PARENT SESSION
Organized Oral Session 11: Hydraulic limitations in vascular plants
Organizer(s): F Berninger, L Lauzon, and E Nikinmaa
Monday, August 8, 1:30 PM - 5:00 PM, Meeting Room 511 C, Level 5, Palais des congrès de Montréal

Hierarchical analysis of structural and functional tradeoffs in hydraulic properties of Douglas-fir xylem.

Dunham, Sonya^*,1, Ganio, Lisa ¹, Gartner, Barbara¹, ¹ Oregon State University, Corvallis, OR

ABSTRACT- We explored the question of whether there are tradeoffs between structural and functional properties of Douglas-fir xylem at multiple physiological and organizational scales. Tradeoffs between water transport properties (e.g. specific conductivity, k_s), mechanical stability (e.g. density), and hydraulic safety parameters (e.g. vulnerability to embolism) may be unique at different scales within and between individual trees. The 32 trees in the study were organized in 8 plots in two 54-year old stands (the 4 trees in each plot being geographically much closer to together than the plots). Within each tree we studied 7 different organs and xylem ages. We hypothesized that each level of scale would have a different degree of tradeoff and, in general, that vulnerability to embolism would be positively correlated with k_s and negatively correlated with wood density. Also, specific conductivity would decrease with increasing density. Vulnerability to embolism, density, and k_s were measured on the 52-year old bole, a 52-year old root and about a 25-year old branch on each individual. Density and k_s were also measured on 5-year old branches, about 20-year old roots, and the 5-year old leader on each tree. A Bayesian hierarchical model was used to simultaneously describe the relationship between ₅₀ (xylem tension at which 50% loss of conductivity has occurred) and k_s and account for random variation at the multiple scales of organ, tree, and stand. Preliminary results indicate that there is an exponential relationship between ₅₀ and k_s (R² = 0.31). Neither ₅₀ nor k_s are correlated with density. These results indicate that there is no tradeoff between xylem structural and functional properties between multiple organs and xylem ages in these trees.

Key words: wood density, vulnerability to embolism, hydraulic conductivity, xylem properties