Abstract Perennial plants have a greater reliance on internal cycling of nitrogen and are less influenced by external fluctuations of soil fertility than annuals. Despite their importance, the major mechanisms in which annuals and perennials differ in the way they couple nitrogen conservation strategies to imbalances in carbon economy are not fully understood. We characterized the functional mechanism by which Physaria (Brassicaceae) species differing in life cycle adjust nitrogen use efficiency and productivity, in response to variations in carbon gain (CO2 assimilation rate). We set up a field experiment with a split-plot design with two factors: species (2 annuals and 2 perennials) and incident radiation IR (100 % of IR – control, and 35 % of IR). Reduced photosynthesis (brought about by artificial shading) resulted in lower total biomass accumulation in all species. This reduction was linked to a differential plasticity in leaf traits (specific leaf area – SLA – and nitrogen pool) between annuals and perennials, and had different consequences for nitrogen conservation. Annuals showed a decrease in Nitrogen Use Efficiency (NUEleaf), and nitrogen conservation was dependent on carbon economy. Annuals also had higher nitrogen loss due to higher proportion of senescent leaves, and a decrease in resorption efficiency and proficiency, relative to control plants. Perennials kept NUEleaf stable, but the strategy was species-specific: on one hand shaded P. mendocina plants had conservative leaves (non-plastic and low SLA), lower leaf senescence and higher residence time in relation to control. On the other hand, Physaria pinetorum, a short-lived perennial, combined both strategies: greater nitrogen loss due to lower resorption and proficiency, low SLA, and lower leaf senescence under lower IR. These differences in quantity and quality of leaf litter may have consequences beyond the plant’s C and N economy, providing differences in functions such as soil N cycling and thus in ecosystem services.

中文翻译：

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C 下氮保护策略的可塑性在一年生和多年生 Physaria (Brassicaceae) 中获得变异

摘要 多年生植物比一年生植物更依赖氮的内部循环，受外部土壤肥力波动的影响较小。尽管它们很重要，但一年生植物和多年生植物在将氮保护策略与碳经济失衡相结合的方式上存在差异的主要机制尚不完全清楚。我们描述了生命周期不同的 Physaria (Brassicaceae) 物种调整氮利用效率和生产力的功能机制，以响应碳增益（CO2 同化率）的变化。我们设置了一个带有两个因素的裂区设计的田间试验：物种（2 年生植物和 2 个多年生植物）和入射辐射 IR（100% 的 IR - 对照，以及 35% 的 IR）。减少的光合作用（由人工遮荫引起）导致所有物种的总生物量积累降低。这种减少与一年生植物和多年生植物之间叶片性状（特定叶面积 - SLA - 和氮库）的不同可塑性有关，并对氮保护产生不同的影响。一年生植物的氮利用效率 (NUEleaf) 下降，氮保护依赖于碳经济。与对照植物相比，一年生植物由于衰老叶片的比例更高以及吸收效率和吸收能力的降低而具有更高的氮损失。多年生植物保持 NUEleaf 稳定，但该策略是物种特异性的：一方面，阴影 P. mendocina 植物具有保守的叶子（非塑性和低 SLA），与对照相比，叶子衰老较低，停留时间较长。另一方面，短命的多年生植物Physaria pinetorum 结合了两种策略：由于较低的再吸收和熟练度、低SLA 和较低IR 下的较低叶片衰老导致更大的氮损失。 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 凋落物数量和质量的这些差异可能会产生超出植物碳和氮经济的后果，提供土壤氮循环等功能的差异，从而导致生态系统服务的差异。