Soil seed bank can complement restoration efforts in a coastal freshwater creek

Riparian vegetation is a keystone ecosystem element heavily impacted by livestock grazing. Historically, regeneration approaches of the riparian vegetation use either active (planting) or passive (natural regeneration) strategies. Frameworks based on an understanding of the soil seed bank are needed to help guide the approach adopted. This study compared the soil seed bank composition to the extant riparian vegetation to assess the potential for natural regeneration to supplement active plantings, following livestock exclusion on the south-coast of Australia. At each of four sites, we surveyed the extant vegetation, and collected five soil samples from each of three zones (instream, slope, bank). Our results show that the proportions of species nativeness, growth forms, and life cycle was similar for both communities. However, while there were more terrestrial species recorded in the standing vegetation, there were more wetland specialists in the soil seed bank. A persistent native seed bank, combined with other basic management strategies, could potentially compete and limit the abundance of non-native or invasive grasses. The high abundance of native grass-types (Cyperaceae, Juncaceae, Juncaginaceae, Asparagaceae, Poaceae, Typhaceae), can be relied upon to regenerate the understorey to complement active planting of the trees and shrubs. As such, resources could be prioritised to sites where native species abundance in the seed bank is low. This study recommends that land managers should investigate the composition of the soil seed bank prior to allocating resources for active planting activities to ensure the most efficient use of resources across the landscape.

Automated summary

This study compares the composition of soil seed bank with the extant riparian vegetation, aiming to evaluate the potential of natural regeneration as a supplement to active plantings. The results show that although the proportions of species nativeness, growth forms, and life cycle are similar for both communities, the soil seed bank has more wetland specialists. The study recommends investigating the composition of the soil seed bank before allocating resources for active planting activities.