Effects of Stellera chamaejasme settlement on pH and chemical nutrient contents of root-zone soil in alpine meadows

Stellera chamaejasme is a major poisonous weed distributed in northern China and an important indicator of grassland degradation. In this study, a natural population of S. chamaejasme in an alpine grassland located on the eastern edge of the Qilian Mountains was taken as the research object, and the plant sizes (branches) of S. chamaejasme were used to represent the variations in settlement time. We aimed to explore the effect of settlement of S. chamaejasme on soil pH and chemical nutrients in its root microenvironment at different time scales. The results showed that with an increase in plant branches, the content of soil available potassium (AK), which is close to the root of S. chamaejasme, increased significantly (P < 0.01), while the pH value decreased significantly (P < 0.05). No significant linear relationship was observed between total nitrogen (TN), total potassium (TK), total phosphorus (TP), available phosphorus (AP), and branching number (P > 0.05). The contents of TN and AP in the marginal soil of the root zone decreased significantly with an increase in the number of plant branches (P < 0.05), and there was no significant linear relationship between the pH, TK, TP, and AK contents in the marginal soil and branching number (P > 0.05). In conclusion, the natural population of S. chamaejasme in alpine grasslands has no obvious selectivity for the soil environment of the habitat to be settled, but it can change the soil environment in its habitat by affecting soil pH and chemical nutrients after settlement.