Sub-aerial Cyanobacteria In Grassland Ecosystems

The species and distribution of subaerial bule-green algae in northeast grassland are researched in this paper, the relation between the algal crust and the environmental factors is also discussed and analysed. During the growth season in the year 2002~2003, I selected 4 different research sites, every site was repeated. There are 31 species subaerial blue-green algae which subordinated to 3 families, 9 genus are founded, there are different superior species in different communities. It is verified that the algal crust has certain structure through using the scaning electron microscope. The filiment algae interwined rope-like bundles or nets among the soil particles, they live in the lowest layer of algal crust . These main species are M. paludosus ,M. vaginatus,S. javanicum ,L. martensiana. The spherical thallus live in the up-layer of the crust .The main species are N. commune,N. muscorum,G. fusco-lutea .Consequently express the algal crust in the grassland ecosystem has certain ecological effects . The algal crust affect the moisture content . In the same research site , the moisture content of soil is higher than that without algal crust . The main reason is that the blue-green algae have thick sheath , the sheath can absorb more water, and the higher temperature and more rain thicken the algal crust . they help to maintain moisture in the soil .The algal crust also affect the nitrogen content of the soil . In the same research site the nitrogen content of the soil with algal crust higher than that non-crust . It is because that some species of blue-green algae can fix nitrogen and release some of it in the soil. The degradation of the thallus increase the organic matter of soil and fertilize the soil . The degradation rate of algal crust in every community is different , the difference mainly due to the thickness of algal crust and species of the blue-green algae.