Soil-related Constraints to the Carbon Dioxide Fertilization Effect

Abstract

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.

Keywords:

• N availability
• plant tissue N
• organic matter decomposition
• phosphorus uptake
• soil evaporation
• soil moisture
• climate change
• net primary production

ACKNOWLEDGMENTS

The article was prepared when the senior author was undergoing the USDA Norman E Borlaug fellowship program at Ohio State University, Columbus, USA. The financial support of USDA is gratefully acknowledged.