Deadwood for Recovery? Woody Debris Addition Did Not Accelerate Small Fauna Recovery After Major Flooding

ABSTRACT

Periodic flooding is an intrinsic feature of floodplain ecosystems. The 2022–23 Murray River flood, the largest flood event in almost 70 years, inundated extensive floodplain areas on Calperum Station, South Australia. This depauperate vertebrate fauna community is the focus of restoration activities, including woody debris addition to rehabilitate degraded soils, vegetation and fauna. This study investigated the effects of woody debris addition and subsequent major flooding on the small mammals and reptiles by surveying terrestrial fauna, vegetation and groundcover before and two years after flood, with and without pre‐flood woody debris. Two years post‐flood, terrestrial fauna abundance and diversity had not recovered, and woody debris did not influence recovery. The two most common species in pre‐flood surveys, the fat‐tailed dunnart ( Sminthopsis crassicaudata ) and tessellated gecko ( Diplodactylus tessellatus ) declined markedly post‐flood, with no dunnarts detected. Pre‐flood, dunnarts were associated with areas of less bare ground; post‐flood, bare ground increased across all sites, likely reducing habitat suitability. Camera trapping in adjacent habitats recorded fat‐tailed dunnarts on dune tops. The mechanisms of flood avoidance or survival remain unknown, raising questions about the capacity of small terrestrial fauna to escape major floods and recolonise formerly suitable habitat. With larger, less predictable flood events predicted and ongoing habitat degradation, understanding the vulnerability of threatened floodplain communities to such disturbances is critical.