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Title: Responses of two semiarid conifer tree species to reduced precipitation and warming reveal new perspectives for stomatal regulation

Here, relatively anisohydric species are predicted to be more predisposed to hydraulic failure than relatively isohydric species, as they operate with narrower hydraulic safety margins. We subjected co-occurring anisohydric Juniperus monosperma and isohydric Pinus edulis trees to warming, reduced precipitation, or both, and measured their gas exchange and hydraulic responses. We found that reductions in stomatal conductance and assimilation by heat and drought were more frequent during relatively moist periods, but these effects were not exacerbated in the combined heat and drought treatment. Counter to expectations, both species exhibited similar gs temporal dynamics in response to drought. Further, whereas P. edulis exhibited chronic embolism, J. monosperma showed very little embolism due to its conservative stomatal regulation and maintenance of xylem water potential above the embolism entry point. This tight stomatal control and low levels of embolism experienced by juniper refuted the notion that very low water potentials during drought are associated with loose stomatal control and with the hypothesis that anisohydric species are more prone to hydraulic failure than isohydric species. Because direct association of stomatal behaviour with embolism resistance can be misleading, we advocate consideration of stomatal behaviour relative to embolism resistance for classifying species drought response strategies.
Authors:
 [1] ;  [2] ;  [2] ;  [2] ;  [2] ;  [3] ;  [4] ;  [5] ;  [2] ;  [1] ;  [2]
  1. CREAF (Spain); Univ. Autonoma Barcelona (Spain)
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  3. Univ. of New Mexico, Albuquerque, NM (United States)
  4. Macquarie Univ., Sydney, NSW (Australia)
  5. Univ. of California, Santa Cruz, CA (United States)
Publication Date:
OSTI Identifier:
1257819
Report Number(s):
LA-UR--14-28231
Journal ID: ISSN 0140-7791
Grant/Contract Number:
CGL2013-46808-R; CGL2010-16373; AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Plant, Cell and Environment
Additional Journal Information:
Journal Volume: 39; Journal Issue: 1; Journal ID: ISSN 0140-7791
Research Org:
Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; 54 ENVIRONMENTAL SCIENCES drought; increased temperature; global change; mortality; iso- vs. anisohydric behavior; stomatal conductance; hydraulic conductivity; hydraulic failure; carbon starvation