Climate warming disrupts the carbon balance of young trees

Young trees play a key role in forest regeneration and maintaining biodiversity. More vulnerable than adult trees due to their limited energy reserves and reduced photosynthetic capacity, they are fully exposed to the effects of climate warming. An in-depth analysis of 62 plant species reveals that rising temperatures profoundly alter their carbon balance, a mechanism essential for their growth and survival.

Exposure to higher temperatures leads to an acclimation of their photosynthesis rate, but it also stimulates nighttime respiration and photorespiration. The latter, a lesser-known process, occurs when plants fix oxygen instead of carbon dioxide during photosynthesis, resulting in a loss of energy and carbon. With rising temperatures, this reaction intensifies, reducing photosynthetic efficiency and disrupting the carbon balance of young seedlings.

The leaves of young trees also respond by increasing their mass per unit area, a defensive mechanism that strengthens their resistance to external threats such as herbivores or pathogens. However, this adaptation does not offset the carbon losses caused by increased respiration and photorespiration. Tropical species, already close to their optimal thermal limit, could be particularly affected, although the results show a surprising capacity for acclimation in some of them.

The methods used to study these effects, such as growth chambers or greenhouses, also influence the observed physiological responses. For example, the increase in the ratio between internal and atmospheric carbon in leaves appears more pronounced under certain experimental conditions. Methodological differences partly explain the variability in results, particularly for indicators such as the quantum efficiency of Photosystem II, a measure of the health of the photosynthetic system.

Heatwaves and record temperatures are becoming more frequent, directly threatening forest regeneration. Young trees, already weakened by their dependence on metabolic reserves, see their ability to store carbon decline, limiting their growth and survival. Tropical forests, although less studied, could be among the most vulnerable due to their low tolerance to thermal variations.

This analysis highlights the urgency of deepening research, particularly in tropical regions where data is still lacking. Understanding these mechanisms is crucial for anticipating the impact of warming on forest ecosystems and adapting conservation strategies.

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Primary Source

DOI: https://doi.org/10.1007/s40626-026-00400-y

Title: The impacts of warming on leaf carbon balance of young woody plants: implications to forest regeneration—a systematic review and meta-analysis

Journal: Theoretical and Experimental Plant Physiology

Publisher: Springer Science and Business Media LLC

Authors: Carolina Reis de Brito; Junior Pastor Pérez-Molina; Martielly Santana dos Santos; Dulce Mantuano; Marcelo Schramm Mielke