CO enrichment increases element concentrations in grass mixtures by changing species abundances.

mospheric carbon dioxide (CO) enrichment may increase plant growth more than the uptake of chemical elements from soil. Increased CO also may alter element levels in biomass from multi-species vegetation by changing plant species abundances. We measured concentrations of ten elements in aboveground tissues of three C grasses that had been exposed for 2-3 growing seasons to a continuous gradient in CO from 250 to 500 μmol mol. The grasses, Bouteloua curtipendula, Schizachyrium scoparium, and Sorghastrum nutans, are competitive dominants in assemblages of tallgrass prairie vegetation growing on each of three soil types along a field CO gradient in central Texas, USA. Our objective was to determine whether CO influences element concentrations in grass mixtures by changing concentrations in individual species or shifting species abundances. Increased CO had little effect on element concentrations in grasses compared to differences observed among grass species and soils. Increasing CO from the pre-Industrial to elevated levels reduced the phosphorus concentration in grasses grown on a clay and sandy loam soil. Concentrations of most other elements did not respond to CO treatment. Cover of the mid-grass Bouteloua declined at higher CO levels as cover of the taller grass Sorghastrum increased. Concentrations of several elements were lower in Bouteloua than Sorghastrum; hence, this exchange of species at higher CO increased element concentrations in grass assemblages. Potential consequences include an improvement in the nutritional quality of plants for herbivores. Results highlight the underappreciated impact that CO enrichment may have on ecosystem functioning by changing plant composition. [ABSTRACT FROM AUTHOR]

Copyright of Plant Ecology is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)