Austrocedrus Chilensis (D. Don) Pic.Serm. & Bizzarri adaptability to drought: Growth and drought tolerance mechanisms

SERGENT AS; FERNÁNDEZ M.E.; DALLA SALDA G; MARTÍNEZ MEIER A

Le Corum, Montpellier

Congreso; EcoSummit 2016 Ecological Sustainability: Engineering Change; 2016

Elsevier

The Cordilleran cypress (Austrocedrus chilensis (D. Don Pic.Serm. & Bizzarri) is a native conifer from Patagonia, South-America, with a large geographical distribution, covering more than 1200 km (north-south) and a strong west to east precipitation gradient, demonstrating its capacity for adaptation to xeric conditions. Nevertheless its forests are one of the most threatened ecosystems of Patagonia, due to decline and mortality events observed during last decades when climatic variation and drought are considered as the main contributing factors. Determining the adaptability to water stress of these populations is crucial to preserve Cordilleran cypress forests. Stomatal conductance (n=30) and leaf water potential (n=75) were monitored in fifteen years old trees from five populations during one growing season in a common garden. Monitoring was conducted during 2014-2015 growing season, considered as the third driest season of the last 58 years. Vulnerability to cavitation was determined by the air injection method in branches (n=30). The hydraulic safety margin of each population was assessed. Growth was measured atthe end of the 2015 and 2016 growing seasons. The results obtained showed that Cordilleran cypress can be considered as an anisohydric - isohidrodynamic species. The minimum water potential observed was -2.9 MPa, whereas stomatal closure was observed at -1.5 MPa. We observed a relatively high resistance to cavitation, leading to differences in the hydraulic safety margins between populations. A negative relationship between drought resistance and growth potential was observed. These results show Cordilleran cypress high tolerance to drought and lead to revise the assumptions made in the literature since it is described as a cavitation sensitive- drought avoiding species. Significant differences were found between adaptive drought traits demonstrating not only Cypress adaptation potential to unfavorable hydric growth conditions, but also the possibility to select appropriate genetic material for ecosystem restoration programs after forest decline or fire.