Severe wildfire increased variability in the response of gross primary production to climate in an Eucalyptus dominated semi-arid woodland in South Australia

Abstract

Frequency and severity of wildfires have intensified in many regions in the world. High severity fires often initiate vegetation regrowth and succession, and thus alter ecosystem processes and functioning. Understanding how high severity fire-induced variations in gross primary production (GPP) respond to climate variability is critically important. This study aimed to quantify fire-induced changes in the response of GPP to concurrent and antecedent precipitation and air temperature in a semi-arid woodland in South Australia, using MODIS derived near-infrared reflectance of vegetation (NIRv) time series data (2000–2021) and associated climate data. Additionally, the magnitude and time course of climate legacies on GPP of unburnt and severely burnt sites were determined. The results showed that fire severity increased the variability in post-fire vegetation recovery. Prior to fire disturbance, NIRv as a proxy of GPP, was predominately affected by both concurrent and antecedent precipitation. Pre-fire precipitation legacy was about 9 months. Post-fire precipitation legacy duration was shorter in the unburnt patches within fire scar (ca. 9 months) than outside the fire scar (ca. 15 months), suggesting that the unburnt patches remaining within fire scar were more vulnerable to climate change than the adjacent intact woodland. In addition, the temperature legacies varied over time, likely mediated by water availability in this woodland. Post-fire regrowth from lignotubers was not significantly affected by concurrent and antecedent climate variables, but dependent upon endogenous growth which depends on previous growth conditions. This may be due to the smaller root system which reduced the capacity for taking up rain water after the fire event when annual precipitation was relatively low. We suggest that higher temperature together with reduced and more variable precipitation in the future could induce greater uncertainty in recovery of Eucalyptus trees post-fire.