Carbon dioxide and temperature effects on forage dry matter production

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 c hange, A 3-yr study was conducted to determine the effects of elevated atmo spheric CO2 and temperature on dry matter (DM) harvested from the CP legume (Florigraze' rhizoma peanut (RP, Arachis glabrata Benth,) and the C-4 gras s 'Pensacola' bahiagrass (BG, Paspalum notatum Flugge), Both species were f ield grown in Millhopper fine sand (loamy siliceous Grossarenic Paleudult) in temperature-gradient greenhouses under different CO2 (360 and 700 mu mol mol(-1)) and temperature conditions (baseline [B], B+1.5, B+3.0, and B+4.5 degreesC, where B equaled ambient temperature), Plots (2 by 5 m) were harv ested three times in 1996 and four times each in 1997 and 1998, Analyzed ac ross years, yield increased 25% for RP (P = 0.02) and tended to increase fo r BG (15%; P = 0.18) with the near doubling of CO2, but there was species b y CO2 interaction (P = 0.06) as a result of the greater response to CO2 by the C) legume, There was a positive effect of increasing temperature on yie ld of both species. Averaged across species, yield increased 11% in 1996, 1 2% in 1997, and 26% in 1998 as temperature increased from B to B+4.5 degree sC. Under well-watered conditions in this experiment, elevated CO2 increase d DM harvested of a C-3 legume and tended to increase that of a C-4 grass, while the yield response to increasing temperature was positive for both sp ecies.