Effectiveness of plant guards in reducing grazing of Tetraria capillaris in restored bauxite mines in Western Australia

Abstract

Herbivores can exert significant impacts on vegetation composition, particularly in open, newly established restored sites where plants are visible and often represent high quality forage. While tree species can potentially outgrow herbivores, understorey plants are unable to do so and may remain prone to herbivory in developing restored sites. We assessed the effectiveness of various mechanical and biological guards (Acacia companion plants) against grazing of the palatable dryland sedge Tetraria capillaris (hair sedge), in sites restored after bauxite mining in the jarrah forest of Western Australia. Six months after planting, grazing was severe and repetitive, and affected plant survival. Grazing intensity and severity reduced over time (from 95% to 64% of surviving plants grazed after six and a half years). No method of guarding entirely prevented grazing. Plants with plastic sleeves and Polynet mesh tubes showed significantly higher survival rates in short and longer term compared with unprotected controls (62% survival for both treatments compared with 30% survival of controls after six and a half years). Plastic sleeves were most effective at guarding T.capillaris against grazing although they were less cost-effective than Polynet tubes. While companion planting also reduced grazing it was less effective than artificial guards and not cost-effective. These data indicate that plant guards can have a positive impact on plant performance, even 6.5years after planting.