Valentin Journé

Valentin Journé
French National Institute for Agriculture, Food, and Environment (INRAE) | INRAE · LESSEM

Post-doc in forest ecology

About

15
Publications
4,108
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76
Citations
Citations since 2016
14 Research Items
76 Citations
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Introduction
PostDoc on FORBIC project with JS Clark, G. Kunstler and B. Courbaud (INRAE Grenoble). Have a look on the website for more details : https://sites.nicholas.duke.edu/clarklab/projects/

Publications

Publications (15)
Chapter
L’étude des systèmes écologiques est souvent rendue difficile car certaines composantes échappent à une observation parfaite, comme les trajectoires d’animaux en mouvement ou la banque de graines des plantes. La modélisation statistique permet de traiter efficacement ces composantes cachées en utilisant le cadre des variables latentes, qui permet d...
Article
Full-text available
Lack of tree fecundity data across climatic gradients precludes the analysis of how seed supply contributes to global variation in forest regeneration and biotic interactions responsible for biodiversity. A global synthesis of raw seedproduction data shows a 250‐fold increase in seed abundance from cold‐dry to warm‐wet climates, driven primarily by...
Article
Full-text available
The relationships that control seed production in trees are fundamental to understanding the evolution of forest species and their capacity to recover from increasing losses to drought, fire, and harvest. A synthesis of fecundity data from 714 species worldwide allowed us to examine hypotheses that are central to quantifying reproduction, a foundat...
Chapter
Evolutionary trade‐offs are considered as one of the most critical factors in the evolution of life history traits, and play a key role in the evolution of organisms, as they limit the range of possible adaptive variations. One major challenge for evolutionary biologists is to detect and observe these trade‐offs in natural environments, in order to...
Article
Despite its importance for forest regeneration, food webs, and human economies, changes in tree fecundity with tree size and age remain largely unknown. The allometric increase with tree diameter assumed in ecological models would substantially overestimate seed contributions from large trees if fecundity eventually declines with size. Current esti...
Article
Full-text available
Phenology and fruit production are sensitive to climate. Variation of leaf phenology alters canopy duration (an indicator of growing season length), which in turn affects forest ecosystem functioning and tree productivity. However, the influence of canopy duration on tree reproduction is poorly explored. In this study, we investigated if and to wha...
Article
Background and Aims Abiotic and biotic stresses related to climate change have been associated with increased crown defoliation, decreased growth and a higher risk of mortality in many forest tree species, but the impact of stresses on tree reproduction and forest regeneration remains understudied. At dry warm margin of species distributions, flowe...
Preprint
Full-text available
A trade-off between growth and fecundity, reflecting the inability of simultaneously investing in both functions when resources are limited, is a fundamental feature of life history theory. This particular trade-off is the result of evolutionary and environmental constrains shaping reproductive and growth traits, but it remains difficult to pinpoin...
Thesis
Full-text available
Les changements climatiques en cours induisent des dépérissements forestiers massifs, qui peuvent aller jusqu'à la mortalité des arbres. Un des processus majeurs de la dynamique forestière est la reproduction sexuée, qui permet la régénération des peuplements, détermine la composition des communautés forestières, et affecte la capacité des populati...
Article
Full-text available
Climate is one of the main factors driving species distributions and global biodiversity patterns. Obtaining accurate predictions of species’ range shifts in response to ongoing climate change has thus become a key issue in ecology and conservation. Correlative species distribution models (cSDMs) have become a prominent tool to this aim in the last...
Presentation
Full-text available
Many perennial species, such as trees, show large variations of fruit production between years (the so-called masting) which can have major consequences on forest dynamic and species interactions. Among other drivers of fruit production failure, years of reduced fruit production can be due to the increase of temperature and the resulting advance in...
Preprint
Full-text available
Abiotic and biotic stresses related to climate change have been associated to increased crown defoliation, decreased growth and a higher risk of mortality in many forest tree species, but the impact of stresses on tree reproduction and forest regeneration remains understudied. At dry, warm margin of species distributions, flowering, pollination and...
Article
Stylidium javanicum, a very poorly known species formerly only recorded from Java, Sumba, and New Guinea, is here reported as a new record for the Philippines, where it was found in grasslands in Antique Province of Panay Island. It is morphologically similar to S. alsinoides, the only other Stylidium species known for the country, but can be disti...

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Projects

Project (1)
Project
Global changes affect species distribution and ecosystems functioning due to long term climatic trends and extreme climatic events. Forests are notably subject to massive growth decline and even mortality. One of the major processes of forest dynamics is sexual reproduction, but there are still many uncertainties about the effect of climate on trees reproduction, especially on when and how resources are allocated to pollen and seeds. Reproduction also allows species to persist over generations, through adaptation and migration. The main objective of this PhD thesis is to develop an approach based on resource and phenology modelling, in order to understand and predict climate effects on forest trees reproduction. First, we quantified the allocation of resources between vegetative versus reproductive functions, with a hierarchical Bayesian model and observation of growth, male and female reproduction over several years. Results allowed us to identify trade-off during floral initiation, and highlighted the importance of resources levels to ensure reproduction. In a second step, we will develop a process-based model of reproduction and include it in an existing model of forest functioning (CASTANEA). The reproduction model, which runs from flower initiation to seed maturation, will simulate spatial and temporal patterns of seed production. It will be calibrated and validated at the national scale through long-term fructification data. Then, we will use this model to study how climate constrains trees species distribution through reproduction and mortality.