Effects of slashing on native and invasive species, and community structure of a remnant natural grassland of South Australia

Questions We investigated the feasibility of slashing as a management tool to reduce the abundance of the exotic invasive species Avena barbata and favour native species and diversity in remnants of semi‐arid native grasslands. We asked how slashing affects: (1) the seed production and seed bank of A. barbata, (2) the mortality of perennial native tussock grasses, and (3) plant community composition. Location Near Burra, Mid North region of South Australia. Methods We established two parallel experiments in an invaded grassland: one in a stand dominated by exotic and invasive species (“poor” condition), and the other in a less‐degraded stand with an abundance of native perennial grasses (“good” condition). The experiments had a randomized block design (six blocks) with three treatments each: no slashing, slashing once a year or slashing every other year, applied over 3 years. We assessed the effects of the treatments on the number of seeds per m2 and soil seed bank of A. barbata, number of death native tussock grasses, and floristic composition and diversity. Results Slashing reduced seed production and the soil seed bank of A. barbata in both stands. Slashing increased the mortality of native grasses in the stand in good condition, and slightly changed floristic composition only in the stand in poor condition. Here, slashing decreased the abundance of the invasive species A. barbata and Bromus rigens but favoured other exotic species. No changes in species richness or diversity were detected. Conclusions The slight response of the plant community to slashing suggests that these grasslands are resistant to changes in management. However, the reduction in seed production and soil seed bank of A. barbata suggest that longer term application of slashing could reduce its abundance and allow native species to recruit. The mortality of native tussocks can, however, negate the benefit of reducing abundance of invasive species. Remnant grasslands in Mid North South Australia require management strategies that enhance their biodiversity. Slashing with biomass removal reduced seed output and the seed bank of the dominant invasive species, Avena barbata, but increased the mortality of native tussocks grasses. Minor changes in community composition after slashing suggest that these grasslands are resilient to changes in management. Slashing can only be advocated here when the level of invasion of A. barbata is extreme and no sensitive native species are present.