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。     

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。     

黄土高原生物结皮形成过程中土壤胞外酶活性及其化学计量变化特征

生物土壤结皮在增强土壤抵抗水蚀风蚀能力、改善土壤养分等方面发挥着重要作用,土壤胞外酶活性可作为土壤生化反应强度的微生物指标,对理解荒漠生态系统微生物参与的养分循环过程具有重要意义.选取黄土高原神木县六道沟小流域5个生物结皮发育阶段(裸沙地、全藻结皮、藻-藓混生结皮、藓-藻混生结皮、全藓结皮)的土壤作为研究对象,研究生物...     

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。     

古尔班通古特沙漠生物结皮影响下土壤水分的日变化

对新疆古尔班通古特沙漠生物结皮影响下土壤水分的日变化特征进行了定量研究,结果表明:①无论是结皮覆盖区还是无结皮覆盖区,其土壤含水量随深度的变化均表现出明显的层次性,其中以距地表 20 cm处的土壤含水量最高.②结皮覆盖区距地表5 cm和10 cm处的土壤含水量显著高于无结皮覆盖区(LSD检验, p ＜0.05);而45 cm和60 cm处的土壤含水量则表现为结皮覆盖区极显著低于无结皮区(LSD检验,p＜0.05),说明生物结皮具有较强的保持土壤表层水分的能力.③结皮覆盖区与无结皮覆盖区土壤水分的日变化特征明显不同于距地表5 cm处,而其他各土层的变化趋势则较为一致.无结皮覆盖区距地表5 cm处土壤水分的日变化呈先上升后下降的趋势,而结皮覆盖区的变化则恰恰相反.     

排土场土体裂缝特征对土壤物理性质的影响

以内蒙古胜利东二号露天煤矿南排土场为研究对象,研究排土场不同土体裂缝区土壤机械组成、孔隙状况、水分空间分布以及饱和导水率的特征和差异。结果表明：3个样地土壤机械组成以砂粒为主,土壤质地为砂质土壤,具有质地疏松、通气透水能力强、蓄水能力差等特点;3个样地土壤容重为1.22~1.45 g·cm^-3,且随着土层深度的增加先增大后减小;3个样地土壤含水率偏低,且随着土层深度的增加而减小;土壤饱和含水量、田间持水量和土壤有效水含量呈先减小后增大的变化规律,凋萎系数呈先增大后减小的变化规律,且不同土层之间存在差异。随着土层深度的增加,3个样地各个土层（0~10、10~20、20~30、30~40、40~50、50~60 cm）土壤饱和导水率平均值依次为1.16、1.02、0.95、0.71、0.47、0.27 mm·min^-1;土壤饱和导水率与土层深度之间具有较好的幂函数关系。土体裂缝的出现改变土壤容重、孔隙状况和土壤水分空间分布等土壤物理性质,进而影响排土场水分入渗、地表径流及产流产沙等水土流失过程。     

不同保护性耕作措施对黄土高原旱作农田土壤物理结构的影响

选取黄土高原半干旱区连续4年进行保护性耕作的玉米样地,定位试验,研究了不同耕作方式对耕层土壤理化性质的影响。结果表明:免耕秸秆覆盖(NTS)可显著降低0~5 cm表层土壤容重,传统耕作秸秆粉粹还田(TS)和NTS处理可显著降低5~10 cm、10~30 cm土层的土壤容重;NTS处理可显著增大0~5 cm表层土壤孔隙度,TS和NTS处理可显著提高5~10 cm1、0~30 cm土层的土壤孔隙度;NTS处理可显著降低各层土壤的坚实度,其它处理对表层0~5 cm无显著影响,免耕无秸秆覆盖(NT)处理显著增加了5 cm以下的土壤坚实度;NTS处理0~5 cm表层土壤水分入渗率显著加强,而NT处理则显著减弱;土壤水稳性大团聚体含量均为:NTSNTTS传统耕作(T)。本试验中NT处理对土壤结构的改良效应不明显,NTS处理对于黄土高原土壤结构改良效果最佳。     

土壤水分对毛乌素沙地油蒿群落演替的影响

采用空间代替时间的方法,对毛乌素沙地三种不同演替阶段的油蒿(Artemisia ordosica)群落(半固定沙地油蒿群落、具生物结皮的油蒿群落、油蒿+本氏针茅群落)的群落特征及生物量、叶片气体交换过程、不同土层(0-10cm、10-20cm、20-40cm、40-60cm、60-80cm)土壤含水量、根系垂直分布等进行测定.结果表明:油蒿群落演替是油蒿与草本植物竞争、生物结皮发育、土壤发育以及土壤水分垂直变化等生物非生物因素综合作用的结果.随着油蒿群落演替的发展,群落物种数、草本层盖度和生物量、群落总盖度逐渐增加,而油蒿个体数、油蒿盖度、油蒿叶生物量以及生物土壤结皮盖度则先增加后减少,油蒿根系有向下分布的趋势,0-10cm土层逐渐以草本植物根系占优势.土壤水分是毛乌素沙地油蒿群落演替的主要驱动力,通过影响油蒿叶片气孔导度和净光合速率,以及根系垂直分布影响油蒿在群落中的竞争力.不同演替阶段油蒿群落土壤水分低值区不同,半固定沙地油蒿群落0-10cm和20-40cm土壤含水量最低,具生物结皮的油蒿群落10-20cm土壤含水量最低,而油蒿+本氏针茅群落60-80cm土壤含水量最低.     

黄土丘陵沟壑区沟道造地土壤水分时空变异特征

基于Van Genuchten模型测定土壤水动力学参数,采用定点监测方法,在沟道中不同位置以及对照坡面进行土壤水分观测,分析了延安市典型治沟造地项目沟道造地土壤水分的时空变异特征,阐明治沟造地工程对沟道土壤水分的影响。结果表明：（1）土壤水力学参数在沟道土层深度为40 cm附近发生了显著改变,0~40 cm土层土壤容重1.12 ~1.25 g·cm^-3,导水率达到40 mm·min^-1以上,入渗能力强,同时饱和含水率较大,40 cm以下土层土壤容重在1.5 g·cm^-3左右,导水率在1.25~1.41 mm·min^-1之间,入渗速率明显减小;（2）沟道土壤水分显著大于对照坡面,其季节变化稍滞后于降水的季节变化,整个生长季在15.76%~21.91%间波动,高出对照坡面5%左右,垂直分布随土层深度的增加而增加,表层最低,为15.07%,160 cm土层最高,为22.84% ,深层土壤含水量优势更加显著;沟道土壤水分变异系数在0.131~0.234之间,相比较坡面,沟道表层以下土壤水分存在较强的空间异质性,100 cm以下土层变异系数在0.2左右,土壤水分变化活跃;（3）沟口土壤含水量显著高于沟头,土层深度40 cm以下的土壤含水量长期达到甚至超过田间持水量。通过治沟造地工程水分综合调控体系,沟道能够为作物生长提供水分充足的生境条件,提高水资源利用效率的同时改善农业生态环境。     

不同降雨历时梯田和坡耕地的土壤水分入渗特征

以黄土高原丘陵沟壑第三副区庄浪县为例,研究不同降雨历时条件下坡耕地和水平梯田土壤(黄绵土)水分入渗变化特征,应用Hydrus-1D模型对不同降雨条件下的土壤水分入渗进行定量模拟研究。结果表明:(1)与实测数据相比,Hydrus-1D模型模拟降雨后土壤水分的运移较合理。(2)地表层(0~40 cm)土壤含水量变异系数(CV)呈中等变异,即5 d的时间内梯田和坡耕地地表层的土壤含水量变化大,随着土层深度的增加变异系数减小,呈弱变异性。(3)在1.45 mm/min降雨强度下,在23 min时拔节期的小麦坡耕地产生径流,水平梯田在整个过程中没有产生径流。(4)降雨历时为10 min时,在土层深度为0~15 cm,梯田土壤含水量比坡耕地多0.13%~1.65%,在土层深度为30~200 cm,梯田和坡地都没有下渗。降雨历时为20min、30min时,在土层深度为0~20 cm,梯田的土壤含水量比坡耕地的分别多0.05%~2.22%、0.01%~2%。     

Topographic differentiations of biological soil crusts and hydraulic properties in fixed sand dunes,Tengger Desert

Biological soil crusts(BSCs) play an important role in surface soil hydrology. Soils dominated with moss BSCs may have higher infiltration rates than those dominated with cyanobacteria or algal BSCs. However, it is unnown whether improved infiltration in moss BSCs is accompanied by an increase in soil hydraulic conductivity or water retention capacity. We investigated this question in the Tengger Desert, where a 43-year-old revegetation program has promoted the formation of two distinct types of BSCs along topographic positions, i.e. the moss-dominated BSCs on the interdune land and windward slopes of the fixed sand dunes, and the algal-dominated BSCs on the crest and leeward slopes. Soil water retention capacity and hydraulic conductivity were measured using an indoor evaporation method and a field infiltration method. And the results were fitted to the van Genuchten–Mualem model. Unsaturated hydraulic conductivities under greater water pressure(–0.01 MPa) and water retention capacities in the entire pressure head range were higher for both crust types than for bare sand. However, saturated and unsaturated hydraulic conductivities in the near-saturation range(–0.01 MPa) showed decreasing trends from bare sand to moss crusts and to algal crusts. Our data suggested that topographic differentiation of BSCs significantly affected not only soil water retention and hydraulic conductivities, but also the overall hydrology of the fixed sand dunes at a landscape scale, as seen in the reduction and spatial variability in deep soil water storage.     

黄土地与沙地生物结皮的发育特征及其生态功能异同

基于课题组已有研究成果,选取陕北水蚀风蚀交错区内气候条件相同但土壤质地迥异的试验区,探讨黄土地和沙地生物结皮发育特征及其生态效应的异同。结果表明:(1)苔藓结皮是2种土地生物结皮的重要类型,其中,黄土地的优势藓种为尖叶对齿藓[Didymodon constrictus(Mitt.)Saito.]、真藓(Bryum argenteum Hedw.)、狭网真藓(B.algovicum Sendt.);沙地的优势藓种为黄色真藓(B.pallescens Scheich.)、弯叶真藓(B.recurvulum Mitt.)、银叶真藓(B.argenteum Hedw.)。沙地乔灌植物下生物结皮盖度(77.5%)、厚度(11.8 mm)及容重(1.9 g·cm~(-3))均高于黄土地生物结皮,而黄土地多年生草本植物下生物结皮抗剪强度(26.5 k Pa)高于沙地生物结皮,总体上,沙地生物结皮发育的更好。(2)黄土地的入渗增幅和0~200 cm剖面的平均土壤含水率增幅均显著高于沙地(P0.05),且在旱季和雨季其0~200 cm剖面的平均土壤含水率增幅分别比沙地高1.4%和1.9%。(3)两地生物结皮均表现出了较好的减蚀作用,其减蚀效率分别为81.0%和90.6%。     

Precipitation and soil particle size co-determine spatial distribution of biological soil crusts in the Gurbantunggut Desert,China

Biological soil crusts(BSCs) are bio-sedimentary associations that play crucial ecological roles in arid and semi-arid regions. In the Gurbantunggut Desert of China, more than 27% of the land surface is characterized by a predominant cover of lichen-dominated BSCs that contribute to the stability of the desert. However, little is known about the major factors that limit the spatial distribution of BSCs at a macro scale. In this study, the cover of BSCs was investigated along a precipitation gradient from the margins to the center of the Gurbantunggut Desert. Environmental variables including precipitation, soil particle size, soil p H, electrical conductivity, soil organic carbon, total salt, total nitrogen, total phosphorus and total potassium were analyzed at a macro scale to determine their association with differing assemblages of BSCs(cyanobacteria crusts, lichen crusts and moss crusts) using constrained linear ordination redundancy analysis(RDA). A model of BSCs distribution correlated with environmental variables that dominated the first two axes of the RDA was constructed to clearly demonstrate the succession stages of BSCs. The study determined that soil particle size(represented by coarse sand content) and precipitation are the most significant drivers influencing the spatial distribution of BSCs at a macro scale in the Gurbantunggut Desert. The cover of lichen and moss crusts increased with increasing precipitation, while the cover of cyanobacteria crusts decreased with increasing precipitation. The cover of lichen and moss crusts was negatively associated with coarse sand content, whereas the cover of cyanobacteria crusts was positively correlated with coarse sand content. These findings highlight the need for both the availability of soil moisture and a relatively stable of soil matrix, not only for the growth of BSCs but more importantly, for the regeneration and rehabilitation of disturbed BSC communities in arid and semi-arid lands. Thereby, this study will provide a theory basis to effectively increase soil stability in desert regions.     

Microbiotic Crust Influence on Unsaturated Hydraulic Conductivity

Microbiotic crusts occur extensively in rangeland soils . Developed by filaments of cyanobacteria and algae , and thalli of lichen and moss entanglement of soil particles , they create a physical discontinuity in the surface profile with greater concen trations of clay , silt , and potentially hydrophobic organic matter. These conditions potentially contribute to variability in soil hydrology of arid land and should be considered in the development of hydrologic and erosion models. However, there is limited manipulative research examining the functional relationships between soil and microbiotic crusts . We investigated the influence of cyanobacterial-dominated microbiotic crust on measured hydraulic conductivity (K) in a sandy loam soil at a southeastern Utah site . Using a tension infiltrometer , we determined K under three surface treatments: undisturbed , chemically killed (representing dead microphytes within the crust), and removed (scalped) microbiotic crusts. We applied treatments to spatially interspersed intact surface soils within shrub interspaces . Microbiotic crusts at this site and in this stage of successional development had no discernible influence on K. This finding supports results from research conducted in a variety of soils from sandy to silt dominated with a range of microbiotic development . Because this research was site and time specific , and because the role of microbiotic crusts in the environment continues to be debated , additional research is warranted to deter mine how stage of development of microbiotic crust influences soil hydrology .     

生物土壤结皮结构、功能及人工恢复技术

生物土壤结皮作为典型的有机地被层,广泛分布在干旱半干旱地区。由于其具有良好的水土保持及土壤稳定等功能,可有效控制土地沙漠化,防治水土流失,因此,生物土壤结皮恢复被看作是荒漠生态系统修复和重建的关键。本文系统综述了国内外学者在生物结皮领域开展的研究工作,包括生物土壤结皮的生物组成、演替过程、生态功能、干扰响应、人工培育及生态恢复。以期深入认识生物土壤结皮的结构和功能及干旱半干旱地区的荒漠化治理提供参考。     

Carbon fixation and influencing factors of biological soil crusts in a revegetated area of the Tengger Desert,northern China

Biological soil crusts （BSCs） are an important type of land cover in arid desert landscapes and play an important role in the carbon source-sink exchange within a desert system. In this study, two typical BSCs, moss crusts and algae crusts, were selected from a revegetated sandy area of the Tengger Desert in northern China, and the experiment was carried out over a 3-year period from January 2010 to November 2012. We obtained the effec- tive active wetting time to maintain the physiological activity of BSCs basing on continuous field measurements and previous laboratory studies on BSCs photosynthesis and respiration rates. And then we developed a BSCs carbon fixation model that is driven by soil moisture. The results indicated that moss crusts and algae crusts had significant effects on soil moisture and temperature dynamics by decreasing rainfall infiltration. The mean carbon fixation rates of moss and algae crusts were 0.21 and 0.13 g C/（m2.d）, respectively. The annual carbon fixations of moss crusts and algae crusts were 64.9 and 38.6 g C/（m2.a）, respectively, and the carbon fixation of non-rainfall water reached 11.6 g C/（m2.a） （30.2% of the total） and 8.8 g C/（m2.a） （43.6% of the total）, respectively. Finally, the model was tested and verified with continuous field observations. The data of the modeled and measured CO2 fluxes matched notably well. In desert regions, the carbon fixation is higher with high-frequency rainfall even the total amount of seasonal rainfall was the same.     

风沙土水分入渗与再分布过程中湿润锋运移试验研究

利用室内模拟试验系统,对塔克拉玛干沙漠腹地风沙土在滴灌条件下的水分入渗与水分再分布过程中湿润锋的运动规律进行了模拟试验研究。根据模拟试验描述了风沙土在滴灌条件下水分入渗与再分布情况下湿润体的形状变化,研究了在水平方向上与垂直方向上风沙土的湿润锋推进规律及运动特征,揭示了随着累计入渗量的增加,湿润锋推进过程在入渗初期速率较大,逐渐成减小趋势,并最终达到稳定入渗状态;在土壤水分再分布过程中土壤湿润锋面不断向外部推移,最后达到相对稳定;对风沙土水分入渗及再分布过程中其湿润锋的推进距离与时间做了函数关系拟合,其中乘幂函数关系式拟合最好。     

An experimental study on the influences of water erosion on wind erosion in arid and semi-arid regions

Complex erosion by wind and water causes serious harm in arid and semi-arid regions. The interaction mechanisms between water erosion and wind erosion is the key to further our understanding of the complex erosion. Therefore, in-depth understandings of the influences of water erosion on wind erosion is needed. This research used a wind tunnel and two rainfall simulators to investigate the influences of water erosion on succeeding wind erosion. The wind erosion measurements before and after water erosion were run on semi-fixed aeolian sandy soil configured with three slopes(5°, 10° and 15°), six wind speeds(0, 9, 11, 13, 15 and 20 m/s), and five rainfall intensities(0, 30, 45, 60 and 75 mm/h). Results showed that water erosion generally restrained the succeeding wind erosion. At a same slope, the restraining effects decreased as rainfall intensity increased, which decreased from 70.63% to 50.20% with rainfall intensity increased from 30 to 75 mm/h. Rills shaped by water erosion could weaken the restraining effects at wind speed exceeding 15 m/s mainly by cutting through the fine grain layer, exposing the sand layer prone to wind erosion to airflow. In addition, the restraining effects varied greatly among different soil types. The restraining effects of rainfall on the succeeding wind erosion depend on the formation of a coarsening layer with a crust and a compact fine grain layer after rainfall. The findings can deepen the understanding of the complex erosion and provide scientific basis for regional soil and water conservation in arid and semi-arid regions.     

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.