Contrasting water-use strategies to climate warming in white birch and larch in a boreal permafrost region.

This article investigates the contrasting responses of two boreal tree species, white birch (Betula platyphylla) and larch (Larix dahurica), to rising atmospheric CO₂ concentrations (Ca) and climate warming in a permafrost region of northeast China over 68 years (1951–2018). Using tree-ring width and stable isotope analyses (δ¹³C and δ¹⁸O), the study found that white birch exhibited increased radial growth and intrinsic water-use efficiency (iWUE) driven mainly by elevated Ca and a conservative water-use strategy involving stomatal regulation, while larch showed increased iWUE without significant growth enhancement and a profligate water-use strategy with less stomatal sensitivity. These physiological differences may explain the recent expansion of broad-leaved species like white birch relative to larch in warming permafrost forests. The findings highlight the importance of species-specific water-use strategies in mediating tree growth responses to climate change and elevated CO₂ in boreal ecosystems.