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。

The contribution of Microcoleus vaginatus to the formation of algal crust in the arid desert

Microcoleus vaginatus, the dominant species in the algal crust in desert regions, plays a significant role in the early development stage of the algal crust. In this study, we examined each development stage of the crusts under laboratory setup to explore the effect of different compositions of M. vaginatus on the algal biomass and crust thickness and hardness. In addition, we studied the physical interactions based on the observation of microstructure of the algal crust with the assistance of light microscopy and scanning electron microscopy, this paper analyzes the cementation style and mechanism of sand grains in different stages. We found that: (1) In the early stage of the crust development the crust was thin and fragile with a hardness of merely (12.21±1.58) Pa. At this stage the crust was formed by aggregating sand particles through adhesive materials which were made of extra\|cellular polymeric substances, excreted by microorganisms or algae. With further development of the algal community the M. vaginatus became the dominant species and the crust was maintained mainly through the mechanical binding of filaments surrounding sand particles at this stage. As a result, the crust became thicker and stronger with a organic layer on the surface. (2) The algal biomass and the crust thickness and hardness increased with the increase of the proportion of M. vaginatus (P < 0.01), with the maximum biomass and the highest crust thickness and hardness occurred at 80% of M. vaginatus in the total algal biomass. However, with further increase in the M. vaginatus proportion the algal biomass and the highest crust thickness and hardness started declining. This study provided valuable data and experimental methods for further investigating the dynamics and functions of the desert algal crust ecosystems and for desert ecosystem restoration.