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CO 2 ‐caused change in plant species composition rivals the shift in vegetation between mid‐grass and tallgrass prairies
Author(s) -
Polley H. Wayne,
Jin Virginia L.,
Fay Philip A.
Publication year - 2012
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1111/j.1365-2486.2011.02529.x
Subject(s) - forb , perennial plant , grassland , soil water , agronomy , biomass (ecology) , growing season , environmental science , vegetation (pathology) , competition (biology) , ecosystem , precipitation , ecology , biology , soil science , geography , medicine , pathology , meteorology
Atmospheric CO 2 enrichment usually changes the relative contributions of plant species to biomass production of grasslands, but the types of species favored and mechanisms by which change is mediated differ among ecosystems. We measured changes in the contributions of C 3 perennial forbs and C 4 grasses to aboveground biomass production of tallgrass prairie assemblages grown along a field CO 2 gradient (250–500 μmol mol −1 ) in central T exas USA . Vegetation was grown on three soil types and irrigated each season with water equivalent to the growing season mean of precipitation for the area. We predicted that CO 2 enrichment would increase the forb contribution to community production, and favor tall‐grasses over mid‐grasses by increasing soil water content and reducing the frequency with which soil water fell below a limitation threshold. CO 2 enrichment favored forbs over grasses on only one of three soil types, a M ollisol. The grass fraction of production increased dramatically across the CO 2 gradient on all soils. Contribution of the tall‐grass S orghastrum nutans to production increased at elevated CO 2 on the two most coarse‐textured of the soils studied, a clay M ollisol and sandy A lfisol. The CO 2 ‐caused increase in S orghastrum was accompanied by an offsetting decline in production of the mid‐grass B outeloua curtipendula . Increased CO 2 favored the tall‐grass over mid‐grass by increasing soil water content and apparently intensifying competition for light or other resources ( M ollisol) or reducing the frequency with which soil water dipped below threshold levels ( A lfisol). An increase in CO 2 of 250 μmol mol −1 above the pre‐industrial level thus led to a shift in the relative production of established species that is similar in magnitude to differences observed between mid‐grass and tallgrass prairies along a precipitation gradient in the central USA . By reducing water limitation to plants, atmospheric CO 2 enrichment may alter the composition and even structure of grassland vegetation.