High temperature can improve the performance of invasive plants by facilitating root growth.

Abstract

The ever-increasing temperatures of the Anthropocene may facilitate plant invasions. To date, studies of temperature effects on alien plants have mainly focused on plant aboveground traits but ignored belowground roots, which may hinder our predictions of plant invasion risks under climate change. The temperature effects on the root growth dynamics of two alien shrubs, invasive Mimosa sepiaria and naturalized Corchorus capsulari, were studied through a 3D transparent growth system under five temperature treatments (18/13°C - 34/29°C), which cover the present and future warming scenario temperature distributions in China. We measured the dynamics of both root depth and width growth in response to temperature treatments across time (84 days). We also investigated the intraspecies and interspecies competitions of the two alien species along the temperature gradient by planting two individuals together. Both M. sepiaria and C. capsularis showed optimum shoot growth in the middle-temperature treatment, whereas M. sepiaria exhibited the fastest root growth under the highest temperature treatment (34/29°C), and the root growth of C. capsularis persistently decreased as temperature increased. Root depth growth was more susceptible than root width to neighbor competition pressure in both species. Compared to C. capsularis, M. sepiaria had relatively stronger intraspecies and interspecies competition advantages with increasing temperature, possibly because high temperature improved root growth. These results suggest that temperature increases can improve the performance of alien plants by facilitating the groth of their underground root widths and depths, which deserves serious concern in future invasion risk management. This article is protected by copyright. All rights reserved.