Logging impact on giant herb density and reproductive strategies in central African moist forests

Tropical moist forests face increasing threats from human activities, including logging, which accounts for a quarter of global forest disturbances. However, the effects of logging on plant life forms other than trees remain poorly documented for tropical forests, despite their potentially strong influence on post-logging forest dynamics and resilience. Here, we investigate the effects of logging on giant herbs of the Zingiberales order, well known to dominate the understory and to hinder tree regeneration in many African tropical forests. We explore post-logging changes in giant herb density and reproductive strategies in response to disturbance combining repeated field and drone measurements, genetic analyses and a seed bank germination test, in a 5-year logging experiment in northern Congo. We show that low-intensity logging increases giant herb density and alters the reproduction and morphology of the locally dominant herb Haumania danckelmaniana , with a higher proportion of clones than seed-origin plants in logging gaps and a higher proportion of short shoots in unlogged areas. No giant herb seedlings emerged from the soil seed bank germination test, suggesting that these herbs may not rely on a persistent soil seed bank in the short term. Our work highlights the importance of considering tropical forests understory to fully comprehend the impact of disturbances. We show that logging affects giant herb density and reproduction, enabling them to persist and dominate the understory, potentially leading to a lower recruitment of trees and thus compromising sustainability of future logging activities. We suggest that improved knowledge of Zingiberales reproductive phenology might help anticipate their post-disturbance dynamics. More broadly, our study emphasizes that considering often overlooked plant life forms is crucial for understanding forest resilience in managed tropical forests. ● Low-intensity logging increases giant herb abundance in tropical forest understories. ● Logging alters the reproductive strategy and morphology of giant herbs. ● More clonal reproduction in logging gaps, while more short shoots in unlogged forest. ● No apparent role of the soil seed bank for giant herb post-disturbance regeneration. ● Key role of understory plant life forms in post-logged forest dynamics and resilience.