黄土丘陵区生物结皮对坡面流水动力特征的影响

[目的]探究生物结皮对坡面流水动力特征的影响,为黄土高原丘陵区生物结皮防蚀机理研究提供理论指导。[方法]设置生物结皮覆盖及破坏处理,进行人工模拟降雨试验。[结果](1)生物结皮覆盖及破坏处理下坡面流均属于层流急流。(2)生物结皮可显著降低坡面流流速,增加水流剪切力,阻力系数和水流功率(p<0.05)。其中,藻结皮处理和苔藓结皮处理较裸地流速分别减少了48.74%和62.24%,水流剪切力、阻力系数、水流功率较裸地分别增加了130.01%和308.07%;703.35%和2 532.01%;21.16%和57.43%。(3)生物结皮破坏后其阻力系数与裸地无显著变化,流速、水流剪切力、水流功率均显著高于裸地(p<0.05)。其中,藻结皮破坏和苔藓结皮破坏处理较裸地流速、水流剪切力、水流功率分别增加了10.84%和16.46%;36.83%和42.44%;60.90%和62.14%。[结论]生物结皮覆盖会增大坡面流阻力系数,降低流速。生物结皮破坏后坡面流阻力系数与裸地无差异,流速增加。此外,生物结皮覆盖及破坏处理均会增大坡面流水流剪切力及水流功率,进而增加径流侵蚀能量。     

黄土高原不同降雨强度下生物土壤结皮对坡面流水动力参数的影响

[目的]明确不同降雨强度下生物土壤结皮对坡面流水动力参数的影响,进一步评估生物结皮的水土保持功能。[方法]以黄土高原典型藻结皮和苔藓结皮为研究对象,系统研究了60,90,120,150,200 mm/h雨强下生物土壤结皮对坡面流水动力参数的影响。[结果](1)所有雨强下藻结皮和苔藓结皮坡面流流型均为层流,除200 mm/h雨强下苔藓结皮坡面流为急流外,所有雨强下藻结皮和苔藓结皮流态均为急流;(2)藻结皮在90,120,150,200 mm/h雨强下流速、径流量和径流系数分别是60 mm/h雨强的1.76～3.9,4.89～9.26,3.91～4.13倍,苔藓结皮则为1.34～2.56,5.86～13.81,2.46～4.26倍,流速和径流量均随雨强呈线性函数增加(R²≥0.85,p<0.01),径流系数呈幂函数增加(R²≥0.49,p<0.05);(3) 60,90,120,150,200 mm/h雨强下藻结皮阻力系数和曼宁糙率系数变化范围分别为0.15～0.74,0.01～0.03,苔藓结皮则为0.82～3.02,0.03～0....     

暴雨条件下典型红壤区生物结皮坡面水土流失过程研究

为探明暴雨条件下典型红壤区生态恢复工程实施后生物结皮覆盖对坡面水土流失过程的影响,通过模拟降雨和室内分析试验,探究不同结皮覆盖度(0,20%,40%,60%,80%)坡面的土壤物理属性、水动力学特征及产流产沙过程。结果表明:(1)生物结皮覆盖下的红壤坡面土壤黏结力平均增加13.26%,土壤容重与穿透阻力平均分别减小8.97%和61.51%,表明生物结皮可有效增强红壤区坡面土壤稳定性,提升土壤抗蚀能力;(2)相较对照坡面,其余盖度坡面均可有效改善水流流态,坡面径流剪切力介于0.08~0.12。水流功率和断面单位能量分别减小12.22%~78.89%,8.32%~53.15%,坡面阻力系数增大1.09~1.50倍;(3)各生物结皮盖度坡面减流、减沙效益分别介于12.50%~78.76%,17.03%~94.31%,其中高覆盖度(80%)坡面土壤侵蚀强度较小。研究结果为有效防治红壤区坡面水土流失工作提供理论依据和实践参考。     

毛乌素沙地人为干扰苔藓结皮的土壤水分和风蚀效应

[目的]为了探讨在毛乌素沙地人为干扰生物结皮的必要性与可行性,并为该区生物结皮的高效利用提供实验依据。[方法]在毛乌素沙地东南缘设置裸沙、苔藓结皮、干扰苔藓结皮、沙蒿、沙蒿+苔藓结皮以及沙蒿+干扰苔藓结皮6个处理小区,通过动态监测各小区土壤水分及风蚀变化过程,分析人为干扰苔藓结皮对土壤水分及风蚀过程的影响。[结果](1)沙地苔藓结皮能够显著提高浅层土壤含水量,降低深层土壤含水量。(2)人为干扰苔藓结皮会引起浅层土壤含水量的降低和降雨入渗深度的增加。(3)与裸沙对照相比,几种处理的减蚀效率大小顺序为:沙蒿+苔藓结皮(97.01%)沙蒿+干扰苔藓结皮(90.87%)苔藓结皮(89.63%)干扰苔藓结皮(69.50%)沙蒿(64.62%)。[结论]植被覆盖度较高时,对苔藓结皮进行适当破坏,能够在不加剧土壤风蚀的前提下,一定程度上改善土壤水分状况。而在无植被或低植被覆盖的地块,要禁止对苔藓结皮的干扰破坏。     

不同降雨强度下土壤结皮强度对侵蚀的影响

为定量分析土壤结皮对坡面侵蚀的影响,该文选择塿土、黄绵土、黑垆土和黄墡土4类土壤,分析其在3种雨强(60、90、120 mm/h)下的结皮强度变化规律。结果表明,当土壤含水率高于30%时,不同降雨强度下结皮强度差异不显著(P0.05),当含水率小于30%时,结皮强度随降雨强度增大而增强。以杨凌塿土10°坡面为例,进行坡面人工模拟降雨试验,分析计算不同强度结皮坡面的侵蚀产沙、径流剪切力、阻力系数以及流速,结果表明:结皮对坡面产流的影响并不显著,但其存在有效地减少坡面的侵蚀产沙量。结皮存在能有效地减少坡面产沙量,无结皮坡面的产沙量是结皮坡面产沙量的1.24~8.72倍。相同降雨条件下,结皮强度越大,其产沙量越小。进一步通过灰色关联分析得出:随着坡面结皮强度增加,水流功率对坡面侵蚀的作用效益不断减小,而阻力系数的作用效益增加,即水流增加产沙的正效应不断减弱;另一方面,结皮强度增大使得坡面土壤抗蚀性增强,因此,结皮强度越大,坡面侵蚀量将大幅度减少。研究可为准确有效预报坡面土壤侵蚀提供重要依据。     

科尔沁沙地生物结皮的土壤种子库特征

通过野外取样和室内分析,初步研究了科尔沁沙地两种生物结皮在干、湿两种处理下土壤种子库种类组成、密度以及物种多样性等特征。结果表明：①科尔沁沙地藻结皮和苔藓结皮土壤种子库的总密度为干旱藻结皮〈湿润藻结皮〈干旱苔藓结皮〈湿润苔藓结皮。两种结皮上种子库的数量存在显著差异,对于干、湿处理的两种结皮,苔藓结皮上种子库的总密度均大于藻结皮上种子库的总密度;②两种生物结皮在干旱、湿润两种处理中共出现了6科、15种植物,种子库的组成以一年生草本植物、中生植物为主,二者百分比均超过76%;③在干旱藻结皮、湿润藻结皮、干旱苔藓结皮和湿润苔藓结皮上,种子库物种多样性表现出湿润处理下的结皮高于干旱处理的结皮。由此表明,在半干旱的科尔沁沙地,水分是限制结皮土壤种子库中种子萌发的主要因子,而生物结皮则通过对水分入渗与再分配的调控作用影响结皮种子库中种子的萌发。     

不同结皮类型对植被混凝土基材团聚体及有机碳的影响

[目的] 分析土壤团聚体分布和有机碳含量特征,揭示生物结皮对边坡稳定和养分固持的影响,为生物结皮在修复工程中的运用提供参考和指导意见。[方法] 以植被混凝土基材修复边坡为例,运用土壤干筛法、土壤湿筛法分别对结皮覆盖和无结皮覆盖坡面土壤的结皮层(0—2 cm)和结皮下层(2—7 cm)团聚体和有机碳特征进行研究。[结果] ①生物结皮的存在明显影响了土壤团聚体分布、机械稳定性及R_0.25含量。结皮覆盖层较CK(无结皮覆盖坡面)稳定性指标分别增加27.42%~33.51%(MWD),21.66%~28.88%(GMD),大团聚体含量(R_0.25)增加10.68%,且苔藓类结皮影响最为显著。②湿筛法测定的不同结皮类型土壤团聚体均以＞0.25 mm粒径为主,其中结皮覆盖边坡的团聚体水稳性参数MWD,GMD,R_0.25分别介于1.93~5.33 mm,0.85~3.16 mm,70.97%~87.50%,以苔藓覆盖边坡最大,D_d值介于2.48~2.74间,以苔藓类值最小。团聚体水稳定性表现为苔藓覆盖边坡最好,裸坡最差。③结皮的存在促进了土壤有机碳累积,有机碳含量是CK组的两倍以上。其中对表层土壤有机碳水平提升作用明显,对下层土壤作用较低。④土壤有机碳含量与土壤水稳性参数MWD,GMD,R_0.25呈显著正相关性(p＜0.05),有机碳水平和团聚体稳定性联系密切,相互影响,有机碳水平的提高对增加团聚体稳定性具有重要作用。[结论] 生物结皮的存在对修复边坡团聚体稳定和有机碳累积具有促进作用,结皮对生态修复边坡稳定和养分固持有一定的作用,且不同结皮类型作用强度不一,其中苔藓类和混生结皮固土和固碳效果最优。     

模拟降雨条件下侧柏林地枯落物对坡面产流产沙的影响

以北京山区人工侧柏林地坡面为研究对象,基于2个2m×5m径流小区,设枯落物覆盖自然坡面与裸露坡面2种处理、大小2种雨强(126,70mm/h),通过对比分析2种处理下坡面产流产沙过程,揭示林下枯落层覆盖对北京山区坡面产流产沙的影响。结果表明:(1)与裸坡相比,枯落物覆盖自然坡面产流产沙分别减少了67.0%和90.6%,其中,减沙效益大于减水效益。(2)无论是枯落物覆盖自然坡面还是裸坡,坡面产流过程均表现为先增大后趋于稳定的变化规律,但枯落物覆盖坡面产流趋于稳定的时间较裸坡有所提前。(3)枯落物覆盖坡面70,126mm/h降雨平均产沙速率分别为2.8,80.8g/min,裸坡分别为51.4,872.7g/min,枯落物覆盖坡面产沙率显著小于裸坡(p0.05)。当地表有枯落物覆盖时,产沙速率与含沙量随产流历时均波动变化不大,坡面产沙是一个基本稳定的过程;于裸坡而言,产沙速率与含沙量在小雨强条件下呈现先增加后趋于稳定的变化规律,而大雨强条件下,两者随产流历时先急剧增加后波动降低。(4)枯落物覆盖坡面产沙量与产流量为线性关系,而裸坡产沙量随产流量的增加呈幂函数急剧上升。研究结果可为评价北京山区人工林恢复水土保持效益提供理论依据,同时增进了对北京山区林地坡面产流产沙机制的认识。     

小麦秸秆长度、覆盖量对坡面产流产沙的影响

为定量研究小麦秸秆覆盖对坡面产沙产流过程及减水减沙效益的影响,采用室内人工模拟降雨试验,研究在降雨强度为90 mm/h时,不同秸秆长度和秸秆覆盖量下的坡面产流产沙特征和产流产沙过程规律,结果表明:(1)在相同秸秆长度下,随秸秆覆盖量增加,产流量产沙量极显著减少(p0.01)。相同覆盖量水平下随秸秆长度增加,产流量显著增加(p0.05),在4.5 t/hm~2覆盖量下产沙量极显著增加(p0.01)。(2)秸秆覆盖坡面的初始产流时间较裸露坡面延迟6.23倍,产流量平均下降19.5%,产沙量下降31.6%。覆盖措施通过保护土壤的结构有效抑制了细沟侵蚀过程向切沟侵蚀发展。产流产沙过程受秸秆长度和覆盖量的交互作用影响,交互效应对产流过程的影响更突出。(3)随覆盖量增加,减水减沙效益极显著增加(p0.01);随长度增加,减水减沙效益分别减少为17.26%,27.97%。不同覆盖条件下的坡面产流量、产沙量和减水、减沙效益均与秸秆长度、秸秆覆盖量呈二元线性关系。(4)在当前试验条件下,当秸秆长度为3～5 cm,覆盖量为4.5 t/hm~2时达到最优减水减沙效益。     

黄土高原坡耕地土壤物理结皮对坡面产流产沙过程的影响

探究黄土高原坡耕地土壤物理结皮对坡面产流产沙的影响和作用机理,为黄土高原坡耕地水土流失防治提供科学依据.通过室内人工模拟降雨试验,研究坡耕地沉积结皮和翻耕以后形成的击溅结皮对坡面产流产沙过程的影响.根据研究区坡耕地结皮形成的特点,试验共设计5个处理,分别为裸地、沉积结皮、沉积结皮破坏、翻耕和翻耕击溅结皮,每个处理对应2...     

Wind transport of sand surfaces crusted with photoautotrophic microorganisms

Wind tunnel experiments show that while surfaces inoculated with photoautotrophic organisms are stable in winds up to 19 m s⁻¹, only filamentous cyanobacteria, especially Nostoc commune, afford considerable protection against abrasion from windborne particles. Crusts formed by the polysaccharide secreting alga Chlamydomonas acidophila break down easily under impact, the entrainment of large, low density aggregates possibly contributing to higher transport rates than would otherwise be expected for untreated sediment. Surface disintegration encompasses a suite of complex, scale dependent processes which vary with the structure, thickness and strength of the crust. Independent measurements of crust strength based on flexure testing are in good agreement with wind tunnel evaluation of crust stability. The accommodation of a relatively large amount of deformation without rupture is an important property of fibrous, photoautotrophic mats, perhaps outweighing consideration of their peak strength.     

人工降雨条件下土壤结皮的形成以及与土壤溅蚀的关系

通过人工模拟降雨溅蚀实验,测定土壤溅蚀速率,同时采样制作土壤切片,观察分析结皮的发育特征以及与土壤溅蚀的关系。结果表明,降雨过程中有两种类型结皮形成,即沉积结皮和结构结皮。土壤结皮随着土壤表面大团聚体或者大颗粒的分散而形成,并且伴随着下层大孔隙的出现。土表结皮的完善过程,也是土壤抗溅蚀能力增强的过程     

Laboratory methods for the estimation of infiltration rate of soil crusts in the Tabernas Desert badlands

Soil crusting is a crucial factor for runoff generation in the Tabernas Desert badlands; however, very few methods have been developed for the measurement of infiltration in crusts, which are often distributed on steep slopes where experimental devices are very difficult to install, making measurement difficult. We have used the trickle irrigation (TI) method and mini-disk infiltrometers (MDI) in the laboratory to measure steady infiltration rate under nearly saturated condition and tensions, respectively, in soil crust samples removed from the field. Steady infiltration rate under tensions were performed at three water pressure heads (h=−0.5, −2.0, and −6.0 cm).Steady infiltration rate of soil crusts in the Tabernas Desert badlands ranged from 21.3 to 30.7 mm h⁻¹ measured by TI method. Steady infiltration rate under tensions decreased with increasing tensions; it was 9.9–18.4 mm h⁻¹, 0.4–5.7 mm h⁻¹, and 0.2–3.3 mm h⁻¹ at −0.5-, −2.0-, and −6.0-cm pressure heads, respectively. Steady infiltration rate measured by TI method and that at a tension of 0.5 cm by the MDI is consistent with the results from the previous simulated rainfall studies in the same soil crust surfaces, suggesting that the TI and MDI methods may be potentially a useful lab measurement for approximating field infiltration rate.     

模拟降雨条件下土壤结皮的发展和聚丙烯酰胺对黄土上结皮形成的影响

This study evaluated the morphological characteristics and dynamic variation in characteristics of soil crust and iden-tified the relationships between soil crust and splash erosion under simulated rainfall.The effect of polyacrylamide (PAM) on soil aggregate stabilization and crust formation was also investigated.A laboratory rainfall simulation experiment was carried out using soil sample slices.The slices were examined under a polarized light microscopy and a scanning electron microscope (SEM).The results revealed that the soil crusts were thin and were characterized by a greater density,higher shear strength,finer porosity,and lower saturated hydraulic conductivity than the underlying soil.Two types of crusts,i.e.,structural and depositional crusts,were observed.Soil texture was determined to be the most important soil variable influ-encing surface crust formation;depositional crust formation was primarily related to the skeleton characteristics of the soil and happened when the soil contained a high level of medium and large aggregates.The crust formation processes observed were as follows:1) The fine particles on the soil surface became spattered,leached,and then rough in response to raindrop impact and 2) the fine particles were washed into the subsoil pores while a compact dense layer concurrently formed at soil surface due to the continual compaction by the raindrops.Therefore,the factors that influenced structural crust formation were a large amount of fine particles in the soil surface,continual impact of raindrops,dispersion of aggregates into fine particles,and the formation of a compact dense layer concurrently at the soil surface.It was concluded that the most important factor in the formation of soil crusts was raindrop impact.When polyacrylamide (PAM) was applied,it restored the soil structure and greatly increased soil aggregate stabilization.This effectively prevented crust formation.However,this function of PAM was not continuously effective and the crust reformed with long-term rainfall.In conclusion,this study showed that soil micromorphological studies were a useful method for evaluating soil crust formation.     

Tensile test of natural microbiotic crust

The mechanical properties of microbiotic crust are important to stabilize sandy surfaces in arid and semi-arid regions. We developed a new experimental approach to perform the tensile test of natural microbiotic crust. The modulus of elasticity, ultimate stress and one-dimensional stress–strain relation was obtained. The microbiotic crust we measured exhibits linear elastic behavior firstly and then breaks. This mechanical character was applied to the study of the rupture of microbiotic crust under the impact of one saltating grain. A very simple dimensionless variable was suggested to quantitatively assess surface stability.     

NaCl含量对风沙土盐结皮特性及其抗风蚀性能的影响

土壤盐结皮能够抑制水分蒸发，减少地表粉尘释放，在干旱区生态环境中具有十分重要的作用。为了获得干旱或半干旱区风沙土盐结皮的合理盐溶度，选取新疆塔克拉玛干沙漠东部风沙土为实验土壤，分别加入0.1%、0.2%、0.5%、1.0%、2.0%、3.0%、4.0%、5.0%、6.0%和7.0%（盐占混合物的百分比）的NaCl进行盐结皮实验，测试盐结皮的强度和韧性。利用电镜观察盐结皮微观结构，分析NaCl盐溶度对结皮抗压强度以及其抗风蚀性能的影响。实验结果表明：NaCl含量对风沙土结皮抗压强度和韧性有较大影响，随着NaCl含量的增加盐结皮的强度和韧性均呈现出先增加后降低的特殊现象；但盐结皮的抗压强度峰值和韧性峰值不同步，NaCl含量3.0%时，盐结皮韧性达到峰值；NaCl含量4.0%时，盐结皮的抗压强度才达到峰值。盐结皮表观和微观结构显示，盐含量>4.0%后结皮盐晶体出现盐斑聚集，这种盐晶体聚集导致盐结皮不均匀，进而导致盐结皮抗压强度复杂变化。     

花岗岩风化壳土地退化及其危害

土地退化地持续发展中的重要环境问题之一。该讨论了花岗岩风化壳土地退化特点，成因及危害，给出了退化土地评价指标。     

土壤结皮与降雨溅蚀的关系研究

在单雨滴和次降雨溅蚀实验的基础上 ,讨论了结皮土壤的溅蚀规律。通过与无结皮土壤的对比分析得知 ,两者的变化特征完全相同 ,但溅蚀量差异明显 ,即有结皮土壤的溅蚀量总是小于无结皮土壤 ,且两者溅蚀量的大小与坡度、前期含水率、雨滴直径、结皮厚度和降雨强度的因素有关 ,可用式 W =1.6915 S0 .1 777θ0 .4 6 6 7D0 .76 32 H- 0 .4 92 5和 W =0 .4 5 2 3 ( PI) 0 .7538S0 .1 450进行估算。     

Properties and spatial distribution of microbiotic crusts in the Negev Desert,Israel

Playing a cardinal role in surface stabilization and in carbon and nitrogen fixation, microbiotic crusts play a crucial role in arid regions where they may serve as useful biomarkers for wind power and wetness duration. This is especially the case on relatively unstable and infertile sand dunes in the Negev Desert where high correlations between the crust chlorophyll content and the daytime wetness duration were found. Yet, only scarce data are available as to the possible link between the chlorophyll content and other physical (color, thickness, strength, crack density, surface roughness and infiltrability) and biological (protein, carbohydrate, organic matter and species composition) factors, which determine, in turn, the crust type and its effect upon geomorphological and ecological processes. No data are available on crust type distribution. These were the aims of the current research.