Species diversity and ecology of microalgaae in biological soil crusts in Gurbantunggut Desert

文中以古尔班通古特沙漠生物结皮中的藻类植物为研究对象，通过野外调查、采样、实验室培养、显微观察、物种纯化、实验室测试和理论分析相结合的方法，对该沙漠生物结皮中藻类植物的区系特征、时空分布格局、演替规律以及高等植物对藻类分布的影响、生理培养进行了研究。本研究将为藻类在生物结皮中的人工应用提供理论依据，在新疆特殊的干旱环境下利用生物结皮进行防风固沙具有重要的实践意义。通过对该沙漠生物结皮中藻类区系和种类组成的研究结果发现，研究区有藻类植物120种，隶属4门25科52属，其中蓝藻87种，绿藻14种，硅藻11种，裸藻8种。研究区藻类的优势科/属均是丝状蓝藻，是生物结皮中的优势类群，寡种科/属和单种科/属占有很大比例，反映了研究区藻类区系的复杂性。典型沙垄的不同地貌部位和垂直层次对藻类的物种丰富度、种类组成和生物量均有一定的影响。藻类物种丰富度由垄顶至垄间低地逐渐升高；在垂直层次上则由表及里逐渐降低；藻类优势物种主要集中分布在0-2cm土层中，在0-0.5cm土层中第一优势种多为具鞘微鞘藻；藻类最常见的物种有铜绿蓝杆藻、小聚球藻、大型集胞藻、土生绿球藻、脆杆藻1和双尖菱板藻等，同时在不同地貌部位和垂直层次中存在一些特有种；藻类生物量在垄间低地最高，迎风坡与背风坡居中，垄顶最低，在沙垄垂直层次上由表及里急剧降低。除垄顶外，藻类生物量均有明显的季节变化，表现为春季生物量最高，夏季次之，秋季最低；同时，季节对同一地貌部位中藻类种类组成亦有一定的影响。生物结皮的不同演替阶段对土壤理化特性、种类组成和生物量均有一定的影响。生物结皮不同的演替阶段对土壤有机C、全N、速效N影响显著（P<0.05），但对全P、速效P、全K、速效K影响不显著；藻类的种类组成在不同演替阶段发生一定的变化，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、具鞘微鞘藻、眼点伪枝藻或集球藻，其中具鞘微鞘藻在藻结皮、地衣结皮两个演替阶段均有出现；生物结皮不同演替阶段对藻类生物量影响显著，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，在地衣结皮中达到最高；土壤理化特性、藻类种类组成和生物量之间存在一定的互馈作用；丝状藻类在生物结皮的演替过程中逐渐占明显的优势（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。在古尔班通古特沙漠生物结皮中，藓类植物物种多样性低，其中占优势的藓类植物是齿肋赤藓，此外还有泛生墙藓无芒变种、绿色流苏藓、真藓和柔叶真藓；除以真藓为优势的藓类结皮中藻类优势物种是眼点伪枝藻和念珠藻，其它几种藓类为优势的结皮藻类优势种均是具鞘微鞘藻；在其它几种藓类结皮中，眼点伪枝藻、拟短形颤藻、念珠藻、集球藻和土生绿球藻也是最常见的物种。具鞘微鞘藻和齿肋赤藓之间存在一种互利共生的关系，适当浓度的齿肋赤藓提取物能有效地促进具鞘微鞘藻的生长，具鞘微鞘藻提取液对齿肋赤藓的萌发、生长亦有一定的促进作用。蛇麻黄和沙蒿植丛对藻类物种多样性、种类组成和群落结构均有一定的影响。如具鞘微鞘藻在两种植物覆盖的表层土壤中均为优势物种，但随着与蛇麻黄或沙蒿植丛距离的增大，其优势度逐渐增大；蓝藻和丝状藻类的优势度由植丛内至植丛外有明显的上升，而绿藻、硅藻、单细胞和球形种类的优势度则呈明显的下降趋势，这可能是由光照强度、紫外线、温度和土壤水分等多种因素综合影响所致。通过对几种典型蓝藻的生理培养表明，K+、Ca2+、Mg2+和pH对于不同物种的影响不同，同时确定了具鞘微鞘藻、眼点伪枝藻、念珠藻的最适培养条件。Biological soil crusts (BSCs), most notably lichen crusts, develop and diversify in the Gurbantunggut desert, the largest and semi-fixed desert in China. Focused on the pioneer component (microalgae) in BSCs, we conducted to flora characteristic, ecological distribution, succession, and interspecfic relationship of microalgae by using field investigation, sampling, lab incubation, micro-observation, purification and separation, lab test and statistic analysis. The results would be helpful to better understand the mechanism of BSCs and their function on desertification control, and it should contribute to further study on the growth and development of artificial BSCs. The main results were as followings: In BSCs of the Gurbantunggut Desert, 120 taxa, belonging to 52 genus, 25 families and 4 divisions, were found. Four divisions are cyanophytes, chlorophytes, diatoms and euglenoids, in which 87 species are cyanophytes, 14 species are chlorophytes, 11 species are diatoms and 8 species are euglenoids. Document families or genus were filamentous cyanobacteria, which were document communities in BSCs. Some families or genus, only containing few or single taxa, account for a large proportion in the flora of the study areas, which indicates complexity of microalgal flora. In the typical sand dunes, different sand locations and soil layers with different depth had effects on species diversity, species composition and biomass of microalgae. Species diversity of microalgae was increased from the top of sand dunes to the interdune areas of sand dunes whereas decreased from the surface to the deeper layers. Microalgal dominant species mainly focused on 0-2 cm layer. In most case, the 0-0.5 cm layer was dominated by Microcoleus vaginatus. In different sand locations, the most common species were Cyanothece aeruginosa, Synechococcus parvus, Synechocystis crassa, Microcoleus vaginatus, Chlorococcum humicola, Fragilaria sp.1, and Hantzschia amphioxys. Additionally, some species were rare, they only appeared in a single layer in some sand location. Microalgal biomass was significantly affected by locations of sand dunes and soil layers with different depth. Microalgal biomass was highest in inter-dune areas, followed by the windward and leeward of sand dunes, and lowest in the top of sand dunes. In spite of the top of sand dunes, microalgal biomass in other sand locations was obviously influenced by seasons, which represented by the highest in spring, followed by summer, and the lowest in autumn. Different successional stages of BSCs significantly affected the content of soil organic C, total and available N, but not the total and available P and K content of soil. Composition of microalgal communities differed among the four successional stages. Dominant species in bare sand, microalgal crusts, lichen crusts, and moss crusts were represented by Fragilaria sp.1, M. vaginatus and Scytonema ocellatum or Palmellococcus miniatus. M. vaginatus was the same dominant species in algal and lichen crusts. Some species were specific of the successional stage. Significant differences in microalgal biomass were observed among the four successional stages. Microalgal biomass was the lowest in bare sand, increased with BSCs development and reached the highest value in lichen crusts. Some interaction existed among soil physiochemical properties, microalgal composition and biomass. Bare sand was mainly uncompacted sand gains. Filamentous cyanobacteria, particularly M. vaginatus, were the dominant species in the early phase of crust succession. The presence of fungal mycelium and moss rhizoids prevented water and wind erosion. Bryophyte diversity in BSCs of the Gurbantunggut Desert was low, which was mainly composed of Syntrichia caninervis, Tortula muralis var. aestiva, Crossidium squamiferum, Bryum argenteum, and Bryum cellulare. In moss crusts dominated by Bryum argenteum, dominant species of microalgae were Scytonema ocellatum and Nostoc sp.. And the other moss crusts were dominated by M. vaginatus. The most common species in moss crusts were S. ocellatum, Oscillatoria subbrevis, Nostoc sp., Palmellococcus miniatus, and Chlorococcum humicola, which were sub-dominant species. There exists a symbiotic relationship between M. vaginatus and S. caninervis. Suitable concentration extracts of S. caninervis may facilitate the growth of M. vaginatus, on the other hand, the extracts of M. vaginatus can promote the germination and growth of S. caninervis. Species diversity, species composition and community structure were showed some change in the areas of Ephedra distachya and Artemisia arenaria. In the surface soil layer of shrubs, the dominant species of microalgae was M. vaginatus. However, the dominant degree of M. vaginatus increased gradually away from the shrubs. From inward shrubs to outward shrubs, the dominant degree of cyanobacteria and filamentous microalgae increased clearly, whereas that of green microalgae, diatom, unicellular and coccoid species showed a decreasing trend, possibly due to integrative effects of light intensity, ultraviolet radiation, temperature and soil moisture. Physiological cultivation of several cyanobacteria indicated that K+, Ca2+, Mg2+ and pH may have different effects for different species. The author explored and advanced the optimal conditions of cultivating M. vaginatus, S. ocellatum and Nostoc sp

古尔班通古特沙漠生物结皮藻类的组成和生态分布研究

通过对新疆古尔班通古特沙漠中9个样地73份生物结皮土样藻类的培养和鉴定,分析了古尔班通古特沙漠中生物结皮藻类的种类组成和生态分布特点。结果表明,该沙漠中有藻类植物49属121种,隶属于蓝藻门、绿藻门、硅藻门和裸藻门。其中蓝藻83种,绿藻20种,硅藻11种,裸藻7种。蓝藻占总种数的68.60%,其中又以丝状种类为优势,占66.27%;绿藻则以单细胞种类为主。在古尔班通古特沙漠不同地带中,其藻类物种多样性和群落组成均有所不同,中部藻类物种最为丰富,北部和南部次之,而东部和西部则明显减少。在沙垄不同部位的分布中,少数种类对地貌部位的选择性不明显,但有些种类在不同地貌部位分布有差异。藻类在结皮不同层次的分布不同,在结皮层中藻类的种类和数量都较丰富,且以丝状种类较多,而在结皮下层藻类的种类和数量明显减少

新疆古尔班通古特沙漠生物结皮绿藻研究

通过对古尔班通古特沙漠中39块样地253份生物结皮土样的分析,研究了古尔班通古特沙漠中绿藻的区系组成、生态分布特点和结皮不同发育阶段绿藻的种类组成的动态变化。结果表明:该沙漠中有绿藻门植物10科14属26种,其中以单细胞种类占优势;绿藻在该沙漠不同地貌部位的分布,以背风坡的种数最多(9种),迎风坡、丘间低地和垄顶逐渐降低;在结皮的不同层次中,绿藻主要分布在结皮层,而在结皮层以下种类很少;在生物结皮的几个不同发育阶段中,绿藻的物种多样性差别不大,其种类组成略有差别

准噶尔盆地古尔班通古特沙漠生物结皮蓝藻研究

通过对古尔班通古特沙漠中9个样地73份生物土壤结皮蓝藻的研究,分析该沙漠生物结皮中蓝藻的区系组成、生态分布特点和蓝藻在生物结皮中的作用机制。研究表明,该沙漠中有蓝藻门植物6科25属77种,其中以丝状种类占优势;蓝藻在不同地貌部位分布略有差异,在丘间低地种类最为丰富;不同种类的蓝藻对地貌部位的选择性不同,大部分对地貌部位具有选择性;蓝藻种类和数量在结皮层较多,在结皮下层明显减少。生物结皮的显微观察揭示了丝状蓝藻和胞外多糖形成错综复杂的网状结构,起着捆绑、黏结沙粒和固定沙粒的作用

新疆古尔班通古特沙漠南部沙垄不同部位藻类的垂直分布特征

通过2005和2006年夏季两次对新疆古尔班通古特沙漠南部荒漠土壤中藻类植物进行采样、培养、鉴定和生物量测定,分析了该区沙漠沙垄不同部位藻类物种组成、优势种和生物量的垂直变化。结果表明:1)在不同地貌部位的不同层次中,藻类的种类组成均有所差异。2)藻类优势物种主要集中在0~2cm层次中,2cm以下的土层中藻类细胞很少,绝大部分土层以具鞘微鞘藻(Microcoleus vaginatus)为第一优势种,有些部位的土层中第一优势种是伪双点颤藻(Oscillatoria pseudogeminata),如垄间低地和迎风坡的1~2cm中。此外,大型集胞藻(Synechocystis crassa)、舟形藻(Navicula sp.)、卵圆双眉藻(Amphora ovalis)数量也较多。3)除垄顶外,藻类生物量在其它3个部位不同层次的差异呈极显著水平(p<0.01),生物量由表及里锐减;在同一土层,藻类生物量基本表现为垄间低地最高,迎风坡与背风坡居中,垄顶最低,不同地貌部位对藻类生物量影响呈显著或极显著水平

荒漠藓类结皮层中齿肋赤藓形态结构适应性及其原丝体发育特征

在实验室内通过光镜与扫描电镜相结合的手段观察了新疆古尔班通古特沙漠藓类结皮层的优势物种——齿肋赤藓(Syntrichia caninervis Mitt.)的形态结构特征及其原丝体发育的全过程,并分别从藓类植物生长发育所必经的配子体和原丝体两个阶段对齿肋赤藓形态结构与荒漠干旱的生态环境之间的适应性关系进行了探讨。研究结果表明,①植物体密集丛生;叶片边缘强烈背卷,两面均具马蹄形细疣;中肋粗壮并突出叶尖成白色长毛尖。②原丝体系统的细胞短粗,细胞质高度浓缩,液泡较小,细胞壁较厚;原丝体系统具有短枝群

新疆古尔班通古特沙漠生物结皮层藓类物种多样性及适应性研究

[目的]探讨生物结层皮中藓类植物的物种组成以及对荒漠生态环境的适应机制。[方法]分别对各种藓类植物的形态结构及适应性进行观察和分析。[结果]结果表明,荒漠地表生物结皮中的藓类植物群落均呈垫状丛生。优势种刺叶墙藓(Tortula desertorumBroth.)的叶片强烈背卷且具长毛尖,上下表面密被透明的马蹄形细疣,茎皮部细胞壁明显增厚;绿色流苏藓[Crossidium squamiferum(Vi-viani)Juratzka]的叶片强烈内凹且具有专门进行光合作用的绿色丝体;真藓(Bryum argenteumHedw.)的叶片上部无色透明,茎的外皮部细胞强烈加厚,内皮部细胞壁薄,中轴部细胞仅角隅处加厚;双色真藓(Bryum bicolorDicks.)的叶片覆瓦状排列,外皮部细胞壁强烈加厚,内皮部细胞壁稍有加厚,中轴部分不明显;泛生墙藓(Tortula muralisHedw.)与泛生墙藓无芒变种(Tortula muralilsHedw.var.aestiva Bird.exHedw.)的叶片均具马蹄形疣,无明显的中轴分化,细胞壁强烈增厚。[结论]该研究对古尔班通古特沙漠地区植被恢复与重建具有深远的理论价值和实践意义

不同理化因子对分离于荒漠生物结皮中念珠藻生长的影响

通过对分离于生物结皮中的念珠藻(Nostoc sp.)进行室内培养,研究了K+浓度、Ca2+浓度、Mg2+浓度、pH值、温度、光照等理化因子对其生长的影响,初步探讨了念珠藻生长所需的最适生理条件.研究结果表明,K+浓度、Ca2+浓度对念珠藻生长的影响为显著水平,pH值、Mg2+浓度对念珠藻生长的影响为极显著水平,温度和光照强度对念珠藻的影响不显著.多因素方差分析结果进一步表明,pH值、Ca2+浓度、Mg2+浓度对念珠藻生长的影响呈极显著水平,K+浓度对念珠藻生长的影响不显著.念珠藻的最适生长条件为温度25℃,光照强度66μmol.m-2.s-1,pH=11,K+浓度为5.38×10-5mol/L,Ca2+浓度为1.77×10-5mol/L,Mg2+浓度为1.02×10-4mol/L

生物结皮对5种不同形态的荒漠植物种子萌发的影响

生物结皮广泛分布于干旱、半干旱区,强烈影响着土壤表层理化特性,进而对种子散布、萌发和定居产生影响。目前关于生物结皮与植物种子萌发关系的研究结论存在争议。该文通过室内人工控制实验,研究了生物结皮对古尔班通古特沙漠5种具不同种子形态特征的荒漠植物白梭梭(Haloxylon persicum)、蛇麻黄(Ephedra distachya)、角果藜(Ceratocarpus arenaarius)、涩芥(Malcolmia africana)和狭果鹤虱(Lappula semiglabra)的种子萌发的影响。结果表明,在干燥和湿润两种条件下,生物结皮对不同形态植物种子萌发均具有不同的作用。在干燥条件下,生物结皮显著抑制了角果藜和涩芥种子的萌发(p<0.05),对其它3种植物无显著影响;而湿润条件下,生物结皮显著抑制了白梭梭、角果藜和狭果鹤虱种子的萌发(p<0.05),对蛇麻黄、涩芥则无显著影响

生物结皮影响下沙漠土壤表面凝结水的形成与变化特征

在水资源匮乏的沙漠生境,凝结水是植物、生物结皮、无脊椎和脊椎小动物的重要水分来源之一。采用微渗计法对比研究3种生物结皮类型(藻结皮、地衣结皮和苔藓结皮)和自然裸沙对地表凝结水量及凝结水蒸散过程的影响。微渗计的规格为内径6cm,高3.5cm的PVC管。研究结果表明:不同类型地表的总凝结水量之间存在极显著的差异(P<0.01),总凝结水量随生物结皮发育水平呈显著增加的趋势,依次为:裸沙<藻结皮<地衣结皮<苔藓结皮,即生物结皮的存在有利于沙漠地表凝结水的形成。不同类型地表凝结水量的日均值有所差异。对于同一地表类型,凝结水量的最大值为最小值的数倍。黎明时,苔藓结皮的凝结水量最大,而裸沙的凝结水量最小,地衣结皮和藻结皮居中。凝结现象自20:00～22:00,次日8:00～9:00结束。大多数日出后凝结现象仍继续发生。不同类型地表的凝结及蒸散过程经历2个阶段:日出前凝结水量呈缓慢增加的趋势,日出后随温度的升高凝结水量快速减少,其中以苔藓结皮凝结水量下降最为迅速。凝结水量主要受温度、大气湿度、凝结面类型、气象条件和生境等方面因素的影响