Changes to species diversity, spatial distribution, and shifts to younger, actively growing vegetation following wildfires may modify stand transpiration and the amount of water available to other parts of the hydrologic cycle. Therefore, the objective of this study was to determine how burn severity affected transpiration through alterations in stand structure and age in mixed pine/oak stands following a wildfire in the Lost Pines eco-region (Bastrop, TX, USA). Transpiration was monitored in loblolly pine (Pinus taeda)/ oak (Quercus stellata, Q. marilandica) stands across three burn severities: an unburned, mature stand; a moderately burned mature site; and a severely burned stand (pine saplings and oak resprouts).� From May � October 2016, pines had 31% and 39% greater sap flux rates (Js) than oaks at the unburned and moderately burned stands, respectively.� Pines at the severely burned site started the period with greater Js than the resprouts, but Js decreased as shallow soil moisture was depleted. As a result, young pines had ~9% less Js than the resprouting oaks across the measurement period.� Pine transpiration made up 75% and 86% of unburned and moderate stand daily transpiration, respectively.� Alternatively, resprouting oaks dominated the severely burned stand, contributing over 95% of daily transpiration. Transpiration was greatest at the moderately burned stand (2.08 mm day-1), followed by the unburned stand (1.48 mm day-1), and the severely burned stand (0.46 mm day-1).� Although resprouts and saplings exhibited greater Js than mature trees, reductions in total sapwood area after the severe fire resulted in lower daily transpiration at the stand level.� Results suggest light to moderate burns may enhance transpiration through reductions in competition and increased irradiance, while severe fires reduce stand transpiration through reductions in vegetation density.� Oaks will likely dominate some severely burned stands post-fire and consequently affect the hydrological cycle through changes in transpiration.
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