Observed declines in leaf nitrogen explained by photosynthetic acclimation to CO2

• 成果类型: Article
• 署名作者: Bassiouni, Maoya; Smith, Nicholas G.; Reu, Jacqueline C.; Penuelas, Josep; Keenan, Trevor F.
• 署名单位: University of California System; University of California Berkeley; Texas Tech University System; Texas Tech University; Autonomous University of Barcelona; Consejo Superior de Investigaciones Cientificas (CSIC); Centro de Investigacion Ecologica y Aplicaciones Forestales (CREAF-CERCA); Centro de Investigacion Ecologica y Aplicaciones Forestales (CREAF-CERCA); United States Department of Energy (DOE); Lawrence Berkeley National Laboratory
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-12656
• DOI: 10.1073/pnas.2501958122
• 发表日期: 2025-08-19
• 关键词: temperature response functions; carbon gain; atmospheric co2; MODEL; water; ecosystems; parameters; nutrition; GROWTH; plants

摘要

Widespread evidence of decreasing leaf nutrients has raised concerns about ecosystem productivity under global change. Interpreting trends in leaf nutrients has important implications for the fate of ecosystem services, particularly the role of forests in mitigating climate change and sustaining quality food sources. Here, we challenge the common interpretation that decreasing leaf nitrogen concentration (LNC) is evidence of increasing nutrient limitations on ecosystem primary productivity.Instead, we show that declines in LNC (4% decrease per 50 ppm CO2 increase), observed across 409 European forest plots over 22 y, can be explained by reduced photosynthetic nitrogen demand. This regional trend is consistent with leaf acclimation to increasing atmospheric CO2 according to optimality theory. This finding suggests that enhanced photosynthetic nitrogen use efficiency due to CO2 fertilization may lead to less nitrogen uptake and/or reallocation of nitrogen for plant growth and other functions. Our results have large implications for understanding and simulating interactions between ecosystem nitrogen and carbon cycles and suggest nitrogen requirements for terrestrial carbon uptake under elevated CO2 may be lower than previously thought.