Association between environmental factors and the occurrence of six fumitory species (Fumaria spp.L.) in southern-eastern Australia

The occurrence of Fumaria as a weed in south-eastern Australian cropping systems is believed to have increased substantially in recent decades. To study this, a survey was conducted in contrasting regions of this zone, viz. southern New South Wales, mid-north South Australia. The survey analysed the pattern of occurrence of each of the six naturalized species found (Fumaria bastardii, F. densiflora, F. muralis, F. officinalis, F. parviflora and F. capreolata) and the natural environmental factors associated with their distribution. While five species were primarily found in agricultural environments, F. capreolata occurred exclusively in non-agricultural situations characterized by the presence of high soil organic matter. F. densiflora and F. bastardii were the most widespread and abundant species. F. officinalis was the rarest. Environmental factors were significantly associated with the occurrence of each species. Soil texture and/or rainfall during one of the autumn months were important. Factors associated with some species overlapped with other species and it was common to find more than one species at a site. Occurrence over a wide range of soil types in some species suggests the presence of substantial bio- and ecotypical heterogeneity.