Demographic, seed and microsite limitations to seedling recruitment in semi-arid mine site restoration

Abstract

Understanding limitations to plant recruitment is a key element in devising effective restoration of semi-arid ecosystems: only when these limitations are identified can management interventions be effectively targeted. This study investigated demographic, seed and microsite limitations to establishing native plant species in a semi-arid, post-mining restoration context. We assessed ex situ and in situ germination and in situ emergence for eight key tree, shrub and annual herb species. We sowed non-treated seeds and seeds that were pre-treated to overcome dormancy, at differing densities and across diverse microsites to assess the roles of dormancy, seed density and microsite type as limiting factors for seedling recruitment. We found that dormancy loss, in situ germination and in situ emergence limited one or more species, and we were able to improve emergence of one species by seed addition and targeted manipulation of microsites. The study has resulted in management implications including the importance of understanding methods to overcome dormancy to maximise germination; identifying key and species-specific demographic transitions; the importance of species-specific testing of seed sowing density; and the potential for increasing emergence by sowing seeds in furrows rather than broadcasting across rises and furrows, or on flat, unripped soil.