Water relations and hydraulic architecture of evergreen and deciduous tree species with different wood density: the effect of a severe dry spell in the semideciduous Atlantic Forest

RODRIGUEZ SA; DI FRANCESCANTONIO D; KOSTLIN MR; OLIVA CARRASCO L; TRENTINI C; LEZCANO OA; CAMPANELLO,PI; SCHOLZ FG; BUCCI SJ; GOLDSTEIN G

Bonito

Congreso; 49th ATBC Meeting; 2012

Association for Tropical Biology and Conservation

The wood density is an important attribute for understanding the physiology and ecological behavior of trees. It is functionally related to a large number of variables and processes, such as growth rate, water transport and size of the stem water reservoirs. We studied some aspects of the water relations and hydraulic architecture of ten species differing in wood density and phenology from a semideciduous Atlantic Forest in Northern Argentina. Although the study area normally receives an annual precipitation of 2000 mm, unpredictable dry spells may occur during the year. We measured wood density (wd), wood relative water content (RWC), leaf water potential at midday (ψmd) during a severe dry spell in summer, and estimated vulnerability to xylem cavitation (P50) in terminal branches for each species. Stem growth was also measured every two months with band-dendrometers. Species with lower wood density were expected to be more vulnerable to cavitation assuming that there is a trade-off between xylem efficiency and safety. However, we found no relationship between these two characteristics of the hydraulic system. The species with the highest wd (0.86 g cm-3) was also the most vulnerable to cavitation (P50 = -1MPa). There was a negative relationship between ψmd and wd (p=0,0035) indicating that species with lower wd have a more favorable water balance during the day due to the presence of reservoirs of water in their stems. Some species showed a sharp decrease in stem diameter due to the depletion of the internal water storages in the main stem regardless of their wood density and phenology.