Lowland plant migrations into alpine ecosystems amplify soil carbon loss under climate warming
Climate warming is releasing carbon from soils around the world1–3, constituting a positive climate feedback. Warming is also causing species to expand their ranges into new ecosystems4–9. Yet, in most ecosystems, whether range expanding species will amplify or buffer expected soil carbon loss is unknown10. Here we used alpine grasslands as a model system to determine whether the establishment of herbaceous lowland plants in alpine ecosystems influences short–term soil carbon storage under warming. We found that warming (< 1 year) led to negligible alpine soil carbon loss, but its effects became significant and 52% ± 31% (mean ± 95% CIs) larger after lowland plants were introduced at low density into the ecosystem. We present evidence that soil carbon loss likely occurred via lowland plants increasing rates of root exudation, soil microbial respiration and CO2 release. Our findings suggest that warming–induced range expansions of herbaceous plants may yield a rapid positive climate feedback in this system, and that plant range expansions among herbaceous communities may be an overlooked mediator of warming effects on carbon dynamics.