Knowledge of when the maximum number of seeds occur in river channels is critical in understanding how changing flow regimes, either as a consequence of climate shifts or human induced flow modifications will influence plant communities. In this study, I investigated seasonal variation in abundance and diversity of seeds occurring in the drift of four lowland rivers in north east, Victoria, in 2017- 2018. Drifting seeds were collected by placing drift nets on the water surface to catch floating seeds and on the river bed to catch non-floating seeds and tested the hypothesisthat community diversity and abundance of seeds in lowland rivers differ seasonally with higher abundances occurring with naturally higher flows in winter spring.
Seasonal influence on the diversity and abundance of seeds in riverine habitats is influenced by the connectivity of the river to major seed sources in the riparian zone. Theoretically connectivity should occur at a time that maximises the mobilisation of seeds that have either been shed and lying dormant on exposed sediment or shed directly into flowing water.Therefore, I predict that higher abundances of seeds will occur in winter and spring when river height and connectivity with the riparian zone is greatest. In contrast I predict that during declining flows over summer and autumn when connectivity with riparian zone is low, the numbers of seeds in the drift will be lower.
Resultssuggest that there are differences in the drifting seed communities between the four lowland rivers studied and between seasons. Abundances of seeds is greatest in spring with declining abundance over summer and autumn. Results from this study will improve the understanding of seed transport both seasonally and spatially within river channels and improve our understanding of the possible consequence of flow modifications on seed dispersal and associated plant communities in lowland rivers.