黄土丘陵区生物结皮对土壤入渗的影响

为了明确生物结皮对土壤入渗的影响,在黄土丘陵区沿降雨梯度从南到北大致按等间距分别在宜君、富县、延安、子长、子洲、榆林、东胜选取7个生物结皮发育较好的试验样地,并分别以无结皮样地作为对照,使用盘式入渗仪记录入渗过程并计算各入渗参数。结果表明,生物结皮可显著增大土壤表层有机质含量,但对土壤容重和土壤质地的影响不显著。生物结皮具有显著抑制土壤入渗的作用,从南到北土壤入渗性能呈现逐渐增加的趋势,但存在局部波动;从南到北7个生物结皮样地的饱和导水率、土壤初渗率及30min累积入渗量分别为0.18~0.39mm/min,1.31~2.72mm/min及15.18~43mm,从南到北7个对照样地的饱和导水率、土壤初渗率及30min累积入渗量分别为0.13~0.60mm/min,1.19~2.45mm/min及11.90~52.34mm。土壤初渗率和累积入渗量主要受土壤质地和初始含水量影响,土壤初始含水量对有无生物结皮生长土壤入渗过程的影响比较类似,而土壤质地对有生物结皮生长的样地入渗过程影响更显著;有无生物结皮条件下土壤饱和导水率均受土壤质地的影响,且土壤质地对无结皮样点的影响更显著。     

红壤丘陵区不同盖度生物结皮对水分入渗的影响

为探究不同盖度生物结皮对入渗特征的影响,在红壤丘陵区咸宁选取第四纪黏土发育土壤(S型)和泥质页岩发育土壤(N型)上的生物结皮,设计6个盖度水平(裸地,1%~20%,20%~40%,40%~60%,60%~80%,80%~100%),使用微型圆盘入渗仪(mini disk)测定土壤入渗过程,探究入渗过程的影响因素,同时采用3种常见的入渗模型对入渗过程进行拟合,并评价模型适用性。结果表明:(1)相对于裸地,生物结皮发育提高土壤有机质和黏粒含量,增加结皮厚度和生物量,降低砂粒含量。(2)第四纪黏土发育土壤水分入渗特征随生物结皮盖度的增加而逐渐降低,初始入渗速率、稳定入渗速率、平均入渗速率、非饱和导水率的变化范围分别为0.25~1.55,0.13~0.91,0.17~1.11,2.04~8.48 mm/min。泥质页岩发育土壤除40%~60%盖度砾石含量较高,土壤水分入渗也随盖度的增加而逐渐减小,80%~100%盖度的初始、平均和稳定入渗率较裸地分别降低91.14%,87.64%和91.30%,生物结皮的存在阻碍土壤水分入渗。冗余分析表明,对于第四纪黏土发育土壤,生物量(54.30%)对其入渗特征的解释度最高,泥质页岩发育土壤则为盖度(39.30%)和砾石含量(34.00%)。(3)Horton模型、Kostiakov模型、Philip模型3种主流入渗模型中Horton模型拟合效果最优。研究结果可为揭示湿润区生物结皮水分运移规律提供科学参考。     

黄土高原藓类生物结皮对表层土壤水分运动参数的影响

生物结皮普遍存在于干旱和半干旱地区土壤表层,对土壤水分有重要影响。为了进一步探究生物结皮对表层土壤水力学特性和水分运动过程的影响,该研究以黄土高原风沙土和黄绵土上发育的藓结皮为研究对象,通过野外采样与室内试验相结合,测定了藓结皮覆盖土壤和无结皮土壤的Boltzmann变换参数、土壤水分扩散率、入渗过程、比水容量和非饱和导水率,对比分析了有无藓结皮覆盖对表层土壤水分运动参数的影响。结果表明:藓结皮覆盖抑制了表层土壤水分的扩散,藓结皮覆盖土壤的Boltzmann变换参数和水分扩散率分别比无结皮土壤降低7.9%～27.3%和99.2%～99.6%;藓结皮覆盖后表层土壤渗透性显著降低,其水分入渗参数(初始入渗率、稳定入渗率、平均入渗率、累积入渗量)和非饱和导水率分别降低了17.1%～55.4%和84.8%～92.3%;藓结皮显著提升了表层土壤的持水和供水能力,藓结皮层的水分常数(田间持水量、萎蔫系数、重力水含量、有效水含量和易利用水含量)比无结皮土壤高40.9%～1 233.3%,土壤水吸力在100k Pa时的比水容量比无结皮土壤高7.4%～1 540.5%;相比黄绵土,藓结皮覆盖对风沙土的渗透性影响较小,而对土壤持水和供水性的影响较大。综上,黄土高原藓结皮覆盖降低了土壤渗透性,同时显著提高了表层土壤的水分有效性,这可能导致土壤表层在雨后截留较多水分,进而使土壤水分分布趋于浅层化,并改变该地区的土壤水分有效性和植物水分利用策略。     

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。     

晋西黄土丘陵区主要人工林土壤饱和导水率研究

饱和导水率是表征土壤入渗能力的重要参数之一,研究饱和导水率对土壤入渗过程分析具有重要的意义。对晋西黄土丘陵区主要人工林土壤饱和导水率(K_s)进行了分析,并利用方差分析(ANOVA)和主成分分析方法探讨了其与土壤物理因子和有机质的相关性,得出影响饱和导水率的主导因子。结果表明,与荒地相比,各林分对饱和导水率均有显著提高;土壤饱和导水率随着土层深度加深呈现负指数递减规律;影响该地区人工林地土壤饱和导水率的主导因子为容重、毛管孔隙度、>0.25mm水稳性团聚体含量、土壤有机质及土壤质地。土壤有机质含量的提高可改善土壤容重、团聚体含量等物理性质;在植被经营过程中,建议采用适宜的混交类型,树种可选择白桦、落叶松等。     

毛乌素沙地生物结皮对水分入渗和再分配的影响

生物结皮的发育影响着干旱半干旱区小尺度土壤水文过程。对两种自然降雨条件下（降雨量为8.5 mm和14.8 mm）的3种放牧管理类型（持续放牧地、围栏5 a禁牧区、围栏15 a禁牧区）有、无生物结皮土壤的降雨入渗速率和再分配规律进行了测定。结果如下：（1）入渗速率禁牧5 a和禁牧15 a样地的有结皮土壤的入渗速率极显著低于无生物结皮土壤。持续放牧样地上,生物结皮发育很差,其对土壤的入渗速率无显著影响。（2）入渗深度自然降雨为8.5mm的次日在持续放牧区能入渗到15～20 cm,而在禁牧5 a和禁牧15 a围栏区仅能入渗到10～15 cm。自然降雨为14.8 mm的次日在持续放牧区能入渗到30～40 cm,在禁牧5 a和禁牧15 a围栏区能入渗到20～25 cm。在无雨条件下,禁牧15 a围栏区50 cm以下土壤水分状况较禁牧5 a和持续放牧区更差。测定结果表明：生物结皮的形成降低了水分的入渗速率和自然降雨的下渗深度,使下渗水分减少,渗透深度变浅,由此可见当地高频率（84.6%）的小降雨（〈10mm）事件只能对浅根系的草本有效,这将使得草本植物生长旺盛而深根系半灌木油蒿生长不良,逐渐衰退。     

不同生物炭施加量的土壤水分入渗及其分布特性

为了揭示生物炭施加到黑土区土壤后形成的特殊双层土壤结构对土壤水分入渗及其分布的影响,该研究采取室内与田间试验相结合的方法,探讨了积水入渗条件下不同生物炭施加量(0、10、20、40和80 t/hm~2)的土壤水分入渗特性,并建立了生物炭-土壤双层土壤结构水分分布模型,对不同生物炭施加量的农田土壤水分分布进行了模拟。结果显示,生物炭-土壤双层结构土壤水分入渗过程表现为斜率由大变小的两段非线性曲线,转折点为入渗锋面到达生物炭-土壤交界面后暂停继续下渗,上层土壤质量含水率累积到界面含水率超过临界含水率42.5%的时间;生物炭的施加使土壤入渗率、饱和导水率和临界吸力与对照相比提高的比例范围分别为21.95%~112.20%、14.29%~52.38%和13.75~78.69%,同时也可显著增强上、下层土壤的持水性能。在上层土壤厚度为20 cm时,影响临界吸力的因素只有生物炭的施加量,且其与施炭量的相关性大于土壤入渗率和饱和导水率;施用生物炭条件下的土壤水分分布规律可以用本研究所建立的生物炭-土壤双层土壤结构水分分布模型来表达。研究表明,生物炭添加能够改善黑土区土壤持水能力和水分入渗特性,有利于作物生长,减少地表径流和水土流失;同时也为生物炭在黑土区农业生产上的应用选择合理施加量提供科学参考。     

踩踏干扰下生物结皮的水分入渗与水土保持效应

为改善生物结皮对土壤水分的负面影响,通过野外定位观测试验,从入渗、产流产沙两方面探讨了黄土高原水蚀风蚀交错区生物结皮在3种踩踏强度下的水土保持效应。结果表明:(1)相比裸土,未被踩踏的生物结皮对水分入渗、地表径流的表现形式并非单一的增加或降低,在雨季初期增渗减流,初期过后减渗增流;(2)不同踩踏强度对水分入渗、地表径流的影响存在明显差异。同裸地对照相比,轻度踩踏结皮增渗12%,减流23.2%,中度踩踏结皮减渗3.6%,减流5.3%,重度踩踏结皮减渗25.5%,增流21.3%;(3)不论是否被踩踏,生物结皮产生的泥沙量都显著低于裸土。同裸土产生的泥沙量相比,轻度踩踏减少56.3%,中度踩踏减少43.5%,重度踩踏减少37.9%,但中度、重度踩踏结皮改变了原先土壤侵蚀格局,增加了泥沙含量。综合考虑入渗和土壤侵蚀认为:轻度踩踏生物结皮可在不增加土壤侵蚀的前提下,促进入渗,减少径流,改善土壤水分状况。     

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。     

黄土丘陵区生物结皮对土壤磷素有效性及碱性磷酸酶活性的影响

黄土丘陵区生物结皮广泛发育,可影响土壤磷素有效性。目前鲜见生物结皮对土壤磷素有效性的研究报道。本文以该区不同年限退耕地的生物结皮为研究对象,通过野外调查和室内分析,研究了生物结皮对土壤全磷、有效磷及碱性磷酸酶活性的影响。结果表明,1）生物结皮的形成可显著提高结皮层土壤全磷含量,而下层(010 cm)全磷含量差异不显著; 2）生物结皮的形成可显著提高结皮层土壤有效磷含量,研究区生物结皮层土壤有效磷含量为3.27~5.87 mg/kg,占到同层土壤全磷含量的0.57%~0.95%,生物结皮层磷酸酶活性高于下层(010 cm) 381倍; 3）生物结皮对土壤磷素有效性及碱性磷酸酶活性的影响与生物结皮发育阶段有关; 4）生物结皮主要通过提高结皮层土壤碱性磷酸酶活性和有机质含量,降低土壤pH,进而提高了土壤磷素有效性。本文研究结果表明,生物结皮的形成有助于提高黄土丘陵区退耕地土壤磷素有效性。     

黄土丘陵区典型植被土壤物理性质差异及其对导水特性影响

选取黄土丘陵区12种典型植被样地,通过测定各样地不同土层植物残体生物量、土壤容重、毛管孔隙度、非毛管孔隙度及饱和导水率,研究各指标随土层深度和植被类型的变化规律及其对土壤饱和导水率的影响。结果表明:(1)除容重随土层深度增加外,植物残体、毛管孔隙度、非毛管孔隙度和饱和导水率均随土层深度减少,其中植物残体大多集中于表层土壤(0—10 cm),占总残体生物量的51.4%～85.7%。(2)不同植被类型其植物残体及土壤物理性质存在显著差异,乔木林地植物残体、农耕地土壤容重、灌木林地非毛管孔隙度及饱和导水率均最大,而毛管孔隙度与不同土地利用类型间无显著差异。(3)饱和导水率随植物残体生物量密度(0—10 cm)和土壤容重呈幂函数减小,随毛管孔隙度和非毛管孔隙度呈幂函数增大;土壤容重(BD)和非毛管孔隙度(NCP)是影响土壤饱和导水率(K_s)的主要因素,且土壤饱和导水率可表示为两者的综合非线性方程(K_s=0.6BD~(-4.717)NCP~(0.203),P0.01,R~2=0.63,NSE=0.50)。此外,沙棘灌木林地平均饱和导水率最大,有利于降雨过程中土壤水分入渗,具有较强的水土保持功能。本研究结果可为黄土高原植被恢复生态水文效益评价提供理论依据。     

Controlling effects of surface crusts on water infiltration in an arid desert area of Northwest China

Purpose

Surface crusts are important features in arid desert areas and are critical to hydrological processes and ecosystem development. This paper aims to understand the effects of crusts on water movement in the soil and the factors that affect this and to provide the soil parameters for estimation of saturated hydraulic conductivity (K _s) in ecohydrological models.

Materials and methods

The study area was located in the middle and lower reaches of the Heihe River Basin, an arid desert area in Northwest China. There were three crust types in this region: physical soil crusts (PSCs, formed by water drop and erosion), biological soil crusts (BSCs, formed by microorganisms, moss, algae, lichen, and soil materials), and salt soil crusts (SSCs, formed by soluble salts). The infiltration rates of different soil and crust types and scalped soils were determined in situ in the field conditions using a disc infiltrometer with three repetitions. Crusts and soils were collected, and their properties were determined in the laboratory.

Results and discussion

The K _s of crust were significantly lower than that of scalped soils with a decrease of 13–70 %. The K _s of crusts were related to the type of crust and the properties of soil beneath the crusts. In this region, the soil textures are similar throughout, due to ubiquitous loess sedimentation, so textural differences had no significant effect on K _s. Soil organic matter (SOM) played a weak negative role on K _s because most crusts had higher SOM than the underlying soil. However, both crust thickness and electrical conductivity (EC, an index of salt concentration) showed significantly negative exponential relationship with K _s. Therefore, the SSC with high EC and thick crust have the lowest K _s among all crust types. Because soil development is related to salt accumulation, structure, and crust formation, the K _s follows the order of Solonchaks < Cambisols < Regosols, from lowest to highest.

Conclusions

Crusts have different characteristics compared with original soils and are the limiting layer of water infiltration in these arid soils. Therefore, the characteristics of crust must be considered in ecohydrological models. The main apparent controlling parameters of water infiltration rate in this area are crust thickness and EC.

     

渝东北紫色土饱和导水率传递函数研究

为研究渝东北紫色土理化性质在垂直空间上的分布情况以及对饱和导水率的影响,进而建立饱和导水率与各理化性质间的关系函数,推求饱和导水率的传递函数,选择渝东北开州区、云阳县等7个区县内45个紫色土典型田块为研究区域,运用Excel 2013和Matlab 2015b软件统计分析后,利用多元非线性回归法推求并验证了渝东北紫色土饱和导水率传递函数模型和模型参数。研究表明:①研究区土壤饱和导水率变化范围在0.16～195.68 cm/d,变化范围广,空间变异系数大,变异性较强;同一采样点深度越大,饱和导水率越小;②土壤饱和导水率与有机质含量有显著的指数函数关系,与饱和含水量有较强的二次函数关系,与土壤容重和土壤颗粒的相关性不大;③本次试验建立的土壤饱和导水率传递函数模型及模型系数检验合格,预测值与实际测算值误差较小,精度良好,可用于渝东北紫色土饱和导水率的预测工作。     

重庆市四面山不同土地利用类型饱和导水率

[目的]探讨不同土地利用类型和土壤理化性质对饱对导水率的影响。[方法]采用定水头法测定四面山不同土地利用类型的饱和导水率,并运用回归分析,相关分析和主成分分析法分析其与土壤物理因子和有机质的关系,以及影响饱和导水率的主导因子。[结果]各土地利用类型的平均饱和导水率均高于荒地,其顺序为:林地农地草地,林地中天然林饱和导水率大于人工林;饱和导水率随土层深度的增加呈负指数递减规律;饱和导水率与容重呈幂函数关系,与孔隙度呈正相关,与黏粒含量呈负相关;有机质含量的提高对饱和导水率有积极的促进作用。[结论]影响饱和导水率的主导因子是容重、有机质、非毛管孔隙度和毛管孔隙度,其次,土壤机械组成对其也有一定影响。     

宁南山区草地植被恢复方式对土壤饱和导水率的影响

为评价宁南山区草地植被不同恢复方式对土壤入渗性能的影响,以不同植被群落的饱和导水率为研究对象,采用逐步回归研究退耕农地、禁牧荒地、封育草地导水率的变化及影响因子,并探讨了其作用机制。结果表明：3种植被恢复方式均有利于0-40 cm土壤饱和导水性能提高;各土层土壤饱和导水率均随植被恢复而不断提高,0-5 cm土层改善作用最为明显;农地退耕序列和荒地禁牧序列5-40 cm土层、封育草地序列0-40 cm土层土壤饱和导水率随土层深度下降而降低;影响土壤饱和导水率的因子为土壤有机质因子和土壤结构因子;3种植被恢复方式土壤有机质质量分数与Ks均呈显著的线性相关关系,在该区域有机质质量分数越高,Ks增加越快;土壤有机质积累是土壤饱和导水率提高的根本动力。因此,草地封育更利于提高使该地区土壤导水性能提高,促进生态恢复。     

Effects of a bentonite–water mixture on soil-saturated hydraulic conductivity

To reduce water loss in light-textured soils, hydraulic conductivity should be reduced by mixing the soils with some soil conditioners, e.g. sodium-bentonite. The objectives of this study were to investigate the effects of irrigation water with different bentonite concentrations (0, 0.05, 0.1, 0.15 and 0.2%) on hydraulic gradient (i) and relative saturated hydraulic conductivity (K _rs) in a laboratory soil column with a loamy sand soil. Addition of sodium-bentonite to the soil increased i throughout each experiment. Furthermore, addition of bentonite reduced K _rs, and a 0.2% bentonite–water concentration after infiltration of 48 mm of bentonite–water mixture (BWM), reduced the K _rs value to 56% of K _s. K _rs was reduced as the concentrations of bentonite increased and its value reached ～0.5 to 0.6 as the infiltration of BWM increased. The lowest value of K _rs and the greatest reduction rate occurred at a bentonite concentration of 0.2%. It is concluded that BWM can be used as a channel liner. Using a 0.2% bentonite concentration resulted in a reduction in the seepage ratio from 1.0 to 0.08.     

Effects of wastewater application on saturated hydraulic conductivity of different soil textures

As metropolitan areas expand, the municipal and industrial uses of freshwater increase. Therefore, water resources for irrigation become limited and wastewater reuse for irrigation becomes a good alternative. For this purpose, the effects of suspended solids in wastewater on the soil physical properties, i.e., saturated hydraulic conductivity, K_s, have to be considered. The objectives of this research were to study the effects of applying freshwater and differently treated wastewater on K_s in the surface and subsurface layers of sandy‐loam, loam, and clay‐loam soils. This effect was studied by investigating the ratio of K_s for wastewater to K_s for fresh water in soil surface as K_r1 and in soil subsurface as K_r2. The results showed that the application of freshwater did not reduce the K_r1 considerably. However, the reduction in K_r1 mainly occurred in soil depth of 0–50 mm due to the application of wastewater. This effect is more pronounced in clay‐loam soil than in loam and sandy‐loam soils. It is concluded that application of wastewater with TSS (total suspended solid) of ≥ 40 mg L^–1 resulted in K_r1 reduction of >50% in different soil textures. However, the K_r2 reduction at soil depth of 100–300 mm is not considerable by application of wastewater for different soil textures. Further, it is concluded that less purified wastewater can be used in light‐texture soils resulting in less reduction in K_r1. Empirical models were developed for predicting the value of K_r1 as a function of amounts of wastewater application and TSS for different soil textures that can be used in management of wastewater application for preventing deterioration of soil hydraulic conductivity.     

Ploughing frequency and compost application effects on soil infiltrability in a cotton–maize (Gossypium hirsutum–Zea mays L.) rotation system on a Ferric Luvisol and a Ferric Lixisol in Burkina Faso

One of the key issues to increase soil productivity in the Sahel is to ensure water infiltration and storage in the soil. We hypothesised that reducing tillage from annual to biennial ploughing and the use of organic matter, like compost, would better sustain soil hydraulic properties. The study had the objective to propose sustainable soil fertility management techniques in the cotton–maize cropping systems. The effects of reduced tillage (RT) and annual ploughing (AP) combined with compost application (Co) on soil infiltration parameters were assessed on two soil types. Topsoil mean saturated hydraulic conductivities (K_s) were between 9 and 48 mm h⁻¹ in the Luvisol, while in the Lixisol they were between 18 and 275 mm h⁻¹. In the two soil types compost additions with reduced tillage or with annual ploughing had the largest effect on K_s. Soil hydraulic behaviour was in reasonable agreement with soil pore size distribution (mean values varied from 19.5 to 237 μm) modified by tillage frequency and organo-mineral fertilization. Already the first 3 years of this study showed that use of organic matter, improved soil infiltration characteristics when annual ploughing was used. Also biennial ploughing showed promising results and may be a useful strategy for smallholders to manage these soils.     

青海省东部不同土地利用方式下土壤饱和导水率分布及其影响因素

研究高寒地区土壤饱和导水率分布特征及其影响因素可为评估脆弱生态系统水源涵养能力和构建区域水文模型提供参数。通过测定青海省东部南北样线24个样点(0—30 cm)土壤基本理化性质和饱和导水率(K_s),分析了不同土地利用方式下K_s分布特征及其影响因素。结果表明:K_s均值表现为林地(1.89 cm/h)草地(1.62 cm/h)农地(1.41 10 cm/h),其中农地K_s(0.10～3.92 cm/h)随着土层深度增加逐渐减小,而林地(0.28～7.69 cm/h)和草地K_s(0.10～5.34 cm/h)随土层深度增加表现为先增加后减小。不同利用方式下K_s均与pH、容重、孔隙度、黏粒含量、有机质含量及饱和含水量显著相关(P0.05)。利用多元回归分析获得了农地以总孔隙度、非毛管孔隙度和饱和含水量为输入因子的K_s传递函数,林地以毛管孔隙度和非毛管孔隙度为输入因子的K_s传递函数和草地以容重、非毛管孔隙度和饱和含水量为输入因子的K_s传递函数。研究结果可为其他高寒地区不同土地利用方式下K_s的模拟和预测提供参考。     

Estimation of saturated hydraulic conductivity from double‐ring infiltrometer measurements

This research aims to determine soil vertical saturated hydraulic conductivity (K_s) in situ from the measured steady infiltration rate (I), initial soil properties and double‐ring infiltrometer (DRI) test data. Characterizing the effects of these variables on the measured steady infiltration rate will enable more accurate prediction of K_s. We measured the effects of the ring diameter, head of ponding, ring depth, initial effective saturation and soil macroscopic capillary length on measured steady infiltration rates. We did this by simulating 864 DRI tests with the finite element program HYDRUS‐2D and by conducting 39 full‐scale in situ DRI tests, 30 Mini‐Disk infiltrometer experiments and four Guelph Permeameter tests. The M5′ model trees and genetic programming (GP) methods were applied to the data to establish formulae to predict the K_s of sandy to sandy‐clay soils. The nine field DRI tests were used to verify the computer models. We determined the accuracy of the methods with 30% of the simulated DRI data to compare I/K_S values of the finite element models with estimates from the suggested formulae. We also used the suggested formulae to predict the K_s values of 30 field DRI experiments and compared them with values measured by Guelph Permeameter tests. Compared with the GP method, the M5′ model was better at predicting K_S, with a correlation coefficient of 0.862 and root mean square error (RMSE) of 0.282 cm s^?1. In addition, the latter method estimated K_svalues of the field experiments more accurately, with an RMSE of 0.00346 cm s^?1.