Emma Sage1, Jana Heisler-White2, Jack Morgan3, Elise Pendall4, David G Williams1. 1. Department of Botany, University of Wyoming, 1000 E. University Ave., Laramie, WY, 82071, USA. 2. Trihydro Corporation, 1252 Commerce Dr., Laramie, WY, 82070, USA. 3. USDA-ARS Crops Research Laboratory, 1701 Center Ave., Fort Collins, CO, 80526, USA. 4. Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, Australia.
Abstract
PREMISE: The impact of elevated CO2 concentration ([CO2 ]) and climate warming on plant productivity in dryland ecosystems is influenced strongly by soil moisture availability. We predicted that the influence of warming on the stimulation of photosynthesis by elevated [CO2 ] in prairie plants would operate primarily through direct and indirect effects on soil water. METHODS: We measured light-saturated photosynthesis (Anet ), stomatal conductance (gs ), maximum Rubisco carboxylation rate (Vcmax ), maximum electron transport capacity (Jmax ) and related variables in four C3 plant species in the Prairie Heating and CO2 Enrichment (PHACE) experiment in southeastern Wyoming. Measurements were conducted over two growing seasons that differed in the amount of precipitation and soil moisture content. RESULTS: Anet in the C3 subshrub Artemisia frigida and the C3 forb Sphaeralcea coccinea was stimulated by elevated [CO2 ] under ambient and warmed temperature treatments. Warming by itself reduced Anet in all species during the dry year, but stimulated photosynthesis in S. coccinea in the wet year. In contrast, Anet in the C3 grass Pascopyrum smithii was not stimulated by elevated [CO2 ] or warming under wet or dry conditions. Photosynthetic downregulation under elevated [CO2 ] in this species countered the potential stimulatory effect under improved water relations. Warming also reduced the magnitude of CO2 -induced down-regulation in this grass, possibly by sustaining high levels of carbon utilization. CONCLUSIONS: Direct and indirect effects of elevated [CO2 ] and warming on soil water was an overriding factor influencing patterns of Anet in this semi-arid temperate grassland, emphasizing the important role of water relations in driving grassland responses to global change.
PREMISE: The impact of elevated CO2 concentration ([CO2 ]) and climate warming on plant productivity in dryland ecosystems is influenced strongly by soil moisture availability. We predicted that the influence of warming on the stimulation of photosynthesis by elevated [CO2 ] in prairie plants would operate primarily through direct and indirect effects on soil water. METHODS: We measured light-saturated photosynthesis (Anet ), stomatal conductance (gs ), maximum Rubisco carboxylation rate (Vcmax ), maximum electron transport capacity (Jmax ) and related variables in four C3 plant species in the Prairie Heating and CO2 Enrichment (PHACE) experiment in southeastern Wyoming. Measurements were conducted over two growing seasons that differed in the amount of precipitation and soil moisture content. RESULTS: Anet in the C3 subshrub Artemisia frigida and the C3 forb Sphaeralcea coccinea was stimulated by elevated [CO2 ] under ambient and warmed temperature treatments. Warming by itself reduced Anet in all species during the dry year, but stimulated photosynthesis in S. coccinea in the wet year. In contrast, Anet in the C3 grass Pascopyrum smithii was not stimulated by elevated [CO2 ] or warming under wet or dry conditions. Photosynthetic downregulation under elevated [CO2 ] in this species countered the potential stimulatory effect under improved water relations. Warming also reduced the magnitude of CO2 -induced down-regulation in this grass, possibly by sustaining high levels of carbon utilization. CONCLUSIONS: Direct and indirect effects of elevated [CO2 ] and warming on soil water was an overriding factor influencing patterns of Anet in this semi-arid temperate grassland, emphasizing the important role of water relations in driving grassland responses to global change.
Authors: Kevin E Mueller; Troy W Ocheltree; Julie A Kray; Julie A Bushey; Dana M Blumenthal; David G Williams; Elise Pendall Journal: Glob Chang Biol Date: 2022-08-04 Impact factor: 13.211