坡耕地黄墡土结皮的理化性质分析

在实验和对比分析的基础上 ,讨论了黄土善土结皮的一些主要物理化学性质特征。结果认为 ,结皮的形成是以细砂和粗粉砂为骨架 ,以小于 0 .0 1mm的细小颗粒填塞土壤空隙的一个物理过程 ,其腐殖质含量几乎与土壤相同 ,而碳酸钙含量则略低。结皮的坚实度与前期含水率呈负相关 ,与容重和厚度呈正相关 ,而容重与厚度间的关系较为复杂     

黄土丘陵区生物结皮覆盖对土壤团聚体分布特征及稳定性影响

【目的】以吕梁离石区结皮覆盖（藻结皮、藓结皮、藓草混生结皮，裸地为对照）下土壤为研究对象，研究结皮种类对其下层土壤有机碳及土壤团聚体稳定性的影响。【方法】通过干筛和湿筛法对土壤团聚体分级，探究土壤容重、土壤有机碳含量和土壤静水崩解速率与团聚体稳定的相关性。【结果】在0～5 cm和5～10 cm深度，3种结皮下土壤容重与裸地间均达到显著差异；土壤有机碳含量表现为藓草混生结皮和藓结皮分别比裸地显著增加。不同深度土层，团聚体破坏率、分形维数表现为裸地>藻结皮>苔藓结皮>藓草混生结皮；平均重量直径和几何平均直径变化规律正好相反。相关性分析表明，> 0.25 mm土壤团聚体含量与土壤容重呈显著负相关关系；团聚体破坏率、分形维数与土壤容重、土壤静水崩解速率呈极显著正相关关系，与土壤有机碳含量呈极显著负相关关系；平均重量直径、几何平均直径与土壤容重呈极显著负相关关系，与土壤静水崩解速率呈显著负相关关系，与土壤有机碳含量呈极显著正相关关系。【结论】黄土丘陵吕梁随结皮层次提高，土壤团聚体形成能力和土壤团聚体水稳定性逐渐增高，对土壤水稳定性起主导作用的是土壤有机碳含量。     

冻融交替对不同生物结皮土壤饱和导水率的影响

  目的  生物土壤结皮在干旱、半干旱地区分布广泛,能显著影响土壤饱和导水率的大小,为探明冻融交替对不同类型生物结皮土壤饱和导水率的变化。  方法  以神木六道沟流域混合结皮（藻结皮 + 苔藓结皮）和苔藓结皮土壤为研究对象,采用室内模拟冻融实验的方法,测定不同冻融交替次数和初始含水率共同作用下生物结皮土壤饱和导水率（Ks）的变化。  结果  （1）冻融条件下,苔藓结皮和混合结皮的存在相比裸土均降低了土壤Ks。（2）同一冻融次数下,苔藓结皮和混合结皮土壤Ks随初始含水率增加总体呈现先增大后减小的趋势;同一初始含水率下,两种结皮土壤Ks随冻融次数增加呈现逐渐增大的趋势。（3）冻融后苔藓结皮土壤Ks显著大于混合结皮土壤,在同一冻融条件下,初始含水率为8%时,冻融3次和7次后两种结皮土壤Ks相差最大,表现为苔藓结皮土壤Ks分别是混合结皮土壤的2.1和2.3倍。（4）冻融通过影响结皮层容重和结皮厚度及结皮下层土壤有机质和 > 0.25 mm团聚体含量进而影响Ks,冻融次数对结皮厚度及有机质含量有极显著影响（P < 0.01）,对结皮容重有显著影响（P < 0.05）,初始含水率对 > 0.25 mm团聚体含量有极显著影响（P < 0.01）。（5）冻融环境下苔藓结皮和混合结皮土壤的Ks均与冻融次数呈极显著正相关（P < 0.01）,与结皮容重呈极显著负相关（P < 0.01）。并对两种结皮Ks与其他因子进行偏最小二乘回归分析,结果表明苔藓结皮土壤Ks的主要影响因子依次为结皮容重 > 冻融次数 > 结皮厚度,而混合结皮土壤Ks的主要影响因子为冻融次数 > 结皮容重。  结论  冻融交替对生物结皮土壤饱和导水率有较显著影响,且冻融作用主要是通过影响结皮厚度、结皮容重及结皮下层土壤大团聚体颗粒及有机质含量来影响生物结皮土壤饱和导水率。     

黄土丘陵区不同盖度生物结皮土壤抗冲性研究

按藓类植物所占结皮面积比例为盖度划分标准,采用变坡度水槽研究了不同盖度生物结皮对土壤抗冲性及黏结力、有机质、容重等理化属性的影响,探索了生物结皮理化属性与抗冲性之间的关系。结果表明:结皮容重随结皮盖度的增加呈不断减小的变化趋势4,盖度(苔藓盖度>80%)平均结皮容重比1盖度(苔藓盖度<20%)减小了16%;土壤黏结力、有机质、>5 mm水稳性团聚体百分比均随着结皮盖度的增加而增大。生物结皮通过本身分泌的有机凝胶体和多聚糖等胶结物质及菌丝之间的缠绕、包裹等作用,不但改善了土壤本身的理化属性,而且增强了松散土粒与土粒之间的黏结作用;结皮土壤抗冲刷时间随着结皮盖度的增加而延长,土壤侵蚀率随着结皮盖度的增加而减少,证实了结皮的形成和发育减少或避免了土壤侵蚀的发生与发展;生物结皮提高土壤抗冲性的作用主要表现在生物结皮提高了土壤黏结力与团聚体含量上。     

科尔沁沙地结皮发育对土壤理化性质影响的研究

通过野外取样和室内分析,初步研究了科尔沁沙地植被恢复过程中结皮的理化性质及其结皮发育对下层土壤特性的影响。结果表明,半流动、半固定和固定沙丘分别发育了物理、地衣及苔藓结皮,结皮的厚度、紧实度、水分、粘粉粒含量及各种全效、速效养分随沙漠化逆转趋势依次增加。同时,结皮的存在增加了其下层土壤的容重值,提高了颗粒组成中的极细砂和粘粉粒含量,富集了结皮下土壤的有机质、全N、全P、速效N、速效P等养分,随着结皮的发育,结皮对下层土壤的上述影响作用从半流动沙丘到半固定、固定沙地呈逐渐增长的趋势。沙漠化逆转过程中,结皮对土壤养分的富集在0-5 cm范围内,由表及里呈递减趋势。同一沙丘结皮下0-2.5 cm层土壤的容重、粘粉粒含量、养分含量均高于2.5-5 cm层及对照无结皮层相对应的值。     

陕北毛乌素沙地生物结皮发育特征的初步研究

通过野外采样和室内分析相结合,掌握了陕北毛乌素沙地不同采样点生物结皮层的理化性质以及该地区生物结皮的发育特征,为以后进一步研究毛乌素沙地生物结皮的防风固沙效应奠定了理论基础.结果表明:随着生物结皮的发育,结皮层厚度增加.最大值为11.82 mm;土壤颗粒细化,0.02～0.05 mm之间的颗粒含量为7.3%～27.7%,高于流沙中的颗粒含量;由于颗粒的细化,结皮层容重增加,其抗剪强度明显提高,且抗剪强度与厚度和容重之间存在一定的相关性.生物结皮层pH值为7.23～7.81,低于流动沙地的pH值;有机质、N和K含量明显高于流沙的含量;P含量有所增加但不明显.研究表明,各个样点的生物结皮效应表现有所不同,原因有多方面.主要是结皮的发育程度、植被盖度以及采样点地形地貌之间的差异所引起.     

黄土高原藓结皮覆盖土壤的穿透阻力特征及其影响因素

生物结皮的发育显著地影响并改变了表层土壤的理化性状,从而影响土壤穿透阻力。为探明生物结皮层对土壤穿透阻力的影响,针对黄土高原风沙土和黄绵土两种典型土壤,利用高精度土壤贯入仪测定并比较了不同含水量下藓结皮土壤和无结皮土壤的穿透阻力差异,定量分析了藓结皮层对土壤穿透阻力的影响及其与土壤性质(含水量、容重和有机质含量以及颗粒组成)的关系。结果表明:风沙土和黄绵土藓结皮层最大穿透阻力的变化范围为0.38~3.74 MPa和0.43~8.01 MPa,分别为同等深度下无结皮土壤的2.14~9.45倍(P=0.001)和1.38~6.27倍(P=0.051)。藓结皮对风沙土穿透阻力的影响深度为表层2~12 mm(P=0.028),而对黄绵土的影响深度为3~24 mm(随含水量变异较大)。同时,与无结皮土壤的穿透阻力随深度增加而线性增加的趋势不同,藓结皮土壤的穿透阻力随深度增加在结皮层呈先增后减的趋势,在结皮下层呈线性增加的趋势。此外,藓结皮土壤的横向穿透阻力和纵向穿透阻力差异显著(P≤0.03),但在无结皮土壤上差异不显著(P≥0.052)。藓结皮土壤的穿透阻力与含水量呈显著的幂函数关系(P<0.001),与容重、有机质含量以及砂粒含量呈线性关系,这些因素均为藓结皮改变表层土壤穿透阻力的重要途径。     

高寒草甸生物结皮发育特征及其对土壤水文过程的影响

为了明确不同退化程度高寒草甸生物结皮发育特征及其对土壤水文过程的影响,以三江源泽库高寒草甸生物结皮为研究对象,分析了不同退化程度(原生植被、轻度退化、中度退化及重度退化)高寒草甸生物结皮的优势种、盖度、厚度、容重及其对土壤水分入渗、蒸发的影响。结果表明:(1)不同退化程度泽库高寒草甸生物结皮以苔藓结皮为主,其优势种为土生对齿藓。原生植被至轻度退化阶段,生物结皮盖度、厚度无显著变化。至中度退化阶段,生物结皮容重无显著变化,其盖度、厚度分别较轻度退化样地分别下降74.85%,35.49%(p0.05)。至重度阶段,生物结皮完全消失。(2)生物结皮对高寒草甸土壤水分入渗、蒸发过程无显著影响。覆盖和移除生物结皮处理初始入渗速率分别为0.20,0.22 mm/s,二者稳定入渗速率均为0.03 mm/s;覆盖和移除生物结皮处理平均土壤日蒸发量分别为1.79,1.78 mm/d。研究结果可为该区域其他生物结皮的相关研究提供数据基础。     

鄂尔多斯沙地土壤生物结皮的理化性质

本文通过野外取样和室内分析相结合, 对鄂尔多斯沙地不同植物群落下的土壤生物结皮的理化性质进行了初步的研究。研究表明沙地固定的时间越久,其下的生物结皮越多,厚度也越大,结皮的厚度在0.3 ~ 1.5cm之间;在流动沙丘表面形成生物结皮后,结皮中的颗粒组成发生明显的变化,其中0.25 ~ 0.05mm级别的粗砂粒明显减少,而且随着结皮形成的厚度增加,其减少的幅度越大,最大减少的幅度可达30%;随着结皮厚度的增加,结皮的容重也明显增大,室内测定的毛管持水量明显增加,表现出强烈非孔隙吸水现象。但较厚的生物结皮也具有明显的阻水作用,也是导致老固定沙丘植物群落衰退的原因之一。结皮厚度越大,其有机质、全N、全P、速效N、速效P、速效K含量也越高,且以沙地柏下的各种养分含量最高,结皮中的最高有机质含量是流沙的13.5倍(未除去生物残体时),说明生物结皮具有显著的养分富积作用。随着有机含量的增加,其C/N和C/P比呈增加趋势,而pH有轻微的下降趋势。总之,通过对鄂尔多斯沙地生物结皮的初步分析,可以明显看出沙地生物结皮对土壤理化性质有明显的影响,对沙地的生态系统的影响需要进一步研究。     

人工生物土壤结皮特性及其集雨潜力的研究

为探讨在太行山半干旱区利用人工土壤生物结皮进行集雨的潜力和可行性,以自然生长的生物土壤结皮为种子,通过培育建立人工土壤生物结皮和生物结皮集雨,对人工土壤生物结皮建成后土壤物理性状、渗透率的变化及人工生物结皮集雨面的集流效率进行了研究。结果表明,人工土壤生物结皮与自然生长的生物结皮一样,可显著改变土壤的颗粒组成,使0~1 cm表层土壤的小颗粒物质含量增加、大颗粒物质减少,但对0~5 cm的土壤容重影响不显著。对土壤入渗速率的测定结果表明,人工培育的土壤生物结皮具有降低入渗速率的作用,与自然土壤相比,生物结皮的土壤初始入渗速率和稳定入渗速率分别下降59.1%和44.4%,达到稳定入渗的加水量也减少50.0%。人工营建的生物结皮集雨面的平均集雨效率达60.86%,与自然土面相比,提高23.0%。对集雨面效益分析表明,生物结皮集雨面不仅具有较高的集雨效果,且使用年限较长,并具有明显的减少地表径流沉积物含量,提高土壤抗蚀性的作用。综上结果可以看出,人工土壤生物结皮是一种极具潜力的绿色环保型集雨材料。     

初始含水量和容重对黑土压缩特性的影响

东北黑土区农业机械化水平高,农机作业压实导致的土壤结构和物理性状退化问题日益严重,压缩特性是定量分析土壤压实过程的有效手段,但目前黑土压缩特性随初始含水量和初始容重的变化规律尚不明确。为了解初始含水量和初始容重对黑土压缩特性的影响程度及其变化关系,该研究以重塑黑土为对象,设0.15、0.20、0.25、0.30、0.35、0.40 g/g共6个初始含水量水平,设1.00、1.10、1.20、1.30、1.45、1.60 g/cm³共6个初始容重水平,使用固结仪进行单轴压缩试验测定土壤压缩曲线,分析初始含水量和容重对压缩特性影响。结果表明,土壤初始含水量、容重及两者交互作用均极显著影响重塑黑土压缩特性(P<0.001),据此建立了预测压缩特性的土壤传递函数。黑土的预固结压力为10.42～1 106.17 kPa,与初始含水量显著线性正相关、与初始容重显著线性负相关(P<0.05);压缩指数为0.311～0.852,与初始含水量和容重呈二元多项式方程的关系,随初始容重的增大而降低,在中等含水量时最大;回弹指数为0.007～0.321,与初始含水量正相关,与...     

Einfluß physikalischer Eigenschaften und anthropogener Tätigkeit auf die Hysterese der Wasserspannungskurve organogener Böden

Influence of the soil properties and human activity on the hysteresis of the moisture retention function in organic soils The hysteresis of the moisture retention function is characterized by the greatest difference of water content during drying and wetting (Θ_AΘ_B) at the same suction. It diminishes by an increased degree of peat decomposition, ash content, bulk density and pH and increases with the volume of macropores (Ø > 50 μm). In the soil suction range Ψ = –1 to –6 kPa the hysteresis can be calculated by multiple regression equations (Tab. 3). Under arable land compared with grassland the hysteresis increases depending on the soil looseness and diminution of soil aggregates. A sand cover on peatland leads in the upper (20–30 cm) layer to a diminution of hysteresis proportional to the sand thickness.     

Phosphate Diffusion Coefficients in Soil as Affected by Bulk Density and Water Content

Phosphate diffusion coefficients (D_e) were determined by the quantity of P that diffused from a soil block with P addition into a soil block without P addition. To compare the results with theoretical concepts and to quantify the influencing factors, D_e was also calculated using the equation of Nye (1968). This equation takes into account the P diffusion coefficient in water, D₁, the volumetric water content, θ, the impedance factor, f, and the buffer power, b, of the soil. The results show that D_e strongly depends on volumetric water content whereas the effect of bulk density on D_e values was relatively small. If the weighted average buffer power was used, calculated D_e values were in good agreement with measured values at higher soil moisture contents. At θ < 0.22 g cm^?3 the measured values for D_e were smaller than the calculated. This effect is attributed to incomplete contact between the two soil blocks. The only small influence of bulk density on D_e is caused by the fact that bulk density affects both θ and b in a way which compensates each other.     

Vulnerability of Bavarian silty loam soil to compaction under heavy wheel traffic: impacts of tillage method and soil water content

Soil compaction caused by traffic of heavy vehicles and machinery has become a problem of world-wide concern. The aims of this study were to evaluate and compare the changes in bulk density, soil strength, porosity, saturated hydraulic conductivity and air permeability during sugar beet (Beta vulgaris L.) harvesting on a typical Bavarian soil (Regosol) as well as to assess the most appropriate variable factors that fit with the effective controlling of subsequent compaction. The field experiments, measurements and laboratory testing were carried out in Freising, Germany. Two tillage systems (conventional plough tillage and reduced chisel tillage) were used in the experiments. The soil water contents were adjusted to 0.17 g g⁻¹ (w₁), 0.27 g g⁻¹ (w₂) and 0.35 g g⁻¹ (w₃).Taking the increase in bulk density, the decrease in air permeability and reduction of wide coarse pore size porosity (−6 kPa) into account, it seems that CT (ploughing to a depth of 0.25 m followed by two passes of rotary harrow to a depth 0.05 m) of plots were compacted to a depth of at least 0.25 m and at most 0.40 m in high soil water (w₃) conditions. The trends were similar for “CT w₁” (low soil water content) plots. However, it seems that “CT w₁” plots were less affected than “CT w₃” plots with regard to bulk density increases under partial load. In contrast, diminishments of wide coarse pores (−6 kPa) and narrow (tight) coarse pores (−30 kPa) were significantly higher in “CT w₁” plots down to 0.4 m. Among CT plots, the best physical properties were obtained at medium soil water (w₂) content. No significant increase in bulk density and no significant decrease in coarse pore size porosity and total porosity below 0.2 m were observed at medium soil water content. The soil water content seemed to be the most decisive factor.It is likely that, CS (chiselling to a depth of 0.13 m followed by two passes of rotary harrow to a depth 0.05 m) plots were less affected by traffic treatments than CT plots. Considering the proportion of coarse pore size porosity (structural porosity) and total porosity, no compaction effects below 0.3 m were found. Medium soil water content (w₂) provides better soil conditions after traffic with regard to wide coarse pore size porosity (−6 kPa), air permeability (at 6 and 30 kPa water suction), total porosity and bulk density. Proportion of wide coarse pores, air permeability and bulk density seems to be suitable parameters to detect soil compaction under the conditions tested.     

利用时域反射仪测定饱和砂土中非水相液体

利用时域反射技术,以饱和砂土和菜籽油、机油为研究对象,室内模拟研究了非水相液体(NAPLs,nonaqueous phase liquids)污染土壤的介电常数和电导率的变化规律,确定了饱和砂土中NAPLs含量的预测模型。研究表明:1饱和砂土中体积含油量在0~0.05 cm~3/cm~3时,土壤介电常数并无显著变化;随着NAPLs体积含量的进一步增加,介电常数呈线性减小趋势;土壤体积质量和NAPLs类型对相同饱和度的土壤介电常数未产生影响。2饱和土壤的电导率与NAPLs含量存在良好的线性负相关关系(R2=0.96);土壤体积质量对相同饱和度的土壤电导率未产生影响。3混合介电模型(a=0.5)高估了饱和砂土中NAPLs含量,平均RMSE为0.038 cm~3/cm~3;参数a调整为0.52后,混合介电模型提高了预测精度,比原混合介电模型(a=0.5)预测精度可以提高23.2%。本研究结果表明可利用时域反射技术监测污染土壤的介电常数与电导率并测定饱和土壤中NAPLs的含量。     

Estimating soil stress distribution by using depth‐dependent soil bulk‐density data

Depth‐dependent soil bulk density (BDS) is usually affected by soil‐specific factors like texture, structure, clay mineralogy, soil organic‐matter content, soil moisture content, and composition of soil solution and is also affected by external factors like overburden‐stress history or hydrological fluxes. Generally, the depth‐dependent BDS cannot be predicted or extrapolated precisely from a limited number of sampling depths. In the present paper, an easy method is proposed to estimate the state of soil mechanical stress by analyzing the packing characteristics of the profile using soil bulk‐density data. Results for homogeneous loess profiles exposed to the site‐specific climatic conditions show that the depth‐dependent relation of void ratio vs. weight of overburden soil can be described systematically so that deviations from the noncompacted reference state can be detected. We observed that precompaction increased from forest soils (reference) to agricultural soils with decreasing depth.     

Effect of bulk density and soil water tension on denitrification in the rhizosphere of spring wheat (Triticum vulgare

Summary Pot experiments were carried out to study the influence of bulk density (D _b), soil water tension (pF) and presence of plants (spring wheat) on denitrification in a low-humus B_t-horizon of a udalf. Pots of only 5-cm depth were found to be most suitable for the experiments when using the acetylene inhibition method. Almost homogeneous soil compaction between 1.1 and 1.6g soil cm^–3 was achieved by a Proctor tamper. Water tensions were adjusted by means of ceramic plates on which negative pressure was applied. No denitrification was detected in unplanted pots. With planted pots and increasing bulk density denitrification increased more in pots with 14-day-old plants than in pots with 7-day-old plants. With 14-day-old plants N₂O emission pot^–1 increased steadily from 2 mol at D _b 1.1 to 8 mol at D _b 1.6, when soil moisture was adjusted to pF 1.5, although root growth was impaired by higher bulk density. From an experiment with different bulk densities and water tensions it could be deduced that the air-filled porosity ultimately determined the rate of denitrification. When low water tension was applied for a longer period, water tension had an overriding effect on total denitrification. Denitrification intensity, however, i.e. the amount of N₂O g^–1 root fresh weight, was highest when low water tension was accompanied by high bulk density. The results suggest that the increase in denitrification intensity at oxygen stress is partly due to higher root exudation.