Impacts of warming and elevated CO₂ on a semi-arid grassland are non-additive, shift with precipitation, and reverse over time

Authors

K. E. Mueller, USDA-ARS
D. M. Blumenthal, USDA-ARSFollow
E. Pendall, Western Sydney UniversityFollow
Y. Carrillo, Western Sydney University
F. A. Dijkstra, University of SydneyFollow
D. G. Williams, University of WyomingFollow
R. F. Follett, USDA-ARSFollow
J. A. Morgan, USDA-ARS

Date of this Version

2016

Citation

Ecology Letters (2016) 19: 956–966

Comments

U.S. Government Work

Abstract

It is unclear how elevated CO₂ (eCO₂) and the corresponding shifts in temperature and precipitation will interact to impact ecosystems over time. During a 7-year experiment in a semi-arid grassland, the response of plant biomass to eCO₂ and warming was largely regulated by interannual precipitation, while the response of plant community composition was more sensitive to experiment duration. The combined effects of eCO₂ and warming on aboveground plant biomass were less positive in ‘wet’ growing seasons, but total plant biomass was consistently stimulated by ~ 25% due to unique, supra-additive responses of roots. Independent of precipitation, the combined effects of eCO₂ and warming on C₃ graminoids became increasingly positive and supraadditive over time, reversing an initial shift toward C₄ grasses. Soil resources also responded dynamically and non-additively to eCO₂ and warming, shaping the plant responses. Our results suggest grasslands are poised for drastic changes in function and highlight the need for long-term, factorial experiments.