EFFECTS OF CLONE, IRRIGATION AND PLANTATION DENSITY ON XYLEM HYDRALULIC CONDUCTIVITY IN A SRC WILLOW PLANTATION

LUQUEZ V; RODRÍGUEZ ME; MOZO I; ACHINELLI FG; MONTEOLIVA S

Novi Sad

Simposio; Eight International Poplar Symposium (IPS VIII); 2022

IUFRO

Short rotation coppice (SRC) plantations with willows are important for the production of bioenergy and for environmental services because of their fast growth rates. The rapid growth implies high transpiration rates, that needs to be sustained by a concomitant water transport capacity of the xylem. The aim of this work was to analyze the effects of water availability, genotype and plantation density on xylem hydraulic conductivity in willows.The field trial was situated in La Plata, Argentina, and included two irrigation treatments (rainfed and irrigated), two plantation densities (13,333 and 20,000 plants ha-1) and two willow clones (Barrett and Yaguareté), arranged in a split-split plot design. The plants were coppiced every year during winter. The sampling dates were December 15, 2021 and February 15, 2022. The stems were harvested in the morning, moved to the laboratory and the segment to be measured was re-cut under water. The hydraulic conductivity determinations were performed the same day by perfusion and weighing of the extruding water. The parameters determined were: hydraulic conductivity per unit stem length (kh), hydraulic conductivity per unit xylem area (ks) and hydraulic conductivity per unit leaf area (kl). Data were analyzed with a mixed model with irrigation, density and clone as fixed effects and the block as random effect. The block and interaction effects were non-significant in all measurements. We expected that a higher density would increase competition between the plants and affect the hydraulic conductivity, but the plantation density had no significant effect on any measurement.There was no significant effect of any of the factors on ks. Nevertheless, the xylem conductive area was significantly affected by irrigation and clone. In consequence the total conductive area per plant was different, even if the conductivity per unit of xylem area did not change. Clone and irrigation had a significant effect on kh in the first sampling date, but only clone was significant in the second date. Irrigation had a significant effect on kl in the first date, but not in the second one. Clone and irrigation had a significant effect on leaf area per branch, irrigated plants had a higher leaf area than rainfed ones, and clone Barrett had a higher area than Yaguareté. From previous studies, we know that Barrett is more tolerant to drought than Yaguarete, probably because they have different susceptibility to cavitation. This point will be addressed in future studies.