Abstract: Biological soil crusts (BSCs) are an important component of ecosystems, especially in arid and semiarid ecosystems, but we know little about their distribution and function on the Tibetan Plateau. In this study, we investigated the effects of alpine meadow degradation and artificial grassland construction on the distribution and growth of BSCs. Results showed that community coverage decreased with the degradation of alpine meadow. The occurrence frequency of moss was the highest in Graminaceous+Kobresia community and 6-year-old artificial grassland, and then decreased along alpine meadow degradation succession, being the lowest in black soil beach (43.6%). Black patches, white patches and lichen formed in K. humilis community, and were most abundant at Mattic epipedon crack stage of K. pygmaea meadow or Mattic epipedon erosion stage as indicated by the highest occurrence frequency, but were not observed in Graminaceous+Kobresia community, 6-year-old artificial grassland and black soil beach. The correlation analysis showed that the occurrence frequency of moss was significantly positively correlated with vegetation coverage, but negatively correlated with the occurrence frequencies of both black patches and white patches. A significant positive correlation was observed between the occurrence frequency of white patches and lichen (P<0.05). These findings demonstrate that BSCs distribute widely in alpine meadows, and vary greatly in distribution and species composition, indicating strong heterogeneity in distribution pattern due to the changes in vegetation growth and soil surface stability with meadow degradation.

Key words: salinity, Cyperus tegetiformis., nitrification, Minjiang River Estuary