Responses of Selected Plant Species to Elevated Carbon Dioxide in the Field

Abstract

It has become of interest to study long‐term effects of CO₂ concentration on plant growth, because intensive burning of fossil fuels and destruction of forests promise to continue the recent rise in atmospheric partial pressures of CO₂ into the next century (Bolin, 1977; Stuiver, 1978). Effects of CO₂ enrichment on growth of crop and forest species were therefore studied for the first time in the field in open top exposure chambers at daytime mean CO₂ concentrations of 612, 936, 1292, and 1638 mg m⁻³, and in ambient control plots. Increased growth of plant parts of corn (Zea mays L. ‘Golden Bantam’), soybean [Glycine max L. (Merr.) ‘Ransom’], loblolly pine (Pinus taeda L.), and sweetgum (Liquidambar styraciflua L.) were recorded. Growth increases for soybean and sweetgum in elevated CO₂ atmospheres were due to increases in leaf area and photosynthesis per unit leaf area, and decreases in conductance and, therefore, water use. For corn, however, photosynthesis was unaffected by CO₂ enhancement, and growth stimulation appeared to be due to lowered conductance and increased water use efficiency alone.