Above-ground carbon in mulga-dominated rangelands, Murchison Bioregion, Western Australia

Abstract

The paper reports outcomes of surveys conducted between 2012 and 2014 in mulga (Acacia aneura) dominated arid rangelands of the Murchison Bioregion of Western Australia, approximately 470 km north-east of Perth, the State capital. The bioregion covers 281,200 km². The purpose of the surveys was to measure the stocks of above-ground biomass (AGB) and sequestered organic carbon within 140 plots, each 25 m × 25 m. The resulting large database was interrogated to (1) find a relationship between AGB and contained carbon in trees and in shrubs, and (2) find plant metrics to predict AGB. At the plant level, analysis confirmed the finding that tree AGB was composed of a mean 47% carbon, with shrub AGB averaging 46%. This allowed biomass to be used as a surrogate for carbon in our further analysis. Tree canopy area was found to provide the best linear relationship with tree and shrub AGB. The linear relationships held true for individual plants across the survey sites and across the land systems involved. At the plot level, measures of AGB and carbon stocks varied across land systems. Because tree canopy can be measured by remote-sensing, the results of these field-only surveys indicated a potential for AGB and carbon in mulga-dominated rangelands to be assessed remotely.