科尔沁地区不同类型沙地土壤饱和导水率特征分析

土壤饱和导水率反映了土壤的入渗性质,是研究水分在土壤中运动规律的重要水力参数。利用Guelph入渗仪测量了科尔沁地区樟子松林、灌木林和草地0-20cm、20-40cm和40-60cm三个不同土层深度的土壤饱和导水率,分析了这三种类型沙地土壤饱和导水率的差异及其随土层深度的变化特征。结果表明:1)平均土壤饱和导水率樟子松林较大,草地次之,而灌木林较小,它们的平均取值在0.63～12.50mm/min范围内;随土层深度增加,樟子松林土壤饱和导水率逐渐增大,而草地的逐渐减少,灌木林的随土层深度变化不大;2)樟子松林和灌木林土壤饱和导水率与容重显著负相关;灌木林和草地土壤饱和导水率与细沙百分含量显著负相关,而与中沙百分含量显著正相关;樟子松林和草地土壤饱和导水率与粗沙百分含量显著正相关。     

沃特多功能保水剂保水性能研究

通过室内实验对沃特多功能保水剂在黄土高原主要类型土壤持水性能及保水作用的研究,结果表明:该保水剂在土壤持水方面,对黑垆土效果最明显,持水性均高于对照。而对土和黄绵土来讲,效果不太明显。但在土壤导水方面,黄绵土的改善效果最明显,饱和导水率随保水剂用量的增多而增大;对黑垆土导水率的提高也有一定的作用;对于土来讲饱和导水率在施入保水剂后反而降低。在土壤抗蒸发方面,保水剂抗蒸发作用明显,随用量的增多而各土壤的蒸发量减少。     

生物炭对和田风沙土水力特性的影响

为探究生物炭的施入量对和田风沙土水力特性的影响,设置了5个生物炭施用量处理,质量比(生物炭质量/干土质量)分别为0%(CK)、4%(T1)、8%(T2)、12%(T3)、16%(T4),利用离心机法获取土壤水分与吸力关系,定水头法获得饱和土壤导水率,通过VG-M组合模型拟合土壤水分特征曲线,探究生物炭对风沙土持水性、土壤水分有效性、释水性和导水规律的影响。结果表明:生物炭显著影响了风沙土的持水特性,改变了其孔隙分布规律,对VG模型参数θ_s、θ_r、α、n均有不同程度的影响。随着生物炭的增加,田间持水量(体积含水量)由19.42%增加到30.64%,全有效水含量由18.15%增加到25.63%,萎蔫系数由1.27%增加到5.01%,饱和导水率平均降低80.93%,各处理的比水容量在PF=1.8～3.8(土壤水吸力对数值)阶段为T3T4T2T1CK,在相同的土壤含水量下各处理的非饱和导水率表现为CKT1T2T3T4,毛管孔隙比例与生物炭用量呈二次函数趋势变化。生物炭能够改善风沙土的孔隙结构,增大其有效水分含量,减小其入渗速率。从土壤水力特性角度出发,利用生物炭改良和田风沙土生物炭适宜的施入量为12%。     

黄土高原藓结皮覆盖土壤导水性能和水流特征

生物结皮具有特殊的水文物理性质,为探究其对土壤水分渗透性和水流特征的影响,以黄土高原风沙土和黄绵土上3种典型地表覆盖类型(裸地、藓结皮、藓结皮-草本植物混合)为对象,采用环刀法和染色示踪法对其导水性质与水流特征进行探究。结果表明:藓结皮对2种土壤类型0~5 cm土层土壤理化性质影响较大,与裸地相比土壤容重降低了9.85%~10.00%,土壤黏粒含量增加了1.01~1.29倍,表层有机质含量提高了2.73~3.02倍;藓结皮使0~5 cm土层土壤饱和导水率降低了61.32%~88.89%,而在5~10 cm土层饱和导水率则有明显上升。另外,由于草本植物的影响,藓结皮-草本植物0~5 cm土层与藓结皮土壤相比土壤饱和导水率提高了1.32~6.43倍;黄绵土藓结皮与藓结皮-草本植物的染色面积比均高于裸地,且水分下渗深度增加了10 cm,而风沙土藓结皮与风沙土裸地的染色面积比差异不明显。综上所述,藓结皮和藓结皮-草本植物的存在改变了表层土壤水分渗透性以及水流运动特征和水分下渗深度,影响着黄土高原土壤水分保持和生态恢复。     

干旱区湿地土壤有机质空间分布及关系研究——以艾比湖湿地为例

通过对干旱区湿地-艾比湖湿地土壤有机质、碱解氮、速效磷、速效钾等土壤质量指标分析,结果表明:湖区土壤有机质含量呈现出盐化草甸土>盐土>灰棕漠土>风沙土的规律。湿地土壤有机质空间上表现为湖区以东、以西、以南方向上层土壤有机质依次递减,湖区以北上层土壤有机质先递减后递增。湖区以西中层土壤有机质与上层趋势一致,以北有机质含量较大,湖区以东、以南方向有机质含量较小。下层土壤样品中,湖区以西、以北位置均呈现递减趋势,以东方向有机质含量较高,以南较小。盐化草甸土有机质含量自上而下依次递减,趋势明显。盐土、风沙土、灰棕漠土有机质含量上层>中、下层,中下层含量差异较小。土壤中的碱解氮、速效磷、速效钾含量与土壤中有机质含量具有较好的相关性。     

黄土区坡沟系统容重、饱和导水率和土壤含水量变化分析

切沟是黄土高原侵蚀沟的重要类型之一,对流域水文、植被、地貌和生态等地表过程具有深刻影响。为明确土壤物理参数对切沟地形、坡位和深度的响应,在陕北黄土高原选择典型切沟,根据其走向设置沟道、沟缘及坡面3条样线,对40个样点按照10 cm深度间隔采集0~30 cm各土层原状土样,利用定水头法和烘干法对土壤容重、饱和导水率和土壤含水量进行测定并分析。结果表明:(1)地形对容重、饱和导水率和土壤含水量具有显著或极显著影响,3个参数随坡位自下而上均呈波浪式变化趋势;沟缘和坡面位置容重随坡位上升总体呈微弱减小趋势,沟缘表层坡下土壤含水量较其他坡位明显偏低;(2)沟缘和坡面位置不同土层深度饱和导水率及容重的大小变化规律与沟道恰好相反;(3)对于各土层深度而言,沟缘和坡面土壤含水量均与沟道内差异显著,且沟缘土壤含水量总是低于坡面。以上结果表明,切沟分布改变了土壤容重、饱和导水率和土壤含水量在坡面的空间格局,在黄土区坡沟系统内不同地形条件对相关土壤物理参数的影响不应忽视。     

不同土体构型土壤的持水性能

通过GMS软件三维建模功能,将宁夏某葡萄基地土壤划分为4种土体构型:壤砂型、砂型、壤砂粘型和壤粘砂型结构,并对基地土壤的田间持水量、饱和导水率和容重进行了分析,研究了不同土体构型下的土壤持水性能。结果表明,土壤土体构型不同,其容重、田间持水量、土壤饱和导水率也不同。砂型结构的田间持水量和容重最小,分别为13%和1.5 g·cm~(-3),而土壤饱和导水率最大,为3.2 m·d~(-1);壤粘砂型结构田间持水量和容重最大,分别为16.5%和1.63 g·cm~(-3),而土壤饱和导水率最小,为1.02 m·d~(-1);田间持水量与土壤饱和导水率的相关系数为-0.92,呈显著负相关,与容重的相关系数为0.73,呈显著正相关。壤粘砂型土体构型上壤下粘,利于保水保肥,持水性能最好;砂型结构持水性能最差,其他土体构型持水性能一般,需要进行改良以提高土壤的持水性能。     

荒漠结皮对土壤水分状况的影响

本研究针对鄂尔多斯沙地生物结皮进行调查 ,利用人工喷水模拟降雨分析结皮对土壤入渗性能的影响。研究表明 :生物结皮能显著地降低土壤水分的入渗速率。在去掉结皮时 ,表层下 5 cm处的土壤含水量在 1 0分钟时即开始显著增加 ,而有结皮时 ,此处的含水量则在 1 5分钟时才开始显著增加。利用圆盘入渗仪测定有结皮和无结皮条件下的土壤饱和导水率表明 :固定沙丘间地有生物结皮的土壤饱和导水率范围是 :2 9.1 0 - 82 .2 1 mm/ h;半固定沙丘有微弱结皮时饱和导水率为 1 43.5 4 - 2 30 .2 5 ;去掉结皮后土壤的饱和导水率可显著上升数倍 ,无结皮的流沙的饱和导水率最高。     

毛乌素沙地复配土壤水分特征曲线模型筛选研究

针对国家增加可利用土地、降低水土流失的需求,利用复配土壤对风沙土进行改良,是实现毛乌素沙地治理、区域生态修复的重要手段。测定不同复配比例土壤的水力学性质,并进一步筛选出合适复配土壤使用的水分特征曲线模型,运用高速离心机法测定对复配土壤水分特征曲线,环刀法测定复配土饱和导水率,并对比不同水分特征曲线模型对于不同比例复配土壤的模拟效果。研究表明:相同土壤水吸力下,添加砒砂岩处理的土壤含水率均高于纯风沙土处理;复配比例中砒砂岩含量越高,土壤保水性越高;当砒砂岩与风沙土复配比例高于5:1后,土壤水分特征曲线与纯砒砂岩差异不大;低吸力阶段,砒砂岩的添加减少了土壤中大孔隙的比例,而在中高吸力阶段,砒砂岩的添加增大了土壤中小孔隙的比例,进而提高土体的持水能力。模型适宜性分析结果表明,能够适配各处理的非饱和导水率模式最优模型为van Genuchten模型;砒砂岩与沙复配比例高于1:5后,Gardner模型的相关系数从0.9473上升至0.9929,残差平方和0.041降低至0.010,模拟效果逐渐超越van Genuchten模型,间接推求公式Arya-Paris模型物理概念明确,但影响因素过多,相较经验公式拟合效果不佳。     

六盘山林区土壤物理性质分布特征

研究了六盘山林区土壤物理性质分布特征及其与海拔和林型的关系,结果表明:六盘山林区阔叶林地土壤有机质和饱和导水率显著高于针叶林地,土壤容重显著低于针叶林地,阔叶林地0~10 cm和10~20 cm土层土壤有机质和饱和导水率分别比针叶林地高27.7%、21.2%和38.0%、42.2%,容重比针叶林地低13.8%和7.6%;高海拔处林地土壤有机质含量较高,容重较低;研究区土壤饱和导水率不受海拔影响,土壤水稳性团聚体分布不受林型和海拔的影响;阔叶林地0~20 cm土层土壤平均重量直径和几何平均直径平均值分别比针叶林地高3.46%和5.21%,但不受海拔影响,大团聚体数量与饱和导水率极显著正相关。研究表明六盘山林区阔叶林地土壤物理性状显著优于针叶林地,林地土壤结构的改良主要体现在大团聚体增加方面。     

Effect of Pisha sandstone on water infiltration of different soils on the Chinese Loess Plateau

The infiltration of water into soil is one of the most important soil physical properties that affect soil erosion and the eco-environment, especially in the Pisha sandstone area on the Chinese Loess Plateau. We studied the one-dimensional vertical infiltration of water in three experimental soils, created by mixing Pisha sandstone with sandy soil, irrigation-silted soil, and loessial soil, at mass ratios of 1:1, 1:2, 1:3, 1:4, and 1:5. Our objective was to compare water infiltration in the experimental soils and to evaluate the effect of Pisha sandstone on water infiltration. We assessed the effect by measuring soil bulk density(BD), porosity, cumulative infiltration, infiltration rate and saturated hydraulic conductivity(Ks). The results showed that Pisha sandstone decreased the infiltration rate and saturated hydraulic conductivity in the three experimental soils. Cumulative infiltration over time was well described by the Philip equation. Sandy soil mixed with the Pisha sandstone at a ratio of 1:3 had the best water-holding capacity. The results provided experimental evidence for the movement of soil water and a technical support for the reconstruction and reclamation of mining soils in the Pisha sandstone area.     

Effect of Pisha sandstone on water infiltration in different soils on the Chinese Loess Plateau

The infiltration of water into soil is one of the most important soil physical properties that affect soil erosion and the eco-environment, especially in the Pisha sandstone area on the Chinese Loess Plateau. We studied the one-dimensional vertical infiltration of water in three experimental soils, created by mixing Pisha sandstone with sandy soil, irrigation-silted soil, and loessial soil, at mass ratios of 1:1, 1:2, 1:3, 1:4, and 1:5. Our objective was to compare water infiltration in the experimental soils and to evaluate the effect of Pisha sandstone on water infiltration. We assessed the effect by measuring soil bulk density (BD), porosity, cumulative infiltration, infiltration rate and saturated hydraulic conductivity (Ks). The results showed that Pisha sandstone decreased the infiltration rate and saturated hydraulic conductivity in the three experimental soils. Cumulative infiltration over time was well described by the Philip equation. Sandy soil mixed with the Pisha sandstone at a ratio of 1:3 had the best water-holding capacity. The results provided experimental evidence for the movement of soil water and a technical support for the reconstruction and reclamation of mining soils in the Pisha sandstone area.     

四种方法推求土壤导水参数的差别与准确性研究

利用土壤水分特征曲线拟合公式和实测的饱和导水率间接推求土壤非饱和导水参数K(θ)和D(θ)是目前大多数水文模型普遍采用的方法。以长武黑垆土为例,对其中比较流行的Broadbrige-White模型、VanGenuchten模型、Burdine模型和Mualem模型推求土壤导水参数的差别和准确性进行了比较分析。结果发现:在较高含水量范围内,4种方法推求的土壤导水参数与实测值相差很小,具有较高精度;用4种方法计算土壤水分扩散率D精度要明显高于对非饱和土壤导水率K计算精度;对黑垆土而言,用Broadbrige-White模型推求的土壤非饱和导水参数K和D精度最高。     

Effects of the invasive shrub,Lantana camara,on soil properties in the Eastern Cape,South Africa

Lantana camara L. is an invasive alien shrub of worldwide significance due to its impacts on biodiversity. It can alter the soil properties of invaded ecosystems and, as a result, affect management outcomes. However, knowledge on the impacts of L. camara on soil properties is scanty, especially in South Africa, despite the pervasive presence of the plant in the country. In this comparative study, the soils underneath L. camara were assessed in order to determine if they had different properties (soil physico‐chemical properties, penetration resistance, infiltration, hydraulic conductivity and water repellency) in comparison to the soils in adjacent natural sites in the Eastern Cape, South Africa. Soil samples were collected from the top soil beneath the canopy of both L. camara‐invaded and adjacent natural sites in five different locations over three summer months. The soils that were collected from underneath L. camara had a significantly higher total C, total P, gravimetric soil moisture (in November and December) and were repellent, compared to the soils in the adjacent natural sites. Soil penetration resistance was significantly higher in the natural sites than in the L. camara‐invaded sites. The soil hydraulic conductivity, soil infiltration rate, soil pH, exchangeable cations and total N showed no significant difference between the invaded and the natural sites. It appears that the soils underneath L. camara have a high total C and total P, soil moisture and are repellent, thus influencing nutrient cycling, potentially making the soil properties underneath it ideal for its own growth. This could contribute to the success of L. camara as an invasive species.     

Straw Management Effects on Organic Matter Mineralization and Salinity in Semiarid Agricultural Soils

The impact of straw incorporation (6 Mg ha -1 year -1 ) into agricultural soils compared with straw removal on organic matter mineralization and salinity was studied. The mineralization coefficient (CO 2 -C evolved/organic C ratio) was obtained to evaluate organic matter mineralization. Soil salinity was measured as means of electrolytic conductivity of saturation paste extract. Both parameters were measured seasonally during two years in two salt-affected soils of the semiarid Central Ebro Valley (northeast Spain), a saline soil and a saline-sodic soil. The electrolytic conductivity (ranging from 2.5 dS m -1 to 24.3 dS m -1 ) and the mineralization coefficient (ranging from 5.9 10 -4 day -1 to 37.9 10 -4 day -1 ) varied widely during seasonal samplings of both soils. The lowest electrolytic conductivity values, coincided with the highest mineralization coefficient values. Straw mulching and burying decreased significantly the average seasonal electrolytic conductivity of both soils: 2.5 times in the saline soil, and 1.9 times in the saline-sodic soil. The EC reduction only increased significantly (P < 0.05) the mineralization coefficient on saline soil (1.6 times). Straw amendment, followed by rainy periods, allowed the soluble salts leaching but did not modify significantly sodium content. A logarithmic regression was found between mineralization coefficient and electrolytic conductivity (r 2 = 0.41), considering both soils. Infiltration, water aggregate stability, and qCO 2 were improved with the straw amendment, but only in saline soil. Soil differences showed the existence of a double effect: an osmotic and a specific ion effect.     

Leaching of atrazine into ground water

A study of the leaching of atrazine from soils in Denmark with high hydraulic conductivity demonstrated only small quantities of the herbicide in the upper ground-water zone. The atrazine-treated fields were situated in a region where the water table was high and free lying and where the cover layer consisted of sand. Samples were taken from the upper 1–5 m ground-water zone at three well-defined levels. The atrazine content was between 0.01 and 0.05 μg litre^?1 the highest concentrations being found at the top of the ground-water zone.     

宁夏不同类型盐渍化土壤水溶盐含量与其电导率的关系

根据宁夏盐渍化土壤的分布区域,采集了不同类型盐渍化土壤样品(0~20 cm)141个,测定了土壤浸提液电导率与水溶性盐含量及其盐分组成,系统研究了残渣烘干法土壤水溶盐含量与电导率之间的关系。结果如下:(1)土壤水溶性盐分离子阳离子以钠离子含量最高,镁、钙离子含量次之,阴离子以氯离子含量最高,硫酸根离子含量次之;(2)从阴离子组成来看,供试土壤以硫酸盐-氯化物型、氯化物-硫酸盐型和硫酸盐型为主,从阳离子组成来看,以镁钙盐型、钙镁盐型和钠盐型为主;(3)从5种函数模式中筛选出土壤浸提液电导率与其残渣烘干法水溶盐含量之间的最优回归关系,当不区分土壤盐分类型时,可采用二次式(通式)y=0.1609x2+2.9176x-0.0141求解土壤含盐量;当已知土壤盐分类型时,有针对性地选用不同盐分类型最优回归式计算;(4)提出了电导率法测定土壤水溶盐含量校正为残渣烘干法水溶盐含量的关系式。     

Soil hydraulic conductivity as affected by vegetation restoration age on the Loess Plateau,China

The Loess Plateau of China has experienced extensive vegetation restoration in the past several decades,which leads to great changes in soil properties such as soil bulk,porosity,and organic matter with the vegetation restoration age.And these soil properties have great effect on the soil infiltration and soil hydraulic conductivity.However,the potential changes in soil hydraulic conductivity caused by vegetation restoration age have not been well understood.This study was conducted to investigate the changes in soil hydraulic conductivity under five grasslands with different vegetation restoration ages(3,10,18,28 and 37 years)compared to a slope farmland,and further to identify the factors responsible for these changes on the Loess Plateau of China.At each site,accumulative infiltration amount and soil hydraulic conductivity were determined using a disc permeameter with a water supply pressure of –20 mm.Soil properties were measured for analyzing their potential factors influencing soil hydraulic conductivity.The results showed that the soil bulk had no significant changes over the initial 20 years of restoration(P0.05);the total porosity,capillary porosity and field capacity decreased significantly in the grass land with 28 and 37 restoration ages compared to the slope farmland;accumulative infiltration amount and soil hydraulic conductivity were significantly enhanced after 18 years of vegetation restoration.However,accumulative infiltration amount and soil hydraulic conductivity fluctuated over the initial 10 years of restoration.The increase in soil hydraulic conductivity with vegetation restoration was closely related to the changes in soil texture and structure.Soil sand and clay contents were the most influential factors on soil hydraulic conductivity,followed by bulk density,soil porosity,root density and crust thickness.The Pearson correlation coefficients indicated that the soil hydraulic conductivity was affected by multiply factors.These results are helpful to understand the changes in hydrological and erosion processes response to vegetation succession on the Loess Plateau.