Soil Seedbank Dynamics and Species Diversity in Pimelea-Infested Paddocks Under Pasture and Cultivated Conditions

Pasture lands, while appearing uniform in species diversity, exhibit notable variations upon closer examination. The study on Pimelea (or riceflower) seedbank dynamics revealed significant variations in seed density and distribution across soil depths, sites, years, and between pasture and cultivated paddocks in the same region of western Queensland. For the total number of germinable riceflower seeds across both the years 2019 and 2020, there is a clear distinction between pasture and cultivated paddocks. Pasture paddocks exhibited a gradual increase in total seed count from 108 seeds m^-2 in 2019 to 121 seeds m^-2 in 2020, resulting in a combined total of 229 seeds m^-2 over the 2 years across both depths. In contrast, cultivated paddocks showed a more substantial increase, with seed counts rising from 146 seeds m^-2 in 2019 to 255 seeds m^-2 in 2020, resulting in a combined total of 401 seeds m^-2 across both depths. Additionally, the Shannon-Wiener index at Site 1 indicated increased species diversity in the topsoil of pasture paddocks in 2020 compared to 2019, while deeper soil diversity decreased. Cultivated paddocks showed a declining trend, while pasture sites exhibited stable or increasing diversity. Pasture management generally maintained or enhanced diversity better than cultivation, especially in the topsoil layer. These findings highlight site-specific differences influenced by soil properties, land management practices, and local environmental conditions, shaping riceflower seedbank dynamics. Understanding these patterns is crucial for developing targeted management strategies to control riceflower in affected areas. Long-term field studies focusing on seedbanks are essential to develop sustainable control strategies.