Ecological Effects of <i>Solanum rostratum</i> Invasion on the Diversity and Functional Traits of Native Plant Communities

Severe invasion by invasive plants can reduce the diversity of native plants, thereby limiting the functional diversity of ecosystems and threatening their stability in the invaded areas. In this study, the invasion area of <i>Solanum rostratum</i> in Urumqi, Xinjiang, China, was analyzed to determine the impact of different degrees of invasion on the species and functional diversity of plant communities in desert steppe and the ecological effects and driving mechanisms of invasion. Community-weighted mean trait values of invasive and coexisting local plants were also calculated to explore changes in species diversity and functional diversity at different degrees of invasion. <i>S. rostratum</i> invasion was associated with significant differences in soil nutrient patterns and exhibited phase-specific disturbance characteristics. Compared with the non-invaded quadrats, low and moderate invasion levels increased local community diversity and stability (<i>p</i> < 0.05), whereas high invasion significantly reduced local community diversity (<i>p</i> < 0.05). The community stability index dropped from 2.29 (light invasion) to 1.23 (severe invasion), representing a decrease of 46.21%. The invasibility index rose from 0.29 to 0.51, representing an increase of 73.86%. The <i>S. rostratum</i> invasion index increased from 0.64 to 1.95, representing an increase of 50.27%. Thus, plant species diversity was the primary factor affecting the stability and invasiveness of native plant communities. The weighted average character value of invasive plants was higher than that of native plants; the functional difference was < 0 for the low- and medium-invasion quadrats and > 0 for the high-invasion quadrat. <i>S. rostratum</i> invasion restructured soil nutrient regimes. The competitive strategy of <i>S. rostratum</i> is to promote and restrict local plant growth under low and high invasion levels, respectively, leading to a sharp decline in biodiversity and ecosystem imbalance. The results indicate that timely control measures should be implemented upon the initial invasion to prevent further spread and maintain ecological security, sustainable agriculture, and animal husbandry development.