Japanese larch (Larix kaempferi (Lamb.) Carr.) and its hybrid are economically important coniferous trees widely grown in the Northern Hemisphere. Ground-level ozone (O₃) concentrations have increased since the pre-industrial era, and research projects showed that Japanese larch is susceptible to elevated O₃ exposures. Therefore, methodologies are needed to (1) protect Japanese larch against O₃ damage and (2) conduct biomonitoring of O₃ in Japanese larch forests and, thus, monitor O₃ risks to Japanese larch. For the first time, this study evaluates whether the synthetic chemical ethylenediurea (EDU) can protect Japanese larch against O₃ damage, in two independent experiments. In the first experiment, seedling communities, simulating natural regeneration, were treated with EDU (0, 100, 200, and 400 mg L⁻¹) and exposed to either ambient or elevated O₃ in a growing season. In the second experiment, individually-grown saplings were treated with EDU (0, 200 and 400 mg L⁻¹) and exposed to ambient O₃ in two growing seasons and to elevated O₃ in the succeeding two growing seasons. The two experiments revealed that EDU concentrations of 200–400 mg L⁻¹ could protect Japanese larch seedling communities and individual saplings against O₃-induced inhibition of growth and productivity. However, EDU concentrations ≤ 200 mg L⁻¹ did offer only partial protection when seedling communities were coping with higher level of O₃-induced stress, and only 400 mg EDU L⁻¹ fully protected communities under higher stress. Therefore, we conclude that among the concentrations tested the concentration offering maximum protection to Japanese larch plants under high competition and O₃-induced stress is that of 400 mg EDU L⁻¹. The results of this study can provide a valuable resource of information for applied forestry in an O₃-polluted world.

日本落叶松 ( Larix kaempferi (Lamb.) Carr.) 及其杂交种是北半球广泛种植的具有重要经济意义的针叶树。自前工业时代以来，地面臭氧 (O ₃ ) 浓度有所增加，研究项目表明，日本落叶松易受 O ₃升高的影响。因此，需要方法论来（1）保护日本落叶松免受 O ₃损害，（2）对日本落叶松林中的 O _{3进行生物监测，从而监测日本落叶松的 O 3}风险。本研究首次评估了合成化学乙二脲 (EDU) 是否可以保护日本落叶松免受 O _3的侵害损伤，在两个独立的实验中。在第一个实验中，模拟自然再生的幼苗群落用 EDU（0、100、200 和 400 mg L ^-1）处理，并在生长季节暴露于环境或升高的 O ₃。在第二个实验中，用EDU（0、200和400 mg L ^-1）处理单独生长的树苗，并在两个生长季节暴露于环境O ₃并在随后的两个生长季节暴露于升高的O _{3 。}这两个实验表明，200-400 mg L ^-1的 EDU 浓度可以保护日本落叶松幼苗群落和个体树苗免受 O _3的侵害- 诱导抑制生长和生产力。然而，EDU 浓度≤200 mg L ^-1确实在幼苗群落应对较高水平的O ₃诱导胁迫时仅提供部分保护，并且只有400 mg EDU L ^-1在较高压力下完全保护群落。因此，我们得出结论，在所测试的浓度中，在高度竞争和O ₃诱导的胁迫下为日本落叶松植物提供最大保护的浓度是400mg EDU L ^-1的浓度。这项研究的结果可以为 O ₃污染世界中的应用林业提供宝贵的信息资源。