Contrasting water‐uptake and growth responses to drought in co‐occurring riparian tree species

摘要: Growth responses of riparian trees to changes in water availability are poorly understood, thereby limiting understanding regional droughtimplicationsinrivercorridors.Weuseddendrochronologicalmethodstodevelopgrowthseriesandanalysedoxygenisotopic ratios (d 18 O) ina-cellulose from individual tree rings for two co-occurring species,Fraxinus excelsiorandPopulus nigra. Trees were sampled along the Ain River (France) assess growth and annual source availability, inferred tree-ringd O, compared with variations streamflow precipitation. Both species exhibited decreased during drought years, butF. excelsiordemonstrated less variation across sites withP. The latter expressed a smaller range ofd O among individuals but greaterd sensitivity river discharge, indicating more consistent hyporheic source.P. nigraalso suffered inhibition thanF. excelsiorin dry years when tables suppressed. These differences suggest contrasting patterns use, whereinF. excelsioruses primarily vadose zone maintain moderategrowthrates,andP.nigrademonstratesmoreconsistentphreaticwaterusageandsuffersindroughtyearswhenwatertables observations data onfloodplain rooting depths, which show thatF. excelsiormaintains its rootsabovethegravellayer,whereasP.nigragenerallyrootsdeeplyintophreaticzonegravels.Theseresultsindicatethatsurprisingly, poplars may be sensitive than ash vulnerable climate affecting corridors. Copyright © 2012 John Wiley & Sons, Ltd. KEY WORDStree rings; oxygen isotopes; drought; forests; Mediterranean climate; table; dendrochronology; stress