Hydraulic prediction of drought-induced plant dieback and top-kill depends on leaf habit and growth form

Hydraulic failure caused by severe drought contributes to aboveground
dieback and whole-plant death. The extent to which dieback or whole-plant
death can be predicted by plant hydraulic traits has rarely been tested
among species with different leaf habits and/or growth forms. We
investigated 19 hydraulic traits in 40 woody species in a tropical savanna
and their potential correlations with drought response during an extreme
drought event during the El Niño–Southern Oscillation in 2015. Plant
hydraulic trait variation was partitioned substantially by leaf habit but
not growth form along a trade-off axis between traits that support drought
tolerance versus avoidance. Semi-deciduous species and shrubs had the
highest branch dieback and top-kill (complete aboveground death) among the
leaf habits or growth forms. Dieback and top-kill were well explained by
combining hydraulic traits with leaf habit and growth form, suggesting
integrating life history traits with hydraulic traits will yield better
predictions.