Soil-related Constraints to the Carbon Dioxide Fertilization Effect

The significance of CO2 fertilization in increasing net primary production (NPP) and of the underpinning mechanisms is widely recognized. This article focuses on soil resources, particularly availability of plant nutrients (e. g., nitrogen, phosphorus) and water affecting the NPP under enhanced levels of atmospheric CO2. The review of the literature indicates the critical role of N in enhancing NPP at higher than ambient CO2 concentration. Elevated CO2 increases the total N uptake by 3-33% and induces a negative feedback in soil N dynamics. Decrease in tissue N concentration by 10-33%, and increase in the recalcitrant C-fractions in plant biomass results in progressive decline in soil N availability over time and necessitates supplemental application of N. In addition, higher quantity of soil available P is required. Despite a reduction in stomatal conductance and transpiration by about 20-27% at leaf level, these benefits are offset at the ecosystem level by higher water losses through soil evaporation, runoff and a rise in leaf temperature due to physiological forcing. A three-way interaction between atmospheric CO2, soil nutrients and water availability may be the decisive factor to harnessing the benefits of CO2 fertilization effect.