Nitrogen use efficiency (NUE), defined as the ratio of biomass growth and the nitrogen (N) taken up from a soil, is widely used in the evaluation of plant N economy. We conducted a fertilization experiment with Quercus serrata seedlings under different soil N and phosphorus (P) levels to determine the influence of high N deposition levels under different P availabilities upon NUE, plus the NUE components N productivity (NP), and mean residence time of N (MRT). The seedlings were grown for one growing season in the potted soil under three N levels (0, 50, and 100 kg N ha) combined with two P levels (0 and 50 kg P ha). Nitrogen supply to the soil reduced NUE by decreasing NP and MRT, whereas P supply enhanced NUE. Although P supply did not have a significant influence on the reduction of NUE with increasing N levels, it affected the response of the NUE components with increasing N levels. Within leaves, N supply reduced the photosynthetic nitrogen use efficiency (PNUE), P alleviated this reduction. Therefore, P is considered as one of the key factors determining the change of NUE in Q. serrata under the influence of high N supply.

中文翻译：

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不同土壤氮磷供给条件下锯缘栎幼苗氮素利用效率

氮利用效率 (NUE)，定义为生物量增长与从土壤中吸收的氮 (N) 的比率，广泛用于评价植物氮经济。我们对锯齿栎幼苗在不同土壤氮和磷 (P) 水平下进行施肥试验，以确定不同 P 有效性下高 N 沉积水平对 NUE 的影响，以及 NUE 组分 N 生产力 (NP) 和平均停留时间否（捷运）。在三种氮水平（0、50 和 100 kg N ha）与两种磷水平（0 和 50 kg P ha）结合的盆栽土壤中，幼苗在一个生长季节生长。土壤的氮供应通过降低 NP 和 MRT 降低了 NUE，而 P 供应增加了 NUE。尽管随着 N 水平的增加，P 供应对 NUE 的减少没有显着影响，随着 N 水平的增加，它影响 NUE 组件的响应。在叶片内，N 供应降低了光合氮利用效率 (PNUE)，P 缓解了这种降低。因此，P被认为是决定高氮供应影响下锯缘青蟹NUE变化的关键因素之一。