Land use alters soil propagule banks of wetlands down the soil-depth profile

Many studies have investigated the effects of human disturbances on floodplain propagule banks, but few have examined how these propagule banks change down the soil depth profile. Changes in soil propagule banks with depth can indicate the state of past vegetation and potentially demonstrate the effects of different land uses on the soil profile. Here, we examined changes in soil propagule banks down the soil-depth profile in an Australian floodplain wetland with five different land-use histories, ranging from a, in this case, relatively minor disturbance (clearing) through to more major disturbance (continuous cultivation). Land use had a larger influence than floodplain geomorphology on the propagule distribution of wetland plant-group numbers. An observed decrease in individuals over the depth profile also altered terrestrial plant groups in fields with longer land-use histories. Overall, soil-propagule profiles for terrestrial plants were not as affected by land use as were those of wetland plants. The geomorphological position on the floodplain also altered the soil propagule bank, with areas subject to the most flooding having the highest number of wetland species and retaining more of these species with greater depths. In conclusion, land-use impacts alter soil-propagule banks down the profile, despite most studies focussing on the top few centimetres.