Francis Colin

Epicormic ontogeny in Quercus petraea constrains the highly plausible control of epicormic sprouting by water and carbohydrates

BACKGROUND AND AIMS There is increasing evidence that suppressed bud burst and thus epicormic shoot emergence (sprouting) are controlled by water-carbohydrate supplies to entire trees and buds. This direct evidence is still lacking for oak. In other respects, recent studies focused on sessile oak, Quercus petraea, have confirmed the important constraints of sprouting by epicormic ontogeny. The main objective of this paper was thus to provide provisional confirmation of the water-carbohydrate control and direct evidence of the ontogenic constraints by bringing together results already published in separate studies on water status and distribution of carbohydrates, and on accompanying vegetation and epicormics, which also quantify epicormic ontogeny. METHODS This paper analyses results gained from a sessile oak experiment in which part of the site was free from fairly tall, dense accompanying vegetation. This experiment was initially focused on stand water status and more recently on the carbohydrate distribution of dominant trees. External observations of the epicormic composition and internal observations with X-ray computer tomography were undertaken on 60 and six trees, respectively. KEY RESULTS Sprouting was more intense in the part of the stand free from accompanying vegetation and on upper trunk segments. A clear effect of epicormic ontogeny was demonstrated as well: the more epicormics a trunk segment bears, the more chances it had to bear sprouts. CONCLUSIONS These results indirectly infer water-carbohydrate control and show direct evidence of constraints by epicormic ontogeny. These results have far-reaching consequences related to the quantification of all functions fulfilled by any type of epicormic structure in any part of the tree.

Epicormics in 13-year-old Quercus petraea: small effect of provenance and large influence of branches and growth unit limits

Abstract• The provenance effect on epicormics is poorly documented and restricted to epicormic shoots. Our objective was to characterize the relationship between epicormics and provenance on 13-year-old Quercus petraea trees, taking into account their growth traits.• On the growth units (GU) studied, epicormics were essentially isolated buds (95%) and they were mainly located at branch bases, secondarily on GU limits and marginally on lateral position. Provenance effect was very small on the number of epicormics and slightly larger on the number of branches and GU limits. On the contrary, the growth situation-independently from provenance-proved to have a larger effect on the 2 latter growth traits.• Altogether, these results clearly show the predominant effect of morphological traits and thus of ontogeny. This opens important research perspectives: how growth conditions and genetics (at progeny and individual levels) influence height growth, setting and fate of axillary buds on the one hand and fate of epicormic buds inserted directly on the stem, or at branch bases on the other hand.Résumé• L’effet provenance sur les épicormiques est peu documenté et concerne exclusivement les gourmands. Notre objectif était de caractériser l’effet de la provenance sur les épicormiques présents sur des chênes sessiles âgés de 13 ans, décrits par des marqueurs de croissance.• Sur les unités de croissance (UC) décrites, les épicormiques sont essentiellement des bourgeons isolés (95 %), localisés à la base de branche, puis en limite d’UC et enfin en position latérale sur le tronc. L’effet provenance s’est avéré très faible sur le nombre d’épicormiques et légèrement plus fort sur le nombre de branches et d’UC développées. À l’inverse, un effet de la situation de croissance a été noté sur les deux derniers paramètres, et ceci indépendamment de la provenance.• L’ensemble des données obtenues montre une prédominance de l’effet des marqueurs morphologiques de l’arbre sur les épicormiques, et donc de l’ontogénèse. Ceci ouvre d’intéressantes perspectives de recherche : quels sont les effets des conditions de croissance et de la génétique (au niveau descendance et individuel) sur la croissance en hauteur, la mise en place et le devenir des bourgeons axillaires d’une part, et du devenir des bourgeons épicormiques, situés directement sur la tige ou en base de branches séquentielles d’autre part.

X-ray computed tomography to decipher the genetic architecture of tree branching traits: oak as a case study

A new method for obtaining internal views of tree trunks was recently developed using X-ray computed tomography (CT). This technology makes it possible to observe and measure rameal traces that are left by latent buds, sequential branches, and epicormic branches in the wood. Epicormic branches are undesirable for producing high-value solid wood, especially in Quercus robur, an important hardwood forest tree species in Europe, which is prone to epicormic branches that develop from abundant latent buds. For the very first time, branching-related traits deduced from X-ray CT observation make it possible to analyze the genetic architecture of oak branching through a quantitative trait locus (QTL) analysis. Highly significant QTLs were detected for traits related to latent buds and epicormic branches. The number and effect of these QTLs suggest a moderate genetic determinism for the formation of latent buds and the development of epicormic branches. Three hotspots were found, grouping QTLs for different branching traits. An analysis of the common physiological denominators of these coincident traits suggests that their genetic controls are related to either the regulation of the axillary meristem initiation or to bud dormancy. Conversely, the position of only the separate QTL related to the number of sequential branches suggests an independent genetic control.

Segmentation of defects on log surface from terrestrial lidar data

Segmentation of defects on the tree log surface remains a challenge due to the unclear seperation between the foreground and the background and the high variability of the tree surface. Even if some first works exist to process specific tree species, a generic method robust to various species is missing. We propose a new approach for segmenting defects on log surface based on the tabular object analysis. We firstly compute the log centerline by surface normal accumulation and then threshold the point cloud by the the difference between the distance to the centerline and the reference distance estimated from a patch of neighbors. The performance of the proposed approach was experimented and compared on ten logs recovered from different species. The results showed that our approach outperformed other method based on cylinder detection and was robust to several tree species. The results can be reproduced and compared on an online demonstration.

Algorithms and Implementation for Segmenting Tree Log Surface Defects

This paper focuses on the algorithms and implementation details of a published segmentation method defined to identify the defects of tree log surface. Such a method overcomes the difficulty of the high variability of the tree log surface and allows to segment the defects from the tree bark. All the algorithms used in this method are described in link to their source code which guarantees a full reproducible method associated to an online demonstration.