The effects of burial depth and water stress on Melastome weed seeds.
Two seed trials were conducted to provide insight into the conditions under which high priority tropical rainforest weeds from the family Melastomataceae can establish. Seeds of Clidemia hirta, Miconia calvescens, Miconia nervosa and Miconia racemosa were placed at depths of 0, 2, 5, 9, 14 and 20 mm in small containers and incubated. Emergence declined with depth, with no emergence from 9 mm depth or greater. Seeds of the same species were also subjected to moisture stress in incubated Petri dishes, via exposure to water potentials (stress) between 0 and -1 MPa. Despite their different native and invasive home ranges seeds of the Miconia species germinated at relatively low water potentials between 0 and -0.33 MPa. In comparison, Clidemia hirta seed germinated under higher moisture stress at -0.5 and -0.67 MPa. These weeds form persistent soil seed banks which may need managing for decades. Management actions and potential impacts can be informed by understanding the factors influencing their establishment from seed.