The spatial influence of scattered paddock trees on soil and pasture attributes

Abstract

Scattered paddock trees are keystone features in temperate grazing landscapes in Australia. These scattered trees provide a range of ecological functions, and the impact of these trees on the environment is large relative to the small area they individually occupy. However, our understanding of the influence of these trees on their immediate environment is limited. In this thesis, the effects of scattered mature Eucalyptus trees on both native and sown pasture systems are examined in the temperate landscapes of the Northern Tablelands of New South Wales, Australia. Specifically, the influence of scattered trees on soil fertility, litter distribution, the nutrient pools in litter, pasture production and nutrient status, as well as the root distribution of a mature tree and the influence of shade on pasture biomass, are observed. The coarse tree roots (≥10 mm) of a scattered tree decreased with increasing depth in the soil and distance from the tree, forming a broad inverted conical structure. Most roots were largely restricted to within 2 canopy radii of the tree, and 80% of coarse roots were found below 20 cm in the soil profile. This suggests that coarse tree roots and pasture roots are unlikely to compete for the same soil resources because they occur largely at separate depths in the soil profile.