Effects of climate warming on tree growth and physiology may be driven by direct thermal effects and/or by changes in soil moisture. Dioecious tree species usually show sexual spatial segregation along abiotic gradients; however, few studies have assessed the sex-specific responses to warming in dioecious trees. We investigated the sex-specific responses in growth, photosynthesis, nonstructural carbohydrate (NSC), water-use efficiency and whole-plant hydraulic conductance (K_P) of the dioecious tree species Populus cathayana Rehd. under +4 °C elevated temperature with and without supplemental water. For both sexes, high-temperature treatments significantly decreased growth (height and biomass), photosynthetic rate (A), the ratio of A to dark respiration rate, stomatal conductance (g_s), transpiration rate, NSC, leaf water potential and K_P, but increased water-use efficiency (estimated from carbon isotope composition). Under warming with supplemental water, most traits of females did not change relative to ambient conditions, but traits of males decreased, resulting in greater sexual differences. Females showed a lower K_P, and their g_s and A responded more steeply with water-related traits than males. These results show that the effect of summer warming on growth and photosynthesis was driven mainly by soil moisture in female P. cathayana, while male performance was mainly related to temperature. Females may experience less thermal stress than males due to flexible water balance strategy via stomata regulation and water use.

中文翻译：

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夏季变暖对雌雄青杨生长、光合作用和水分状况的影响：对性别特异性干旱和耐热性的影响。


气候变暖对树木生长和生理的影响可能是由直接热效应和/或土壤湿度的变化驱动的。雌雄异株的树种通常沿着非生物梯度表现出性别空间隔离；然而，很少有研究评估雌雄异株树木对变暖的性别特异性反应。我们研究了雌雄异株的青杨树种在生长、光合作用、非结构碳水化合物（NSC）、水分利用效率和全株水导度（ K _P ）方面的性别特异性反应。在 +4 °C 高温下，有或没有补充水。对于两性，高温处理均显着降低生长（高度和生物量）、光合速率（ A ）、 A_与暗呼吸速率的比率、气孔导度（ g _·s ）、蒸腾速率、NSC、叶水势和KP ，但提高了用水效率（根据碳同位素组成估算）。在补充水变暖的情况下，雌性的大多数性状相对于环境条件没有变化，但雄性的性状下降，导致性别差异更大。与男性相比，女性表现出较低的K _P ，并且她们的g _s和A对与水相关的特征的反应更剧烈。这些结果表明，夏季变暖对雌性青杨生长和光合作用的影响主要由土壤湿度驱动，而雄性表现主要与温度有关。由于通过气孔调节和用水实现灵活的水平衡策略，女性可能比男性经历更少的热应激。