Bark water vapour conductance (g_bark) is a rarely considered functional trait. However, for the few tree species measured to date, it appears high enough to create stem water deficits associated with mortality during droughts, when access to water is limited. I tested whether g_bark correlates with stem water deficit during drought conditions in two datasets of tropical trees: one of saplings in forest understories during an annual dry season and one of potted saplings in a shadehouse during extreme drought conditions. Among all 14 populations of eight species measured, g_bark varied more than 10-fold (0.86–12.98 mmol m⁻² s⁻¹). In the forest understories, g_bark was highly correlated with stem water deficit among four deciduous species, but not among evergreen species that likely maintained access to soil water. In the shadehouse, g_bark was positively correlated with stem water deficit and mortality among all six species. Overall, tree species with higher g_bark suffer higher stem water deficit when soil water is unavailable. Incorporating g_bark into soil–plant–atmosphere hydrodynamic models may improve projections of plant mortality under drought conditions.

树皮水蒸气传导性 ( g _bark ) 是一种很少被考虑的功能特性。然而，对于迄今为止测量的少数树种而言，当获得水的途径有限时，它似乎足以造成与干旱期间死亡相关的茎水分亏缺。我在两个热带树木数据集中测试了g_树皮是否与干旱条件下的茎水分亏缺相关：一年一度的旱季林下林下的树苗和极端干旱条件下遮荫棚中的盆栽树苗。在测量的 8 个物种的所有 14 个种群中，g_树皮的变化超过 10 倍（0.86–12.98 mmol m ^-2 s ^-1）。在林下林木中，g_树皮与四种落叶物种的茎水分亏缺高度相关，但在可能维持土壤水分的常绿物种中则不然。在遮荫棚中，g_树皮与所有 6 个物种的茎水分亏缺和死亡率呈正相关。总体而言，当土壤水不可用时，具有较高g_{树皮的树种}会遭受更高的茎水分亏。将g _bark纳入土壤-植物-大气流体动力学模型可能会改善干旱条件下植物死亡率的预测。