Urbanization and climate jointly shape the composition of plant life forms

Urbanization and climate change are rapidly altering large-scale plant distributions and local community compositions, with profound impacts on ecosystem functions and services. However, it remains unclear how life form compositions, as one of the key functional biodiversity components in urban ecosystems, are influenced by urbanization under different climate scenarios.<b> </b>Here we investigated the life form compositions of 2,864 spontaneous plant species across 129 cities in a global biodiversity hotspot, Yunnan province of China. The results showed that, for naturally regenerated spontaneous plants in urban ecosystems, herbaceous plants (74.2%) significantly outnumbered woody plants (25.8%), while perennial herbs (45.0%) prevailed over annual herbs (29.2%). The compositions of plant life forms were significantly controlled by urbanization intensity and annual mean temperature. Specifically, annual plants were not sensitive to climate factors and thrived mainly in cities under intensive urbanization. Rising temperatures led to a monotonic decrease in the proportion of perennial herbs and an increase in woody plants. Along each temperature gradient, perennial herbs peaked under moderate urbanization intensity, while woody plants exhibited at troughs. Overall, perennial herbaceous were promoted by lower temperatures and moderate urbanization, while woody plants were mainly dominated in higher temperatures and lower degree of urbanization. Our findings highlight the profound combined effects of urbanization and climate in shaping functional traits of plants in human-dominated ecosystems.