CO₂ enrichment increases nutrient leaching from model forest ecosystems in subtropical China

Abstract

The effect of high atmospheric CO2 concentrations on the dynamics of mineral nutrient is not well documented, especially for subtropical China. We used model forest ecosystems in open-top chambers to study the effects of CO2 enrichment alone and together with N addition on the dynamics of soil cations and anions. Two years of exposure to a 700 ppm CO2 atmospheric concentration resulted in increased annual nutrient losses by leaching below 70 cm soil profile. Compared to the control, net Mg2+ losses increased by 385%, K+ by 223%, Ca2+ by 167% and NO3−-N by 108%, respectively. Increased losses following exposure to elevated CO2 were related to both faster weathering of minerals/organic matter decomposition and greater amounts of leaching water. Net annual nutrient losses in the high CO2 concentration chambers reached 22.2 kg ha−1 year−1 for K+, 171.3 kg ha−1 year−1 for Ca2+, 8.2 kg ha−1 year−1 for Mg2+ and about 2 kg ha−1 year−1 for NO3−-N. The N addition alone had no significant effect on the mineral nutrient leaching losses. However, addition of N together with the high CO2 treatment significantly reduced mineral nutrient losses.We hypothesize that forests in subtropical China might suffer from nutrient limitation and reduction in plant biomass under elevated CO2 concentration due to mineral leaching losses in the future.