Retaining trees in a grazing landscape: impacts on ground cover in sheep-grazing agro-ecosystems in southern Queensland

Abstract

In low-input, low-productivity grazing systems, the modification of natural woodlands through overstorey tree and woody regrowth removal are management options used by graziers to increase native grass production for livestock grazing. This paper describes studies that determine if vegetation management by graziers affect floristic composition, species richness and plant cover in the Traprock wool-producing region of southern Queensland. Forty-seven sites in the region were sampled according to vegetation type (ironbark/gum woodland and box woodland), density of mature trees (low: 6 trees/ha, medium: 6-20 trees/ha, and high: >20 trees/ha), and the presence or absence of woody regrowth in the understorey to determine vegetation patterns. A subset of 18 sites was selected to establish grazing exclusion experiments in both vegetation types under varying mature tree densities. Here we describe the general patterns in vegetation under differing mature tree densities and provide some preliminary results of the 4-year grazing exclusion experiment. While grass production is low under high overstorey tree densities, no differences between medium tree densities and open paddock areas is apparent, suggesting retaining trees in a low-input, low-productivity grazing system can provide biodiversity benefits without adversely impacting upon production.