title: Impacts of warming and elevated CO2 on a semi-arid grassland are non-additive, shift with precipitation, and reverse over time.
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 supra-additive 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.
authors.affiliation: Rangeland Resources Research Unit, Agricultural Research Service, United States Department of Agriculture, Fort Collins, CO, 80526, USA.
authors.forename: K E
authors.initials: KE
authors.lastname: Mueller
authors.affiliation: Rangeland Resources Research Unit, Agricultural Research Service, United States Department of Agriculture, Fort Collins, CO, 80526, USA.
authors.forename: D M
authors.initials: DM
authors.lastname: Blumenthal
authors.affiliation: Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, 2751, Australia.
authors.forename: E
authors.initials: E
authors.lastname: Pendall
authors.affiliation: Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, 2751, Australia.
authors.forename: Y
authors.initials: Y
authors.lastname: Carrillo
authors.affiliation: Centre for Carbon, Water and Food, Faculty of Agriculture and Environment, School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW, 2006, Australia.
authors.forename: F A
authors.initials: FA
authors.lastname: Dijkstra
authors.affiliation: Department of Botany, University of Wyoming, Laramie, WY, 82071, USA.
authors.forename: D G
authors.initials: DG
authors.lastname: Williams
authors.affiliation: Soil Plant and Nutrient Research Unit, Agricultural Research Service, United States Department of Agriculture, Fort Collins, CO, 80526, USA.
authors.forename: R F
authors.initials: RF
authors.lastname: Follett
authors.affiliation: Rangeland Resources Research Unit, Agricultural Research Service, United States Department of Agriculture, Fort Collins, CO, 80526, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Morgan
mesh_terms: D002245:Carbon Dioxide / Q000737:chemistry / Q000494:pharmacology*; D057231:Climate Change; D065948:Grassland; D011891:Rain; D013997:Time Factors
chemical_list: D002245:Carbon Dioxide
keywords: Artemisia frigida; Bouteloua gracilis; C3 grass; C4 grass; climate change; forb; nitrogen; plant productivity; root biomass; soil moisture