Associations Between Species Distribution Patterns and Soil Salinity in the Songnen Grassland

The Songnen grassland is one of the grasslands in China characterized by concentrated heterogeneous patches of saline-alkaline soils. However, our understanding of how these patchy structures develop and how biochemical factors change within patches is limited. Thus, three representative semi-vegetated patches were selected and analyzed for soil electrical conductivity (EC), soil pH, soil organic matter (SOM), and soil nitrogen (N). Based on the different appearance and distribution of species, the patches were divided into a center, middle, and outer section. Our results showed that in contrast to EC, SOM significantly increased from the center to the outer section. Aboveground biomass and species distribution patterns were strongly associated with SOM and contrasted to EC. In the center section, the annual species Kochia scoparia (L.) Schrad represented more than 90% of the total biomass, whereas the perennial species Leymus chinensis (Trin.) Tzvel and Phragmites australis (Cav.) Trin. ex Steud were the most dominant species in the outer section with a contribution of more than 90% to the total biomass. In the middle section, most of the species achieved mutual coexistence and the perennial species appeared to benefit from the interspecific relationships with their neighbors. Our results suggest that a feasible means of restoration management for heterogeneous degraded grassland should be achievable through revegetation by species such as L. chinensis and P. australis, which improve soil organic matter and reduce EC.