Carbon storage in remnant trees and soils of grazing lands in Australia

Abstract

A large-scale research project was established in 2001 on a commercial grazing property in Queensland. Various aspects of grazing management at plot/catchment scales were studied for six years. This paper reports on the possible use of remnant trees in grazing lands as a carbon sequestration pathway in comparison to soil carbon. Trees growth was assessed using yearly height/girth measurement of 86 trees (Eucalyptus dealbata) in two plots. Some trees were harvested in 2001 and 2005 and the carbon (C) and nitrogen (N) concentrations measured on trunk, leaf and root samples. Total C and N were also measured in surface soil samples in 2001 and 2005. A Linear Mixed Effect model (LME) was developed from the growth data and used in combination with C concentration and tree density to predict C storage per hectare. Though there was no significant change in C storage in surface soil in the treed plots in the measurement period (2001-2005), there was a significant increase in C stored in the trees themselves. Although high tree densities are unrealistic for the entire grazing property, they may be appropriate for the less productive areas of land and could offset C emission from the rest of the grazing paddock.