Carbon Dioxide and Temperature Effects on Forage Dry Matter Production

Abstract

Atmospheric CO2 and temperature may significantly modify plant production. Grasslands occupy in excess of 25% of the Earth's land area, but grassland species have received limited attention from researchers studying climate change. A 3‐yr study was conducted to determine the effects of elevated atmospheric CO2 and temperature on dry matter (DM) harvested from the C3 legume ‘Florigraze’ rhizoma peanut (RP, Arachis glabrata Benth.) and the C4 grass ‘Pensacola’ bahiagrass (BG, Paspalum notatum Flügge). Both species were field grown in Millhopper fine sand (loamy siliceous Grossarenic Paleudult) in temperature‐gradient greenhouses under different CO2 (360 and 700 μmol mol−1) and temperature conditions (baseline [B], B+1.5, B+3.0, and B+4.5°C, where B equaled ambient temperature). Plots (2 by 5 m) were harvested three times in 1996 and four times each in 1997 and 1998. Analyzed across years, yield increased 25% for RP (P = 0.02) and tended to increase for BG (15%; P = 0.18) with the near doubling of CO2, but there was species by CO2 interaction (P = 0.06) as a result of the greater response to CO2 by the C3 legume. There was a positive effect of increasing temperature on yield of both species. Averaged across species, yield increased 11% in 1996, 12% in 1997, and 26% in 1998 as temperature increased from B to B+4.5°C. Under well‐watered conditions in this experiment, elevated CO2 increased DM harvested of a C3 legume and tended to increase that of a C4 grass, while the yield response to increasing temperature was positive for both species.