Transpiration in artificial forests has a vital role in the ecohydrological cycle and evolution of afforestation in semi-arid regions. However, further research is required to understand the impacts of biotic and abiotic factors on transpiration and water regulation strategies in tree species under climate change. We used the sap flow method to quantify transpiration in three adjacent plantations (Pinus tabuliformis, Populus simonii, and Ulmus pumila) spaced 40 m apart, and concurrently monitored soil moisture and meteorological variables. Significant differences in average transpiration were observed in the following order: P. simonii (1.31 ± 0.49 mm d–1) > U. pumila (1.04 ± 0.45 mm d–1) > P. tabuliformis (0.75 ± 0.31 mm d–1), due to differences in the canopy conductance, which followed the order of P. simonii (2.02 ± 0.18 mm s−1) > U. pumila (1.70 ± 0.15 mm s−1) > P. tabuliformis (1.26 ± 0.11 mm s−1) (P < 0.05). Under severe soil water stress, high vapor pressure deficit, and high solar radiation, transpiration was reduced in all species during the drought period in 2022 because of reduced canopy conductance (P < 0.05). Our findings demonstrate that a fast growth rate, deep root systems, and close relationships between the leaf water potential and stomatal regulation are vital strategies for trees responding to drought. Consequently, we recommend P. simonii for shelter forests and P. tabuliformis for ecological landscape forests to improve the stability of afforestation in semi-arid regions.

中文翻译：

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黄土高原环境变化下影响典型造林树种蒸腾作用的生物物理因子


人工林中的蒸腾作用在半干旱地区的生态水文循环和造林演变中起着至关重要的作用。然而，需要进一步研究以了解生物和非生物因素对气候变化下树种蒸腾和水调节策略的影响。我们使用树液流法量化了相距 40 m 的三个相邻种植园（油松、Simonii 杨和 Ulmus pumila）的蒸腾作用，同时监测土壤水分和气象变量。按以下顺序观察到平均蒸腾量的显著差异： P. simonii （1.31 ± 0.49 mm d–1） > U. pumila （1.04 ± 0.45 mm d–1） > P. tabuliformis （0.75 ± 0.31 mm d–1），由于冠层导度的差异，遵循 P. simonii （2.02 ± 0.18 mm s-1） > U. pumila （1.70 ± 0.15 mm s-1） > P. tabuliformis （1.26 ± 0.11 mm s-1） （P < 0.05）。在严重的土壤水分胁迫、高蒸气压亏缺和高太阳辐射下，由于冠层导度降低，2022 年干旱期间所有物种的蒸腾作用均有所减少（P < 0.05）。我们的研究结果表明，快速的生长速度、深根系以及叶片水分潜力与气孔调节之间的密切关系是树木应对干旱的重要策略。因此，我们推荐将 P. simonii 用于防护林，将 P. tabuliformis 用于生态景观林，以提高半干旱地区造林的稳定性。