Impacts of climate change drivers on C4 grassland productivity: Scaling driver effects through the plant community

Authors: Polley, Herbert; Derner, Justin; JACKSON, ROBERT - Duke University; WILSEY, BRIAN - Iowa State University; Fay, Philip

Submitted to: Journal of Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/17/2013
Publication Date: 2/5/2014
Publication URL: http://handle.nal.usda.gov/10113/59469
Citation: Polley, H.W., Derner, J.D., Jackson, R.B., Wilsey, B.J., Fay, P.A. 2014. Impacts of climate change drivers on C4 grassland productivity: Scaling driver effects through the plant community. Journal of Experimental Botany. 65(13):3415-3424.

Interpretive Summary: Plant growth increasingly is influenced by climate change drivers, such as rising atmospheric carbon dioxide (CO2) concentration and modification of precipitation patterns. Climate drivers may directly affect plant growth or productivity by altering environmental conditions or plant physiological processes, but also may ‘indirectly’ modify the productivity of natural and semi-natural plant communities by favoring more or less productive species at the expense of other species (plant community change). We used data from three experiments in central Texas, USA to assess the poorly-understood role of plant community change or differences in mediating the response of grassland productivity to two climate change drivers applied singly, atmospheric CO2 enrichment and augmented summer precipitation. Higher CO2 increased aboveground productivity in separate, multi-year experiments with pasture and tallgrass prairie vegetation. In a third experiment, augmenting summer precipitation increased productivity more among communities of native than non-native perennial species. Community change increased the CO2 benefit to community productivity by 15% in the pasture experiment and by 21-38% in the prairie experiment, depending on soil type, by favoring species that maximized growth per unit of water transpired. Growth was greater among native than non-native perennials because growth per unit of transpired water was greater among natives. Our results indicate that the response of grassland productivity to climate change drivers cannot be predicted accurately from knowledge of direct driver effects alone. Shifts or management-imposed differences in community composition play a major role in determining grassland responses to climate change drivers.

Technical Abstract: Climate change drivers affect the plant community productivity via three pathways: 1) direct effects of drivers on plants, 2) the response of species abundances to drivers (community response), and 3) the feedback effect of community change on productivity (community effect). The contribution of each pathway to driver-productivity relationships depends on functional traits of dominant species. We use data from three experiments in Texas, USA to assess the role of community dynamics in the aboveground productivity (ANPP) response of C4 grasslands to two climate drivers applied singly, atmospheric CO2 enrichment and augmented summer precipitation. The ANPP-driver response differed among experiments because community responses and effects differed. ANPP increased by 80-120 g m-2 per 100 µL L-1 rise in CO2 in separate experiments with pasture and tallgrass prairie assemblages. Augmenting ambient precipitation by 128 mm during one summer month each year increased ANPP more in native than exotic communities in a third experiment. Feedbacks of the community effect accounted for 21-38% of the ANPP-CO2 response in the prairie experiment, but little of the response in the pasture experiment. Community response to CO2 was linked to species traits associated with greater soil water from reduced transpiration (e.g., greater height). Community effects on the ANPP-CO2 response and the greater ANPP response of native than exotic communities to augmented precipitation depended on species differences in transpiration efficiency. Results indicate that community feedbacks altered the ANPP response to drivers and species traits favored by drivers differed from the traits that most influenced community effects on ANPP.