Root exudation describes a process in which plants allocate labile carbon (C) through roots into soils, thereby influencing microbial C and nutrient cycling. We implemented root exudation in a computer model that simulates ecosystem processes. Increased atmospheric CO₂ increased root exudation, but the additional input was partially offset by enhanced microbial respiration. Our research brings new perspectives in modelling soil C and nutrient cycling in forests under increasing CO₂.