Trends in evapotranspiration and streamflow following wildfire in resprouting eucalypt forests
- Publication Type:
- Journal Article
- Journal of Hydrology, 2015, 524 pp. 614 - 624
- Issue Date:
© 2015 Elsevier B.V. The objective of this study was to estimate the recovery trajectory of evapotranspiration (E
t) and streamflow (Q) in resprouting forested catchments following wildfire. Recovery dynamics were assessed in mixed species eucalypt forests in south-eastern Australia which recover from disturbance largely via vegetative resprouting, and to a lesser degree, via seedling recruitment. Changes in E t were evaluated in two ways. Firstly, we developed semi-empirical models of post-fire E t following moderate and high severity wildfire. These models were based on datasets of plot-scale E t, measured within five years post-fire, and published literature on post-fire changes in vegetation structure. Secondly, we analysed long-term Q records (25years) from a mixed species catchment, including a 1-5year period following a predominately moderate severity wildfire. We found that the overall length of recovery time for E t and Q following wildfire was 8-12years, which is much less than for eucalypt forests recovering via seedlings only. This emphasises the importance of functional responses to fire in forest ecosystems as a key driver of the hydrologic resilience of catchments, with resprouting forest types conferring relatively rapid recovery following disturbance. We also found that the recovery trajectory of post-fire E t was dependent on fire severity. Increased E t and consequent declines in Q occurred following moderate severity fire. In contrast, there was no evidence of increased E t following high severity fire. Based on patterns of long-term Q and rainfall observed in a small mixed species catchment, declines in Q due to increased E t following moderate severity wildfire were of similar magnitude to Q declines driven by a drought that coincided with the fire. We conclude that the coincidence of wildfire with drought exacerbates reductions in Q under moderate severity fire, resulting in greater Q declines. This is due to the enhanced rates of E t, primarily driven by regenerating seedlings and higher rates of transpiration from surviving trees.
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