Spatial distribution patterns of Themeda japonica populations and relationships with soil factors a regional scale

Soil is a major environmental factor that affects plant population dynamics. Spatial variations in physical and chemical properties of soil determine, to some extent, the spatial differences of plant population distribution. To investigate the spatial distribution of populations of the dominant plant Themeda japonica in Henan grassland, the spatial distribution pattern of the T. japonica population was evaluated on a regional scale using the point-and-spot combination method, and the relationship between the distribution features and soil factors was analyzed. The diffusion coefficient (C), clumping index (I), mean crowding (m^*), and patchiness index (PAI) indicated that T. japonica populations were distributed in clumped pattern in each region. In addition, the T-test of variance/mean ratio, patchiness index, Cassie index (C_A), and negative binomial parameter (K) revealed that the T. japonica populations in different regions presented a highly aggregated distribution pattern. RDA redundancy analysis showed that the soil factors that significantly affected the spatial distribution pattern of T. japonica populations included soil organic carbon, soil carbon-nitrogen ratio, and soil pH values in northern Henan (P < 0.05), while it was soil total phosphorus content (P < 0.01) in western and southern Henan. In general, there were significant correlations between soil organic carbon, soil total phosphorus, and the spatial distribution pattern of the T. japonica population (P < 0.01).