水分对具鞘微鞘藻构建人工藻结皮的作用

为探讨水分在利用室内培养具鞘微鞘藻构建人工藻结皮中的作用,本文研究了不同施水量和施水时间下人工藻结皮中的藻类生物量、结皮厚度、抗压强度和微结构变化.结果表明:利用具鞘微鞘藻在裸沙上接种,无水处理藻类生物量极低,无藻结皮形成.随着施水量的增加,藻结皮开始出现直至形成稳定的藻结皮,藻类生物量、结皮厚度和抗压强度显著增加,藻丝和胞外多糖逐渐增多,与沙粒缠绕成复杂的网状结构.施水15 d,形成稳定的藻结皮,藻类生物量、结皮厚度和抗压强度最高.具鞘微鞘藻形成藻结皮的最适施水量是3～4L·m-2·d-1,施水时间为15 d.土壤可利用水分可促进具鞘微鞘藻的代谢活动和胞外多糖合成,从而增加藻类生物量,提高其耐旱能力,早期的水分获得是其成功形成藻结皮的关键因素.研究结果将为利用荒漠藻类进行人工生物结皮恢复提供重要的理论依据.     

具鞘微鞘藻在荒漠藻结皮形成过程中的作用

具鞘微鞘藻(Microcoleus vaginatus)是荒漠藻结皮主要的优势物种,在藻结皮的形成和发育过程中发挥着非常重要的作用。为了探讨具鞘微鞘藻在荒漠藻结皮形成过程中的作用,通过实验室内模拟藻结皮不同发育阶段,研究了具鞘微鞘藻在结皮形成过程中对藻类生物量、结皮厚度及其抗压强度的影响;同时利用光学显微镜和扫描电镜对藻结皮微结构观察,分析了不同发育阶段沙粒和具鞘微鞘藻之间的胶结方式和作用机理。结果表明:(1)藻结皮形成的最初阶段,结皮状态主要由细菌及小型蓝绿藻分泌胞外多糖的黏结作用和结皮表面有机质层的保护作用维持,但该阶段的藻结皮比较脆弱,抗压强度仅为(12.21±1.58)Pa;当具鞘微鞘藻大量出现后,逐步占据了明显的优势地位,沙粒间的黏结作用被更高强度的具鞘微鞘藻机械束缚力所取代,成为该阶段藻类结皮硬度提高的重要贡献者;(2)随着具鞘微鞘藻接种比例的逐渐增加,藻结皮中的藻类生物量、结皮厚度及抗压强度均呈现出升高的趋势(P0.01),当接种比例增加为80%时达到最高值;然而,当具鞘微鞘藻接种比例为100%时,各项指标却又有所下降。重点探讨藻结皮不同发育阶段沙粒间的胶结形式及微形态变化,深入揭示具鞘微鞘藻在藻结皮形成和发育过程中的作用机理,为旱生藻类广泛应用于荒漠植被恢复与重建过程提供重要的试验数据和理论依据。     

古尔班通古特沙漠生物结皮不同发育阶段中藻类的变化

通过在古尔班通古特沙漠南缘相同的地貌部位,选择裸沙、藻结皮、地衣结皮和苔藓结皮4种不同演替阶段中的生物结皮,研究了藻类的种类组成、优势种和生物量的变化.结果表明:(1)在结皮的不同演替阶段,藻类种类组成不同,其常见物种有一定的差异,如裸沙中藻类常见种是脆杆藻2(Fragilaria sp.2)、威利颤藻(Oscillatoria willei)和奥克席藻(Phormidium okenii),藻结皮的常见种是小聚球藻(Synechococcus parvus)、颗粒常丝藻 (Tychonema granulatum)、韧氏席藻(Phormidium retzli);同时在不同发育阶段亦存在一些特有种.(2)在裸沙发育到成熟生物结皮的过程中,藻类的优势物种也发生相应的变化.裸沙、藻结皮、地衣结皮和苔藓结皮的优势种分别是脆杆藻1(Fragilaria sp.1)、具鞘微鞘藻(Microcoleus vaginatus)、具鞘微鞘藻、眼点伪枝藻(Scytonema ocellatum)或集球藻(Palmellococcus miniatus).(3)藻类生物量在生物结皮不同演替阶段差异极显著(P<0.01),在裸沙中藻类生物量最低,随着生物结皮的逐渐发育,藻类生物量明显升高,地衣结皮最高,约是裸沙的8.3倍,当发育至苔藓结皮时,藻类生物量又有所下降.(4)在裸沙中基本为松散的沙粒,随着生物结皮的演替,丝状种类占明显的优势,尤其是具鞘微鞘藻,另外真菌菌丝和苔藓假根分别在地衣结皮和苔藓结皮中起着重要作用.     

温度和初始pH对生物结皮中4种优势蓝藻生长的影响

生物土壤结皮对干旱半干旱地区生态环境健康及可持续发展有重要意义。具鞘微鞘藻、伪枝藻、念珠藻和鱼腥藻是生物结皮中蓝藻的优势种,对其大规模培养有着广阔的应用前景。以4种蓝藻为材料,采用室内液体培养方法,研究了5个温度(10、20、25、30、35℃)和5个溶液初始pH(4、6、8、10、12)对4种藻生物量和溶液pH的影响。结果表明：在20℃以下温度培养,供试4种藻生物量增长缓慢,在25～35℃下4种藻均能正常生长,其中25和30℃下藻类生物量增长最快。不同藻种的最适培养温度略有区别,伪枝藻和念珠藻最适培养温度为25～30℃,具鞘微鞘藻和鱼腥藻为30℃。供试4种藻对溶液pH有极强的调节能力,均能够在5个初始pH环境中进行增殖,在初始pH为4的培养环境下能达到最大生物量和比生长速率,在初始pH为12下生物量和比生长速率最低。研究为生物结皮中优势藻的扩繁提供了科学依据。     

微鞘藻胞外多糖在沙漠土壤成土中的作用

研究了沙坡头藻结皮中的优势物种——微鞘藻的胞外多糖对沙漠表层土壤水分分布状况的影响及其光合特性。随着胞外多糖浓度的升高 ,土壤持水量增大 ,土壤水分蒸发速率降低 ,水分在土壤中运动的速率被延缓。藻总水溶性多糖产率为 2 8.82 % ,胞外水溶性多糖产率为 1 6 .0 9% ;多糖产量在稳定期生物量最大时增长最快。微鞘藻光合作用最适温度为 2 5℃ ,最适光强为 40 0 μE.m- 2 .s- 1,在 0 .3 mol/ L Na Cl浓度下其光合作用活性被强烈抑制 ;微鞘藻的吸收光谱表明它比生长在湿润地区的藻类含有更多的胡萝卜素成分 ;叶绿素 a荧光 (Fv/ Fm)分析表明在失水约为初始湿重的 5 6 %时 Fv/ Fm值恢复到水培养的 96 % ;其光合作用特性有利于对逆境的适应和生物量的积累。表明微鞘藻胞外多糖可影响沙漠表层土壤水分分布状况 ,并可作为一种潜在的生物肥料 ,在荒漠原始成土过程中扮演着重要角色。     

库布齐沙地三年生人工藻结皮发育特征及微生物分布

对库布齐沙地4种三年生不同立地条件下人工藻结皮的发育特征和微生物分布进行研究,结果表明:(1)将荒漠蓝藻接种到沙面,形成的人工藻结皮经过3年的生长和发育,结皮的平均厚度达到2.23-5.36mm,呈现深黑色和灰绿色,结皮盖度大于70%.其中沙柳(Salix cheilophila Schneid.)-羊草(Aneurolepidium chinensis)-藻(algae)结皮(SAA)发育最好、生物量最高,且演替成苔藓结皮.在人工藻结皮区普遍出现沙生植物的拓殖和大量生长,如沙米(Agriphyllum squarrosum Bieb.)、披碱草(Elymus dahuricus Turez.)、猪毛菜(Salsola collina Pall.)等,植被盖度达60%-90%.4种不同立地条件下人工藻结皮中藻类的组成都比较单一,在藻类的种类数量上变化并不明显,仍然以具鞘微鞘藻(Microcoleus vaginatus Gom.)占绝对优势,其次是爪哇伪枝藻(Scytonema.javanicum (Kutz.)Born etFlah.),且不同的藻种在结皮中分布的位置不同;人工藻结皮具有较高的抗压强度,抗压强度普遍达到35-70 N/cm2.丝状蓝藻通过紧密和高强度的机械束缚作用以及藻体胞外分泌物对沙粒的黏结作用,对维持藻结皮的强度起着至关重要的作用.对人工藻结皮的超微结构研究发现,经过3年的野外生长和发育,藻结皮沙粒土壤中含有丰富的藻丝体.可以观察到大量藻丝体缠绕或黏结着沙粒,从而实现人工藻结皮的胶结过程;(2)微生物总数变化趋势变现为:沙柳(S.cheilophila)-羊草(A.chinensis)-藻(algae)结皮(SAA)＞草方格(grass pane)-藻(algae)结皮(GA)＞沙米(A.squarrosum)-藻(algae)结皮(AA)＞流沙(shifting sand)-藻(algae)结皮(SA)＞流沙(CK).人工藻结皮的生物量变化趋势与其微生物总数的变化趋势相一致;在微生物各主要类群中,细菌数量、放线菌数量和真菌数量在不同人工藻结皮中的变化趋势同微生物总数的变化趋势相同;在4种人工藻结皮中,细菌所占微生物总数的比例均明显高于放线菌和真菌.结皮中细菌所占微生物总数的百分比呈依次增加的趋势,放线菌所占微生物总数的比例呈递减趋势,真菌占微生物总数的比例非常小,且比例差别不大.     

生物结皮粗糙特征——以古尔班通古特沙漠为例

摘要：空气动力粗糙度可以反映地表气流与下垫面的相互作用。古尔班通古特沙漠是我国最大的固定、半固定沙漠,其间广泛分布的生物结皮在稳定地表和改善环境方面意义重大。对未经扰动的4种类型生物结皮进行表面微形态观察,并通过风洞实验确定动力粗糙度Z0和摩阻风速u*,结果表明：（1）不同生物结皮类型,其组成和表面微形态等都具有明显差异。藻结皮以表面致密光滑为显著特征,由藻类分泌物和藻丝体粘结细粒物质所形成;地衣结皮表面藻类和真菌形成的叶状体匍匐沙面生长,呈现三维生长方式,形成有明显凹凸的壳状覆被;苔藓结皮以苔藓植物体密集丛生为特点,地上部分出现了茎叶分化,有一定的柔韧性。（2）就动力粗糙度的大小而言,是按地衣结皮>藻类－地衣结皮>苔藓结皮>藻结皮的顺序排列的,Z0平均值依次为（6.5890.850）mm、（4.1790.239）mm、（2.5420.357）mm和（0.3930.220）mm,与定床裸沙面的（0.0420.019）mm相比,生物结皮Z0值提高了10—150倍。随着风速的增大Z0值有所减小,其中以地衣结皮的减小趋势较为明显。（3）由风速廓线对比发现,四类生物结皮对气流阻滞作用的差异主要局限于4 cm以下的高度范围,风速越大这种差异也越大。各类生物结皮摩阻风速u*随风速增大而增大,其中藻结皮的增大速率明显低于其它三类结皮,说明藻结皮随风速增大的阻滞效应较其它三类结皮要差。（4）在净风条件下,地衣结皮具有最好的防风效果,其次为藻类－地衣结皮和苔藓结皮,藻结皮最差。当生物结皮破损后,床面结构和气流性质将发生变化,对空气动力学粗糙度和摩阻风速产生的影响将有待于进行更深入的研究。     

雪衣藻叶绿素荧光特性及抗氧化系统对汞胁迫的响应

文章选用对汞(Hg)具有较强耐受性的雪衣藻(Chlamydomonas nivalis)为对象,探究藻细胞对汞胁迫的响应及其耐受机制。结果表明, Hg²⁺对藻细胞的胁迫具有明显的时间依赖的量效关系, 48h半数效应浓度EC₅₀为1.44 mg/L。与对照组相比, 1.0和1.5 mg/L Hg²⁺处理组能维持生长和光合活性; 2.0 mg/L Hg²⁺处理组生物量和色素含量在胁迫6h时无显著变化(P>0.05), 48h时均显著降低(P<0.05)。随着Hg²⁺浓度和暴露时间的增加,藻细胞最大光化学量子产率(F_v/F_m)、最大电子传递速率(ETR_max)、半饱和光强(I_k)及光能利用效率(α)均降低,OJIP快速荧光诱导动力学曲线和Q_A^-再氧化变化明显,光合电子传递受阻。Hg²⁺胁迫导致能量流的变化,藻细胞部分反应...     

温度变化对藻类光合电子传递与光合放氧关系的影响

由于直接测定藻类的光合速率耗时且不方便,研究者们常通过测定藻类光合电子传递速率的方式来间接反映其光合速率,理论上,以氧气产生来度量的总光合速率（PGross）与电子传递速率(ETR)之间应该存在很好的线性关系。然而,由于温度的变化会影响藻类的光呼吸等耗氧的生理过程从而影响光合作用中的氧气释放,因此温度可能会对PGross与ETR之间的线性关系产生影响。研究了温度变化对蛋白核小球藻（Cholorella pyrenoidosa）、菱形藻（Nitzschia sp.）和水生集胞藻（Synechocystis aquetilis Sauv.）的总光合放氧速率（PGross）与电子传递速率(ETR)之间比率的影响,结果表明PGross/ETR随温度的升高而降低,低温条件下PGross/ETR比值较高,说明在相同的电子传递速率的情况下水的光裂解产生的氧有更多的可以释放出来;在高温条件下PGross/ETR比值相对较低,说明高温条件下可能有相对更多的水光裂解产生的氧被用于耗氧的生理过程而没有释放出来。研究表明当温度发生变化时,光合放氧与电子传递之间并不呈线性关系,这说明将ETR作为实际光合生产的评价指标时要谨慎,不能不加分析地直接应用。     

几种固沙荒漠藻的温度适应性

蓝藻结皮在干旱和半干旱区广泛分布,它们在环境状态的维持和改良过程中发挥着重要的作用。在荒漠藻固沙技术的应用过程中,温度不仅影响藻类在培养池中的培养,还影响接种后藻类的生长。因此,摸清优势固沙藻类的温度生长特征及对不同温度的生长适应性,对于接种蓝藻固沙技术的应用具有积极的意义。实验分3部分:研究了室温培养条件下3种荒漠优势蓝藻-具鞘微鞘藻(Microcoleus vaginatus)、爪哇伪枝藻(Scytonema javanicum)、纤细席藻(Phormidium tenue)的生长曲线,在不同温度(2、5、10、15、25、35℃)、开放式载体培养状态下3种蓝藻的生长状况及形态观察,以及爪哇伪枝藻在不同温度(10、15、20、25、30℃)培养条件下的光合活性、光合色素含量和伪枝藻素含量的变化。实验结果表明:(1)在液体培养基中,纤细席藻生长速率最快,高于具鞘微鞘藻和爪哇伪枝藻;(2)开放式载体培养条件下,藻株的生长速率低于液体培养,因此荒漠优势藻类的培养优先选择液体培养,具鞘微鞘藻和爪哇伪枝藻不易被细菌污染,纤细席藻容易受到细菌污染,在培养该藻株时要考虑添加抗生素类药物抑制细菌过度繁殖;(3)爪哇伪枝藻短期培养(18d)宜选择相对较高的培养温度(25-30℃),而长期培养(30d)宜选择相对较低的培养温度(15-20℃)。       

Genome of the cyanobacterium Microcoleus vaginatus FGP-2, a photosynthetic ecosystem engineer of arid land soil biocrusts worldwide

The filamentous cyanobacterium Microcoleus vaginatusis found in arid land soils worldwide. The genome of M. vaginatus strain FGP-2 allows exploration of genes involved in photosynthesis, desiccation tolerance, alkane production, and other features contributing to this organism's ability to function as a major component of biological soil crusts in arid lands.     

Response of desert biological soil crusts to alterations in precipitation frequency

Biological soil crusts, a community of cyanobacteria, lichens, and mosses that live on the soil surface, occur in deserts throughout the world. They are a critical component of desert ecosystems, as they are important contributors to soil fertility and stability. Future climate scenarios predict alteration of the timing and amount of precipitation in desert environments. Because biological soil crust organisms are only metabolically active when wet, and as soil surfaces dry quickly in deserts during late spring, summer, and early fall, the amount and timing of precipitation is likely to have significant impacts on the physiological functioning of these communities. Using the three dominant soil crust types found in the western United States, we applied three levels of precipitation frequency (50% below-average, average, and 50% above-average) while maintaining average precipitation amount (therefore changing both timing and size of applied events). We measured the impact of these treatments on photosynthetic performance (as indicated by dark-adapted quantum yield and chlorophyll a concentrations), nitrogenase activity, and the ability of these organisms to maintain concentrations of radiation-protective pigments (scytonemin, beta-carotene, echinenone, xanthophylls, and canthaxanthin). Increased precipitation frequency produced little response after 2.5 months exposure during spring (1 April–15 June) or summer (15 June–31 August). In contrast, most of the above variables had a large, negative response after exposure to increased precipitation frequency for 6 months spring–fall (1 April–31 October) treatment. The crusts dominated by the soil lichen Collema, being dark and protruding above the surface, dried the most rapidly, followed by the dark surface cyanobacterial crusts (Nostoc-Scytonema-Microcoleus), and then by the light cyanobacterial crusts (Microcoleus). This order reflected the magnitude of the observed response: crusts dominated by the lichen Collema showed the largest decline in quantum yield, chlorophyll a, and protective pigments; crusts dominated by Nostoc-Scytonema-Microcoleus showed an intermediate decline in these variables; and the crusts dominated by Microcoleus showed the least negative response. Most previous studies of crust response to radiation stress have been short-term laboratory studies, where organisms were watered and kept under moderate temperatures. Such conditions would give crust organisms access to ample carbon to respond to imposed stresses (e.g., production of UV-protective pigments, replacement of degraded chlorophyll). In contrast, our longer-term study showed that under field conditions of high air temperatures and frequent, small precipitation events, crust organisms appear unable to produce protective pigments in response to radiation stress, as they likely dried more quickly than when they received larger, less frequent events. Reduced activity time likely resulted in less carbon available to produce or repair chlorophyll a and/or protective pigments. Our findings may partially explain the global observation that soil lichen cover and richness declines as the frequency of summer rainfall increases.     

Effects of Salt Stress on Carbohydrate Metabolism in Desert Soil Alga Microcoleus vaginatus Gom.

The effects of salt stress on carbohydrate metabolism in Microcoleus vaginatus Gom., a cyanobacterium isolated from desert algal crusts, were investigated in the present study. Extracellular total carbohydrates and exopolysaccharides （EPS） in the culture medium produced by M. vaginatus increased significantly during the growth phase and reached a maximum during the stationary phase. The production of extracellular carbohydrates also significantly increased under higher salt concentrations, which was attributed to an increase in low molecular weight carbohydrates. In the presence of NaCI, the production of cellular total carbohydrates decreased and photosynthetic activity was impaired, whereas cellular reducing sugars, water-soluble sugars and sucrose content and sucrose phosphate synthase activity increased, reaching a maximum in the presence of 200 mmol/L NaCI. These parameters were restored to original levels when the algae were transferred to a non-saline medium. Sodium and K＋ concentrations of stressed cells decreased significantly and H＋-ATPase activity increased after the addition of exogenous sucrose or EPS. The results suggest that EPS and sucrose are synthesized to maintain the cellular osmOtic equilibrium between the intra-and extracellular environment, thus protecting algal cells from osmotic damage, which was attributed to the selective exclusion of cellular Na＋ and K＋ by H＋-ATPase.     

毛乌素沙地南缘沙丘生物结皮对凝结水形成和蒸发的影响

在水分极度匮乏的荒漠生态系统,凝结水是除降雨之外最重要的水分来源之一,它对荒漠生态系统结构、功能和过程的维持产生重要的影响。为探明半干旱沙区生物结皮表面的凝结水形成和蒸发特征,采用自制的微型蒸渗计(直径7 cm、高5 cm的PVC管)实验观测了不同类型地表(裸沙、浅灰色藻类结皮、黑褐色藻类结皮和苔藓结皮)对凝结水形成和蒸发的影响。结果表明:(1)观测期间共有20次凝结水形成记录,除降雨天气外,几乎每天都能观测到水分凝结现象;(2)不同类型地表凝结水总量依次为(1.998±0.075),(2.326±0.083),(2.790±0.058)和(3.416±0.068) mm,生物结皮表面的凝结水总量显著大于裸沙(P < 0.05);随生物结皮的发育,不同类型生物结皮表面的凝结水总量呈增加的趋势,凝结水总量之间差异显著(P < 0.05);观测期间不同类型地表日平均凝结水量依次为(0.100±0.003),(0.116±0.004),(0.140±0.002)和(0.171± 0.003) mm,不同类型地表日平均凝结水量之间差异极显著(P < 0.01);(3)凝结水形成过程的观测结果显示,凝结水19:00开始形成,23:00-凌晨1:00形成不明显,1:00-7:00继续形成,除浅灰色藻类结皮外,太阳升出后在黑褐色藻类结皮和苔藓结皮表面继续形成少量的凝结水;凝结水7:30开始蒸发,10:30到11:00之间结束蒸发,凝结水在裸沙和浅灰色藻类结皮中的保持时间显著大于黑褐色藻类结皮和苔藓结皮中的保持时间(P < 0.05);(4)凝结水的形成受大气温度、地表温度、空气相对湿度和大气地表温度差等气象因素的影响,但其形成过程不与某一个气象因素呈简单的线性关系。     

Cyanobacterial Microbiotic Crusts in Eroded Soils of a Tropical Dry Forest in the Baja California Peninsula,Mexico

This study deals with the cyanobacterial composition, and the nitrogen fixation of four members, of cryptobiotic crusts collected from eroded soils in a transitional area between arid and tropical climatic environments. Identification was based on microscopic analyses. Morphotypes were identified directly from reactivated natural crusts and from cultured strains. The identified morphotypes were Scytonema cf. ocellatum, Scytonema sp., Microcoleus cf. paludosus, M. cf. sociatus, Calothrix cf. elenkinii, C. cf. marchica, Nostoc cf. microscopicum, and Phormidium sp. Results show that the cyanobacterial composition of the microbiotic crusts studied is different from those in warmer and cooler deserts, particularly the absence of Microcoleus cf. vaginatus and Nostoc cf. commune in our samples. Such differences could be caused by the transitional character of the area. The results of the acetylene reduction assay show that the capacity of nitrogen fixation of some morphotypes is limited to the heterocyst-forming morphotypes.     

Why are higher plants green? Evolution of the higher plant photosynthetic pigment complement

The physiological reason that higher plants are green is unknown. Other photosynthetic organisms utilize pigments that strongly absorb green light; therefore, there must have been natural forces that ‘selected’ the photosynthetic pigments found in higher plants. Based on previously published data and our recent findings about green light and photosynthesis within leaves (Sun et al.), a specific functional role is described for the primary photosynthetic pigments of higher plants, that were derived from green algal progenitors. The particular absorptive characteristics of chlorophylls a and b appear to perform two contradictory, but necessary functions in higher plants. Firstly, chlorophylls a and b absorb light for maximum utilization under non‐saturating conditions, a function that is well understood. Secondly, they can act as protective pigments under over‐saturating light conditions, when absorbed light is dissipated as heat. Under such conditions, a significant portion of light can also be efficiently utilized, especially in the bottom portion of the leaf, that is mainly illuminated by green light and not down‐regulated. The second function may have been the selective force that gave rise to the extremely successful terrestrial plants, that evolved from green algae.     

不同类型生物土壤结皮覆盖下风沙土的入渗特征及模拟

干旱荒漠区广泛分布的生物土壤结皮(BSCs)对土壤水分入渗过程有重要影响。以古尔班通古特沙漠南缘的BSCs为研究对象,基于野外采样与室内模拟实验等方法,探究藓类、地衣和藻等3种类型BSCs覆盖下沙土的入渗特征。结果表明:与无结皮覆盖的风沙土对照,3种类型BSCs均显著降低了沙土初渗速率,藓类结皮、地衣结皮、藻结皮覆盖下初渗速率降低幅度依次为36.10%、46.42%、50.39%;藓类结皮、地衣结皮(P0.05)和藻结皮(P0.05)均明显降低了沙土稳渗速率,降低幅度依次为16.50%、33.98%和35.92%;3种类型BSCs均限制了湿润锋在沙土的推进过程,表现为:藓类结皮、地衣结皮、藻结皮的渗漏时间分别为裸沙对照的2.13、3.04和2.98倍;各类型BSCs均减小了沙土累积入渗量,阻碍了沙土水分入渗,与裸沙对照相比,藓类结皮、地衣结皮、藻结皮的1 h累积入渗量分别降低16.10%、28.56%和26.56%。在实验条件下,Kostiakov模型最适用于模拟不同类型BSCs覆盖下土壤水分入渗过程,Horton模型模拟效果次之。