title: The carbon fertilization effect over a century of anthropogenic CO2emissions: higher intracellular CO2and more drought resistance among invasive and native grass species contrasts with increased water use efficiency for woody plants in the US Southwest.
abstract: From 1890 to 2015, anthropogenic carbon dioxide emissions have increased atmospheric CO2concentrations from 270 to 400 mol mol-1. The effect of increased carbon emissions on plant growth and reproduction has been the subject of study of free-air CO2enrichment (FACE) experiments. These experiments have found (i) an increase in internal CO2partial pressure (ci) alongside acclimation of photosynthetic capacity, (ii) variable decreases in stomatal conductance, and (iii) that increases in yield do not increase commensurate with CO2concentrations. Our data set, which includes a 115-year-long selection of grasses collected in New Mexico since 1892, is consistent with an increased cias a response to historical CO2increase in the atmosphere, with invasive species showing the largest increase. Comparison with Palmer Drought Sensitivity Index (PDSI) for New Mexico indicates a moderate correlation with Δ13C (r2= 0.32, P < 0.01) before 1950, with no correlation (r2= 0.00, P = 0.91) after 1950. These results indicate that increased cimay have conferred some drought resistance to these grasses through increased availability of CO2in the event of reduced stomatal conductance in response to short-term water shortage. Comparison with C3trees from arid environments (Pinus longaeva and Pinus edulis in the US Southwest) as well as from wetter environments (Bromus and Poa grasses in New Mexico) suggests differing responses based on environment; arid environments in New Mexico see increased intrinsic water use efficiency (WUE) in response to historic elevated CO2while wetter environments see increased ci. This study suggests that (i) the observed increases in ciin FACE experiments are consistent with historical CO2increases and (ii) the CO2increase influences plant sensitivity to water shortage, through either increased WUE or ciin arid and wet environments, respectively.
authors.affiliation: Department of Anthropology, University of New Mexico, Albuquerque, NM 87131, USA.
authors.forename: Brandon L
authors.initials: BL
authors.lastname: Drake
authors.affiliation: Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA.
authors.forename: David T
authors.initials: DT
authors.lastname: Hanson
authors.affiliation: Department of Biology and Museum of Southwestern Biology, University of New Mexico, Albuquerque, NM 87131, USA.
authors.forename: Timothy K
authors.initials: TK
authors.lastname: Lowrey
authors.affiliation: Department of Earth Sciences, University of New Mexico, Albuquerque, NM 87131, USA.
authors.forename: Zachary D
authors.initials: ZD
authors.lastname: Sharp
mesh_terms: D002244:Carbon; D002245:Carbon Dioxide; D055864:Droughts; D009516:New Mexico; D006109:Poaceae / Q000502:physiology*; D014867:Water
chemical_list: D014867:Water; D002245:Carbon Dioxide; D002244:Carbon
keywords: 
  CO
  2
  ; climate change; free-air CO2 enrichment; historic CO2 emissions; stable carbon isotope discrimination; water use efficiency