Chronology of hydraulic vulnerability in trunk wood of conifer trees with and without symptoms of top dieback

S Rosner (1) , S Luss (1) , J Světlík (2) , K Andreassen (3) , I Børja (3) , L Dalsgaard (3) , R Evans (4) , O.E. Tveito (5) , S Solberg (6)

1 BOKU - Universität für Bodenkultur Wien = University of Natural Resources and Life [Vienne, Autriche]
2 MENDELU - Mendel University in Brno
3 The Norwegian Forest and Landscape Institute
4 CSIRO - Commonwealth Scientific and Industrial Research Organisation [Canberra]
5 MET - Norwegian Meteorological Institute [Oslo]
6 NILU - Norwegian Institute for Air Research

There is evidence that recently occurring top dieback of Norway spruce (Picea abies (L.) Karst.) trees in southern Norway is associated with drought stress. We compared functional wood traits of 20 healthy looking trees and 20 trees with visual signs of top dieback. SilviScan technology was applied to measure cell dimensions (lumen and cell wall thickness) in a selected set of trunk wood specimens where vulnerability to cavitation (P 50) data were available. The conduit wall reinforcement ((t/b)²) was a good proxy for P 50. Cell dimensions were measured on wood cores of all 40 trees; theoretical vulnerability of single annual rings could be thus estimated. Declining trees tended to have lower (t/b)² before and during a period of water deficit (difference between precipitation and potential evapotranspiration) that lasted from 2004 to 2006. The results are discussed with respect to genetic predisposition. Introduction In southern Norway, recently occurring top dieback in 40-50 years old forest stands of Norway spruce (Picea abies (L.) Karst.) is thought to be associated with climatic extremes (Hentschel et al. 2014). In this region, the period between 2004 and 2006 was characterized by high water deficits during the growing season, estimated as the difference between the cumulative precipitation and the potential evapotranspiration (see Fig 1 in Hentschel et al. 2014). During this period, trees with symptoms of top dieback (Fig. 1) showed lower intrinsic water-use efficiency that is associated with increased stomatal conductance (Hentschel et al. 2014) and produced wood with lower density, indicating higher vulnerability to cavitation (Rosner et al. 2014). Functional traits for estimating hydraulic vulnerability gain increasing importance as screening tools because hydraulic experiments are labour intensive or prone to errors (Cochard et al. 2013). In this study, we extend an existing dataset (Rosner et al. 2014) with tree samples and derive functional traits for hydraulic vulnerability from tracheid dimensions assessed by SilviScan technology (Evans 1994). Thereafter we document how these proxies changed over the years in 20 healthy looking and in 20 declining trees in order to learn more about the predisposing factors for top dieback in Norway spruce in southern Norway.

Domaines: Biologie végétale

S Rosner, S Luss, J Světlík, K Andreassen, I Børja, et al.. Chronology of hydraulic vulnerability in trunk wood of conifer trees with and without symptoms of top dieback. Journal of Plant Hydraulics, 2016, 3, pp.e001. ⟨hal-01256362⟩