This study was conducted to investigate physiological responses and mortality of P. koraiensis seedlings under warming and drought treatments. In May 2016, 90 P. koraiensis seedlings (aged 2 years) were planted in each plot (n = 20), and exposed to a combination of + 3 °C warming and − 30% drought, with 5 replicates. Net photosynthetic rate (A), stomatal conductance (g_s), transpiration (E), and maximal photochemical efficiency of photosystem II (F_v/F_m) were measured from April 2017 to December 2018. Seedling mortality was measured eight times during the study period at irregular intervals. A, g_s, and E decreased by − 21.99%, − 34.58%, and − 33.6% under the warming treatment, and by − 5.82%, − 11.03%, and − 8.56% under the drought treatment, respectively, in response to decreasing soil water content and increasing soil and leaf temperature. There was no significant difference in the overall F_v/F_m by the warming and drought treatments. The long-term reduction in photosynthesis by the warming treatment might cause carbon starvation, resulting in a 7.43-fold increase in seedling mortality. Moreover, under the drought treatment, seedling mortality was unaffected since its effects on A were occasional and small as compared to the warming treatment. Due to the unusually high temperature in summer of 2018, leaf temperature was 38.28 °C and seedlings were exposed to temperature above 45 °C for 10.7 h under the warming treatment. F_v/F_m in August 2018 decreased sharply by − 11.79% and seedling mortality increased by 15.31-fold during summer, under the warming treatment. Thus, leaf damage by severe heat stress may have triggered a rapid increase in seedling mortality.

本研究旨在探讨红松幼苗在变暖和干旱条件下的生理响应和死亡率。2016年5月，在每个样地（n  = 20 ）中种植了90个2年龄的红松幼苗，并经受+ 3°C的增温和− 30％的干旱的组合，重复5次。从2017年4月至2018年12月测量了光系统II的净光合速率（A），气孔导度（g _s），蒸腾作用（E）和最大光化学效率（F _v / F _m）。学习周期不定期。在增温处理下，A，g _s和E分别降低了-21.99％，-34.58％和-33.6％，在干旱处理下分别降低了-5.82％，-11.03％和-8.56％。减少土壤水分并提高土壤和叶片温度。通过增温和干旱处理，总体F _v / F _m没有显着差异。增温处理使光合作用的长期减少可能会导致碳饥饿，导致幼苗死亡率增加7.43倍。此外，在干旱处理下，苗木死亡率对A的影响不受影响。与加温处理相比，偶尔会变小。由于2018年夏季的异常高温，叶片温度为38.28°C，并且在加温处理下将幼苗暴露于45°C以上的温度下10.7小时。在增温处理下，2018年8月的F _v / F _m急剧下降-11.79％，幼苗死亡率增加了15.31倍。因此，严重的热胁迫对叶片的损害可能已引起幼苗死亡率的快速增加。