Modification of soil aggregation by watering regime and roots growing through beds of large aggregates

The influence of root growth and soil watering regime on aggregation was studied under controlled conditions. The study examined the influence of pea (Pisum sativum cv Greenfeast), ryegrass (Lolium rigidum cv Wimmera) and wheat (Triticum aestivum cv Kite) roots on changes in aggregation and on the properties of the aggregates. The soil was a non swelling red-brown earth which was either kept wet or was allowed to wet and dry during the experiment. Root growth increased the percentage of small sized aggregates (<18 mm diameter), organic carbon, tensile strength and stability of aggregates in comparison with a non planted soil. Changes in aggregate size distribution and properties of the aggregates were related to root length density of the species and also to the soil watering regime. Root length density was in the order ryegrass>pea>wheat. Wetting and drying of soil increased the strength and stability of aggregates. Incubating aggregates allowed some roots to decompose but did not increase the strength or stability of aggregates compared with unincubated soil. The results of this experiment are of practical significance in soil structural management, and in studies of soil aggregation dynamics. It may be possible to use plant roots to alter the size and properties of aggregates.     

陇东雨养苹果覆膜对土壤团聚体结构稳定性与细根分布的影响

不同的果园管理方式可影响果树根系生长、分布与土壤团聚体稳定性、有机碳固存,进而改变“根-土”复合体响应关系。对西北陇东旱塬不同覆膜年限(2 a、4 a和6 a)苹果园表层土壤(0—20 cm)细根生长进行调查,并采用干筛法和湿筛法相结合的方式对土壤团聚体进行分级(>2 mm, 0.5—2 mm, 0.25—0.5 mm和<0.25 mm)。计算团聚体稳定性参数[> 0.25 mm机械稳定性团聚体含量(DR_0.25)、> 0.25 mm水稳性团聚体含量(WR_0.25)、平均重量直径(MWD)、平均几何直径(GMD)、团聚体破坏率(PAD)、水稳系数(WSC)]和团聚体有机碳含量。分析细根生长与土壤物理结构对长期覆膜的响应,探明土壤团聚体稳定性与有机碳固持关系,揭示黄绵土物理结构稳定机制。结果表明：6 a处理通过增加表层土壤黏粒和物理性黏粒比例,改变孔隙结构,抑制细根生长,其根量、根长和根表面积仅为对照(CK)的20.97%、24.66%和41.25%;降低表层土壤团聚体力稳性,其DR_0.25、机械稳...     

The porosity of soil aggregates from bulk soil and from soil adhering to roots

Summary Total porosity and pore-size distribution (p.s.d.) were determined in soil aggregates taken in plots planted with maize and treated with farmyard manure and three rates of compost. Soil aggregates were collected from the soil adherent to the maize roots (root soil aggregates) and from bulk soil (bulk soil aggregates). Mercury intrusion porosimetry was used to evaluate the total porosity and the p.s.d. Treatments did not affect the total porosity of the bulk soil aggregates. The same was observed for the root soil aggregates. However the total porosity of the root soil aggregates was always lower than that of the bulk soil aggregates. The loss of total porosity was found to be due to a decrease in the percentage of larger pores with respect to the total.     

固氮树种马占相思对巨尾桉人工林土壤团聚体粒径分布及稳定性的影响

土壤团聚体稳定性是评价土壤结构和土壤肥力的重要指标。为探究固氮树种马占相思对巨尾桉人工林土壤团聚体粒径分布及稳定性的影响,该文以17年生的巨尾桉纯林(PP)与巨尾桉/马占相思(固氮树种)混交林(MP)为研究对象,采用干筛法和湿筛法分别测定0～10 cm和10～20 cm土层团聚体粒径分布及平均重量直径(MWD)、几何平均直径(GMD)、分形维数(Dm)、水稳定性团聚体含量(WSA)、团聚体破坏率(PAD)和团聚体稳定性指数(ASI)等稳定性指标。结果表明:(1)与PP相比,MP的土壤理化性质有不同程度的提升,其中以土壤pH、有机碳(SOC)及全氮(TN)最为显著。(2)MP的土壤团聚体粒径分布优于PP,差异主要体现在>2.00 mm和<0.25 mm粒径中,均以大团聚体(>0.25 mm)为主; 相较于PP,MP的土壤团聚体机械稳定性仅在0～10 cm土层显著提高,但其团聚体水稳定性在0～10 cm和10～20 cm土层均显著提高。(3)Mantel分析结果显示团聚体稳定性与TN相关性最强,通过RDA分析进一步说明TN是驱动其团聚体稳定性变异的最关键因子。综上认为,固氮树种马占相思对巨尾桉人工林土壤团聚体稳定性具有明显改善作用,该研究结果为南亚热带桉树人工林水土保持、养分管理及可持续经营等提供了科学的理论依据。     

Effects of legumes on soil physical quality in a maize crop

The effect of intercropped legumes and three N fertilizer rates in a continuous maize (Zea mays L.) cropping system on the physical properties of two soils were investigated for three years. The legumes, being a mixture of alfalfa, clover and hairy vetch, had a significant cumulative effect on some physical properties of both soil. The lowest stability and smallest mean weight diameter of soil aggregates were associated with monoculture maize plots. Aggregate size and stability were not affected by N fertilization at any of the rates of 0, 70, and 140 kg ha^-1 in intercropped plots, except that aggregate stability was actually reduced by N fertilization in one soil, the Ste. Rosalie clay. In maize plots in both soils, stability and size of soil aggregates were significantly increased with increased added N. Intercropped legumes significantly decreased dry bulk density and soil penetration resistance. Added N had no measurable influence on these compaction factors. Soil water properties were not significantly affected by either intercropping or N fertilization. Positive effects noted on soil aggregation and other physical properties in intercropped plots are the result of enhanced root activity, or incorporation of legumes as green manure, or both. Improvement of soil structure in maize plots associated with increasing N application was the result of increased maize-root residues.     

秦岭天然林凋落物去除对土壤团聚体稳定性及细根分布的影响

研究凋落物去除对秦岭天然林土壤团聚体稳定性及细根分布特征的影响机制,为森林生态治理提供理论依据。结果表明:(1)凋落物去除导致云杉林10-40 cm土层土壤中粒径大于0.25 mm水稳性团聚体含量(WR_0.25)较对照显著降低(P<0.05);混交林10-40 cm土层的大于0.25 mm机械稳定性团聚体含量(DR_0.25)显著降低(P<0.05);红桦林表层0-10 cm土壤团聚体的平均质量直径(MWD)显著降低(P<0.05);(2)凋落物去除导致三种天然林0-20 cm土层的细根生物量密度(FRBD)较对照显著降低44.18%-57.24%,细根体积(FRV)显著降低24.64%-60.41%;三种天然林中红桦林0-40 cm各土层的FRV最高;(3)凋落物去除导致云杉林0-40 cm土层的土壤容重较对照显著增加5.24%-13.04%,三种天然林0-40 cm土层的土壤有机碳含量显著降低7.92%-25.21%,全氮含量显著降低10.17%-18.10%;(4)相关分析表明,云杉林土壤的团聚体破坏率(PAD)和土壤不稳定团粒指数(E_LT)与FRBD、细根根长密度(FRLD)和FRV均呈极显著负相关,混交林土壤的PAD与FRBD呈极显著负相关关系(r=-0.814),红桦林土壤团聚体MWD与FRBD、FRLD和细根比根长(FSRL)均呈显著负相关关系(r=-0.777、-0.771和-0.786)。综上,凋落物去除在总体上降低了天然林土壤团聚体的稳定性及有机碳和全氮含量,并且不利于林木细根的生长。     

黄土高原天然次生林植被演替过程中土壤团聚体有机碳动态变化

土壤团聚体物理保护是促进有机碳积累主要机制之一。以黄土高原子午岭林区天然次生林植被演替群落为对象,研究从农田、草地（白羊草,Bothriochloa ischaemum）、灌木林（沙棘,Hippophae rhamnoides）、先锋林（山杨,Populus davidiana）到顶级林（辽东栎,Quercus liaotungensis）5个植被演替阶段0-20 cm土壤团聚体稳定性和团聚体有机碳的动态变化,并分析团聚体有机碳的影响因素。结果表明：土壤团聚体稳定性随着植被演替显著提高（P<0.05）,顶级林的团聚体稳定性最高;土壤有机碳含量和各粒径土壤团聚体（> 2 mm、2-0.25 mm、0.25-0.053 mm、<0.053 mm）有机碳含量均随着植被演替而增加。除草地0.25-0.053 mm团聚体有机碳含量最高外,其他演替阶段均为0.25-2 mm粒径最高。根系生物量、凋落物生物量、微生物生物量碳、团聚体稳定性均与团聚体有机碳含量呈显著正相关关系（P<0.05）。总体而言,长期植被演替有助于团聚体稳定性和团聚体有机碳累积。     

马尾松人工林土壤各粒径团聚体湿筛后的有机碳分配

选取25a、45a和65a马尾松人工林为研究对象,采用湿筛法对各粒径土壤团聚体分别湿筛。探究了马尾松人工林各粒径团聚体湿筛后的团聚体有机碳分配,以探讨各粒径团聚体湿筛后分配到同一粒级团聚体有机碳含量及其对团聚体水稳性的贡献差异。结果表明：种植年限增加显著降低土壤团聚体水稳性（P<0.05）;各粒径团聚体湿筛后分配的有机碳随粒级减小含量呈先降后增趋势,以保持原粒级团聚体有机碳（12.96-32.01 g/kg）含量最高,其次是<0.25 mm粒级（8.08-23.53 g/kg）。各粒径团聚体湿筛分配到同一粒级的有机碳以保持原粒级的含量最高（P<0.05）;土壤团聚体水稳性与各粒径团聚体湿筛后保持原粒径的有机碳呈显著或极显著正相关（P<0.05或0.01）,分配到越小的粒级正相关性越不显著。此外,团聚体水稳性与各粒径团聚体湿筛分配到同一粒级的有机碳呈正相关,以保持原粒级相关性最高（P<0.01或0.05）;回归方程及相关性系数表明,有机碳与保持原粒径团聚体呈显著呈或极显著正相关（P<0.05或0.01）,与消散到其他粒级的团聚体呈负相关或极显著负相关（P>0.05或<0.01）。本研究得出有机碳含量增加促进更大粒径团聚体形成。反之,促使大粒径团聚体向较小粒径团聚体转化。同一粒级团聚体间,保持原粒级团聚体比易转化形成更大粒级团聚体有更高的有机碳含量和更强的水稳性,这对团聚体的固碳提供了新的认识。     

Interaction between phenolic substances and microbial polysaccharides in soil aggregation

Summary The stability of synthetic soil aggregates containing the extracellular polysaccharide fromLipomyces starkeyi is increased and is more persistant when aggregates are infiltrated with either tannic acid or the products from decomposing herbage. Mixing tannic acid with polysaccharide during the preparation of aggregates had no effect. In a field experiment, addition of glucose produced a rapid improvement in soil aggregation which was considered to be due to the formation of microbial polysaccharides. The effect, however, had virtually disappeared after six months. By contrast glucose-treated plots receiving tannic acid 28 and 42 days after the glucose had been applied showed no sign of diminished aggregation at the end of the experiment.     

半干旱黄土区植被恢复对土壤团聚体稳定性及抗侵蚀能力的影响

土壤水稳性团聚体强烈影响土壤过程和功能,是反映土壤质量和土壤抗侵蚀能力的重要指标。为探究半干旱黄土区植被恢复对土壤抗侵蚀能力的影响,以甘肃省定西市龙滩流域为研究区,选取3种恢复方式（天然荒草、自然恢复、人工恢复）7种植被类型（大针茅草地、长芒草草地、赖草草地、苜蓿草地、柠条灌丛、山杏林以及油松林）为研究对象,通过测定0-20 cm、20-40 cm和40-60 cm土壤水稳性团聚体,分析土壤团聚体组成、稳定性及抗侵蚀能力特征。结果表明：1）不同恢复方式不同植被类型间土壤水稳性团聚体稳定性差异显著（P<0.05）,自然恢复方式的土壤水稳性团聚体平均重量直径显著高于天然荒草和人工恢复方式,且7种植被类型土壤大团聚体质量百分比均在67.97%-90.12%之间;人工恢复方式土壤水稳性团聚体稳定性较差,其中油松林稳定性最差。2）土壤团聚体破坏率和土壤抗侵蚀能力均表现出自然恢复方式更有利于土壤结构稳定性的提高。3）土壤水稳性大团聚体含量越高,土壤团聚体越稳定,土壤结构稳定性就越好;平均重量直径与土壤可蚀性因子K值呈极显著性负相关（P<0.01）。本研究结果表明自然恢复方式能够显著提高土壤团聚体的稳定性,从而提升土壤的抗侵蚀能力,建议当地在未来植被恢复规划中采取自然恢复方式更有利于生态恢复的有效进行。     

不同恢复类型植被细根分布及与土壤理化性质的耦合关系

针对陕北典型黄土丘陵区吴起县主要人工造林和自然封育植被恢复类型,确定5、15年和40年不同退耕年限下的沙棘、山杏及自然恢复草地样地,进行剖面采样,分析不同植被恢复类型下细根生物量、土壤理化性质,研究了不同恢复类型和不同年限植被细根生物量与土壤理化性质随时间的变异规律及耦合关系。结果表明,(1)总体上,主要造林树种和退耕自然封育草地细根生物量都随林龄和退耕年限的增长呈增加趋势,同年限人工造林树种细根生物量大于自然恢复的草地,不同植被群落细根生物量均表现出随着深度的增加呈指数递减规律。(2)自然封育的草地生态系统土壤含水量大于人工山杏林和沙棘林。人工造林和自然封育植被恢复下,土壤团聚体稳定性都随退耕年限的增加而增强,有机质、全氮、全磷含量也都呈增加趋势,土壤平均含水量则呈减小趋势。(3)细根生物量与土壤容重和团聚体稳定性显著相关,植物细根在土壤结构改善中起到了重要作用。     

Influence of arbuscular mycorrhizal fungi on soil structure and aggregate stability of a vertisol

The influence of arbuscular mycorrhizal (AM) fungi on aggregate stability of a semi-arid Indian vertisol was studied in a pot experiment in which Sorghum bicolor (L.) was grown as test plant for 10 weeks. Pasteurized soil inoculated with AM fungi was studied with pasteurized and unpasteurized soils as references. A part of the soil in each pot was placed in nylon mesh bags to separate effects of roots and hyphae. The sorghum plants were planted outside the mesh bags which permitted AM hyphae to enter while excluding roots. Aggregate stability of the soil was determined by wet-sieving and turbidimetric measurements. Development of the AM fungi was quantified as colonized root length and external hyphal length. Soil exposed to growth of roots and hyphae (outside mesh bags) showed aggregates with larger geometric mean diameter (GMD) in pasteurized soil inoculated with AM fungi than in pasteurized uninoculated soil. There was no significant difference in GMD of the inoculated, pasteurized soil and the unpasteurized soil. No significant effects of inoculation or plant growth were found in pasteurized soil exposed to hyphal growth only (inside the mesh bags). However, the unpasteurized soil had significantly higher GMD than the pasteurized soil, irrespective of plants and inoculum. Turbidimetric measurements of soil exposed to roots and hyphae (outside mesh bags) showed the highest aggregate stability for the inoculated pasteurized soil. These results demonstrate that AM fungi contribute to the stabilization of soil aggregates in a vertisol, and that the effect is significant after only one growing season. The effect was associated with both AM hyphae and the stimulation of root growth by AM fungi. The contribution from plant roots and AM hyphae to aggregate stability of different size fractions is discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Mechanisms of soil carbon accrual and storage in bioenergy cropping systems

Annual row cropping systems converted to perennial bioenergy crops tend to accrue soil C, likely a function of increased root production and decreased frequency of tillage; however, very little is known about the mechanisms governing the accrual and stability of this additional soil C. To address this uncertainty, we assessed the formation and stability of aggregates and soil organic C (SOC) pools under switchgrass, giant miscanthus, a native perennial grass mix and continuous corn treatments in Michigan and Wisconsin soils differing in both texture and mineralogy. We isolated different aggregate size fractions, >2 mm, 0.5–2 mm, and <0.5 mm, using a procedure intended to minimize alterations to aggregate biological and chemical properties. We determined SOC, permanganate oxidizable C (POXC), and microbial activities (i.e. enzyme activities and soil respiration rates) associated with these aggregates. Soil type strongly influenced the trajectory of aggregate formation and stabilization with differences between sites in mean aggregate size, stability, SOC and microbial activity under perennial vs. corn cropping systems. At the Michigan site, soil microbial activities were highest in the >2 mm aggregates, and higher under the perennial grasses compared to corn. Contrastingly, in Wisconsin soils, microbial activities were highest in the <0.5 mm aggregates and evidence for soil C accrual under perennial grasses was observed only in a fast turnover pool in the <0.5 mm aggregate class. Our results help explain cross‐site variability in soil C accrual under perennial bioenergy crops by demonstrating how interactions between belowground productivity, soil type, aggregation processes and microbial communities influence the rates and extent of SOC stabilization. Bioenergy cropping systems have the potential to be low‐C energy sources but first we must understand the complex interactions controlling the formation and stabilization of SOC if we are to maximize soil C accrual.     

Role of root hairs in phosphorus depletion from a macrostructured soil

One rape (Brassica napus cv. Wesroona) plant and four cotton (Gossypium hirsutum cv. Sicot 3) plants were grown in plastic cells containing soil labelled with 407 kBq of³³P g⁻¹ soil. After 5–8 days of growth, the³³P depletion zones of all plants were autoradiographed and³³P uptake by plants was measured. The autoradiographs were scanned with a microdensitometer and the optical densities at several places within the³³P depletion zones of roots were obtained. The volume of soil explored by root hairs was estimated from measurements of root diameters and lengths of roots and root hairs. About half of the total³³P depleted by cotion roots came from outside the root hair cylinder whereas most of³³P taken up by rape was from within the root hair cylinder. Plants grown in a macrostructured soil may have roots growing in voids, within aggregates or on the surfaces of aggregates. The results of this study demonstrate that root hairs have a strong influence on the accessibility of phosphorus to roots in such a soil, and thus on the phosphorus nutrition of plants.     

植物篱-农作坡地土壤团聚体组成和稳定性特征

基于植物篱控制水土流失的长期定位试验,研究植物篱-农作坡地土壤团聚体组成和稳定性特征.结果表明： 与常规等高农作模式相比,植物篱-农作复合农业模式下土壤>0.25 mm机械稳定性和水稳性团聚体含量分别显著增加13.3%~16.1%和37.8%~55.6%,明显提高了各坡位粒级>0.25 mm土壤水稳性团聚体含量,改善了粒级>0.25 mm土壤水稳性团聚体在下坡位的相对富集和上坡位相对贫乏的状况.植物篱显著提高了土壤团聚体平均质量直径和几何平均直径,降低了土壤团聚体分形维数和>0.25 mm土壤团聚体破坏率,进而增强了土壤团聚体的稳定性和抗蚀性.坡度与植物篱类型对土壤团聚体组成、稳定性和坡面变化无显著影响.     

Effect of humic acids from Leonardite on the stability of soil aggregates and melon roots under greenhouse conditions

Leonardite is an oxidized form of lignite carbon, which is obtained from fossilized organic materials. Such materials are used for the extraction of humic acids (HA). The result of the addition of HA of organic origin on soil structure is known; however, the effects of adding HA of Leonardite on soil structure have been scarcely investigated. The objectives of this research were (1) to determine the influence of humic acids derived from Leonardite in increasing the aggregate stability of an Aridisol under greenhouse conditions, and (2) evaluate the morphology of the root xylem during the phenological development of melon plants (Cucumis melo L.). Three treatments of HA solution application to the soil were used: soil without solution application (HA0), and application of HA solution to the soil with pH 6 (HA6) or (HA7). Aggregate stability (As) and bulk density (Da) were evaluated as soil variables. Development and quantification of xylem area were studied on plants. There were significant differences in aggregate stability. Also, there was an increase in the root xylem area, and the best treatment was when AH7 solution was applied. Humic acids derived from Leonardite increased the stability of soil aggregates when plants grew under greenhouse conditions, and fostered the development of xylem conduits during the fruiting stage.     

Influence of maize root mucilage on soil aggregate stability

This study was undertaken to determine the effects of root exudates on soil aggregate stability. Root mucilage was collected from two-month old maize plants (Zea mays L.) Mucilage and glucose solutions were added at a rate of 2.45 g C kg⁻¹ dry soil to silty clay and silt loam soils. Amended soils, placed in serum flasks, were incubated for 42 d with a drying-wetting cycle after 21 d. Evolved CO₂ was measured periodically as well as the water-stable aggregates and soluble sugar and polysaccharide content of the soil. In mucilage-amended soils CO₂ evolution started with a lag phase of 2–3 days, which was not observed in glucose-amended soils. There was then a sharp increase in evolved CO₂ up to day 7. During the second incubation period there were only small differences in evolved C between treatments. Incorporation of mucilage in both soils resulted in a spectacular and immediate increase in soil aggregate stability. Thereafter, the percent of water-stable aggregates quickly decreased parallel to microbial degradation. On completion of the incubation, aggregate stability in the silty clay soil was still significantly higher in the presence of mucilage than in the control. This work supports the assumption that freshly released mucilage is able to stick very rapidly to soil particles and may protect the newly formed aggregates against water destruction. On the silty clay, microbial activity contributes to a stabilization of these established organo-mineral bounds.     

模拟氮沉降增加条件下土壤团聚体对酶活性的影响

氮沉降增加改变了森林土壤生态系统物质输入,影响土壤生物及酶活性,而土壤团聚体内相对稳定的微域生境可能减弱或延缓土壤生物和酶对氮沉降增加的响应强度。以广东省东莞大岭山森林公园荷木人工林为研究对象,用模拟N沉降方法,分析了2011年12月到2012年11月一年内氮沉降增加条件下表层混合土壤和土壤团聚体内脲酶、蔗糖酶和酸性磷酸酶活性的变化及影响因素,旨在理解氮沉降增加条件下土壤团聚体对酶活性的影响。结果表明:氮沉降增加对表层混合土壤中脲酶和蔗糖酶的抑制作用不显著,而酸性磷酸酶受氮沉降显著影响,表现为低氮(50 kg N hm-2a-1)促进,高氮(300 kg N hm-2a-1)抑制的规律。表层土壤团聚体内脲酶活性随氮沉降增加而降低,N300处理显著低于对照;蔗糖酶和酸性磷酸酶活性随氮沉降增加先降低后增加,N100处理最低,分别比其他处理降低了6.46%—25.53%和42.33%—68.25%。试验区内各粒径土壤团聚体内酶活性高于混合土壤,且随团聚体粒径增加酶活性均为先增加后降低。不同粒径土壤团聚体的3种酶活性均以2—5 mm最高,但脲酶、酸性磷酸酶在各团聚体粒径间差异不显著,蔗糖酶活性2—5 mm显著高于5—8 mm。土壤酶相对活性指数和相对活性综合指数结果显示,超过85%的团聚体粒径内的相对酶活性指数大于1,而土壤酶相对活性综合指数均大于1。以上结果表明,氮沉降增加条件下土壤团聚体对其团聚体内的土壤酶活性有隔离保护作用,但其隔离保护效果与酶的种类和土壤团聚体粒径有关。     

双季稻田改制对土壤剖面构型及性质的影响

利用田间试验方法,研究了红壤区双季稻田改为稻-稻-紫云英、牧草、水旱轮作和旱作4种种植模式对土壤剖面构型及耕层土壤性质的影响.结果表明: 与试验前相比,旱作种植模式下,耕作层厚度增加了4 cm、犁底层厚度减少了2 cm、湿筛>2 mm粒级团粒含量提高了6.94%、湿筛法平均质量粒径增加了0.37 mm、水稳性结构商是试验前的1.78倍,腐殖酸碳和富里酸碳含量分别提高了0.15和0.49 g·kg^-1;水旱轮作种植模式下,土壤水稳性结构商较高(95.86)、养分含量变幅小;稻-稻-紫云英种植模式下,除有机质含量(增加1.3 g·kg^-1)和土壤水稳性结构商(降低8.82)变化较大外,其余指标变化不大;牧草种植模式下,耕作层厚度增加2 cm、过渡层厚度增加9 cm、土壤水稳性结构商增加1.39,而土壤有机质和全钾含量分别下降5.6和2.8 g·kg^-1,在所有处理中变化幅度最大.表明在当前红壤地区对灌溉条件较差的双季稻田进行改制是可行的,建议优先考虑改成旱作或水旱轮作,但无论在何种耕作方式下,均应注意土壤钾素的亏损问题.     

黄土高原次生林演替对团聚体有机碳含量及化学稳定性的影响

次生林演替过程中土壤团聚体有机碳的积累机制和化学稳定性研究较少。为探明次生林演替对土壤团聚体有机碳含量及其化学组成稳定性的影响,选取黄土高原次生白桦林(演替初期),山杨辽东栎混交林(演替中期)和辽东栎林(演替后期)为研究对象,分析演替过程中不同粒径土壤团聚体有机碳含量变化特征。采用傅里叶红外光谱技术(FTRI)测定活性(AC)和非活性(IC)有机碳化学组成,以(IC/AC)作为有机碳化学组成稳定性指标,并分析其影响因素。结果表明:次生林演替过程中土壤团聚体有机碳含量表现出逐渐增加的趋势且各群落间差异显著(P<0.05),以演替后期的中等粒径团聚体为最高(37.63 g/kg)。土壤团聚体AC中多糖体有机碳含量最高(55.87%),而IC中芳香族有机碳含量最高(94.45%),演替过程中IC与AC总体变化趋势均呈现先降后增。IC/AC随着演替的进行呈先降低后升高的趋势,其中演替后期微团聚体有机碳化学组成稳定性最强达到了3.95。微团聚体含量(WM)与土壤全氮、全磷、全钾一起,显著促进了团聚体有机碳化学组成稳定性(P<0.05)。综上,次生林演替有利于促进土壤团聚体有机碳的积累以及有机碳化学稳定,其中微团聚体起到了关键性作用。