Scattered native trees and soil patterns in grazing land on the Northern Tablelands of New South Wales, Australia
Brian R. Wilson A C , Ivor Growns A and John Lemon BA NSW Department of Natural Resources, PO Box U245, University of New England, Armidale, NSW 2350, Australia.
B NSW Department of Natural Resources, Gunnedah Resource Centre, PO Box 462, NSW 2380, Australia.
C Corresponding author. Email: brian.wilson@dnr.nsw.gov.au
Australian Journal of Soil Research 45(3) 199-205 https://doi.org/10.1071/SR07019
Submitted: 30 January 2007 Accepted: 20 April 2007 Published: 18 May 2007
Abstract
Over large areas of south-eastern Australia, the original cover of native woodland has been extensively cleared or modified, and what remains is often characterised by scattered trees beneath which the ground-storey vegetation is largely grazed or otherwise managed. This study investigated the influence of scattered Blakely’s red gum (Eucalyptus blakelyi) trees on both near-surface and deeper soil layers in temperate grazed pastures on the Northern Tablelands of New South Wales, Australia. A significant canopy effect was observed with elevated soil pH, carbon, and nutrient status inside the tree canopy indicating soil enrichment in a zone around the tree. This effect, however, was largely restricted to the surface (0–0.20 m) soil layers. Chloride concentrations were elevated near to trees but only in the deeper soil layers, suggesting that a modified water use and deep drainage mechanism occurred near the trees. Close to the tree, however, a significant acidification was observed between 0.40–0.60 m depth in the soil, without any obvious depletion in other soil element concentrations. It is concluded that this acidification provides strong evidence in support of a ‘biological pumping’ mechanism that has been proposed elsewhere. Key questions remain as to the management implications of these results, whether the subsurface acidification that was observed is common among native Australian trees, if it might be persistent through time, and if this might be a soil issue that requires management.
Additional keywords: scattered trees, soil pattern, soil acidity, soil carbon, soil nutrients.
Acknowledgments
The authors would like to acknowledge the assistance of staff of the University of New England in establishing and accessing field sites at Newholme Field Laboratory, especially John Dell, Newholme Field Laboratory Manager. Thanks also to the landholders, Bruce McCarthy, Rockvale, and Richard Vyner, Newby Park, for their assistance and support in undertaking this work. Thanks are also extended to Chris Nadolny at the Department of Natural Resources, Armidale, for constructive comments on earlier drafts of this manuscript and to the two anonymous reviewers who also provided constructive comments. Thanks also to the staff at the INCITEC/PIVOT Werribee laboratory for soils analysis.
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