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ARS Home » Plains Area » Temple, Texas » Grassland Soil and Water Research Laboratory » Research » Publications at this Location » Publication #254072
Title: CO2 effects on grassland productivity differ with soils and land use

Author
item Fay, Philip
item Polley, Herbert
item Jin, Virginia
item Potter, Kenneth

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/30/2010
Publication Date: 10/17/2010
Citation: Fay, P.A., Polley, H.W., Jin, V.L., Potter, K.N. 2010. CO2 effects on grassland productivity differ with soils and land use. In: Proceedings of the Latsis Symposium, October 17-20, 2010, Lausanne, Switzerland.

Interpretive Summary:

Technical Abstract: Increasing atmospheric CO2 concentration usually stimulates aboveground net primary productivity (ANPP) of both natural and managed ecosystems by increasing physiological efficiency at leaf to canopy scales. However few have directly compared CO2 effects on ANPP among hydrologically contrasting soils or included systems representing both diverse, unmanaged ecosystems and simplified systems managed with supplemental resources. We grew C4 dominated mixtures of native grassland (tallgrass prairie) species and monocultures of switchgrass (Panicum virgatum cv. Alamo), a native C4 grass and candidate bioenergy feedstock, on hydrologically contrasting soils along a continuous gradient in atmospheric CO2 concentration ([CO2]) spanning 250 to 500 µL L-1. ANPP of native grassland, grown with ambient precipitation and no nutrient supplementation, was an asymptotically increasing function of [CO2] on two clay soils, suggesting that future increases in [CO2] will elicit little increase in ANPP of native grassland on these soils. However, ANPP of native grassland grown on a sandy alluvial soil increased linearly with [CO2], suggesting that increasing CO2 will increase ANPP more on this soil than on clay soils. Soil water content increased linearly with increasing [CO2] on all three soils, and soil water potential at a given water content was highest in the sandy alluvial soil. Despite these differences among soils in water content and availability to plants, leaf water potential did not differ among soils, was a linearly increasing function of [CO2], and was not correlated with vapor pressure deficit, suggesting that plant water stress and water use of native grassland depended more on leaf stomatal responses to [CO2] than on atmospheric demand or soil supply of water. ANPP of switchgrass, grown with high soil moisture and supplemental nitrogen, differed between the two clay soils, was a linearly decreasing function of vapor pressure deficit, and was not correlated with [CO2]. This result suggested that ANPP and water use of fertilized and well-watered switchgrass was determined primarily by atmospheric demand for water vapor rather than by [CO2]. Taken together, these results suggest that the coupling between ANPP and [CO2] differ among hydrologically contrasting soils, and are likely to differ between C4 dominated systems depending on whether they receive additional water and other resources. Thus, productivity responses to future CO2 and climate scenarios are likely to vary with changing soil properties across the landscape, and among different C4 dominated land uses.