Determining changes in Eucalyptus litter during decomposition

Abstract

This study demonstrated that both natural and thermal decomposition alter litter carbon and nitrogen content, affecting decomposition rates. Climate was the dominant driver, with rapid initial mass loss under warm and wet conditions. At a regional scale, decomposition was governed by initial litter quality, particularly C/N ratio; for example, Eucalyptus litter with high C/N decomposed more slowly than N-rich understorey litter. Under natural environment, N-rich litter facilitated Eucalyptus decomposition through nutrient transfer.

Prescribed burning, while effective for fuel reduction, also regulates litter decomposition and nutrient dynamics. Litter collected one year after fire decomposed faster than pre-fire litter, largely due to fire-induced changes in C/N ratios. In dry sclerophyll forests, post-fire understorey regeneration further enhanced decomposition, potentially supporting forest recovery through increased nutrient availability. However, carbon and nitrogen stored in surface litter are redistributed via volatilisation and mineralisation, with implications for ecosystem nutrient dynamics. These findings highlight the need to consider litter quality, understorey vegetation, and fire regimes in fire prone dry sclerophyll forests.

Traditional methods for measuring litter quality are costly and labour-intensive. Spectroscopic techniques such as visible-near-infrared (vis-NIR) and attenuated total reflectance Fourier transform (ATR-FTIR) offer efficient alternatives. Across this thesis, performance ranked ATR-FTIR > NIR > vis-NIR. While vis-NIR and NIR were effective for predicting the quality of fresh litter, ATR-FTIR provided consistently accurate predictions of carbon and nitrogen across litterfall, decomposition stages, and combustion residues. Overall, spectroscopy is a powerful complement to laboratory analysis for understanding chemical transformations in forest litter.