title: Regulation and acclimation of leaf gas exchange in a piñon-juniper woodland exposed to three different precipitation regimes.
abstract: Leaf gas-exchange regulation plays a central role in the ability of trees to survive drought, but forecasting the future response of gas exchange to prolonged drought is hampered by our lack of knowledge regarding potential acclimation. To investigate whether leaf gas-exchange rates and sensitivity to drought acclimate to precipitation regimes, we measured the seasonal variations of leaf gas exchange in a mature piñon-juniper Pinus edulis-Juniperus monosperma woodland after 3 years of precipitation manipulation. We compared trees receiving ambient precipitation with those in an irrigated treatment (+30% of ambient precipitation) and a partial rainfall exclusion (-45%). Treatments significantly affected leaf water potential, stomatal conductance and photosynthesis for both isohydric piñon and anisohydric juniper. Leaf gas exchange acclimated to the precipitation regimes in both species. Maximum gas-exchange rates under well-watered conditions, leaf-specific hydraulic conductance and leaf water potential at zero photosynthetic assimilation all decreased with decreasing precipitation. Despite their distinct drought resistance and stomatal regulation strategies, both species experienced hydraulic limitation on leaf gas exchange when precipitation decreased, leading to an intraspecific trade-off between maximum photosynthetic assimilation and resistance of photosynthesis to drought. This response will be most detrimental to the carbon balance of piñon under predicted increases in aridity in the southwestern USA.
authors: Department of Biology, University of New Mexico, MSC03 2020, 1 University of New Mexico, Albuquerque, NM 87131-0001, USA. limousin@unm.edu
authors: Jean-Marc
authors: JM
authors: Limousin
authors: Christopher P
authors: CP
authors: Bickford
authors: Lee T
authors: LT
authors: Dickman
authors: Robert E
authors: RE
authors: Pangle
authors: Patrick J
authors: PJ
authors: Hudson
authors: Amanda L
authors: AL
authors: Boutz
authors: Nathan
authors: N
authors: Gehres
authors: Jessica L
authors: JL
authors: Osuna
authors: William T
authors: WT
authors: Pockman
authors: Nate G
authors: NG
authors: McDowell
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D002244:Carbon / Q000378:metabolism; D002980:Climate; D005740:Gases / Q000378:metabolism*; D018653:Juniperus / Q000502:physiology*; D008954:Models, Biological; D009516:New Mexico; D010788:Photosynthesis / Q000502:physiology; D028223:Pinus / Q000502:physiology*; D018515:Plant Leaves / Q000502:physiology*; D054046:Plant Stomata / Q000502:physiology; D011891:Rain; D012621:Seasons; D013045:Species Specificity; D014867:Water
chemical_list: D005740:Gases; D014867:Water; D002244:Carbon
keywords: acclimation; carbon balance; hydraulic limitation; photosynthesis; piñon-juniper woodland; precipitation manipulation; stomatal conductance; water stress