土壤微生物在生物结皮形成中的作用及生态学意义

在荒漠地区的固定、半固定沙地和流动沙地上,微生物、藻类植物及地衣、苔藓植物能参与并形成生物结皮,其在干旱和半干旱荒漠地区具有重要生态意义。其中土壤微生物因其极强的适应性和生存能力,在生物结皮形成各阶段都起着积极的作用。土壤微生物的生长和活性与土壤酶活性的变化具有良好的相关性,它的组成、分布和数量因沙丘类型和沙土层深度的不同而有所变化,也受到季节和植被的影响。土壤微生物的生理代谢活动及数量变化可以改变沙土表面理化性质,在土壤结皮的形成、植物营养的转化过程中发挥积极作用,为植物生长创造了良好的条件。

Effects and Ecological Significance of Soil-inhabiting Microorganisms in the Formation of Biological Soil Crusts

Biological soil crusts formed under the different combinations of mosses, lichens, liverworts, algae, fungi and soil-inhabiting microorganisms are quite common and widespread in the desert regions all over the world thanks to their extraordinary adaptability and surviving capability under the severe environment, such as the high temperature, pH values and salinity. It is revealed that the crusts may be an important source of fixed carbon in the sparsely vegetated areas in arid regions. In the successional pathways of the crust communities, the pioneers in colonizing the soil surface are the soil-inhabit ing microorganisms. Stabilization of sand dunes occurs after the colonization by the filamentous cyanobacteria, which may constitute a prominent crust The polysac charides produced by these cyanobacteria and by soil-inhabiting algae form a mucilaginous sheath on the soil sur face slightly binding the soil surface particles. The high holding capacity of moisture and the typical polysaccha rides enhance further the crust development and facilitate the colonization by other organisms, such as the overground cyanobacteria, soil-inhabiting algae, mosses and lichens. Many studies have revealed that there is a close relation between the growth and activation of soil-inhabiting microorganisms and the soil enzyme activation The quantity, distribution and composition of soil-inhabiting microorganisms vary with soil depth and location of sand dunes, and are also affected by seasons and vegetation situation. The change of physiological metabolisms and the quantity of soil-inhabiting microorganisms can affect the soil physiochemical properties, and plays an impor tant role in the formation and nutrition cycle of soil.