麦秸秆全量还田对稻田土壤溶解有机碳含量和水稻产量的影响

以南粳44为供试材料,在粘土和砂土土壤中,设置麦秸秆不还田和全量还田(6000kg·hm-2)及3种施氮量(0、225、300 kg·hm-2)试验,研究了麦秸秆全量还田的腐解率和有机碳释放量动态变化,及其对稻田0~45 cm土壤溶解有机碳(DOC)含量和水稻产量的影响.结果表明:麦秸秆还田的前期(0~30 d)其腐解率和有机碳释放量最高,腐解率为35.0%(粘土)和31.7%(砂土),有机碳释放率为34.1%(粘土)和33.1%(砂土);30 d后两者均减小.施用氮肥可显著促进秸秆腐解和有机碳释放量,粘土中麦秸秆腐解率和有机碳释放量明显大于砂土.麦秸秆还田后土壤DOC含量逐渐增加,至25 d达最大值,粘土和砂土分别为60.18和56.62 mg·L-1,此后逐渐减小并趋于稳定.麦秸秆还田处理15 cm处土壤DOC含量显著高于未还田处理,但两者在30和45 cm处土壤DOC含量差异不显著,说明秸秆还田主要增加了稻田0~15 cm土层DOC含量.与不施氮处理相比,施氮处理土壤DOC含量降低,2种施氮处理间差异不显著.秸秆还田减少了水稻前期分蘖发生量,显著降低了有效穗数,增加了穗粒数、结实率和千粒重,显著提高了水稻产量.     

广东省主要母质发育水稻土对磷的吸附特性

对广东省5种不同母质上发育的水稻土进行了P素等温吸附试验.结果表明,供试土壤的等温吸附数据与Langmuir、Freundlich和Temkin 3个方程都能很好地拟合,但以Langmuir方程拟合程度最好(相关系数从0.995^**到0.999^**).利用Langmuir方程计算的P最大吸附量(Xm)和吸附强度因子(K)的乘积(KXm:P吸附特性值)可以作为水稻土吸附P素的综合指标,KXm的大小可以表明水稻土施P次序.试验结果还表明供试水稻土对P素吸附存在两种不同的吸附区.     

可溶性有机碳在米槠天然林不同土层中的迁移特征

选取我国中亚热带典型的常绿阔叶林米槠天然林(Castanopsis carlesii)为研究对象,采集林内米槠凋落物并通过挖剖面法分6个土层采集土样至1m。通过浸提米槠凋落物得到可溶性有机碳(dissolved organic carbon,DOC)溶液并在室内模拟其在不同土层的淋溶过程,不仅分析了土壤性质对DOC淋溶的影响,还研究了淋溶前后DOC化学结构的变化,以阐明DOC在不同土层中的迁移特征及影响因素,探寻米槠天然林土壤的固碳潜力和DOC在土壤有机碳循环中的作用。结果表明:(1)下层土壤比上层土壤吸附DOC的能力更强,亲水性DOC与疏水性DOC间会争夺土壤颗粒表面的吸附位点,而且芳香化合物和大分子物质等疏水性DOC组分会被优先吸附;(2)红外光谱表明,芳香类和醚类等疏水性物质会优先被吸附,烷烃类物质却不易被吸附,土壤中原有的酚、醇类亲水性物质会被初始DOC中的疏水性物质置换出来;(3)土壤DOC的截留能力与粘粒、游离氧化铁含量呈极显著正相关,而与土壤有机碳和砂粒含量呈极显著负相关,其中土壤有机碳的含量是影响米槠天然林不同土层DOC截留量的关键因素。     

秸秆全量还田对稻田土壤溶解有机碳含量和水稻产量的影响

以南粳44为供试材料,在粘土和砂土土壤中,设置麦秸秆不还田和全量还田(6000 kg·hm^-2)及3种施氮量(0、225、300 kg·hm^-2)试验,研究了麦秸秆全量还田的腐解率和有机碳释放量动态变化,及其对稻田0～45 cm土壤溶解有机碳(DOC)含量和水稻产量的影响.结果表明： 麦秸秆还田的前期(0～30 d)其腐解率和有机碳释放量最高,腐解率为35.0%(粘土)和31.7%(砂土),有机碳释放率为34.1%(粘土)和33.1%(砂土);30 d后两者均减小.施用氮肥可显著促进秸秆腐解和有机碳释放量,粘土中麦秸秆腐解率和有机碳释放量明显大于砂土.麦秸秆还田后土壤DOC含量逐渐增加,至25 d达最大值,粘土和砂土分别为60.18和56.62 mg·L^-1,此后逐渐减小并趋于稳定.麦秸秆还田处理15 cm处土壤DOC含量显著高于未还田处理,但两者在30和45 cm处土壤DOC含量差异不显著,说明秸秆还田主要增加了稻田0～15 cm土层DOC含量.与不施氮处理相比,施氮处理土壤DOC含量降低,2种施氮处理间差异不显著.秸秆还田减少了水稻前期分蘖发生量,显著降低了有效穗数,增加了穗粒数、结实率和千粒重,显著提高了水稻产量.     

长期植稻年限序列水稻土团聚体有机碳分布特征

通过开展有机质物理分组试验,研究了杭州湾南岸不同植稻年限序列水稻土有机碳含量的粒级分布变化特征.结果表明: 各植稻年限耕层水稻土中,土壤团聚体主要分布在微团聚体(<0.25 mm)中,其中大微团聚体(0.053～0.25 mm)随着植稻年限的增加而减少;在微团聚体(0.053~0.25 mm,<0.053 mm)中,有机碳含量随着植稻年限的增加而增加,在0.053～2 mm粒径范围内,各粒级有机碳占总有机碳比例随着粒级的减小而增加,有机碳主要集中在大微团聚体(0.053～0.25 mm)中;随着种植年限的增加,颗粒有机碳含量减少.栽培年限长的水稻土比栽培年限短的水稻土碳封存量大,早期开垦的水稻土仍有很大的固碳潜力.     

长期植稻年限序列水稻土团聚体有机碳分布特征

通过开展有机质物理分组试验,研究了杭州湾南岸不同植稻年限序列水稻土有机碳含量的粒级分布变化特征.结果表明: 各植稻年限耕层水稻土中,土壤团聚体主要分布在微团聚体(<0.25 mm)中,其中大微团聚体(0.053～0.25 mm)随着植稻年限的增加而减少;在微团聚体(0.053~0.25 mm,<0.053 mm)中,有机碳含量随着植稻年限的增加而增加,在0.053～2 mm粒径范围内,各粒级有机碳占总有机碳比例随着粒级的减小而增加,有机碳主要集中在大微团聚体(0.053～0.25 mm)中;随着种植年限的增加,颗粒有机碳含量减少.栽培年限长的水稻土比栽培年限短的水稻土碳封存量大,早期开垦的水稻土仍有很大的固碳潜力.     

可溶性有机碳在土壤剖面淋溶过程中的分馏

选取中亚热带两种不同类型土壤为研究对象,采集0～10、10～20、20 ～ 40、40～60、60～80、80～ 100 cm土层土壤样品,提取米槠新近凋落物的可溶性有机碳(DOC)溶液为初始DOC,研究其在土样中淋溶时的分馏现象和截留特征.结果表明:初始DOC在土柱中淋溶时,其浓度随深度增加呈逐层下降的趋势,而且化学结构更为简单,被土壤截留的DOC中主要是疏水性组分,但随着土层深度增加,亲水性DOC的截留量呈上升趋势;红外光谱显示含有芳环的疏水性物质最易被吸附,而烷烃和简单的碳水化合物则最有可能随土壤溶液进入下层土壤;由于到达下层土壤的DOC中易被吸附组分含量的减少,限制了其吸附能力的发挥,因此主要的吸附过程发生在40 cm以上土层,表明DOC本身的化学性质比土壤性质更能影响其吸附行为;不同类型土壤的截留量具有显著差异,这与土壤黏粒和铁铝氧化物的含量呈显著正相关.     

长期施肥下红壤性水稻土有机碳储量变化特

研究了1982—2012年长期不同施肥下红壤性水稻土土壤有机碳含量变化、固碳趋势及外源碳输入对土壤固碳的贡献.结果表明： 施肥能提高土壤有机碳含量,连续30年不同施肥后,各施肥处理土壤有机碳含量趋于稳定,有机无机配施的土壤有机碳含量为21.02～21.24 g·kg^-1,增加速率为0.41～0.59 g·kg^-1·a^-1,单施化肥的土壤有机碳含量为15.48 g·kg^-1.各有机无机肥配施处理土壤的平均有机碳储量为43.61～48.43 t C·hm^-2,历年平均土壤有机碳储量显著大于单施化肥处理.土壤固碳速率与年均投入碳量呈显著指数正相关.本试验条件下,每年需要增加外源有机碳为0.12 t C·hm^-2才能维持土壤有机碳的平衡.     

外源有机质对土壤中菲的增强固定作用

从吸附、解吸、可萃取态残留变化3个方面,研究了外源有机质对粘壤土、砂粉土和粉壤土中菲的增强固定作用.外源有机质为有机商品肥和泥炭.结果表明,施加外源有机质后,供试土壤对菲的吸附等温线仍呈线性,分配作用为土壤吸附菲的主导机制.有机商品肥或泥炭能显著促进供试土样对菲的吸附.施加同量的外源有机质,土壤吸附菲的Kd值的增加幅度与土壤有机碳含量（foc）成正比,表明土壤的foc越大,外源有机质对菲吸附的促进效果越好.解吸实验表明,施加外源有机商品肥或泥炭能够抑制土壤中菲的解吸,解吸量显著低于原土.经64d培养,施加外源有机质的3种土壤中的可萃取态残留菲含量降低;由于泥炭的有机质含量高于有机商品肥,施加泥炭的土样中可萃取态残留菲的降幅更大;原土的foc越高,外源有机质对菲可萃取性的抑制效果越明显.可见,施加外源有机质可增强土壤中菲的吸附固定、抑制其解吸、并降低其可萃取态残留.     

改变施肥管理后不同肥力稻田土壤CO2排放特征

利用一个长达30a水稻土长期定位试验,在保证原有定位试验继续正常开展的前提下,将原化肥处理改施有机肥,原有机肥处理改施化肥或者增施有机肥。通过观测田间试验2012—2013年双季稻轮作周期内不同肥力水平稻田土壤施肥管理改变后的土体CO2排放通量(FCO2),研究不同后续施肥管理对不同肥力红壤性水稻土CO2排放的影响。结果表明:变更施肥能明显改变CO2排放动态变化,其中长期施用有机肥处理改施化肥后其FCO2明显减小,长期施用化肥或有机肥处理增施有机肥后其FCO2显著增大。有机肥和土壤有机碳均可促进土体CO2排放,有机肥处理有机物料碳添加量与CO2-C年排放量呈极显著的正相关关系(r=0.9015**,n=21),单施化肥处理土壤有机碳含量与土体CO2-C年排放量符合线性方程:y=10.962x-68.86(R2=0.7507,n=9,P0.01)。长期施用有机肥土壤改施化肥会导致其有机碳矿化损失,土壤有机碳含量越高,矿化损失量越多,最终其有机碳水平将与长期施用化肥的土壤有机碳平衡值一致;长期施用化肥或有机肥土壤改施或增施有机肥可促进土壤有机碳积累,外源添加碳越多,土壤积累碳越多;相同有机肥施用量下土壤有机碳含量越高,有机物料表观分解率越大,积累于土壤中的有机碳越少,不同有机碳水平土壤在相同有机肥管理下其有机碳最终会达到相同的平衡值。在有机碳水平较低(20.46 g/kg)红壤稻田上增施有机肥是提升已培肥水稻土有机碳含量的可持续发展措施,而在有机碳水平较高(14.45 g/kg)红壤稻田上应避免改施化肥。总之,在有机碳含量较高或者较低的中国南方红壤性水稻土上,持续的有机肥施用是保持或者提高其有机碳水平的必要措施。     

Concentration and composition of dissolved organic carbon in streams in relation to catchment soil properties

Two adjacent catchments in the Otway Ranges of Victoria, Australia (Redwater and Clearwater) produce water with markedly different concentrations of dissolved organic carbon (DOC) during summer. Water from Redwater Creek had a DOC concentration of 32 mg L^–1, while water from Clearwater Creek had a DOC concentration of 3.8 mg L^–1. Examination of the catchments revealed that while climate, topography, vegetation and land use were similar, the soils were different. The objective of this study was to examine the relationship between the concentration and chemical composition of DOC in stream waters and the nature of soils in the two catchments. Soil mapping determined that clayey soils formed on Cretaceous sediments (Cretaceous soils) occurred throughout both catchments, but that Redwater Catchment also contained a large area (39%) of sandy soils formed on Tertiary sediments (Tertiary soils). The concentration of DOC in forest floor leachate was high in both the Tertiary and Cretaceous areas; however, the concentration of DOC in water draining areas dominated by Tertiary soils was greater than that in water draining areas dominated by Cretaceous soils. Laboratory experiments showed that the Cretaceous soils had higher adsorption capacities for forest floor leachate DOC than the Tertiary soils. The difference in DOC concentrations of the streams was therefore attributed to the difference in adsorption capacity of catchment soils for DOC. Adsorption capacities of the soils were found to be a function of their clay contents and specific surface areas.Solid-state³C nuclear magnetic resonance spectroscopy and pyrolysis-mass spectrometry were used to determine the chemical structure of DOC found in streams and forest floor leachate samples and that remaining in solution after interaction with soil. Chemistry of DOC in forest floor leachate was similar before and after interaction with soil, indicating no preferential adsorption of a particular type of carbon. Thus, differences between the chemical structure of stream DOC and forest floor leachate DOC could be attributed to microbial modifications during its movement through soils and into the streams, rather than losses by adsorption.     

不同粒径红壤胶体颗粒对DNA的吸附特性

采用平衡法研究了含有机质粗粘粒、去有机质粗粘粒、含有机质细粘粒和去有机质细粘粒4种红壤胶粒对DNA的吸附特征及其热力学特性.结果表明: 4种红壤胶粒对DNA的吸附是快反应过程,Langmuir吸附方程可较好地描述4种红壤胶体对DNA的等温吸附,相应拟合的相关系数r²分别为0.974、0.991、0.958和0.975.最大吸附量表现为含有机质细粘粒>去有机质细粘粒>含有机质粗粘粒>去有机质粗粘粒.电解质浓度和种类及吸附体系pH是影响红壤胶体对DNA吸附的重要因子,一定电解质浓度范围(NaCl<60 mmol·L^-1,CaCl₂<10 mmol·L^-1)内,DNA在红壤胶体表面的吸附量随电解质浓度的增大而显著增加,其中钙离子的促进作用大于钠离子,但随着吸附体系pH的上升而显著降低.含有机质胶粒对DNA的吸附过程是吸热反应,而去有机质胶粒对DNA的吸附过程是放热反应,红壤胶粒对DNA的吸附反应过程是一个熵增过程.     

水溶性有机质对土壤吸附菲的影响

研究了来源于稻草腐熟物的外源水溶性有机质(DOM)和土壤本身固有的内源DOM对有机碳含量不同的3种土壤吸附菲的影响.结果表明,不同处理土壤对菲的吸附曲线均为线性,其吸附系数(K_d)与土壤有机碳含量(f_oc)正相关.去除内源DOM后,黄棕壤、红粘田和黑土吸附菲的K_d值增加了7.08%～21.4%,增加量(ΔK_d)和增加幅度与f_oc正相关,表明土壤中存在的内源DOM抑制土壤对菲的吸附.而外源DOM对土壤吸附菲的影响与其浓度密切相关.在供试浓度范围(0～106 mg DOC·L^-1)内,红粘田吸附菲的K_d值随加入外源DOM浓度的提高先增大后减小.外源DOM浓度为28 mg DOC·L^-1时,红粘田吸附菲的K_d值增加了19.5%;而当外源DOM浓度≥52 mg DOC·L^-1时,则明显抑制菲的吸附.内源和外源DOM对土壤吸附菲的影响,主要与DOM和菲在溶液中的结合作用、在土壤中的累积吸附效应等有关.     

Contribution of organic carbon and clay to cation exchange capacity in a chronosequence of sandy soils

Summary CEC and oxidisable carbon content were highly correlated (r=0.96) whereas a lower coefficient was obtained for a correlation of CEC and clay content (r=0.57) in a chronosequence of sandy soils from New Zealand. Partial regression coefficients for oxidisable carbon were highly significant in multiple regression equations for all soil groupings whereas in only one equation was the coefficient for clay significant. The CEC of the organic matter for all soils was 1.4 me/g and this value decreased from 1.64 me/g in the young soils to 1.22 me/g in old soils. Peroxidation of selected surface samples caused a reduction in CEC but the results indicated that the clay fractions had a considerably higher CEC (0.57 me/g) than that inferred from multiple regression equations for untreated samples. Selective dissolution analysis indicated that the clay fractions of these soils contained an appreciable amount of amorphous material. Reduction in the CEC of the clay fraction apparently occurs through a blocking by organic matter of the negative charge of the clay components.     

The retention of organic matter in soils

The turnover of C in soils is controlled mainly by water regimes and temperature, but is modified by factors such as size and physicochemical properties of C additions in litter or root systems, distribution of C throughout the soil as root systems, or addition as litter, distribution of C within the soil matrix and its interaction with clay surfaces.Soil factors which retard mineralization of C in soils are identified from correlations of C contents of soils with other properties such as clay content and base status. The rate and extent of C mineralization depends on the chemistry of the added organic matter and interaction with clays of the microbial biomass and metabolites.The organomineral interactions are shown to depend on cation bridges involving mainly Ca in neutral to alkaline soils, Al in acid soils and adsorption of organic materials on iron oxide surfaces. The various organomineral interactions lead to aggregations of clay particles and organic materials, which stabilizes both soil structure and the carbon compounds within the aggregates.     

土壤活性有机质及其与土壤质量的关系

活性有机质是土壤的重要组成部分 ,主要包括溶解性有机碳、微生物生物量、轻组有机质。它在土壤中具有重要作用 :(1)可以表征土壤物质循环特征、评价土壤质量 ,可以作为土壤潜在生产力以及由土壤管理措施引起土壤有机质变化的早期指标 ;(2 )在养分周转中起重要作用 ,是植物的养分库 ,可以提供植物所需要的养分如氮、磷、硫等 ;(3)能稳定土壤结构 ,对维持团粒结构稳定性有重要作用。从土壤养分、土壤物理、化学性质方面讨论了活性有机质与土壤质量的关系。土壤中的溶解性有机碳、微生物生物量碳氮含量与土壤有机碳、全氮和碱解氮等物质的含量呈正相关。活性有机质受土壤质地、含水量、温度等因素影响 ,与土壤酸碱度、阳离子交换量等也有关。土壤微生物生物量碳和微生物量 C/有机碳比与土壤粘粒、粉粒含量呈正相关、与砂粒含量呈负相关     

Potential effects of climate change on DOC release from three different soil types on the Northern Pennines UK: examination using field manipulation experiments

Three field manipulation experiments were carried out during 1993–1995 on the Northern Pennines to investigate the influences of temperature, solar radiation and rainfall on the release of dissolved organic carbon (DOC) from vegetated soil cores using zero‐tension lysimeters. The cores were manipulated by being translocated to four sites down a climatic gradient, by artificial soil heating or being exposed to double normal rainfall. In each experiment three soil types, a brown earth, a micropodzol and a peaty gley, with differing organic matter content and distribution within the profile, were studied. DOC data, expressed as mg C m^?2 day^?1, were analysed following log₁₀ transformation, by a repeated measures analysis of variance procedure, using climatic variables measured concurrently with sampling, and 1 and 2 months before sampling. DOC release was dominated by rainfall but was also associated with solar radiation and temperature. With each of the three climatic variables, rainfall, solar radiation and temperature, both positive and negative effects on DOC release have been found significant, indicating that the concurrent and delayed effects of the same variable may be different. DOC release was positively related with all three soils to concurrent rainfall, indicating rainfall's primary leaching action. DOC release was also negatively related to rainfall of the previous month indicating that its action depletes the leachable pool of DOC in the soil. DOC release was positively associated with solar radiation 2 months earlier, indicating that DOC's main source is that of primary production; DOC peaks closely followed peaks of annual primary production. DOC release was linked with temperature, the strongest association being with temperature 2 months earlier, indicating that temperature effects both primary production and DOC regeneration via organic matter decomposition. A conceptual model, relating our findings to those processes known to govern DOC release from soils, has been presented.     

不同土地利用类型下土壤活性有机碳库的变化

分析了中国科学院沈阳生态试验站不同土地利用类型长期定位试验土壤0～40cm活性有机碳含量,结果表明:0～20cm土层内荒地土壤有机碳、易氧化碳、微生物生物量碳、溶解性有机碳和轻组有机碳含量高于割草地和裸地,而割草地颗粒有机碳含量略高于荒地;在20～40cm土层,割草地土壤有机碳、易氧化碳和颗粒有机碳含量较高,而荒地微生物量碳、溶解性有机碳和轻组有机碳含量较高。不同土地利用类型土壤活性有机碳含量均随着土层加深而递减。土壤微生物量碳、溶解性有机碳和轻组有机碳的分配比例为荒地>割草地>裸地,易氧化碳和颗粒有机碳的分配比例为割草地>荒地>裸地。土壤活性有机碳的分配比例随土层加深而下降,但溶解性有机碳的分配比例变化趋势相反。     

外源有机质对土壤中菲的增强固定作用

从吸附、解吸、可萃取态残留变化3个方面,研究了外源有机质对粘壤土、砂粉土和粉壤土中菲的增强固定作用.外源有机质为有机商品肥和泥炭.结果表明,施加外源有机质后,供试土壤对菲的吸附等温线仍呈线性,分配作用为土壤吸附菲的主导机制.有机商品肥或泥炭能显著促进供试土样对菲的吸附.施加同量的外源有机质,土壤吸附菲的K_d值的增加幅度与土壤有机碳含量(f_oc)成正比,表明土壤的f_oc越大,外源有机质对菲吸附的促进效果越好.解吸实验表明,施加外源有机商品肥或泥炭能够抑制土壤中菲的解吸,解吸量显著低于原土.经64 d培养,施加外源有机质的3种土壤中的可萃取态残留菲含量降低;由于泥炭的有机质含量高于有机商品肥,施加泥炭的土样中可萃取态残留菲的降幅更大;原土的f_oc越高,外源有机质对菲可萃取性的抑制效果越明显.可见,施加外源有机质可增强土壤中菲的吸附固定、抑制其解吸、并降低其可萃取态残留.