Poisonous plant grassland expands through adaptive resource strategies of above‐ and below‐ground communities

Abstract The poisonous plant Ligularia virgaurea (Maxim.) Mattf. ( Ligularia ) is proliferating at a rapid rate, forming Ligularia ‐dominated grasslands (LVG) on the Qinghai‐Tibetan Plateau. However, it remains unclear how Ligularia and adjacent non‐poisonous plants compete in life strategies and how associated soil microbial communities adapt for resource supply. Here, we investigated changes in resource strategies of Ligularia and seven adjacent non‐poisonous plants across four stages of LVG formation, focusing on functional traits, resource absorption, transport and allocation inferred from root anatomical structure and hormone levels. To verify the universality of differences in resource strategies between poisonous and non‐poisonous plants, we then examined changes in plant functional traits in expanding areas of nine other poisonous plants. We also examined changes in soil microbial life‐history traits, community composition and functional potentials using 16S rRNA gene amplicon and metagenomic sequencing. During the progression of LVG, Ligularia and non‐poisonous plants adopted different resource strategies to enhance resource acquisition capacity. Specifically, Ligularia intensified resource predation capacity by enlarging body size, while non‐poisonous plants improved their resource‐foraging efficiency by enhancing resource return on investment. These differences in resource strategies between Ligularia and non‐poisonous plants were consistent with nine other areas of expansion of poisonous plants. Hormones related to growth increased in Ligularia , while hormones related to defence increased in non‐poisonous plants. Root structures related to resource transport were increased in Ligularia , but declined in non‐poisonous plants. Concurrently, soil microbial communities changed towards greater resource conservation and efficiency in resource processing during LVG formation, characterised by enhanced specialisation and enzymatic functions while decreased population size. Synthesis . Based on these findings, we propose a “resource involution” framework to define poisonous plant‐dominated grassland formations, highlighting the resource strategies of poisonous and non‐poisonous plants in the acquisition of nutrients and the soil microbiome in the supply of nutrients. This framework provides a robust foundation for predictive understanding and management of poisonous plants in the context of global change.