Increasing Drying Changes the Relationship of Biodiversity and Community Assembly with Ecosystem Multifunctionality in Temporary Streams

Abstract

As climate change worsens, river ecosystems face increased drought stress, emphasizing the importance of river biofilms as ecological indicators. Despite prevailing theory suggesting biodiversity loss impairs ecosystem function, understanding biodiversity's role in ecosystem multifunctionality (B-EMf) along environmental gradients, especially in dry riverine ecosystems, remains limited. In this study, benthic biofilms were exposed to varying drought durations. Results show a decline in biodiversity and an increase in multifunctionality with prolonged drought, suggesting a threshold around 60 days. Consequently, different drought gradients were classified into short-term (0-20 days) and long-term droughts (60-130 days) to analyse the maintenance mechanism of benthic biodiversity on multifunctionality. In conclusion, biodiversity showed significant dominance in maintaining community stability after a short-term drought, while the dominant relationship became uncoupled after a long-term drought. As for the maintenance of benthic ecosystem multifunctionality, community assembly consistently dominates that after experiencing extreme droughts, not biodiversity which is conventionally accepted as an essential indicator of function maintenance. And the dominance becomes more pronounced with increasing drought. This study provides insights into the importance of community assembly in maintaining ecosystem multifunctionality in intermittent rivers and ephemeral streams, expanding theoretical knowledge of B-EMf relationships in extreme environments.

Keywords: Global climate change, Intermittent Rivers and Ephemeral Streams, Benthic Biofilm, Community assembly, Biodiversity and Ecosystem Multifunctionality Relationship