Abstract:

Aims ‘Black soil land’ grassland on the Tibetan Plateau results from degradation of Kobresia alpine meadow and has many weeds and poisonous plants. This disturbed grassland forms in small bottomland patches. There are no studies of community spatial patterns, relationships and scale patterns of adult plants and seedlings are important to explaining the formation of this secondary weed community.

Methods We selected a typical ‘black soil land’ community of about 30 m × 50 m in the headwaters of the Yellow River and used 100 sample plots (50 cm × 50 cm) to investigate number and density of adults and seedlings (determined by pulling) by species. Spatial heterogeneity of the community and the similarity between adult plants and seedlings were analyzed by semi-variance, fractal dimension, spatial correlation spatial autocorrelation, etc.

Important findings Species number of adult plants is highly spatially heterogeneous and plant density homogeneous at large scales. Species number of seedlings is highly spatially heterogeneous at small scales, and its density is highly spatially heterogeneous at large scales. Seedlings have high density in areas of micro-topography and gaps of adult plants, where seedlings grow and establish in empty ecological niches. The ‘black soil land’ community regenerates and recruits in vegetation gaps. The generation of ‘black soil land’ community depends on high density of seedlings of weeds and poisonous plants, and its generation capability is strong. According to our results, the ‘black soil land’ secondary community becomes more stable without interference. We suggest that human management be used to decrease the stability of the ‘black soil land’ weed community and restore alpine meadow.

Key words: Qinghai-Tibetan Plateau, ‘black soil land’ degraded grassland, weed and poisonous plant, seedling, spatial heterogeneity, community regeneration