The early response of subtropical tussock grasslands to restoration treatments

Abstract

Once widespread, Australia's bluegrass tussock grasslands (dominated by Dichanthium sp.) of the Queensland Central Highlands are now severely endangered. Despite being biodiversity rich and highly valued as low input, nutrient‐dense grazing systems, bluegrass tussock grasslands have suffered extensive clearing and degradation over the last 150 years. Natural recovery of these grasslands is possible but rates of recovery are slow. As such, there is an urgent need to assess practical management strategies to accelerate recovery of these grasslands, with a particular focus on early‐successional stages, when aggressive exotic species are most prevalent. To date, no studies have tested whether commonly used grassland restoration strategies can enhance early‐successional stages and accelerate regeneration in this system. Here, we examine the early short‐term impacts (first two seasons) of two common grassland restoration approaches, with two variations each: direct seeding (single species and low seed diversity) and vegetation clearing (prescribed burning and glyphosate application) across two common starting points: a formerly cropped old field and a historically overgrazed natural grassland. No treatment increased native diversity (Shannon's or richness) in plots but the composition of burned plots in the old field did become more similar to healthy reference sites after two seasons. Burning combined with direct seeding also increased the abundance of the dominant grass, Dichanthium sericeum, toward healthy reference levels within the first two seasons post seeding. This study provides a practical assessment of the short‐term impacts and capacity of common grassland restoration treatments to enhance the recovery of Australia's tussock grassland systems.

Opportunities to improve the future of South Australia’s terrestrial biodiversity

“…(5) There is currently a lack of empirical evidence regarding the most effective ways to maximise the potential for biodiversity recovery and maintenance in revegetation projects (i.e., which species to plant, how many different species to plant, what spacing to plant, etc. ), while there are some ongoing experiments to determine these ideal approaches for certain habitats in South Australia (there are also examples of carefully designed restoration experiments elsewhere in Australia; e.g., Charles et al 2018;Ladouceur and Mayfield 2017), there is as yet insufficient information across all vegetation communities in South Australia to provide ideal guidelines.…”