In temperate monsoon climate zones, which feature low precipitation in winter and spring, summer planting of Pinus tabuliformis Carr. seedlings may improve site restoration. The application of moderate water stress to improve seedling drought resistance may be an option to harden summer-plant seedlings. The objective of this study was to assess the effect of watering intensity and duration of acclimation treatments on seedling morphology and physiology attributes in the nursery and on the field performance of Pinus tabuliformis. We applied three watering intensities at 45%, 60%, 75% (control) of container capacity (CC) in the nursery for three durations (2, 3 and 4 weeks) during early summer and then correspondingly outplanted in three dates across July (i.e., 11th, 18th, and 27th). We measured seedling morphology, non-structural carbohydrates (TNC) and nitrogen (N) concentrations in the nursery, and in the field. Additionally, we measured field mortality and plant growth for three years. Drought hardening led to greater bud set and TNC reserves, along with lower shoot-to-root mass ratio (S/R). Longer drought hardening duration produced seedlings with larger stem volume, lower S/R and lower N concentration, but with greater root mass and bud set. Field mortality primarily occurred in the winter, with the three-week drought hardening causing increased winter mortality but enhanced field growth. Mortality during the first winter was negatively related to shoot TNC reserves but positively related to seedling field growth measured at the beginning of the fall, cold season. Mortality during the second winter was negatively related to seedling size but positively related to S/R measured at the end of second growing season. In contrast, drought hardening intensity had no effect on outplanting mortality and only a minor effect on field growth. Field growth in subsequent growing seasons was directly related to the size of the plant, N and TNC content at the beginning of the first fall cold season. This study demonstrates that higher TNC reserves were associated with smaller stem volume during the first growing season, suggesting a trade-off between growth and TNC storage. This suggests that under non-stressed conditions the TNC concentration and growth of seedlings before winter strongly affected their mortality during winter. Study results suggest that summer planting of P. tabuliformis container seedlings is feasible without the application of drought hardening acclimation treatments in geographic locations typically having summer rains. Optimizing the outplanting date during the summer and initial seedling size appear to be critical for good mid-term growth and low winter mortality.

在温带季风气候区，冬春季降水少，夏季种植油松。幼苗可以改善现场恢复。应用适度的水分胁迫来提高幼苗的抗旱性可能是使夏季植物幼苗变硬的一种选择。本研究的目的是评估浇水强度和驯化处理持续时间对苗圃幼苗形态和生理特性以及油松田间表现的影响。. 我们在初夏的三个持续时间（2、3 和 4 周）在苗圃中以容器容量 (CC) 的 45%、60%、75%（控制）应用三种浇水强度，然后相应地在整个 7 月的三个日期进行外栽（即第 11、18 和 27 日）。我们测量了苗圃和田间的幼苗形态、非结构碳水化合物 (TNC) 和氮 (N) 浓度。此外，我们测量了三年的田间死亡率和植物生长情况。干旱硬化导致更大的芽组和 TNC 储备，以及更低的芽根质量比 (S/R)。较长的干旱硬化持续时间产生的幼苗具有更大的茎体积、更低的 S/R 和更低的 N 浓度，但具有更大的根质量和芽集。田间死亡主要发生在冬季，三周的干旱加剧导致冬季死亡率增加，但促进了田间生长。第一个冬季的死亡率与茎部 TNC 储备呈负相关，但与秋季初、寒冷季节测量的苗场生长呈正相关。第二个冬季的死亡率与幼苗大小呈负相关，但与第二个生长季节结束时测量的 S/R 呈正相关。相比之下，干旱硬化强度对外植死亡率没有影响，对田间生长的影响很小。随后生长季节的田间生长与第一个秋季寒冷季节开始时的植物大小、N 和 TNC 含量直接相关。这项研究表明，在第一个生长季节，较高的 TNC 储量与较小的茎体积有关，建议在增长和 TNC 存储之间进行权衡。这表明在非胁迫条件下，冬季前幼苗的 TNC 浓度和生长强烈影响它们在冬季的死亡率。研究结果表明，夏季种植P. tabuliformis容器苗是可行的，而无需在通常有夏季降雨的地理位置应用干旱硬化驯化处理。在夏季优化外植日期和初始幼苗大小似乎对于良好的中期生长和较低的冬季死亡率至关重要。