Collaborations: Eric Badel (PIAF, INRA UBP Clermont Ferrand), Barry Gardiner (EHYSE, INRA Bordeaux), Joseph Gril, Tancrède Alméras (CNRS LMGC Montpellier), Barbara Lachenbruch (Oregon State University), Franck Telewski (Michigan State University), NFZ Wood Group

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Context — WADE analyses how wood properties vary in response to environmental distirbances. WADE is based on integrative modeling of functions and functionalities of wood in trees, from cell wall to tissues and the whole organism. WADE uses wood characterization techniques offered by two technical platforms, Xylosciences and PTEF (INRA Technical Platform for Functional Ecology).

Objectives —WADE aims at linking mechanistic and biophysical modeling to empirical approaches of wood quality, in order to understand and predict how micro-climate changes (of light, mechanical environment …) trigger wood patterns.

Approach —

• Task 1 aims at delivering the general wood framework, involving strongly the Xylosciences platform, with links with the PTEF one, for technical aspects. The three following tasks use this framework to answer biological questions linked to silvicultural or technological issues:

• Task 2 studies how wood responds to mechanical constraints in natural environments using recent advances made by integrative biology in this field,

• Task 3 characterizes wood of branches, especially its chemical properties with relation with diversity and ontogeny, enlarging the point of view developed in Scandinavian industrial studies on Picea abies, and

• Task 4 develops new markers of growth history and canopy disturbances in saplings, as this development stage, poorly understood in growth models, impacts greatly the ability of forests to regenerate under changed climatic conditions. A final task organizes synthesis and dissemination of all results related to i) phenomenological growth and yield of forest models with forest R&D, ii) wood industries through parallel industrial projects, iii) teaching at the master level.

Key results —

• Task 1 : Henri Cuny ‘s post-doctoral work lead to a publication in Nature Plants  about wood formation kinetics related to carbon storage in forest ecosystems (see main conclusions).

• Task 1 : The paper submitted to American Journal of Botany about “how universal physics explains some observed worldwide correlations between wood traits” was rejected but the authors were strongly encouraged to resubmit. The message is important but not easy to communicate to biologists.

• Task 1 : Félix Hartmann ‘s thesis (June 2015) about a biophysical model of wood formation showed that reaction-diffusion of morphogenetic chemical signals can explain growth kinetics (in terms of volume) but not anatomical patterns from early wood made of large cells, or to late wood made of small cells.

• Task 1 : Wood biophysics contributes to improve discussion and valorization of datas obtained before 2014 in ANR EMERGE project (Longuetaud F., Mothe F, Santenoise Ph, Dlouhà J., Fournier M., Deleuze C. “Patterns of within-stem variations in wood specific gravity and water content for four temperate tree species” re-submitted to Annals of Forest Science)

• Task 3 : Works about knot chemistry were published (PhD, Z. Kebbi Benkeder LERFoB, LERMaB). Firsts results about J. Song thesis (QTL of epicormic formation, supervision F. Colin LERFoB and O. Brendel EEF, collaboration with A. Kremer BIOGECO Bordeaux).

• Task 4 : All data was collected for Estelle Noyer PhD about « individual response of trees to gap openings : growth and wood variations », co-supervisors C. Collet ecology/silviculture et J. Dlouha biomechanics, wood physics, with ONF’s help (project “sapling reactivity”). Citra Purba’s Master 2 (Master FAGE BFD, double diploma with Bogor University, Indonesia) was published. E. Noyer spent 3 months at Oregon State University where she worked with B. Lachenbruch on wood hydraulics data analysis and finalized a dissemination strategy for her PhD publication.

• Task 5. WADE has actively contributed to knowledge transfer via several courses curicullums (Master of Engineering at AgroParisTech and Master FAGE at the University of Lorraine).

Main findings  —

The main result from 2015 can be attributed to Henri Cuny’s post doctoral work (Nature Plants, 26 October 2015) : Trees show that growing is not putting on weight!

Our careful (and sometimes cumbersome) methodologies developed by C. Rathgeber, H. Cuny, M. Harroué, E. Cornu in LERFoB for studying intra-annual kinetics of wood formation processes have shown that mechanisms involved in tree growth are active at different times. Stem-girth increase and woody biomass production are two key processes of forest ecosystems, driving respectively stand growth in volume and carbon sequestration in wood. Up to now, these two processes were considered to be synchronous. This study demonstrated that in coniferous forests of the northern Hemisphere, woody biomass production lagged behind stem-girth increase by about one month during the growing season. It also showed that these two biological processes exhibited differential sensitivities to climatic conditions. Indeed, the seasonal dynamics of stem-girth increase matched the photoperiod cycle (change in daytime and nighttime lengths), whereas those of woody biomass production closely followed the seasonal course of temperature.

These new results show how difficult it is to properly infer the seasonal dynamics of carbon sequestration from external measurements of stem size change (e.g., dendrometer records). The amount of biomass produced from photosynthetic carbon cannot be approximated through changes in tree size on the short term. Even if stem size does not evolve in the fall, the forest can still capture carbon, thus increasing the wood mass at an even volume. This work is helping to better quantify the seasonal balance of terrestrial carbon, providing insights and methods to link forest–atmosphere exchanges and woody carbon sequestration at weekly time scales.
Future Perspectives —

The WADE project ends in 2015 (with the exception of Estelle Noyer’s PhD which she will defend at the end of 2016). Designed to support innovative and cross-disciplinary perspectives for understanding wood formation and wood qualities, the project has stimulated the creation of new LabEx projects and has reinforced consistency between several ongoing LabEx projects (WOOD-EP-N2, WIND-IN-WOOD, WOOD ForMS, WOODCAP, EVAQB, Wood@nat transformed into a MOOC offered by the University of Lorraine). It reinforced attractiveness of our community focused on this topic: for example, Cyrille Rathgeber and Henri Cuny are currently participating in international networks and projects, Jana Dlouhà is preparing an ANR project with Eric Badel (PIAF Clermont Ferrand) while supervising a PhD thesis being financed by the INRA EFPA Department. Concerning more industrial research, the WADE experience will help us develop several technological projects that will focus on non-destructive assessment of wood quality in standing trees.