Title: Species Composition and Diversity As Regulators of Temporal Variability in Biomass Production of Tallgrass Prairie Authors
Submitted to: Society for Range Management Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: August 10, 2006
Publication Date: February 9, 2007
Citation: Polley, H.W., Wilsey, B.J., Derner, J.D. 2007. Species composition and diversity as regulators of temporal variability in biomass production of tallgrass prairie. Society for Range Management Meeting Abstracts. Paper No. 337. CDROM. Technical Abstract: Species diversity is thought to stabilize functioning of plant communities, although diversity-stability studies have focused on species richness to the neglect of the second component of diversity, species evenness (equitability with which biomass or abundances are distributed among species). An alternative view is that traits of dominant species constrain effects of diversity on stability. We compared inter-annual variability (inverse of stability) of aboveground biomass in paired restored and remnant tallgrass prairies at two locations in central Texas to test the hypothesis that greater richness and evenness in remnant than restored prairies would reduce variability in aboveground biomass in response to natural variation in rainfall. Remnant and restored prairies at each location are dominated by a common group of perennial grasses. By comparing remnants and restorations, therefore, we sought to determine how diversity affected temporal variability in biomass of grasslands with common dominant grasses. Variability was measured as the coefficient of variation among years (square root of variance/mean; CV), where variance in community biomass equals the sum of variances of individual plant species plus the summed covariances between species pairs. The sum of species variances in biomass was reduced by 34-55% when calculated using the more equitable distribution of biomass observed in remnant than restored prairies, but was reduced by <4% by the greater richness observed in remnant prairies. Still, the CV of community biomass during spring and CV of annual biomass production did not differ consistently between prairie types because biomass of the dominant species in restored prairies (Schizachyrium scoparium; little bluestem) varied less than did biomass of other dominant and sub-dominant species in more-diverse remnant prairies. In these grasslands, biomass response to variation in precipitation depended more on characteristics of dominant species than on differences in diversity.