Key Laboratory of Geographical Processes and Ecological Security in Changbai Mountains, Ministry of Education, School of Geographical Sciences, Northeast Normal University, Renmin Street, Nanguan District, Changchun 130024, China.
Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zürcherstrasse 111, Birmensdorf CH-8903, Switzerland.
Tree Physiol. 2024 Jun 3;44(6). doi: 10.1093/treephys/tpae053.
The effects of rising atmospheric CO2 concentrations (Ca) with climate warming on intrinsic water-use efficiency and radial growth in boreal forests are still poorly understood. We measured tree-ring cellulose δ13C, δ18O, and tree-ring width in Larix dahurica (larch) and Betula platyphylla (white birch), and analyzed their relationships with climate variables in a boreal permafrost region of northeast China over past 68 years covering a pre-warming period (1951-1984; base period) and a warm period (1985-2018; warm period). We found that white birch but not larch significantly increased their radial growth over the warm period. The increased intrinsic water-use efficiency in both species was mainly driven by elevated Ca but not climate warming. White birch but not larch showed significantly positive correlations between tree-ring δ13C, δ18O and summer maximum temperature as well as vapor pressure deficit in the warm period, suggesting a strong stomatal response in the broad-leaved birch to temperature changes. The climate warming-induced radial growth enhancement in white birch is primarily associated with a conservative water-use strategy. In contrast, larch exhibits a profligate water-use strategy. It implies an advantage for white birch over larch in the warming permafrost regions.
大气 CO2 浓度（Ca）随气候变暖对北方森林内在水分利用效率和径向生长的影响仍知之甚少。我们测量了兴安落叶松和白桦的树木年轮纤维素 δ13C、δ18O 和树木年轮宽度，并分析了它们在过去 68 年中与中国东北多年冻土区气候变量的关系，该时期包括增暖前时期（1951-1984 年；基准期）和增暖时期（1985-2018 年；增暖期）。结果表明，白桦的径向生长在增暖期显著增加，而落叶松则没有。两种树种内在水分利用效率的提高主要是由 Ca 的升高而不是气候变暖驱动的。在增暖期，白桦的树木年轮 δ13C、δ18O 与夏季最高温度和蒸气压亏缺之间呈显著正相关，而落叶松则没有，这表明阔叶白桦对温度变化有强烈的蒸腾响应。白桦径向生长的增强主要与保守的水分利用策略有关，而落叶松则表现出挥霍的水分利用策略。这意味着在变暖的多年冻土区，白桦比落叶松具有优势。
