Analyzing the growing stock expansion in French metropolitan forests

Ph.D. defense: Anaïs Denardou-Tisserand

“Changements du stock de bois sur pied des forêts françaises – Description, analyse et simulation sur des horizons temporels pluri-décennal (1975 – 2015) et séculaire à partir des données de l’inventaire forestier national et de statistiques anciennes”,

Friday 8 February 2019 at 9.00 am at Amphi Cuénot (Aquarium), Nancy.

Context. After centuries of decrease, the forest area of most developed countries increase, a phenomenon termed “forest transition”. While current increase in growing stock (GS) is greater than that in area, it remains far less studied. These changes are linked to major current issues. It is essential to assess these changes, to decipher their underlying causes, and to quantify them over the longer term in order to locate current forest resources on a broad trajectory and to anticipate their future dynamics. This thesis is dedicated to French metropolitan forests, which exhibit the most intensive changes in the growing stock in Europe, and relies on data from the French NFI program.


(1) Analyse forest areal, GS and GS density (GSD) changes and their spatio-temporal variations over 40 years (1975-2015). They were related to factors hypothesized to feature forest changes (geographical contexts, ownership and species composition). We screened for changes in the rate of expansion. The relationships between GS changes and some forest attributes (initial GS and GSD, recent forest area increase) were investigated.

(2) Uncover the processes of GS changes and to split the GS expansion magnitude across dynamically-homogeneous forest ensembles. The study was based on GS flux estimation (growth, ingrowth, mortality and harvest).

(3) Locate the actual GS expansion in a secular perspective. This analysis consisted in reconstructing the GS chronology since 1850. Levels of GS in 1892, 1908 and 1929 (associated to area of ancient statistics) were estimated using a conditional imputation approach for GSD estimation. Then, a holistic growing stock densification model was implemented to inquire the conditions required on densification patterns and magnitude to simulate the reconstituted GS chronology.


(1) Over 40 years, GS increases were three times faster than the areal ones, underlining the intensity of forest densification. No sign of saturation was found. Private forests, and mainly broadleaved ones, presented the greatest GS and GSD increases, suggesting the essential role of natural expansion and agricultural land abandonment. Regression models revealed the positive effect of initial GS and of recent areal increases on GS expansion.

(2) The analysis of GS expansion processes evidenced the low level of harvests in comparison to forest growth, and the contribution of recent forests to wood resource development. It led to identify four synthetic forest ensembles contributing to the expansion and of distinct dynamics, mainly composed of private forests.

(3) GS suggested a very low mean GSD at the beginning of the period (25 m3/ha) and a GS increase by almost +300% between 1892 and 2010, underlying the importance of this expansion. A convex growth model was required to simulate historical forest densification, attesting of a significant inertia in wood resource reconstitution after the forest transition, interpreted based on a gradual decrease in harvest rates for which indices were collected, or to a gradual recovery of site fertility. The analysis also suggested a distinct kinetics for GS densification in plantation forests.

Conclusions. These researches reveal the magnitude of GS expansion and the importance of its analysis across forest contexts. This ancient expansion does not present any current sign of saturation and constitute a persistent carbon sink which should not decrease in the next decades assuming similar contextual conditions. According to the process analysis of GS expansion, a significant fraction of the GS increases does not constitute readily available additional wood resources. Thus, future harvest intensification policies must be contextualized and evolving in time.

Keywords: forest expansion – forest transition – forest area – growing stock – volume – basal area – forest composition – forest management – land-use abandonment – plantations – harvest – national forest inventory

A new book on Truffles


Cet ouvrage est le fruit de près de quarante années de recherches sur les truffes. Il aborde le genre Tuber dans son ensemble. Il traite donc des truffes du monde, Europe, Asie et Amérique du Nord. Il décrit les différentes espèces, donne les caractères essentiels de leur écologie et traite ensuite de la paléogéographie et des relations existant entre les espèces des différents continents. Les différents aspects de la biologie du genre Tuber sont ensuite abordés : état symbiotique, génome, « brûlés », cycle sexué, nutrition carbonée et azotée, métabolisme secondaire, bactéries associées. Sont ensuite traitées les principales espèces comestibles et leur état de domestication dans une perspective historique. L’ouvrage intègre les nouvelles connaissances dans les itinéraires techniques des différents types de trufficulture en prenant en compte les progrès réalisés à la fois en Europe et en Australie. En annexe sont abordés des aspects plus techniques : mycorhization contrôlée, matière organique, eau, conduite de l’irrigation, changements climatiques, arômes artificiels. Ce livre est destiné à tous ceux qui s’intéressent aux truffes, scientifiques, ingénieurs et techniciens, trufficulteurs ou amateurs.

Dynamics of responses to canopy opening in beech trees

Ph.D. defense

Estelle NoyerRéponses des perches de hêtre (Fagus sylvativa L.) à l’ouverture de la canopée : approche multidisciplinaire et multi-échelle.

Friday 12 May at 9.30 am at AgroParisTech-Nancy (Amphithéâtre A).

Abstract: Opening of the canopy exhibits advantages (resources availability) but also new constraints (wind, higher evaporative demand). Rather well documented in saplings, response dynamics to canopy opening is less known in large trees. The thesis aims to identify the dynamics of responses to canopy opening in beech trees suppressed during long periods. Adopted approach is multi-disciplinary and multi-scale, based on a retrospective analysis of axial and radial growth, anatomy and biomechanical traits. For suppressed trees, the competition for light results in preferential allocation of biomass to axial growth in comparison with radial growth resulting in trees with high slenderness. Moreover, one third of suppressed trees are sagging. After the release, high slenderness presents a biomechanical risk: 15 from 36 trees are broken by the wind two years after the release. To increase their safety against the wind-break, trees reduce their axial growth during four years after the release and boost their radial growth reaching a stabilisation plateau after two years likely due to the size and resources limitations. Trees with lean angle higher than 6° up-right after the release. The tree ring hydraulic conductivity increases and stabilises after two year also. The dynamics of responses to canopy opening are therefore clearly trait dependent. Moreover, integrative approach highlighted the importance of size in the responses to canopy opening: while saplings adjust both wood tissue properties and tree geometry, large trees rely only on geometry adjustments.

Key-words : Fagus sylvatica, growth, biomechanics, anatomy, canopy opening, wood.

Symposium Regulation Redox regulation: Historical background and future developments

Faculté des sciences, Amphitheater 8, Vandoeuvre-lès-Nancy, Université de Lorraine

March 29-31, 2017

Redox regulation referred to as post-translational modifications affecting protein cysteine residues is of great importance for many biological processes. A milestone was the discovery in the 70s that photosynthesis is regulated at several entry points by such modifications. However, over the last decade, it has become obvious in all organisms that additional cellular functions and signaling pathways are controlled by redox changes, some of these being relevant for human health or microbial development and virulence. This redox biology symposium is the third of a series initiated in 2013 in Kaiserslautern followed by a second edition in 2015 already in Nancy. This edition will deal with redox regulation in eukaryote and bacterial systems with emphasis on plants as it is organized in the honor of Pr Jean Pierre Jacquot, who has made pioneering discoveries in this field and will officially retire in 2017.