A retrospective, dual-isotope approach reveals individual predispositions to winter-drought induced tree dieback in the southernmost distribution limit of Scots pine.
Winter-drought induced forest diebacks in the low-latitude margins of species' distribution ranges can provide new insights into the mechanisms (carbon starvation, hydraulic failure) underlying contrasting tree reactions. We analysed a winter-drought induced dieback at the Scots pine's southern edge through a dual-isotope approach (Δ(13) C and δ(18) O in tree-ring cellulose). We hypothesized that a differential long-term performance, mediated by the interaction between CO(2) and climate, determined the fates of individuals during dieback. Declining trees showed a stronger coupling between climate, growth and intrinsic water-use efficiency (WUEi) than non-declining individuals that was noticeable for 25 years prior to dieback. The rising stomatal control of water losses with time in declining trees, indicated by negative Δ(13) C-δ(18) O relationships, was likely associated with their native aptitude to grow more and take up more water (suggested by larger tracheid lumen widths) than non-declining trees and, therefore, to exhibit a greater cavitation risk. Freeze-thaw episodes occurring in winter 2001 unveiled such physiological differences by triggering dieback in those trees more vulnerable to hydraulic failure. Thus, WUEi tightly modulated growth responses to long-term warming in declining trees, indicating that co-occurring individuals were differentially predisposed to winter-drought mortality. These different performances were unconnected to the depletion of stored carbohydrates.
Department of Crop and Forest Sciences - AGROTECNIO Center, University of Lleida, Av. Rovira Roure 191, 25198, Lleida, Spain. jvoltas@pvcf.udl.cat
Jordi
J
Voltas
Jesús Julio
JJ
Camarero
David
D
Carulla
Mònica
M
Aguilera
Araceli
A
Ortiz
Juan Pedro
JP
Ferrio
D002247:Carbon Isotopes / Q000032:analysis; D002980:Climate; D055864:Droughts; D005843:Geography; D010103:Oxygen Isotopes / Q000032:analysis; D041605:Pinus sylvestris / Q000033:anatomy & histology / Q000254:growth & development* / Q000502:physiology; D018547:Plant Stems / Q000033:anatomy & histology / Q000254:growth & development / Q000502:physiology; D018526:Plant Transpiration; D011891:Rain; D012189:Retrospective Studies; D012621:Seasons; D013030:Spain; D013696:Temperature; D013997:Time Factors; D014197:Trees; D014867:Water / Q000378:metabolism*; D014934:Wood / Q000033:anatomy & histology / Q000254:growth & development* / Q000502:physiology
D002247:Carbon Isotopes; D010103:Oxygen Isotopes; D014867:Water
Pinus sylvestris; carbon reserves; hydraulic failure; stable isotopes; tree rings; water-use efficiency