Oral Presentation Freshwater Sciences 2023

Germinable soil seedbank composition in floodplain wetlands of the lower Fitzroy River, WA (#297)

Caroline Canham 1 , Fiona Freestone 1 , David Brauhart 1 , Thiaggo Tayer 1 , Samantha Setterfield 1 , Leah Beesley 1 , Michael Douglas 1
  1. University of Western Australia, Crawley, WA, Australia

Protecting floodplain wetland vegetation from excessive water harvest is a globally pertinent challenge. Water management decisions that aim to protect ecological values require an understanding of the relationship between water flows and biota. However, in many floodplain systems there is a paucity of data, particularly for herbaceous plant species. To address an identified knowledge gap, we investigated the composition of the germinable soil seedbank from fifteen floodplain wetlands of the Fitzroy River, in the remote Kimberley region in north Western Australia. To assess the relationship between water regime and species emergence, three watering treatments were applied to soil seedbank samples. Three environmental variables were also assessed; water persistence, soil physico-chemistry and wetland location. We found that the composition of the germinable soil seedbank was highly variable among floodplain wetlands, with 51 % of species occurring at a single wetland out of fifteen. However, different watering treatments resulted in differences in seedbank germination at some sites, both in terms of the species which germinated, and the abundance with which they germinated. The composition of the germinable soil seedbank was not strongly correlated to the assessed environmental variables. The high degree of variability in herbaceous species composition across the floodplain landscape prevents establishing a broad relationship between water regime and wetland vegetation. Instead, individual wetlands require further investigation to mitigate impacts from proposed developments that would alter the hydrological regime.