We started with finalising a large sampling campaign in Catalonia (ES) and with sample preparation for phloem and xylem trait assessment. In total, 450 trees from 6 species and 90 populations were selected for the study. For each species (three Fagaceae and three Pinaceae, the dominant forest vegetation of the region), the populations were chosen along a gradient in water availability.
Of each individual tree, a branch section was taken into the lab to make a micrometre thin section with a sliding microtome. With a camera attached to a microscope, digital images from all 450 stained micro-sections were obtained on which xylem and phloem traits could be quantified. This generated a phloem and xylem anatomy dataset of 16 traits (Obj 1) that will be contributed to the TRY Plant Trait Database.
Tree-specific hydraulic traits and population-specific measurements were also taken. In total, 20 leaf and xylem hydraulic traits were measured for each individual tree. Population specific variables were divided in 3 groups: 8 soil variables, 4 forest structure variables and 6 climate variables. Integration of the anatomy and physiology traits and the environmental variables lead to a comprehensive dataset allowing to study trait relationships and describe tree responses to drought (Obj 2).
Through linear modelling, we concluded that variation in tissue balances were larger between species than between populations of the same species and that water availability did not have a large direct effect on tissue proportions or conduit sizes (Obj 3), opposite to what was expected. Joint effort of the PHLOEMAP and FUN2FUN projects showed that: about one fourth of trait variability can be attributed to the within-species level, trait coordination differed between inter- and intra-specific level and hydraulic traits are crucial to predict whole-tree performance under changing environmental conditions (Obj 4). All scientific results will be published in the course of 2018 in four journal papers.
During dataset build-up, 3 dissemination activities were done: (i) the publication of 2 articles and 2 videos for a general public showing the beauty, the complexity and the ecological importance of wood structure, (ii) the publication of a book chapter on the anatomy and xylem functioning of oaks and (iii) the coordination of the outreach activities of the EU COST Action STReESS including two outreaching exhibitions in which several aspect of the PHLOEMAP project were integrated. The first scientific results of the project were presented at the 3rd International Xylem Meeting in Bordeaux (FR) in 2017 and further results will be presented at the TRACE conference (DE, 04/18), the Gordon Research Conference on vascular biology (US, 06/18) and the 42nd New Phytologist Symposium (US, 07/18). An exhibition activity on the future of forests in a changing climate closely related to this project is planned in March 2018 in Barcelona. On my personal website “Let’s tree”, I have included an explanation that is easily understandable by a broader public on the importance of trees and forests and the role the water transporting cells herein.
