库布齐沙地三年生人工藻结皮发育特征及微生物分布

DEVELOPMENT CHARACTERISTICS AND DISTRIBUTION OF MICROORGANISMS WITHIN 3-YEAR-OLD ARTIFICIAL ALGAL CRUSTS IN HOPQ DESERT

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(Salixcheilophila 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 Turcz.)、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 vaginatusGom.)占绝对优势,其次是爪哇伪枝藻(Scytonema.javanicum(Ktz.)Born et Flah.),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。

In this study, development characteristics and distribution of microorganisms within four different types of artificial algal crusts were investigated. The results showed that： （1） artificial algal crusts came into being, when desert cyanobacteria were inoculated onto surface of dunes, with their average thickness of 2.23-5.36mm, highly black and sage green, and coverage of artificial algal crusts over 70% when artificial algal crusts underwent growth and development of three years. As to the four artificial algal crusts, Salix cheilophila Schneid. -Aneurolepidium chinensis -algal crust（SAA） was found to gain the best developments and reached the most biomass, and arrived at the succession of moss crust at the same time. Plenty of desert plants occurred at the locations of artificial algal crusts, such as A. squarrosum, E. dahuricus, S. collina and A. chinensis, etc. , and the coverage of vegetation accounted for 60%-90%. Algal compositions of artificial algal crusts at four different stations were entirely very single, and the quantities of algal species varied inapparently. M. vaginatus was found to be still utterly dominant, whereas, S. javanicum kept secondary. Moreover, different species of algae were discovered to inhabit distinct ecological niche. It was shown in our study that artificial algal crusts could bear high compressive strength, and compressive strength commonly achieved 35-70 N/m^2. Cyanobacteria forming artificial algal crust was found to own abundant filamentous growth forms that could band and felt soil particles by compact and high mechanical force, and simultaneously, they exude polysaccharide with their filaments to hasten soil aggregation and cement soil particles together. All those meant compressive strength of artificial crusts was able to be maintained due to the presence of filamentous eyanobaeteria. The observation to ultra-microstructures of algal crusts indicated that abundant filamentous growth forms occurred between the sand soils within algal crusts during growth and development of 3 years in the fields. A great deal of filamentous growth forms were observed to band up and felt sand particles, which may be contributed to cementation process of artificial algal crusts. （2） Change trend of the total number of microorganisms was： SAA 〉 GA 〉 AA 〉 SA 〉 CK. Changes of biomass of artificial algae crusts accorded with that of the total number of microorganisms. Of all main microorganism groups, the quantities of bacteria, aetinomyees and fungi within different types of artificial algae crusts were consistent with that of the total number of microorganisms. Concerning the four artificial algae crusts, the ratio of bacteria quantities to the total number of microorganisms was distinctly more than that of aetinomyees and fungi. The percentage of bacteria quantities to the total number of microorganisms increased sharply in turn, while the percentage of aetinomyees quantities to the total number of microorganisms decreased evidently. Need to mention that it took on very small ratio of fungi quantities to the total number of microorganisms, and differences of the ratios varied very little.