Integrated study of adaptation of natural and planted forests to biotic and abiotic environmental variation, in the global change context
The LIA FORESTIA aims at investigating adaptive mechanisms and their application to forest tree breeding and silviculture. To achieve that goal, we defined specific objectives:
- To identify relevant adaptive traits by investigating their relation with fitness
- To determine the functional role of these relevant adaptive traits
- To explore the phenotypic, genetic (quantitative and molecular) and environmental variation of the adaptive traits driving the mechanisms of adaptation in different model species submitted to various abiotic or biotic stressors
- To works on the design, test and validation of innovative tools and methods involved in forest tree breeding, forest management and wood quality studies
The substance of the project is built around the hypothesis that a part of the relevant adaptive traits is directly or indirectly based on basic wood properties and annual rings. Annual rings provide convenient retrospective access to tree response to biotic and abiotic stressors. The main abiotic stressors studied by the FORESTIA LIA are drought and frost. The significance of the annual ring response can be investigated in association with major wood functions like sap conduction. Recent drought-induced diebacks associated to the climate change are opportunities to study the relationships between basic wood properties and the survival component of fitness. Annual rings offer original opportunities to study inter and intra annual phenotypic plasticity. In the end, wood studies also provide information about wood production, quantity and quality. Wood is a central study-object of the FORESTIA LIA. Consequently, the LIA elaborates technological innovations associated to wood measurement.
With the intensification of international trade and travel, an increasing number of forest pests are exotic. More forest biomass is lost to insects than to forest fires (FAO). The FORESTIA LIA would contribute to improve the knowledge of invasion pathways, adaptive traits of target pests and invasion risks via modelling studies.
Finally, yet importantly, the FORESTIA LIA wants to be involved in the mitigation of the unfavourable effects of the climate change. That is why it does not only provide basic scientific knowledge but also works on the design, test and validation of innovative tools and methods involved in forest tree breeding and forest management.
The FORESTIA scientific project is strongly integrative and multi-disciplinary, with the main disciplines being wood sciences, dendro-ecology, physiology and ecophysiology, quantitative, population and molecular genetics and evolutionary biology.
The main forest tree model species are native and introduced, planted and naturally regenerated; in Argentina: Douglas-fir, ponderosa pine, cordillera cypress, four nothofagus species, four eucalyptus species, poplars and hybrid pines; in France: Douglas-fir, European larch, hybrid larch and poplars.
Adaptive traits and response to stressors
The adaptive value derives from relationships with the survival component of fitness and common garden studies.
The survival component of fitness: comparing the wood of dead and surviving trees
By definition, an adaptive trait is related to fitness (overall reproductive success). Reproductive success and survival are the two fitness components. Survival is much easier to observe than reproductive success. The relationship between a trait and survival can be detected by comparing dead and surviving trees after an identified stressful event. Only wood features can be observed during a certain time after tree death. This approach has been successfully tested on Douglas-fir, the Cordillera cypress and other species. One goal of the FORESTIA LIA is to continue to monitor forest tree diebacks following drought and other extreme environmental events, organize sample collection, measure annual ring features and analyse the data in order to identify putative adaptive traits and the main drivers of adaptation.
Local adaptation and common garden experiments
We use existing and newly installed common garden experiments like the Douglas-fir provenance trials and the larch and Nothofagus reciprocal transplants to separate genetic and environmental effects and study local adaptation. In addition, correlation study of genetic entities in common garden experiments with environmental data from the places of origin is another efficient approach to discover adaptive traits.
Insects as biotic stressors
Attention is paid to biotic stressors, dealt through forest insects’ studies and their direct and indirect impact on forest adaptation. The LIA will develop tree-ring studies of defoliating insects.
The identification of the functional role of adaptive traits is applied to drought resistance, to the phenology of budburst, budset and annual ring formation, and to frost resistance.
The FORESTIA LIA is working on wood hydraulic properties, primarily on vulnerability to cavitation. Vulnerability to cavitation is a trait measuring the susceptibility of trees to respond to severe drought by breaking the ascending water column in xylem cells. It is considered as a key trait in the climate change context. Our objective is to study directly and indirectly the environmental and genetic variation, and the determinism of this trait. Methods of direct measurement are tedious and time-consuming and will benefit from methodological improvements. INRA and INTA have designed a new promising automated tool for faster and cheaper measurements of vulnerability to cavitation, the Embolitron. A prototype is being tested at the moment in collaboration. We are also working on indirect measurement methods, based, on the one hand, on relationships between wood density and resistance to cavitation, and, on the other hand, on Near Infra Red Spectra (NIRS) calibrations.
Phenology, wood formation and frost resistance
Phenology involves a group of adaptive traits of key interest in the frame of the climate change. Beside budburst, bud set, flowering events and other phenophase traits, FORESTIA also invests in the study of the phenology of annual ring formation in different species like larch, hybrid pines, eucalyptus and others: beginning of ring formation, earlywood-latewood formation and latewood cessation.
Next to the timing of key events, the study of the whole ring formation process gives access to the cambial response to environmental variation. Here, the measurement of ring radial growth can be automatized by using appropriate dendrometers. Since their prices are high, we are putting some work in the development of low-cost dendrometers. However, the main emphasis is on interpreting from a functional perspective the detailed and complex information produced by the dendrometers. One specific goal is the development of intra-annual norms of reaction for the estimation of phenotypic plasticity of cambial response to climate.
Another consequence of the climate change is that earlier (at the beginning of the growing season) or later (at the end of the growing season) timing of phenology traits expose trees to late (at the beginning of the growing season) or early (at the end of the growing season) frost events. Alterations of the apical dormancy cycles resulting from milder winter increases the negative impact of the late frosts at critical stages of plantations and tree growth.
Natural selection is a major evolutionary process that may enable forest trees to adapt to the warmer and dryer conditions associated to the climate change. It relies on the magnitude of genetic variation and heritability of the adaptive traits involved in resistance to the appropriate stressors. One important objective of FORESTIA is to estimate the degree of genetic determinism and of genetic variation of key adaptive traits, or proxies of key-adaptive traits for various populations in several environments. This estimation principally relies on progeny trials installed in the frame of forest tree breeding programs. Alternatively, approaches based on molecular markers and estimation of genetic relatedness in naturally regenerated populations have been proposed and, to some extent, tested and partially validated. Based on previous experience and collaboration, FORESTIA expresses interest in developing experiments on this topic.
Given the high speed of the climate change, adaptive phenotypic plasticity is a key component of the forest trees adaptation potential. FORESTIA will be strongly involved in the development of original methods of estimation of phenotypic plasticity. In particular, radial growth curves produced by automatic point dendrometers will be associated to annual ring microdensity profiles to develop norms of reaction of wood density response to climate.
Since trees face more and more new biotic stresses and while their potential to adapt rapidly is questioned, studies about invasive forest insects will be reinforced in FORESTIA. To assess the invasion likelihood of forest pests and their pathways, the LIA will contribute to (i) model the invasion risk in the frame of pest management, and (ii) study the genetic diversity and structure of exotic pests based on molecular markers.
Molecular tracing of forest pests will contribute to identify target pests and trace the invasion routes in northern and southern hemisphere forests. Characterization of the genetic diversity and population structure will permit to detect as well multiple introductions of different lineages, host shifts or host preferences in the introduced ranges, as adaptive trait in invasive populations. The insect invasion risk model developed for Europe will be the baseline to derive a similar model for Argentina and will illustrate how it can be applied to any part of the world.
Impact (tree breeding and forest management, wood quality)
By defining adaptive traits, identifying the functional processes associated, estimating the corresponding environmental and genetic variation and determinism, by providing detailed results about the effect of major stressors, FORESTIA will deliver relevant information to be used by tree breeding program and forest management. Furthermore, FORESTIA will contribute to the development and the improvement of tree breeding methods, in particular in the context of genomic selection.
The LIA will directly collect information about wood basic properties. This information can and will be used to study the impact of the observed variation and mechanisms on wood production and wood quality.