Invasive alien plants pose a significant threat to biodiversity and ecosystem stability in Shandong Province. In this study， we conducted a field investigation and analyzed the vegetation composition characteristics and risk levels of alien invasive plant species， with an aim to provide a scientific basis for the prevention and control of invasions and for the management of alien species in Shandong Province. We established an invasive alien plant assessment system adapted to the ecological environmental characteristics of the Nishan-Yishan area. We used an analytic hierarchy process to assess the relative invasion risk of each species in the Nishan-Yishan area， and classified the species into four invasion risk grades. In total， 74 species of invasive herbaceous plants belonging to 23 families and 56 genera were identified in Nishan-Yishan. Asteraceae was the dominant family among the invasive species， with 14 genera and 20 species. Of the 74 species of invasive plants， 56 species were annual or biennial herbs， and 49 species originated from the Americas. In the risk assessment， nine species were classified as aggressive invaders， and these included eight genera and seven families. Conyza canadensis and Phytolacca americana had the highest invasion risk score， and were classified as extremely invasive. Additionally， 18 species were classified as locally invasive， and 19 species were classified as generally invasive. Twenty-eight species required further analysis — these species had a relatively light influence on ecosystem services and the economy. Qualitative and quantitative assessments were conducted on both the probability of invasion and potential harm caused by these alien plants to local ecosystems. Based on the invasion risks identified through this assessment， corresponding management practices can be effectively implemented to prevent invasions while safeguarding ecological security.
