Ozone is a phytotoxic gaseous air pollutant and its negative effects on forest production are a major concern. To understand the effects of ozone on forest production, it is important to clarify the nitrogen use efficiency (NUE) for tree growth under elevated ozone conditions, because nitrogen is a primal limiting factor of forest production in many cool-temperate forests. Soil nutrient conditions are considered factors affecting ozone susceptibility of tree growth. Therefore, in the present study, we investigated the effects of ozone on NUE for the growth of Siebold’s beech (Fagus crenata Blume) seedlings grown under different soil nutrient conditions. Seedlings of Siebold’s beech were grown under three gas treatments (charcoal-filtered air or ozone at 1.0 or 1.5 times the ambient concentration) in combination with three soil nutrient conditions (non-fertilised, low-fertilised or high-fertilised) for two growing seasons. Based on the dry mass and nitrogen concentration in each plant organ, we calculated NUE and its components, including nitrogen productivity (NP) and the mean residence time of nitrogen (MRT) during the second growing season. Ozone did not decrease the NUE of the seedlings during the second growing season, whereas leaf level photosynthetic nitrogen use efficiency (PNUE), a component of NP, was decreased by ozone. On the other hand, the soil nutrient supply decreased the NUE of the seedlings. Reductions in both NP and MRT were attributed to the decrease in NUE because of soil nutrient supply, whereas PNUE did not respond to soil nutrient supply. There was no significant interaction of ozone and soil nutrient supply on the NUE, or its components, of the seedlings. Our results indicated that there is a difference in the response between the NUE for individual growth and that of leaf level PNUE of Siebold’s beech seedlings to ozone and soil nutrient supply.

中文翻译：

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高氮和不同土壤养分条件下紫茎泽兰幼苗生长的氮利用效率

臭氧是一种植物毒性气态空气污染物，它对森林生产的负面影响是一个主要问题。要了解臭氧对森林生产的影响，重要的是弄清楚臭氧在升高的臭氧条件下对树木生长的氮利用效率（NUE），因为氮是许多温带森林中森林生产的主要限制因素。土壤养分条件被认为是影响树木生长的臭氧敏感性的因素。因此，在本研究中，我们调查了臭氧对NUE对Siebold山毛榉（Fagus crenata）生长的影响Blume）在不同土壤养分条件下生长的幼苗。Siebold山毛榉的幼苗在三种气体处理条件下（经空气过滤的空气或臭氧，浓度为环境浓度的1.0或1.5倍）与三种土壤养分条件（非肥料，低肥料或高肥料）一起生长了两个生长季节。根据每个植物器官中的干燥质量和氮浓度，我们计算了NUE及其组成，包括氮生产率（NP）和第二个生长季节中氮的平均停留时间（MRT）。在第二个生长季节中，臭氧不会降低幼苗的NUE，而NP会降低叶片水平的光合氮利用效率（PNUE）。另一方面，土壤养分供应降低了幼苗的NUE。NP和MRT的减少均归因于土壤养分的供应，NUE的减少，而PNUE对土壤养分的供应没有反应。幼苗的NUE或其组成部分上，臭氧和土壤养分供应之间没有显着的相互作用。我们的结果表明，个体生长的NUE和Siebold的山毛榉幼苗的叶面PNUE对臭氧和土壤养分供应的响应之间存在差异。