Increasing CO[sub 2]: Comparative responses of the C[sub 4] grass Schizachyrium and grassland invader Prosopis

Journal Article · Wed Jun 01 00:00:00 EDT 1994 · Ecology; (United States)

DOI:https://doi.org/10.2307/1939421· OSTI ID:7008365

Polley, H W; Johnson, H B; Mayeux, H S ^[1]

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1. Department of Agriculture, Temple, TX (United States)

Woody C[sub 3] Prosopis glandulosa (honey mesquite) and C[sub 4] perennial grass Schizachyrium scoparium (little bluestem) were grown along a gradient of daytime carbon dioxide concentrations from near 340 to 200 [mu]mol/mol air in a 38 m long controlled environment chamber. The authors studied the effects of historical and prehistorical increases in atmospheric CO[sub 2] concentration on growth, resource use, and competitive interactions of a species representative of C[sub 4]-dominated grasslands in the SW United States and the invasive legume P. glandulosa. Increasing CO[sub 2] concentration stimulated N[sub 2] fixation by individually grown P. glandulosa and elicited in C[sub 3] seedlings a similar relative increase in leaf intercellular CO[sub 2] concentration, net assimilation rate, and intrinsic water use efficiency (leaf net assimilation rate/stomatal conductance). Aboveground biomass of P. glandulosa was not altered by CO[sub 2] concentration, but belowground biomass and whole-plant water and nitrogen use efficiencies increased linearly with CO[sub 2] concentration in seedlings that were grown alone. Biomass produced by P. glandulosa that was grown with S. scoparium was not affected by CO[sub 2] concentration. Stomatal conductance declined and leaf assimilation rates of S. scoparium at near maximum incident light increased at higher CO[sub 2] concentration, but there was no effect of CO[sub 2] concentration on biomass production or whole-plant water use efficiency of the C[sub 4] grass. Rising CO[sub 2] concentration, especially the 27% increase since the beginning of the 19th century, may have contributed to more abundant P. glandulosa on C[sub 4] grasslands by stimulating the shrub's growth or reducing the amount of resources that the C[sub 3] required. Much of the potential response of P. glandulosa to CO[sub 2] concentration, however, appears to be contingent on the shrub's escaping competition with neighboring grasses. 62 refs., 10 figs., 1 tab.

• OSTI ID: 7008365
• Journal Information: Ecology; (United States), Vol. 75:4; ISSN 0012-9658
• Country of Publication: United States
• Language: English

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