The Species Composition And Microsite-based Distributions Of Crusting Algae In The Songnen Meadow Steppes

The biological soil crusts are a basis of vegetation succession and ecosystem restoration in degraded terrestrial ecosystems. However, previous investigations mainly converged upon that in the extreme environment—desert ecosystem, whereas lacking the issues in better circumstance, like of meadow steppes. But the biological composition, distribution, and relating crusting processes and mechanism of the development of biological soil crusts might be different in different ecosystems.By field survey, lab incubation, identification and analysis, this study attempts to recognize the biological composition and microsite-based distributions of the biological soil crusts and then the relationships between crusts distribution and external ambient-grazing factors like water, salinity and grazing, in the Songnen Meadow Steppes. This may lay a foundation for revealing the development processes and crusting mechanism of biological soil crusts under the influences of typical environmental and disturbance factors—soda salinization and grazing. Also, it may help further understand the ecological restoration in the degraded Songnen Meadow Steppes.By field investigation, lab culturing and identification, the following results were obtained.1. 88 species of cyanophytes were identified in the biological soil crusts of Songnen meadow steppes, belonging to 18 genera of 7 families, of which 11 genera and 33 species were identified by culturing. Filamentous algae are dominant in Cyanophyta which accounts for 78.41%, and its frequency of occurrence is up to 100%, mainly Oscillatoriceae, Nostoceae, Rivulariaceae, Scytonemataceae. In this area, dominant species of algae are Oscillatoria subbreris, Oscillatoria vizagapatensis, Lyngbya martensiana, Aphanothece stagnina and Microcoleus chthonoplastes, which almost distribute in all the areas where there exist algae crusts.2. The species diversity and community composition of algae from biological soil crusts are different in various microsites of the Songnen Meadow Steppes,but the dominant algae appear to be the filamentous cyanophyta. The numbers of algae species shown in descending order are in fenced pastures, in grazing pastures, in paths of grassland, and in the grassland near woods. There are some unique cyanophyta in different microsites, while some algae species are common and not selective to microsites.3. The algae flora composition of crusts in the Songnen area is relatively rich, which is significantly different from other parts of China. And it has its own unique characteristics under the ecologically typical conditions.4. In the Songnen Meadow Steppes, the main factors affecting the composition and distribution of algae are ambient vegetations, soil chem-physical properties, and grazing and trampling disturbances. Hydrolyzable nitrogen contents, soil moistures and pH values of soils, which belong to the physical and chemical properties of soils, have significantly associated with diversity of algae. The grazing disturbance and trampling also influence over the number of algae species.