Abstract: Taking the hill top in semi-arid hilly region of Loess Plateau in North Shaanxi as the object, an investigation was conducted on the herb vegetations in 31 quadrats with an interval of 40 m, and the methods of classic statistics and geostatistics were adopted to analyze the spatial distribution patterns of the vegetations on natural grassland in Loess Plateau interfluve. The linear correlation analysis and rank correlation analysis indicated that slope position was
the main factor affecting the herb coverage and dry/wet mass ratio, slope aspect was the main factor affecting the herb average height and biomass, while slope gradient had no significant effects on the spatial distribution of the herb species. The spatial correlation analysis with Moran’s I index indicated that the herb coverage, average height, and dry/wet mass ratio had positive spatial correlations within 60 m lag distance, and the herb biomass had a significant spatial correlation within 180 m lag distance. The experimental semivariation of herb average height and biomass could be well fitted with spherical model, and that of herb dry/wet mass ratio could be well fitted with Gaussian model, the autocorrelation range values of the three herb parameters being 99.3 m, 66.6 m, and 78.4 m, respectively, showing a strong spatial autocorrelation. The experimental semivariation of herb coverage could be fitted with linear model.

Key words: Species diversity, Community stability, Gap, Non-gap, Jinyun Mountain