Response of seedlings of two hypogeal brush species to CO2 enrichment

Abstract

Previous work has demonstrated that epigeal woody invasive plants (with expanding, photosynthetic cotyledons), such as honey mesquite (Prosopis glandulosa L.), respond positively to elevated atmospheric CO2 concentrations in as little as 3 days after emergence. No research has addressed the behavior of larger seeded, hypogeal invasive plants (common in south Texas) exposed to elevated CO2. We studied two such species, guajillo (Acacia berlandieri Benth.) and cat claw acacia (Acacia greggii Gray var. wrightii (G. Bentham) D. Isley), to quantify growth stimulation at a doubled concentration of CO2. Seedlings were grown in glasshouses in 1.5 m tubes at Temple, TX, in the late summer of 2000. Only seeds within a narrow range of masses were selected for each species, to reduce effects of seed mass on seedling size. Plants were harvested 15 days after emergence. Leaf area, shoot weight, leaf weight, root weight, and depth of root penetration were determined for each plant. Both species exhibited marked root length at sampling, with mean values of about 75 and 90 cm for guajillo and cat claw acacia, respectively. For both species, all parameters demonstrated a positive numerical response to elevated CO2, although no differences were statistically significant. The lack of statistical verification of the observed differences was likely caused by the great deal of variability observed within both species. For example, values for specific parameters varied by as much as a factor of six within a species and CO2 treatment. These results suggest that seedling growth responses to elevated CO2 may be smaller in hypogeal than in co-occurring epigeal species.

Parent Publication

• Proceedings: Shrubland dynamics -- fire and water

Citation

Tischler, Charles R.; Derner, Justin D.; Polley, H. Wayne; Johnson, Hyrum B. 2007. Response of seedlings of two hypogeal brush species to CO2 enrichment. In: Sosebee, Ronald E.; Wester, David B.; Britton, Carlton M.; McArthur, E. Durant; Kitchen, Stanley G., comps. Proceedings: Shrubland dynamics -- fire and water; 2004 August 10-12; Lubbock, TX. Proceedings RMRS-P-47. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. p. 104-106.