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 Nino-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.

Automated summary

This study investigated 19 hydraulic traits in 40 woody species in a tropical savanna, finding significant variation in plant hydraulic traits based on leaf habit. Semi-deciduous species and shrubs showed the highest branch dieback and top-kill during drought, suggesting an important correlation between hydraulic traits and plant response to extreme dry conditions. Combining hydraulic traits with leaf habit and growth form led to better predictions of dieback and top-kill, indicating the potential for integrating life history traits with hydraulic traits for improved understanding and prediction of plant responses to drought.