantly influenced soil loss, CDR, CFI and DR (P??1. Addition of organic matter stabilize the soils against erosion.  相似文献   

黄土丘陵半干旱区人工柠条林土壤固碳特征及其影响因素   总被引：3，自引：0，他引：3  

崔静  陈云明  黄佳健  王琼芳  姚志杰  张飞 《中国生态农业学报》2012,20(9):1197-1203

为了探讨黄土丘陵区不同生长年限的人工柠条林地土壤有机碳含量的变化特征及其影响因素,更好地阐明黄土丘陵区柠条林土壤的固碳机理,本文采用时空替代法,以撂荒2 a的坡耕地为对照,对黄土丘陵半干旱区不同林龄(10 a、17 a、26 a、34 a、40 a、50 a)人工柠条林地土壤有机碳(SOC)、全氮(STN)、全磷(STP)及柠条林的根系生物量和枯落物现存量进行了分析。结果表明:1)在0~60 cm的土层剖面上,0~20 cm土层SOC含量明显高于其他土层,并随土层深度的增加逐层递减,其中柠条林地0~20 cm土层SOC含量变化幅度为2.68~11.44 g·kg-1,而40~60 cm土层SOC含量仅在1.64~2.73 g·kg-1波动;与对照相比,随林龄增加柠条林地0~60 cm土层平均SOC含量先减小后增加最后趋于平稳:10 a和17 a柠条林SOC含量比对照显著降低了34.5%和26.9%,26 a柠条林的SOC含量显著升高,其值是对照的1.43倍,40 a和50 a柠条林SOC含量处于积累与消耗相对稳定的状态。2)对SOC含量与STN、STP含量及根系生物量和枯落物现存量进行相关性分析表明,SOC含量与STN含量、根系生物量及枯落物现存量之间存在极显著线性相关,但与STP含量相关性不明显,说明土壤中氮含量的增加能明显提高土壤的固碳能力,而根系生物量和枯落物现存量的多少能够决定土壤的固碳水平。  相似文献   

长期施肥对红壤性水稻土团聚体稳定性及固碳特征的影响   总被引：21，自引：2，他引：21  

邸佳颖  刘小粉  杜章留  肖小平  杨光立  任图生 《中国生态农业学报》2014,22(10):1129-1138

施用有机肥是提高土壤有机碳(SOC)含量、促进土壤团聚体形成和改善土壤结构的重要措施。本研究旨在探讨长期作物残留和投入有机物料对水稻土团聚体分布及稳定性的影响,分析不同粒级团聚体的固碳特征及其与团聚体形成的相关性,以及土壤和不同粒级团聚体对累积碳投入的响应。长期定位施肥试验始于1986年,设不施肥(CK)、单施化肥(CF)、秸秆化肥混施(RS)、低量粪肥配施化肥(M1)和高量粪肥配施化肥(M2)5个处理。2009年采集0~10 cm土壤样品,测定总土以及大团聚体(LM,2 mm)、较大团聚体(SM,0.25~2 mm)、微团聚体(MA,0.25~0.053 mm)和黏粉粒(SC,0.053 mm)的质量比例及其SOC浓度,并分析闭蓄于SM内部的颗粒有机物(POM)、微团聚体(MA-SM)和黏粉粒(SC-SM)的质量含量和SOC浓度。结果表明,与CK和CF比较,有机肥混施化肥处理(RS、M1和M2)均显著提高了LM和SM的质量比例和平均当量直径(MWD),降低了SC质量含量;两个粪肥配施化肥处理(M1和M2)的效果优于秸秆化肥混施(RS),但是M1和M2间差异不显著;单施化肥则降低了稳定性团聚体的比例。团聚体的SOC浓度没有随粒级增大而增加,各处理均为LM和SM结合的SOC浓度最高,其次为SC,最小为MA。与CK比较,有机肥混施化肥处理均显著提高了各粒级团聚体的SOC浓度。总土SOC的增加主要取决于SM的SOC含量,而MA-SM组分决定了SM固持SOC的能力。总土、LM和SM的SOC含量以及从SM分离出的POM、MA-SM和SC-SM的SOC含量均与累积碳投入量呈显著正相关,但总土分离出的MA和SC的SOC含量对累积碳投入量反应不敏感,表现出碳饱和迹象。因此,尽管长期大量施用有机物料促进了红壤性水稻土大团聚体的形成和团聚体稳定性,增加了其SOC的固持,但有机质可能不是该土壤水稳性团聚体形成的最主要黏结剂。  相似文献   

Variability in carbon sequestration potential in no-till soil landscapes of southern Ontario   总被引：7，自引：0，他引：7  

A. J. VandenBygaart  X. M. Yang  B. D. Kay  J. D. Aspinall 《Soil & Tillage Research》2002,65(2):231-241

Soil organic carbon (SOC) in Canadian agricultural soils plays an important role in the global cycle of C, and management can influence its fate. Although the scientific literature suggests that practicing no-till (NT) can sequester C, this is not always the case. Furthermore, there are many other factors including climate, management history, soil type and soil landscape processes that may affect the dynamics of SOC under NT. We measured the changes in SOC under NT in southern Ontario, at varying positions in the landscape in Gleyic and Orthic Luvisols at the end of a 15-year-period. Soil cores taken to depths beyond the solum, were segmented with depth, and total SOC was determined for each segment on an equivalent mass basis. When the entire soil column was considered, there was a loss of SOC in more profiles than there were gains. Furthermore, the erosion/deposition history at each landscape position appeared to influence the dynamics of SOC. In depression areas where A_p horizons were greater than 27 cm thick due to a history of soil deposition from upslope and local hydrology, there was a loss of total SOC after 15 years of NT. While where the A_p thickness was less than 27 cm, there were 18 profiles with SOC gains and 15 with net losses. Multiple linear regression analysis revealed that the change in SOC after 15 years was negatively related to the initial total SOC content and positively related to mass of clay. The results of this study suggest that landscape position and erosion/deposition history play a significant role in the ability of NT soils to sequester SOC. Interpretations of long-term SOC monitoring studies must take into account the location of samples within fields if useful information is to be gained on C dynamics in agricultural soils.  相似文献   

祁连山区成土过程驱动的土壤地形序列土壤有机碳固存特征          下载免费PDF全文

谷俊  杨飞  李德成  宋效东  张甘霖 《土壤》2023,55(4):871-879

土壤有机碳（SOC）含量和动态是有机碳输入输出平衡和土壤固持能力共同作用的结果，前者主要受生物气候条件控制，而后者则主要受黏粒及无机矿物等土壤理化属性的影响。本研究通过沿海拔梯度选择表土地形序列作为“自然试验场”，探究祁连山区SOC含量及组分变化的控制因素。研究发现：该地形序列土壤母质主要来源于黄土沉积，土壤黏土矿物以绿泥石和水云母为主，指示该区域的整体弱风化特征。在巨大的水热梯度影响下，地形序列内土壤成土强度差异明显，低海拔地区土壤含有碳酸盐，随着海拔上升，碳酸盐物质逐渐淋失，SOC和铁铝氧化物含量增加。进一步分析发现，铁铝氧化物是SOC含量及组分方差的主要解释变量。偏相关分析显示，当控制铁铝氧化物后，气候对SOC含量及组分的影响不显著。这表明气候对SOC的影响可能主要通过影响土壤属性，造成铁铝氧化物等属性的差异，间接影响SOC的长期固存，且该机制主要作用于矿物结合态有机碳（MOC）组分。本研究对理解SOC固存及其对气候变化的动态响应有重要启示。  相似文献   

The relative impact of land use and soil properties on sizes and turnover rates of soil organic carbon pools in Subtropical China     

H. Y. Qian  J. J. Pan  B. Sun 《Soil Use and Management》2013,29(4):510-518

The dynamics of soil organic carbon (SOC) pools determine potential carbon sequestration and soil nutrient improvement. This study investigated the characteristics of SOC pools in five types of cultivated topsoils (0–15 cm) in subtropical China using laboratory incubation experiments under aerobic conditions. The sizes and turnover rates of the active, slow and resistant C pools were simulated using a first‐order kinetic model. The relative influence of soil environmental properties on the dynamics of different SOC pools was evaluated by applying principal component analysis (PCA) and aggregated boosted trees (ABTs) analysis. The results show that there were significantly greater sizes of different SOC pools and lower turnover rates of slow C pool in two types of paddy soils than in upland soils. Land use exerted the most significant influence on the sizes of all SOC pools, followed by clay content and soil pH. The soil C/N ratio and pH were the major determinants for turnover rates of the active and slow C pools, followed by clay content which had more impact on the turnover rates of the active C pool than the slow C pool. It is concluded that soil type exerts a significant impact on the dynamics of SOC.  相似文献   

Organic carbon stocks in topsoil and subsoil in long-term ley and cereal monoculture rotations     

Gunnar?B?rjessonEmail authorView author&#;s OrcID profile  Martin?A.?Bolinder  Holger?Kirchmann  Thomas?K?tterer 《Biology and Fertility of Soils》2018,54(4):549-558

Soil organic C (SOC) in agricultural soils is affected by cropping system. In order to compare the impact of ley-dominated and cereal monoculture rotations on soil properties, a series of experiments was started in Sweden in the early 1980s. This study quantified the effect of rotations and N fertilisation on SOC stocks and microbial community composition. After 35 years, soil samples taken down to 50-cm depth at two sites with contrasting soil texture (clay and loam) were analysed for soil C and N, bulk density and phospholipid fatty acid (PLFA) content. Significant increases in SOC concentrations and stocks were found in the ley-dominated rotation compared with the cereal monoculture rotation, the difference being 0.36 and 0.59 Mg C ha^?1 year^?1 in the topsoil (0–20 cm) for sites with the clay and loam texture, respectively, in average over N fertiliser levels. Nitrogen fertilisation increased SOC stocks significantly in the cereal monoculture, but not in the ley-dominated rotation. In the loam, SOC responses in the subsoil were almost as high as those in the topsoil, but they were insignificant in the clay soil. These results indicate that soil texture and structure can have a great impact on the potential of subsoils to sequester C, which requires attention when scaling up SOC sequestration rates for regional or global assessments.  相似文献   

有机肥对棕壤不同粒级有机碳和氮的影响   总被引：3，自引：1，他引：3  

闫颖  HE Hong-bo  白震  XIE Hong-tu  张旭东 《土壤通报》2008,39(4)

采集棕壤长期肥料定位试验站不施肥和施用不同用量有机肥的土壤,通过超声波分散—离心分离得到细黏粒(<0.2μm)、粗黏粒(0.2～2μm)、粉粒(2～53μm)、细砂粒(53～250μm)和粗砂粒(250～2000μm)5个颗粒级别后,分析全土及不同粒级中土壤有机碳和氮并进行含量与分布的比较。结果表明,有机质主要分布于黏粒级中,其含量占全土有机碳的42.8%、全氮的58.3%,碳氮比随着粒级的增加而逐渐增大,表明氮易于在小粒级中富集。长期施用有机肥后,全土及各粒级有机碳和氮含量均有显著增加;砂粒级中有机碳和氮的富集系数升高,黏粒级中富集系数降低,粉粒级和砂粒级中的碳氮比降低。增加有机肥的用量加强了全土和各粒级对有机碳和氮的积累,同时加强了粉粒级和砂粒级碳氮比降低的程度。  相似文献   

Lability of soil organic carbon in tropical soils with different clay minerals     

Thilde Bech Bruun  Bo Elberling 《Soil biology & biochemistry》2010,42(6):888-895

Soil organic carbon (SOC) storage and turnover is influenced by interactions between organic matter and the mineral soil fraction. However, the influence of clay content and type on SOC turnover rates remains unclear, particularly in tropical soils under natural vegetation. We examined the lability of SOC in tropical soils with contrasting clay mineralogy (kaolinite, smectite, allophane and Al-rich chlorite). Soil was sampled from A horizons at six sites in humid tropical areas of Ghana, Malaysian Borneo and the Solomon Islands and separated into fractions above and below 250 μm by wet sieving. Basal soil respiration rates were determined from bulk soils and soil fractions. Substrate induced respiration rates were determined from soil fractions. SOC lability was significantly influenced by clay mineralogy, but not by clay content when compared across contrasting clay minerals. The lability of SOC was lowest in the allophanic and chloritic soil, higher in the kaolinitic soils and highest in the smectitic soil. Our results contrast with conventional concepts of the greater capacity of smectite than of kaolinite to stabilize SOC. Contents of dithionite-citrate-bicarbonate extractable Fe and Al were inversely related to SOC lability when compared across soil types. A stronger inverse correlation between content of ammonium-oxalate extractable Fe and SOC lability was found when considering the kaolinitic soils only and we conclude that the content of active Fe (hydr-) oxides controls SOC stabilization in the kaolinitic soils. Our results suggest that the validity of predictive models of SOC turnover in tropical soils would be improved by the inclusion of soil types and contents of Fe and Al (hydr-) oxides.  相似文献   

半干旱区县域农田土壤有机碳固存速率及影响因素——以甘肃庄浪县为例   总被引：1，自引：1，他引：0  

张晓伟  许明祥  师晨迪  邱宇洁 《植物营养与肥料学报》2012,18(5):1089-1098

通过对甘肃省庄浪县梯田土壤采样分析,结合第二次土壤普查及庄浪县耕地质量评价数据,估算梯田土壤固碳速率并分析其影响因素。结果表明: 1）该县农田土壤沟谷台地的有机碳含量最高,沟谷、 梁峁坡地次之,沟谷川坪地有机碳最低,不同地形有机碳含量差异显著（P0.05）; 2）80% 的样点土壤有机碳含量在6.0~11.0 g/kg之间,总体上020 cm农田土壤有机碳含量呈现正态分布,剖面有机碳含量从上至下呈逐渐递减规律; 3）现阶段庄浪县020 cm农田土壤有机碳密度为20.02 t/hm2,低于全国耕层土壤有机碳密度平均水平（33.45 t/hm2）,近30年020 cm 土壤固碳速率为C 63 kg /(hm2a),近5年固碳速率为 C 26 kg /(hm2a); 4）在半干旱区县域尺度上,地形部位可解释43%的有机碳变异性,有机肥、 坡向和田面坡度三者之和可解释47.1% 的有机碳变异性,土壤类型可解释9.9% 的有机碳变异性。综合分析表明,庄浪县农田土壤有机碳密度在过去30年间呈增加趋势,可能与庄浪县在60年代开始的大规模梯田建设和水土流失治理有关。  相似文献   

滇中不同植物群落对紫色土表层土壤碳、氮累积的影响   总被引：2，自引：0，他引：2  

艾锐  张国盛  李中杰  和树庄 《水土保持学报》2009,23(6)

通过连续观测2007-2008年滇中飒马场5种植物群落下紫色土表层土壤理化性质及碳、氮含量的旱雨季变化和层次分布特征,以揭示滇中不同植物群落对紫色土碳、氮累积效应的影响.研究结果表明:植物群落对表层土壤有机碳及其组分、全氮含量、pH及容重有显著的影响.云南松林表层土壤(0-20 cm)有机碳贮存量(24.9 t/ha)显著低于次生常绿阔叶林、桉树林和针阔混交林土壤的.不同植物群落表层土壤(0-20 cm)的全氮贮存量之间没有显著的差异.易氧化有机碳含量的变化是引起各植物群落表层土壤有机碳含量的呈现差异的主要原因.旱雨季变化对各土层易氧化有机碳及总有机碳含量、pH有明显的影响.表层土壤有机碳贮量与地表枯落物碳贮量变化特征之间表现出明显的滞后效应,且二者无显著相关性,表明地表枯落物可能不是影响土壤有机碳碳贮量季节变化的主要因素.  相似文献   

Dissolved and Soil Organic Carbon after Long‐Term Conventional and No‐Tillage Sorghum Cropping     

《Communications in Soil Science and Plant Analysis》2012,43(5-6):667-679

Abstract

Distribution of dissolved (DOC) and soil organic carbon (SOC) with depth may indicate soil and crop‐management effects on subsurface soil C sequestration. The objectives of this study were to investigate impacts of conventional tillage (CT), no tillage (NT), and cropping sequence on the depth distribution of DOC, SOC, and total nitrogen (N) for a silty clay loam soil after 20 years of continuous sorghum cropping. Conventional tillage consisted of disking, chiseling, ridging, and residue incorporation into soil, while residues remained on the soil surface for NT. Soil was sampled from six depth intervals ranging from 0 to 105 cm. Tillage effects on DOC and total N were primarily observed at 0–5 cm, whereas cropping sequence effects were observed to 55 cm. Soil organic carbon (C) was higher under NT than CT at 0–5 cm but higher under CT for subsurface soils. Dissolved organic C, SOC, and total N were 37, 36, and 66%, respectively, greater under NT than CT at 0–5 cm, and 171, 659, and 837% greater at 0–5 than 80–105 cm. The DOC decreased with each depth increment and averaged 18% higher under a sorghum–wheat–soybean rotation than a continuous sorghum monoculture. Both SOC and total N were higher for sorghum–wheat–soybean than continuous sorghum from 0–55 cm. Conventional tillage increased SOC and DOC in subsurface soils for intensive crop rotations, indicating that assessment of C in subsurface soils may be important for determining effects of tillage practices and crop rotations on soil C sequestration.  相似文献   

东北黑土有机碳的分布及其损失量研究   总被引：11，自引：0，他引：11  

梁爱珍  张晓平  杨学明  方华军  申艳  李文凤 《土壤通报》2008,39(3)

为了分析东北黑土土壤有机碳(SOC)的分布特征及其开垦以来黑土SOC的损失程度,我们于2004～2005年在黑龙江和吉林两省采集了32个自然黑土剖面样品,在每个自然黑土样品附近对应采集32个景观条件相似的耕作黑土样品。结果表明,自然黑土样品0～30cm土层SOC含量平均为32.20 g kg-1,最高可达63.46 g kg-1,黑龙江省自然黑土SOC含量(34.55 g kg-1)高于吉林省(23.80 g kg-1)。耕作土壤SOC平均含量为22.71 g kg-1,远低于自然土壤。受温度的影响,随着纬度的增加,自然黑土与耕作黑土SOC含量逐渐递增。由于土壤侵蚀以及耕垦和去除作物残留物等农业管理措施的综合作用,使得耕作黑土表层SOC含量小于自然黑土。与自然黑土相比,耕作黑土0～10cm土层SOC损失量在26.84%～46.57%之间,亚表层损失相对较少。黑土SOC含量下降也是土壤水土流失致使黑土层变薄的一个直接表现。耕作黑土表层流失厚度可以通过自然与耕作黑土剖面SOC含量的分异差值来估算。通过对土壤剖面上SOC的分布进行校正剔除土壤侵蚀的影响后得到的同等深度SOC含量的差值才可视为由耕作以及有机质输入量差异等因素造成的SOC损失量。未经校正而进行的自然黑土和耕作黑土同一深度SOC含量的比较可能过高估计了农业管理措施对土壤SOC损失量的影响。  相似文献   

Extractable lipid contents and colour in particle-size separates and bulk arable soils     

G. L. B. Wiesenberg    L. Schwark  & M. W. I. Schmidt 《European Journal of Soil Science》2006,57(5):634-643

Chemical alteration of plant biomass to soil organic matter is often accompanied by characteristic trends, e.g. with decreasing particle size and increasing depth organic carbon and nitrogen concentrations and stable carbon isotope values (δ¹³C) often increase. In agricultural soils, systematic studies of soil organic carbon (SOC) distribution in bulk soils and particle‐size separates of depth profiles are scarce. In this study, three soil profiles from one site with different monoculture crops were analysed for organic carbon and nitrogen concentrations, stable carbon isotopes, bulk extractable lipids, and soil colour. In contrast to most previous observations, stable carbon isotope values were constant over soil depth and within particle‐size separates, probably as a result of little biomass input due to the harvesting techniques applied and the presence of fossil carbon. Bulk extractable lipids contributed 1–10% to the total SOC. Significantly more lipids could be extracted from rye‐ than from maize‐derived SOC. Lipid yields normalized to soil mass increased with decreasing particle size and decreased with depth. When normalized to organic carbon concentration, sand‐size fractions had the largest lipid yields. Soil colour, expressed as Munsell values, was lightest in sand‐ and silt‐size separates. A cross‐plot of Munsell values and their SOC concentrations revealed characteristic, non‐overlapping areas for each particle‐size class and the bulk soils. Clay‐size separates and bulk soils were almost identical in Munsell values, although for clay‐size separates SOC concentrations were much larger than for bulk soils. Thus, the SOC‐rich clay‐size separates exerted the dominant influence on the colour of the bulk soils. Determination of colour and extractable lipid contents could be useful additional parameters for soil characterization.  相似文献   

Organic matter turnover in soil physical fractions following woody plant invasion of grassland: Evidence from natural C and N     

J.D. Liao  J.D. Jastrow 《Soil biology & biochemistry》2006,38(11):3197-3210

Soil physical structure causes differential accessibility of soil organic carbon (SOC) to decomposer organisms and is an important determinant of SOC storage and turnover. Techniques for physical fractionation of soil organic matter in conjunction with isotopic analyses (δ¹³C, δ¹⁵N) of those soil fractions have been used previously to (a) determine where organic C is stored relative to aggregate structure, (b) identify sources of SOC, (c) quantify turnover rates of SOC in specific soil fractions, and (d) evaluate organic matter quality. We used these two complementary approaches to characterize soil C storage and dynamics in the Rio Grande Plains of southern Texas where C₃ trees/shrubs (δ¹³C=−27‰) have largely replaced C₄ grasslands (δ¹³C=−14‰) over the past 100-200 years. Using a chronosequence approach, soils were collected from remnant grasslands (Time 0) and from woody plant stands ranging in age from 10 to 130 years. We separated soil organic matter into specific size/density fractions and determined their C and N concentrations and natural δ¹³C and δ¹⁵N values. Mean residence times (MRTs) of soil fractions were calculated based on changes in their δ¹³C with time after woody encroachment. The shortest MRTs (average=30 years) were associated with all particulate organic matter (POM) fractions not protected within aggregates. Fine POM (53-250 μm) within macro- and microaggregates was relatively more protected from decay, with an average MRT of 60 years. All silt+clay fractions had the longest MRTs (average=360 years) regardless of whether they were found inside or outside of aggregate structure. δ¹⁵N values of soil physical fractions were positively correlated with MRTs of the same fractions, suggesting that higher δ¹⁵N values reflect an increased degree of humification. Increased soil C and N pools in wooded areas were due to both the retention of older C₄-derived organic matter by protection within microaggregates and association with silt+clay, and the accumulation of new C₃-derived organic matter in macroaggregates and POM fractions.  相似文献