Ecology of Nitrogen Cycling in Young Forest Ecosystems: Drivers, Ecosystem Functioning, and Research Perspectives

Nitrogen cycling is a key determinant of ecosystem functioning, productivity, and carbon sequestration during forest development. This review synthesizes ecological evidence on nitrogen cycling in young forest ecosystems established through natural regeneration, afforestation, reforestation, or major disturbance across boreal, temperate, and tropical biomes. The review evaluates how successional stage, plant community composition, soil properties, microbial processes, climate, and disturbance influence nitrogen transformations, retention, and losses during early forest development. The literature indicates that young forests can exhibit rapid nitrogen turnover while maintaining effective nutrient retention, although the balance between conservation and loss varies with biome, site conditions, and disturbance intensity. Boreal forests tend to show more conservative nitrogen cycling, whereas tropical forests generally exhibit faster turnover and greater nitrogen fluxes. The synthesis also highlights important knowledge gaps, particularly the limited availability of long-term studies, insufficient integration of aboveground–belowground interactions, underrepresentation of tropical and Southern Hemisphere forests, and limited assessment of climate-change effects on plant–soil–microbial feedbacks. Addressing these gaps will improve understanding of nitrogen dynamics during forest development and strengthen ecosystem modelling, forest restoration, and climate-change mitigation strategies.