Increasing drying changes the relationship of biodiversity and community assembly with ecosystem multifunctionality in temporary streams

Increased drought in rivers under the impact of global climate change is leading to biodiversity loss. However, it is not clear whether biodiversity loss affects river multifunctionality. In this study, we investigated the changes in community structure and ecological functions of biofilm communities in an artificially simulated stream after different drought durations.A drought period of about 60 days is a critical time point for changes in the structure and functions of river ecosystems under drought stress. Therefore, different drought durations were divided into short-term drought (0 ~ 20 d) and long-term drought (60 ~ 130 d) to analyse the maintenance mechanism of benthic community structure in terms of multifunctionality. In summary, biodiversity showed a significant dominant relationship in maintaining community stability after short-term drought, while the dominant relationship got uncoupled after long-term drought. For the maintenance of multifunctionality in benthic ecosystems, community assembly has been dominant with drought intensification, rather than biodiversity as traditionally perceived. This study reveals the importance of community assembly in maintaining multifunctionality in intermittent river and ephemeral stream ecosystems, extending theoretical knowledge of B-EMf relationships in extreme environments.