Leaf enzyme plays a more important role in leaf nitrogen resorption efficiency than soil properties along an elevation gradient

• Published in: The Journal of ecology 2022-11, Vol.110 (11), p.2603-2614
• Main Authors: Liu, Bai, Gao, Decai, Chang, Qing, Liu, Ziping, Fan, Xianlei, Meng, Di, Bai, Edith
• Format: Article
• Language: English
• Subjects: Altitude; altitudinal gradient; Climate change; Climate prediction; Conservation; Cycles; Enzymes; Forest ecosystems; Glutamate dehydrogenase; glutamate dehydrogenase activity; gross ammonification; gross nitrification; leaf N resorption efficiency; Leaves; Litter fall; Nitrogen; Nutrients; Physiological effects; Physiology; Plant species; Plants; Plants (botany); Resorption; resorption fluxes; Soil properties; Soils; Temperate forests; Terrestrial ecosystems; Translocation
• ISSN: 0022-0477; 1365-2745
• DOI: 10.1111/1365-2745.13971

Nitrogen (N) resorption is a strategy for plant N conservation through which plants withdraw N from senescing leaves prior to litterfall and its underlying mechanisms are important for better understanding of N cycling. However, most current studies focused on the impacts of soil and leaf nutrients on leaf N resorption efficiency (NRE), and plant physiological regulation that is species dependent is still unclear. Here, we conducted a field experiment to investigate the variations of leaf NRE along an altitudinal gradient in a temperate forest of Northeastern China. Results showed that leaf NRE of Quercus mongolica and Fraxinus mandshurica increased with altitude, while leaf NRE of Tilia amurensis, Acer mono and Acer pseudosieboldianum exhibited an opposite trend, although the relationships were not significant for F. mandshurica and A. mono. The inconsistent responses of leaf NRE of different species to increasing altitude were primarily due to the effect of leaf Glutamate dehydrogenase (GDH), an enzyme responsible for N translocation. Leaf GDH activity in senescing leaves explained the variation of NRE more than soil and climate factors did, suggesting that different plant species had different physiological regulation strategies for their N conservation under similar environment. Synthesis. Our study highlights the role of leaf enzyme as a pivotal regulator of leaf NRE and helps us better understand and predict N cycling under climate change in forest ecosystems. 摘要 氮重吸收是植物保存氮的一种策略，通过这种策略，植物在落叶前可以从衰老的叶片中提取氮，其基本机制有助于我们更好地理解氮循环。然而，当前大多数的研究主要关注土壤和叶片养分对氮重吸收效率的影响，而与物种有关的植物生理调节仍不清楚。 因此，我们在中国东北的温带森林进行了一个野外实验，来研究叶片氮重吸收效率随海拔梯度的变化。 结果显示蒙古栎和水曲柳的叶片氮重吸收效率随着海拔的增加而增加(尽管未达到统计显著水平)，而紫椴、色木槭和假色槭则呈现相反的趋势。不同树种叶片氮重吸收效率对海拔增加的不一致响应主要是由于叶片中氮转移的酶，谷氨酸脱氢酶的作用。衰老叶片中谷氨酸脱氢酶活性对叶片氮重吸收效率的影响要大于土壤和气候因素造成的影响。这说明在相同的环境下，不同树种具有不同的保存氮素的生理调节策略。 我们的研究说明叶片酶在调节叶片氮重吸收效率方面起到了至关重要的作用，并且能够帮助我们更好地理解和预测气候变化背景下森林生态系统中的氮循环。 There was an interspecific difference in leaf N resorption efficiency (NRE) along the altitude gradient. This phenomenon was mainly caused by the direct and indirect impacts of altitude gradient on glutamate dehydrogenase (GDH) activity in senescing leaves and soil N content, which co‐regulated leaf NRE. It is worth mentioning that GDH activity plays a more important role in leaf NRE than soil properties. + and – mean positive and negative effect respectively.