东北黑土区冻融作用对黑土水稳性团聚体的影响

Soil aggregate stability,an important index of the physical characteristics of a soil,can provide a good indication of a soil’s erodibility,and deserves special consideration in regions with cold climate.The objective of this study was to study the effect of freeze-thaw on soil water-stable aggregates in the black soil region of Northeast China.Samples of a typical black soil in the region were collected to measure water-stable aggregates after freeze-thaw under different conditions(i.e.,initial moisture contents,freezethaw cycles and freezing temperatures)by wet-sieving into eight particle size groups(10,10–6,6–5,5–3,3–2,2–1,1–0.5,and0.5–0.25 mm).Freeze-thaw had the most effect on aggregate stability when the samples had an initial moisture content of 400 g kg-1.The water-stable aggregates of the four larger particle size groups(5,5–3,3–2,and 2–1 mm)reached a peak stability value,but those of the two smaller particle size groups(1–0.5 and 0.5–0.25 mm)reached a minimum value when the soil moisture content was 400 g kg-1.Water-stable aggregates of the four larger particle size groups decreased while those of the two smaller particle size groups increased with the increase of freeze-thaw cycles.As temperatures fell,the water-stable aggregates of the four larger particle size groups decreased while those of the two smaller particle size groups increased.     

Prediction of carbon mineralization rates from different soil physical fractions using diffuse reflectance spectroscopy

Soil carbon (C) mineralization rate is a key indicator of soil functional capacity but it is time consuming to measure using conventional laboratory incubation methods. Recent studies have demonstrated the ability of visible-near infrared spectroscopy (NIRS) for rapid non-destructive determination of soil organic carbon (SOC) and nitrogen (N) concentration. We investigated whether NIRS (350-2500 nm) can predict C mineralization rates in physically fractionated soil aggregates (bulk soil and 6 size fractions, n=108) and free organic matter (2 size fractions, n=27) in aerobically incubated samples from a clayey soil (Ferralsol) and a sandy soil (Arenosol). Incubation reference values were calibrated to first derivative reflectance spectra using partial least-squares regression. Prediction accuracy was assessed by comparing laboratory reference values with NIRS values predicted using full hold-out-one cross-validation. Cross-validated prediction for C respired (500 days) in soil aggregate fractions had an R² of 0.82 while that of C mineralized (300 days) in organic matter fractions was 0.71. Major soil aggregate fractions could be perfectly spectrally discriminated using a 50% random holdout validation sample. NIRS is a promising technique for rapid characterization of potential C mineralization in soils and aggregate fractions. Further work should test the robustness of NIRS prediction of mineralization rates of aggregate fractions across a wide range of soils and spectral mixture models for predicting mass fractions of aggregate size classes.     

In‐row soil aggregate characteristics for two Iowa soils

Abstract

Chemical and physical characteristics of soil aggregates from Clarion loam (fine‐loamy, mixed, mesic Typical Hapludoll) and Edina silt loam (fine, montmorillonitic, mesic Typic Argialboll) soil were evaluated to compare two alternate farming practices. Aggregate size distribution was measured for the 0‐to‐3 mm and 0‐to‐76 mm fractions collected from within existing ridges to a soil depth of 0.15 m prior to planting corn (Zea mays L.), after the first cultivation, at anthesis, and after harvest in 1990. Selected physical and chemical properties were determined for air‐dry aggregates in six size classes (0‐to‐0.5, 0.5‐to‐1.0, 1.0‐to‐2.0, 2.0‐to‐3.0, 3.0‐to‐4.0, and 4.0‐to‐5.0 mm) collected from the two Iowa soils prior to planting. Temporal changes in aggregate size distribution were observed for both soils, presumably because of combined rainfall and crop management effects. Physical and chemical properties of soil aggregates showed large differences between locations and within size fractions when compared to the bulk soil. Clarion loam had relatively more consistent exchangeable cation concentrations compared to Edina silt loam, presumably because of sustained incorporation of manure and municipal sludge at that site. Soil aggregation and aggregate properties can be used as indicators to evaluate the effects of alternate fanning practices.     

苎麻对红壤旱地土壤团聚体及其特性的影响

采用干、湿筛法研究了种植苎麻和花生对红壤旱地土壤团聚体及其特性的影响,并比较分析了土壤团聚体及土壤理化性质与地表径流和土壤侵蚀量的关系。结果表明:(1)与花生地相比,苎麻地有机质、田间持水量、总孔隙度、沙粒分别升高了28.44%,10.06%,5.65%和53.13%,土壤容重、粉粒和黏粒则分别降低了7.20%,14.85%和34.95%,均达显著性差异水平(p0.05)。(2)团聚体平均重量直径(MWD)、稳定性指数(ASI)显著升高(p0.01),苎麻地土壤团聚体稳定性优于花生地;(3)两处理均以0.25~1mm粒径团聚体保存几率最大,抗水蚀能力最强。(4)地表径流量和土壤侵蚀量与土壤有机质、沙粒含量、1mm的干团聚体、0.5mm的水稳性团聚体、MWD以及ASI呈极显著负相关关系(p0.01),而与粉粒、黏粒、0.25mm干团聚体、0.053mm的水稳性团聚体、呈极显著正相关关系(p0.01)。     

生物炭对豫西丘陵区农田土壤团聚体稳定性及碳、氮分布的影响

为研究生物炭对豫西丘陵地区农田土壤团聚体分布、稳定性及其碳、氮在团聚体中分布的影响,进一步探明生物炭对丘陵区农田土壤结构和养分的长期作用效果。采用田间长期定位试验,生物炭用量为0(C0),20(C20),40(C40)t/hm~2 3个处理,研究生物炭施用5年后对土壤团聚体组成及稳定性的影响,探究土壤团聚体中有机碳和全氮分布特性。结果表明:施加20,40 t/hm~2生物炭可提高0—20,20—40 cm土层的机械性0.5 mm以上粒级和水稳性0.053 mm以上粒级团聚体含量。在0—20 cm土层中,C20和C40处理下0.25 mm的机械性团聚体(DR_(0.25))分别较对照增加3.78%和6.83%,0.25 mm水稳性团聚体(WR_(0.25))分别较对照增加31.0%和49.45%,土壤不稳定团粒指数(E_(LT))分别较对照降低4.30%和6.85%,土壤团聚体破坏率(PAD)分别较对照降低9.71%和14.77%,土壤团聚体平均质量直径(MWD)分别较对照增加28.44%和45.34%,几何平均直径(GMD)分别较对照增加32.04%和54.92%。各粒级的有机碳和全氮含量随生物炭施用量的增加而增加,有机碳和全氮含量都以0.25～0.053 mm粒级最高,且0—20 cm土层的有机碳和全氮含量高于20—40 cm土层的有机碳和全氮含量;随着生物炭施用量的增加,2,2～0.25,0.25～0.053 mm粒级团聚体有机碳和全氮贡献率随之增加,而0.053 mm粒级微团聚体有机碳和全氮贡献率随之降低。总体来说,生物炭能够改善豫西丘陵地区农田土壤的团聚体结构,增加土壤大团聚体的含量,增强团聚体的稳定性,提高土壤团聚体中碳、氮含量,有利于豫西地区农田土壤肥力的保持和持续健康发展。     

Inability of Near Infrared Reflectance Spectroscopy (NIRS) to identify belowground earthworm casts in no-tillage soil

Several studies have emphasised the ability of Near Infrared Reflectance Spectroscopy (NIRS) to identify surface earthworm casts in the field. However, less is known about casts deposited within the soil, which usually represent the majority found in the field. This study tested the ability of NIRS to identify belowground casts in agricultural systems. Casts and surrounding soils were sampled at depths of 20–30 cm in a loamy soil under no tillage for 12 years. To distinguish different types of cast, sizes and orientations relative to the horizontal plane were measured. NIRS analyses and analyses of carbon and nitrogen content were also performed to compare casts to surrounding soils. Casts were classified into 4 size classes, with no preferential orientation. Cast carbon and nitrogen content were not influenced by their size and did not differ from surrounding soils. PCAs performed on the NIRS data did not allow casts to be differentiated from surrounding soils, regardless of size class. However, soil aggregates were clearly differentiated probably due to their spatial distribution in the soil. Although this study did not identify specific NIRS signatures for casts, it shows the utility of this method to investigate the origin of the soil consumed by earthworms. In our case, NIRS analyses suggest that the high bulk density of the soil (1.42 g cm⁻³) forced ingestion by endogeic earthworms, simply to move around, without preferential selection for organic matter. Consequently, their casts were deposited a few mm from where they had ingested soil with similar organic matter quality.     

运用同步辐射显微CT揭示红壤团聚体内孔隙形态与空间分布

团聚体内部复杂的孔隙系统及其空间分布决定土壤团聚体的主要功能,以及发生在团聚体内的各种物理、化学和生物学过程。应用同步辐射X射线显微成像技术(SR-mCT),对第四纪红土发育的红壤团聚体内部孔隙形态、连通性、各向异性、大小分布和空间分布进行了研究。结果表明,红壤团聚体内部的孔隙形态、孔隙生长方向、大小分布存在明显差异。稳定性较好的团聚体表现为团聚体孔隙含有较多大孔隙、孔隙形态各异、各向异性、多联通孔隙等特征,团聚体内>30mm大孔隙分布比较均匀,中心部位较高,呈中间向圆周减小趋势;反之,稳定性较差的团聚体中,孔隙以小孔隙为主,分布密集,孔隙生长方向均匀,团聚体孔隙空间分布为大孔隙,主要分布在团聚体外围,中心部分分布较少。团聚体内部孔隙的空间分布模式能够很好地解释土壤团聚体结构和稳定性差异的原因。同步辐射显微CT结合图像处理技术能够系统地表征团聚体内孔隙的多样性和空间变异规律,为预测土壤团聚体中各种物理过程提供新途径。     

长期施用化肥条件下土团聚体中有机碳与养分分布

[目的]探究长期施肥与小麦—玉米轮作下(蝼)土表层水稳性团聚体组成及对团聚体中有机碳和养分分布的影响,为评价长期施肥对改善(蝼)土肥力状况的影响提供科学依据.[方法]利用田间长期施用化肥与轮作定位试验,通过湿筛法分离土壤水稳性团聚体,得到土壤团聚体构成,并测定不同粒径团聚体中有机碳和养分的含量.[结果]结果表明长期施用化肥显著影响土壤水稳性团聚体含量,长期施肥降低了＞2 mm的水稳性团聚体数量,增加了＜1 mm的水稳性团聚体含量.施肥在一定程度上提高了水稳性团聚体有机碳的含量,但施用高量氮、磷下0.25～0.5 mm和＜0.25 mm水稳性团聚体中有机碳含量明显低于施用低量氮、磷肥料.不同施肥处理土壤水稳性团聚体全氮含量变化趋势与水稳性团聚体有机碳含量基本一致.磷素在不施肥处理各粒径团聚体中均匀分布,低氮、磷处理各粒径团聚体中全磷含量差异较小,高氮、磷处理各粒径土壤团聚体中全磷含量变化无明显趋势.长期施肥降低了＞2 mm水稳性团聚体中全K含量,增加了＜2 mm的水稳性团聚体中全K含量.[结论]水稳性团聚体关系土壤有机碳、氮的数量,水稳性团聚体及其中有机碳、氮含量在氮磷化肥的长期施用下变化无明显规律,并且,长期施用氮、磷化肥下土壤磷素和钾素在土壤中的保存及供应能力也受到影响.因此,需要合理施肥管理,促进农田生产力的可持续发展.     

采煤塌陷区复垦土壤团聚体碳氮分布对施肥的响应

为了揭示长期不同培肥措施下采煤塌陷区复垦土壤团聚体有机碳氮含量的变化规律,通过干筛法研究了不施肥(CK)、单施有机肥(M)、单施化肥(CF)、有机肥与化肥配施(MCF)、生物有机肥与化肥配施(MCFB)5种培肥措施下复垦4年和8年土壤各粒级团聚体分布组成特征以及各团聚体有机碳氮含量的变化规律。结果表明,复垦土壤团聚体含量随粒级减小呈先减小后增大的变化趋势,其中以3~2mm粒级团聚体含量最低,占团聚体总量2%~3%,以2~1mm粒级团聚体含量最高,占团聚体总量25%~31%。不同培肥措施下复垦4年和8年土壤团聚体分布特征无明显差异,但较未复垦生土明显降低了7mm和7~5mm团聚体含量。复垦8年土壤的平均重量直径(MWD)、几何平均直径(GMD)高于复垦4年土壤,分形维数(D)值低于复垦4年土壤。各培肥处理间以单施有机肥MWD、GMD值最高,D值最低。各培肥处理土壤团聚体有机碳氮含量随粒径减小递增,以0.5~0.25mm粒径团聚体最高,而有机碳储量以2~1mm粒级团聚体最高,分别占24.2%~33.8%和17.0%~33.1%。各处理间有机碳氮含量以单施有机肥处理最高,但不同处理间有机碳氮储量无显著差异。总体表明,采煤塌陷区复垦4年和8年土壤团聚体分布特征及碳氮储量无明显变化,单施有机肥可提高复垦土壤团聚体有机碳氮含量及团聚体稳定性。     

滇东岩溶断陷盆地地表/地下不同侵蚀场土壤的可蚀性

以滇东海峰岩溶盆地土壤复合侵蚀过程为研究对象,分析综合土壤可蚀性指数(CSEI)的分布特征,探讨地表、地下土壤可蚀性的关联性、变化趋势及其影响因素,以期深入认识岩溶地区土壤侵蚀机理,治理石漠化现象。通过野外调查取样结合土壤比重计法、团聚体湿筛等方法,分析了滇东岩溶断陷盆地地表、地下不同侵蚀场土壤的理化性质及可蚀性变化特征。结果表明：(1)土壤理化性质随侵蚀过程发生变化。土壤中黏粒、SOC、大团聚体(>0.25 mm)呈递减趋势,粉砂、小团聚体(<0.25 mm)呈递增趋势。不同侵蚀过程土壤特征存在显著差异,地表侵蚀过程土壤黏粒(20.91%～45.62%)、砂粒(44.96%～64.59%)、SOC(4.93～88.72g/kg)、大团聚体(17.82%～99.86%)含量>地下漏失过程(15.30%～30.86%,43.63%～64.59%,3.57～19.05 g/kg, 16.81%～85.94%);粉砂(4.85%～30.84%)、小团聚体(0.14%～82.18%)含量<地下漏失过程(16.03%～25.86%,14.06%～83.19%)。(2)CS...     

Investigating the effects of wettability and pore size distribution on aggregate stability: the role of soil organic matter and the humic fraction

Soil organic matter (SOM) is an important factor influencing aggregate stability. Interactions between SOM and soil structure are widely studied, although the subtle relationship between SOM content, pore size distribution and aggregate stability is not fully known. Here we investigate such a relationship by means of a long‐term experiment established in 1962 in northeastern Italy, which considers different fertilizer practices (organic, mineral and mixed) applied to a continuous maize crop rotation. We measured wet stability of 1–2 mm aggregates subjected to different pretreatments. Both soil physical properties (such as pore size distribution and hydrophobicity) and chemical properties (soil organic and humic carbon content) affecting aggregate stability were considered. The chemical structure of humic substances was characterized by thermal and spectroscopic analyses (TG‐DTA, DRIFT and ¹H HR MAS NMR). The Pore‐Cor network model was then applied to evaluate the contribution of hydrophobicity and porosity to aggregate wetting. Our study suggests that SOM and its humic fraction can affect aggregate wetting and consequently slaking by modifying the pore size distribution with a shift from micropores (5–30 µm) and mesopores (30–75 µm) to ultramicropores (0.1–5 µm); hydrophobicity was also increased as a result of different humic composition. Spectroscopic analysis showed that hydrophobic compounds were mostly associated with complex humic molecules. Models of fast wetting dynamics, however, suggest that the contribution that hydrophobicity makes to aggregate stability, especially to soils with large carbon inputs, may not be the most significant factor.     

生物炭施用下潮土团聚体微生物量碳氮和酶活性的分布特征

[目的]探究生物炭配施化肥对不同粒级团聚体中微生物量碳、氮(MBC、MBN)含量和胞外酶活性的影响,分析影响团聚体胞外酶活性变化的主控因素,为提升土壤质量提供科学依据.[方法]田间微区试验在河南现代农业研究基地进行,供试土壤为石灰性潮土.设置4个处理:不施肥(CK)、单施化肥(NPK)、单施生物炭(BC)和生物炭配施化...     

长期施肥对浙江稻田土壤团聚体及其有机碳分布的影响

以浙江省稻田长期定位试验站为依托,研究长期不同施肥措施对土壤团聚体及其有机碳分布的影响。研究结果表明,与不施肥对照(CK)相比,栏肥与化肥配施(NPKOM)、单施栏肥(OM)、秸秆与化肥配施(NPKRS)和单施秸秆(RS)处理均显著提高了2 mm和2~0.25 mm水稳定性大团聚体的含量和团聚体平均重量直径(p0.05),强化了团聚体对土壤有机碳的物理保护作用。此外,长期有机无机配施(NPKOM和NPKRS)处理显著提高了各个粒级团聚体中有机碳含量,并且显著增加水稳定性大团聚体有机碳的贡献率,而长期单施化肥和单施秸秆处理并未有效增加土壤总有机碳含量。不同施肥处理下,2~0.25 mm粒级团聚体有机碳占土壤总有机碳的34.2%~48.6%,是土壤有机碳的主要载体。利用傅立叶变换红外光谱(FT-IR)技术对2~0.25 mm和0.053 mm团聚体进行结构表征,发现长期单施有机肥或者有机无机配施下芳香族C较CK提高29.9%~45.2%,较NPK处理提高22.3%~36.6%,提高了土壤有机碳的芳构化。在有机碳积累方面,施用有机肥,尤其是栏肥与化肥配施,同时强化了团聚体对有机碳的物理保护以及促进了化学抗性有机碳组分的积累,是加强稻田土壤有机碳库积累的合理施肥模式。     

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

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.     

Influence of Aggregate Size,Electrolyte Concentration,and Sodium Adsorption Ratio on Crack Parameters of a Vertisol

Shrinking–swelling and crack formation influence soil physical behavior and productivity. Soil factors affecting crack formation and dimensions are clay content and mineralogy, aggregate stability as well as total concentration (C_t), and sodium adsorption ratio (SAR) of soil solution. Tillage intensity, which determines aggregate size, may also play a significant role in crack formation and dimensions. In the present work, total length, mean width, total area, and cover percentage of cracks were studied, under laboratory conditions, in beds of two aggregate sizes (<1 and 2–1 mm) of a Vertisol. The beds were saturated, equilibrated with sodium chloride (NaCl)/calcium chloride (CaCl₂) solutions of C_t 2, 5, 10, 20, and 30 mmol/L and SARs 0, 2, 5, 10, and 20 (mmol/L)^1/2, and allowed to air‐dry. After air‐drying, pictures of the samples were taken and used for the calculation of crack parameters by a scanning program. The results showed that aggregate size was the dominant factor determining the crack parameters: the cracks formed in beds of aggregates <1 mm were wider and of a smaller total length, total area, and cover percentage (p < 0.05) than those cracks formed in beds of aggregates 2–1 mm in size. It was also determined that changes of C_t resulted in a greater influence on crack characteristics than changes of SAR in the equilibrating solutions.     

秸秆和生物炭还田对棕壤团聚体分布及有机碳含量的影响

  【目的】  比较长期秸秆和生物炭还田后土壤团聚体的变化与差异,旨在探索棕壤适宜的改良方法。  【方法】  在辽宁沈阳棕壤上连续进行了6年的田间定位微区试验,种植制度为玉米连作,试验共设6个处理:不施肥 (CK)、单施氮磷钾 (NPK)、单施生物炭 (B)、生物炭与氮磷钾配施 (BNPK)、单施秸秆 (S)、秸秆与氮磷钾配施 (SNPK)。在玉米收获后,采集0—20和20—40 cm两土层土壤样品,采用Yoder湿筛法进行了团聚体分级和测定。  【结果】  与NPK相比,BNPK和SNPK处理显著提高了0—20和20—40 cm土层 > 1 mm、1～0.5 mm和 0.25～0.5 mm粒级团聚体含量占比,降低了0.25～0.053 mm粒级团聚体含量占比,SNPK处理提高大团聚体含量占比的效果显著高于BNPK。与NPK处理相比,BNPK和SNPK处理显著增加了团聚体平均重量直径 (MWD)、几何平均直径 (GMD) 和0.25 mm粒级团聚体含量 (R_0.25),即增加了团聚体的稳定性,SNPK处理的团聚体MWD和GMD值又显著高于BNPK,R_0.25值两处理间无显著差异 (0—20 cm土层)。随团聚体粒级减小,不同粒级团聚体有机碳含量随之减少,以 > 1 mm粒级团聚体有机碳含量最高。与CK相比,各施肥处理均增加了各粒级团聚体有机碳含量,BNPK处理对0—20 cm土层0.25～0.053 mm粒级团聚体有机碳含量影响最显著,有机碳含量增加了44.57%。  【结论】  长期秸秆和生物炭还田能够改变土壤团聚体的分布,有利于大团聚体的形成和土壤结构改善,可提高土壤团聚体有机碳含量和团聚体稳定性,增加作物产量;秸秆直接还田提高团聚体稳定性的效果优于生物炭还田,生物炭还田提高团聚体有机碳的效果方面优于秸秆直接还田。     

土粒表面电场对土壤团聚体破碎及溅蚀的影响

团聚体是土壤结构的基本单元,其稳定性是评估土壤抗侵蚀能力的重要指标。土壤团聚体破碎是降雨溅蚀发生的关键一步。土粒表面电场对团聚体稳定性具有重要影响,必然也会深刻影响降雨溅蚀过程。该文以黄土母质发育的黄绵土和塿土为研究对象,采用不同浓度的电解质溶液定量调控土粒表面电场,研究不同电场强度对团聚体破碎及溅蚀的影响。结果发现:1)随电解质浓度的降低,土粒表面电位升高,表面电场增大,黄绵土和塿土团聚体平均重量直径减小,团聚体稳定性降低,降雨溅蚀量增大。2)电解质浓度小于10-2 mol/L,黄绵土和塿土表面电位绝对值分别高于202.0和231.6 mV,此时团聚体稳定性和溅蚀量变化不明显,表明表面电位202.0和231.6 mV分别是影响黄绵土和塿土团聚体稳定性及溅蚀的关键电位。3)随着土粒表面电场的减弱,团聚体破碎后释放的<0.15 mm微团聚体含量减小,>0.25 mm大团聚体含量增加,团聚体倾向于破碎为更大粒级的团聚体。4)电场作用下团聚体的破碎特征对降雨溅蚀具有重要的影响,溅蚀量与团聚体破碎释放的<0.15 mm微团聚体含量呈显著正相关,与>0.25 mm大团聚体含量呈显著负相关。上述结果表明,当降雨进入土壤后,对于干燥的土壤而言,土壤溶液电解质浓度被迅速稀释,土粒表面产生强大的电场,该电场通过影响团聚体破碎程度进而影响降雨溅蚀。该研究有助于加深对降雨溅蚀的科学认识,同时也为土壤团聚体稳定性及降雨溅蚀的人为调控提供了一定的理论依据。     

施用生物质炭对黑土腐殖质组成及水稳性团聚体分布的影响

为探究生物炭对土壤腐殖质组成和团聚体特征的影响，以东北黑土区植烟土壤为研究对象，设置了3个处理，2019-2020年连续施用低量生物炭5t/hm2（C1）；高量生物炭25t/hm2（C2）和不施生物炭（CK），分析了不同用量生物炭对土壤腐殖质组分及水稳性团聚体分布的影响，并利用傅里叶红外光谱(FTIR)和13C核磁共振光谱(13C-NMR)对土壤胡敏酸化学结构进行表征。结果表明：C1和C2处理分别使富里酸减少了16.90%和40.85%，胡敏酸含量显著增加了14.86%和33.78%，胡敏酸在腐殖酸中所占比例（PQ值）也显著增加；FTIR和13C-NMR分析表明，C2处理的土壤胡敏酸的2920/1620值降低了11.82%，脂族C/芳香C比值降低了13.04%，表明高量生物炭使胡敏酸芳构化程度增强，脂肪结构比例降低；生物炭的添加促使土壤大团聚体（>0.25mm）比例增加，C2处理提升大团聚体的作用更显著。结合相关性分析发现，胡敏酸含量与2~0.25mm大团聚体含量显著正相关，胡敏酸分子的脂肪族官能团特征与>2mm粒级团聚体显著正相关。此外，C1和C2处理显著提高了烟叶产量。从而表明，生物炭能提升土壤腐殖质中胡敏酸含量和结构，有利于土壤大团聚体形成，提高土壤固碳潜力，对作物有一定的增产效果。     

秸秆还田对盐渍土团聚体稳定性及碳氮含量的影响

以黄河三角洲典型盐化潮土为研究对象,分析了3种盐渍化程度(轻度、中度、重度)和3 a连续秸秆还田下土壤水稳性团聚体组成、稳定性以及各级团聚体C、N含量的变化。研究结果表明:重度盐渍土0.25～2 mm和0.053～0.25 mm团聚体所占比例显著低于轻度和中度盐渍土;土壤盐分含量与0.25～2mm团聚体中有机碳和全氮的分配比例、0.053～0.25 mm团聚体中全氮的分配比例成显著负相关。秸秆还田使轻度盐渍土平均重量直径(MWD)、几何平均直径(GMD)和0.25 mm团聚体所占比例(R0.25)分别增加47.6%、39.7%和54.0%,使中度盐渍土MWD、GMD和R0.25分别增加31.0%、31.9%和31.4%;各粒级中秸秆还田使轻度盐渍土0.053～0.25 mm粒级有机碳和全氮含量增加最多,增加比例分别为29.1%和28.8%,该粒级中C、N分配比例也显著提高;秸秆还田使中度盐渍土0.25～2 mm团聚体有机碳及其分配比例提高最多,比例分别为56.1%和58.7%。秸秆还田对轻度和中度盐渍土团聚体的稳定性均起到了明显的改善作用,但不同盐渍土秸秆还田对土壤团聚体C、N分布的影响明显不同。     

不同植被恢复模式对红砂岩土壤化学性质及抗蚀特征的影响

通过对不同恢复年限及恢复类型(2a人工恢复湿地松林、5a人工恢复湿地松林、5a自然恢复湿地松林、5a自然恢复荒地和6a种植杨梅园空地)0～30cm红砂岩发育土壤团聚体中有机碳、全磷、全氮分布规律、化学计量比及其与土壤抗蚀性的相关性进行分析,旨在探究红砂岩侵蚀劣地植被恢复过程中土壤养分变化及抗蚀性。结果表明:红砂岩纯裸地土壤养分含量较低,经过不同措施恢复后,土壤理化性质有不同程度的改善。不同类型红砂岩土壤团聚体级配不同。裸地以5 mm粒径团聚体为主,约占60%以上。除自然恢复5a荒地以2～5 mm团聚体为主以外,其余恢复措施的红砂岩土壤均以小于0.25mm粒径微团聚体为主。不同粒径土壤团聚体有机碳、全氮含量均随恢复年限增长呈增加趋势。C、N集中分布在0.25～1 mm团聚体上,尤其是0.5～1 mm团聚体;P则分布较为均匀。采取不同恢复措施后土壤抗蚀性有不同程度的提高,其中结构体破坏率从55.68%降至10%以下。研究区土壤C:N均值为15.0:1;C:P均值为79.7:1;N:P均值为4.0:1。由此可知不同红砂岩发育土壤随着恢复年限而增长,抗蚀性能大幅提升,由于养分主要分布在0.5～5 mm土壤水稳性的团聚体上,而该部分团聚体流失严重,导致土壤养分含量低、土壤抗蚀性差,恢复过程较为困难。