Vincent Badeau

Climate change impacts on tree ranges: model intercomparison facilitates understanding and quantification of uncertainty

Model-based projections of shifts in tree species range due to climate change are becoming an important decision support tool for forest management. However, poorly evaluated sources of uncertainty require more scrutiny before relying heavily on models for decision-making. We evaluated uncertainty arising from differences in model formulations of tree response to climate change based on a rigorous intercomparison of projections of tree distributions in France. We compared eight models ranging from niche-based to process-based models. On average, models project large range contractions of temperate tree species in lowlands due to climate change. There was substantial disagreement between models for temperate broadleaf deciduous tree species, but differences in the capacity of models to account for rising CO(2) impacts explained much of the disagreement. There was good quantitative agreement among models concerning the range contractions for Scots pine. For the dominant Mediterranean tree species, Holm oak, all models foresee substantial range expansion.

Long-Term Growth Trends of Trees: Ten Years of Dendrochronological Studies in France

The study of long-term growth trends in French forests began 10 years ago at the Phytoecological Laboratory of the National Agronomic Research Institute (INRA). Very large surveys have been carried out in several regions and for many species, allowing the study of changes in radial growth of individual trees during the past 150 years. In all cases, a significant increasing growth trend appeared. It varied between +50% and +160% depending on species and location. Careful analysis of possible bias has been made. Beside these biases, possible causes of such trends are discussed. This chapter summarizes the main methods and results of our laboratory. For additional information, our readers may refer to the cited articles.

Empirical Niche Modelling of the Spontaneous Diversity of Forage and Turf Species to Improve Collection and Ex Situ Conservation

Rational sampling of the spontaneous diversity of forage and turf species requires an a priori knowledge of the range of environmental conditions suitable for these species. We introduce some concepts and methods for investigating the environmental range of species by empirical modelling of species ecological niche, and we suggest how such investigations could help to plan collection campaigns and to improve the choice of core-collections. The empirical modelling of the ecological niche of a species consists of building a function of environmental parameters predicting the presence of the species from a calibration dataset including observed presence-absence or abundance records of the species and environmental data at observation sites. We emphasize that data from collection campaigns of plant breeders are valuable information for niche modelling. We introduce two methods for investigating the environmental distribution of species and for niche modelling based on presence-absence data: the canonical correlation analysis and the logistic regression. We give examples combining niche model and GIS software that may contribute to organize collection campaigns. We suggest that models predicting probability of presence of species may be useful for the selection of core-collections. Such models may help to delineate geographically isolated areas of presence of species that should be sampled separately for selecting a core-collection. In each isolated area of presence, we propose to stratify the accessions in clusters according to the predicted probability of presence of the species in collection sites, and to select accessions in each cluster.

L’eau forestière de qualité : comment agir sur les quantités produites ?

Forests have a key influence on the water cycle through properties related to their structure, in particular the development of the canopy and of root systems. Any examination of forests as suppliers of water must consider the following two elements: — overall, the more productive the forest, the greater its water consumption, which accordingly reduces drainage flow. In other words, there is a trade-off between biomass production and the amount of water returned to the environment; — water drained under forest canopies to streams, springs or the water table is generally of good quality. A self-evidence worth remembering is that quality and quantity of water cannot be dissociated: the service of “quality water” implies availability of sufficient quantities over time. Knowledge and management of forest-sourced water are based on knowledge of the water balance and its variations in space and time. This article discusses the various causes of variations in water balance connected with climate, soil conditions, forest species, silvicultural practices, all of which have an impact on the amount of water drained. It also provides some comparisons with other major vegetation types. To answer the question of how to quantitatively assess the amount of water supplied by forests and how to modulate that quantity by management, we implemented a modelling approach that uses a water balance model with a daily time step. Using site-specific parameters and meteorological data, the model simulates the flow from actual evapotranspiration, rainwater at ground level, the water content of the soil and drainage. Two forest sites were selected for the study described in this article. These are forests in eastern France with contrasting rainfall patterns for which we simulated, under current climate conditions, the effect on the volume of water drained of five different silvicultural scenarios.