Soil Seed Bank Holds Some Potential for Natural Regeneration in a Semi-Arid Rangeland

Abstract

Natural regeneration of degraded lands can be facilitated by the recruitment of plant species from the soil seed bank. However, the composition of soil seed banks in arid Australia has seldom been studied. We addressed this knowledge gap by quantifying the soil seed bank of chenopod shrubland and remnant Acacia aneura (mulga) stands in an ex-agricultural site in New South Wales, Australia. We also assessed the effect of three germination pre-treatments. Overall, the soil seed bank yielded 113 species, only 11 of which (14%) were introduced species. Despite mulga historically being a dominant canopy species at our site, we found no evidence that it has a viable seed bank. Distance from water troughs (a proxy for past grazing intensity) did not affect seed bank richness or diversity, but seed bank density doubled between 16 m and 1024 m. Samples treated with gibberellic acid solution and controls (water only) produced a similar density of germinants (4843 vs. 4337 seedlings m⁻²), while soil samples treated with hot water yielded only 1118 seedlings m⁻². Our results suggest a substantial and diverse native seed bank exists for natural regeneration, but some key species will not return without ecological restoration.