Tree water-use recovery after drought-intermittent rainfall events

<p>Short drought-intermittent rainfall (SDIR) events, i.e., short rainfall events after long dry spells, typically re-wet top few centimeters of soil layer and often has little impact on the water balance of the ecosystem. Nevertheless, these SDIR events could provide the much-needed short-term water supply during dry spells to the terrestrial ecosystem, especially trees. An efficient use of these SDIR events could provide the trees with a buffer to withstand longer drought conditions, which will become more frequent and intense with the upcoming changes in climate.</p><p>This study aims to quantify the tree water use (TWU) recovery in terms of sapflow recovery following SDIR events across multiple global forest sites (35 sites) spanning over 250 site-years. SDIR events are identified probabilistically as rainfall periods (1-2 days with daily rainfall < 75^th percentile) occurring after an extreme dry spell (> 90^th percentile of dry spell duration) during the growing season. For each tree, TWU recovery (R_TWU) is estimated based on percentage increase in sapflow rate after the SDIR event (S_a), compared to before the SDIR event (S_b), and standardized by seasonal maximum sapflow (S_max). The inter-species R_TWU and intra-species R_TWU relationship with tree allometry (height and diameter) is used to explain the recovery rates. The main hypothesis tested here is that the intra-species differences in R_TWU are positively related to tree size due to better root development in larger trees. The understanding of R_TWU provides a new axis to understand and predict tree recovery after drought events.</p>