Spatiotemporal land use dynamics filter life history strategies to shape urban spontaneous plant assemblages

Spontaneous plants, such as weeds, are a key component of urban flora that can provide significant ecological benefits like nutrient cycling and soil pollutant removal. Our ability to fully harness these species in urban restoration efforts is hindered, however, due to a lack of understanding of their functional ecology under urban stressors. Here, we analyzed the effects of spatiotemporal urban land dynamics on the functional diversity of spontaneous plants from three life history strategies: colonization, establishment, and nutrient acquisition. Specifically, we measured 11 functional traits of 54 spontaneous plants across 79 sampling sites in Chongqing, a rapidly growing megacity in southwestern China with a population exceeding 16 million. We found that colonization-related traits of spontaneous plants were uncorrelated with nutrient-acquisition traits. When controlled for species richness, functional α- and β-diversity showed clearer responses to urbanization that varied by life history strategy and urban development stage. Spontaneous plant assemblages became more functionally homogeneous in their colonization and nutrient-acquisition strategies within newly urbanized areas than in historically developed areas. Yet, establishment strategies exhibited a neutral response to urbanization. Our findings reveal both challenges and opportunities of utilizing spontaneous plants in urban landscapes, highlighting the need to consider temporal dynamics in urban growth and plant functional diversity across life history strategies. Effective management should focus on controlling high-dispersal spontaneous plants in historically developed areas while retaining those with diverse nutrient acquisition strategies in newly urbanized areas to maximize ecological benefits for sustainable urban development.