Seasonal litter decomposition and accumulation in north Australian savanna

Background

Calculating greenhouse gas emissions from fires relies on estimation of available fuels at time of burn. Fuel accumulation and decomposition occur throughout the year, with seasonality of decomposition poorly researched in monsoonal Australia.

Aims

We investigate the decomposition and accumulation of litter fuels (leaves, twigs), and coarse woody debris (CWD >6 mm–<5 cm diameter) across a full monsoonal cycle.

Methods

The study was undertaken at three sites in long unburned (10 years+) eucalypts-dominated mesic savanna woodland. For measuring decomposition, twelve 50 g samples of leaves and twigs were placed in situ on the soil surface, with one sample removed and dried each month; one sample of CWD was tested after 12 months. Fine fuel accumulation was recorded monthly.

Key results

Significant statistical relationships were observed between soil moisture and leaf decomposition. Across the study period 66% of leaves, 35% of twig, and 27.2% of CWD decomposed. Fine fuel accumulation was consistent with previous studies and peaking in August. Combining monthly rates of accumulation and decomposition, net fine fuel loads were observed to be much greater late in the dry season.

Implications

The present study provides enhanced fine fuel load calculations by including seasonality of decomposition which allows for better estimates of emissions from savanna fires.