Differential responses of root uptake kinetics of NH+4
to enriched atmospheric CO2
concentration in field-grown loblolly pine
The nitrogen requirement of plants is predominantly supplied by NH+4 and/or NO-3 from the soil solution, but the energetic cost of uptake and assimilation is generally higher for NO-3 than for NH+4. We found that CO2 enrichment of the atmosphere enhanced the root uptake capacity for NO-3, but not for NH+4, in field-grown loblolly pine saplings. Increased preference for NO-3 at the elevated CO2 concentration was accompanied by increased carbohydrate levels in roots. The results have important implications for the potential consequences of global climate change on plant-and ecosystem-level processes in many temperate forest ecosystems.