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.

Variation in algal composition among cifferent developmental stages of biological soil crusts in Gurbantunggut Desert

The biological soil crusts (BSCs) are commonly found in Gurbantunggut Desert, the largest fixed and semi-fixed desert in China. Four different BSCs developmental stages, including bare sand, algae crusts, lichen crusts and moss crusts were selected to determine successional changes in cyanobacterial and algal species composition, dominant species, and biomass. The results indicated that species composition differed between the four successional stages. There were some differences for common species. For example, Fragilaria sp., Oscillatoria willei, and Phormidium okenii were common species in bare sand. Species of Synechococcus parvus, Tychonema granulatum, and Phormidium retzli were common in algal crusts. Furthermore, some species were specific to particular successional stages. Dominant species varied from bare sand to mature crusts. The dominant species in bare sand, algae, lichen and moss crusts were Fragilaria sp., Microcoleus vaginatus, M. vaginatus and Scytonema ocellatum or Palmellococcus miniatus, respectively. Algal biomass had significant differences in different successional stages (p<0.01). Algal biomass in bare sand was the lowest and increased with BSCs development (such as algal crusts and lichen crusts). Algal biomass in lichen crusts was the highest, which was 8.3 times higher than in bare sand. However, algal biomass decreased with the development of moss crusts. Bare sand is mainly composed of uncompacted sand gains. Filamentous cyanobacteria, particularly M. vaginatus, were the dominant species early in crust succession. Additionally, fungal mycelium and moss rhizoids played a vital role in preventing water and wind erosion. Algal dominant species variation in different BSCs made the role and status of algae in BSCs change.