Nutrient Uptake and Growth Responses of Virginia Pine to Elevated Atmospheric Carbon Dioxide

Abstract One‐year‐old Virginia pine ( Pinus virginiana Mill.) seedlings with native or Pisolithus tinctorius mycorrhizal associations were grown in pots with soil low in organic matter and in cation exchange capacity and were exposed to one of five atmospheric CO 2 levels in the range of 340 to 940 µ L/L in open‐top field chambers. The mean dry weight of the seedlings increased from 4.4 to 11.0 g/plant during the 122‐d exposure period. Significant increases in dry weight and uptake of N, Ca, Al, Fe, Zn, and Sr occurred with CO 2 enrichment. Greater chemical uptake was associated with greater root weight. Specific absorption rates for chemicals (uptake per gram of root per day) were generally not affected by CO 2 enrichment. The uptake of P and K was not increased with elevated CO 2 , and these elements showed the greater nutrient‐use efficiency (C gain per element uptake). The nutrient‐use efficiency for N and Ca was not influenced by atmospheric CO 2 enrichment. Large increases in Zn uptake at high CO 2 suggested an increase in rhizosphere acidification, which may have resulted from the release of protons from the roots, since it was estimated that cation uptake increasingly exceeded anion uptake with CO 2 enrichment. Potassium, P, and NO − 3 concentrations in the pot leachate decreased with higher CO 2 levels, and a similar trend was found for Al and Mg. These results suggest that soil‐plant systems may exhibit increased nutrient and chemical retention at elevated atmospheric CO 2 .