Marion Carme

Key message: This dataset reports translocation experiments on 15,774 seeds from 43 populations of Abies alba Mill., Acer pseudoplatanus L., Fagus sylvatica L., Quercus petraea (Matt.) Liebl., Quercus pubescens Willd., and Quercus suber L. It informs ecological and evolutionary processes in early tree stages. Dataset access at https://doi.org/10.5281/zenodo.22043408 and metadata accessible at https://metadata-afs.nancy.inra.fr/geonetwork/srv/fre/catalog.search#/metadata/15a31f1d-6658-4264-abed-67b5664b9c12 .

Tree early life stages are particularly sensitive to warming, yet their responses remain poorly understood despite their importance for forest regeneration. Here, we investigated how warming affects early-life traits in two widespread European white oaks: Quercus pubescens and Q. petraea . We conducted a common garden experiment using 17 populations exposed to three temperature regimes. We measured 19 traits encompassing germination, phenology, and functional and fitness-related traits and performed individual trait mixed-effects models based on temperature transfer distance and the climate of the population. We found that population climate was the primary driver of early stages traits responses to warming, with climatic drivers varying strongly among traits and species. Particularly in Q. pubescens , warmer and drier populations showed lower fitness (germination and survival percentages, total biomass) that declined further under warming, consistent with a cost of drought avoidance strategies under continuously wet conditions; in Q. petraea , continental populations outperformed others at low temperature transfer distance but suffered the steepest fitness declines under further warming, suggesting a narrow thermal optimum shaped by cold adaptation. Warming generally advanced germination and leaf emergence, increased leaf pigment concentrations and fine-root allocation, reduced specific leaf area. Extreme warming reduced survival, growth and germination. Nevertheless, moderate warming (+0 to +5 degrees Celsius) was rarely detrimental and sometimes beneficial. Our results demonstrate that population climatic origin is a key determinant of regeneration responses to warming, highlighting the need to consider within-species adaptive variation to understand forest regeneration potential under climate change.

The early life stages of trees, particularly germination, are crucial to fitness and highly sensitive to climate. The influence of temperature on recalcitrant seed germination has rarely been studied due to their desiccation sensitivity, which hampers storage. However, Mediterranean recalcitrant oaks would be particularly affected by the expected increased temperature in this region. Here we investigated the effect of warming temperatures on germination of 975 acorns from 8 range-wide Quercus suber populations. We sowed the acorns at 15, 20 and 25 °C in climatic chambers, and monitored germination during 4 months. The germination dynamics in each chamber was explored by a Cox proportional hazards model. We assessed environment (germination experiment temperatures), population (climate of seed origin) and their interaction effects on germination percentage, time, and synchrony using generalized linear mixed-effects models. Genetic clines on germination percentage, time and synchrony were mostly triggered by temperature, with seeds from warmer origins showing higher germination, earlier timing, and greater synchrony than colder ones. Higher sowing temperatures promoted advanced germination, and this effect was higher in seeds originating from regions with stronger seasonality. Earlier and synchronous germination found in seeds from warm origin may reduce the desiccation probability for acorns and seedlings, while late germination and low synchrony found in seeds from cold origin might be an adaptive response to unpredictable frost events that would impair seedling survival. The germination synchrony adaptive response was unexpected and further investigation on recalcitrant seeds’ germination dynamics in response to increased temperatures is needed to confirm it.

Forestry industry requires high-quantity and quality seeds for afforestation and assisted migration programs. Finding reliable non-destructive methods to characterize seeds would significantly enhance efforts to identify climate-adapted populations. This study presents near-infrared (NIR) spectroscopy models to classify seed origin and predict germination characteristics at different temperatures non-destructively. We focus on Abies alba Mill., a key European forest tree with genetic variation along climatic gradients and seeds with shallow physiological dormancy. Seeds from six populations were analyzed using NIR spectroscopy, and germination was tested at 15°C, 20°C, and 25°C after stratification treatments at 4°C (0 or 3 weeks). Population classification accuracy using Partial Least Squares Discriminant Analysis was 69%, with significant NIR peaks at 1712, 1929, and 2111 nm, linked to moisture content and storage compounds. NIR spectra explained 51% and 65% of the variation in germination probability and timing using Partial Least Squares Regression, with significant peaks at 1712, 1929, 2111, 1632, and 2073 nm. General Linear Mixed-Effects Models showed that a NIR predictor contributed to 39% of the germination probability variance explained by fixed-effects, and the stratification treatment was the most important driver explaining germination time. Our results proved the utility of NIR-based tools to effectively classify bulked seeds and predict germination, opening new perspectives to nursery and forestry sectors and populations’ adaptation and adjustments to warming climate. This study will facilitate further investigations on the physiological processes that occur during dormancy, a critical process for forest regeneration given the expected impact of shorter and warmer winters on seed behavior.

Background and Aims: Assessing intra-specific trait covariation across populations is essential to understand species’ adaptive responses to climatic variation. However, in tree species this is understudied for early-life stages despite their greater vulnerability to environmental changes, and climatic adaptations can differ between tree ages. In this paper we study the integrated phenotype of Quercus suber during the months following germination. For this purpose we assessed the covariation of key traits involved in seedlings’ water and C economies along a gradient of aridity at seed origin. Methods: We performed a provenance trial with 157 Q. suber seedlings originating from seven different populations across the species distribution. The seedlings were germinated and grown for 4 months under common conditions. Acorn mass along with 11 above- and below-ground traits involved in water and carbon use were measured. They were organized into latent variables and their covariation with increasing aridity and temperatures was analysed using structural equation modelling. Individual traits were also analysed with linear mixed-effects models to account for maternal effects. Key Results: Seedlings from arid populations displayed a higher leaf evaporative surface coupled with greater root development. They also showed greater stomatal size and chlorophyll content, strongly linked to traits conferring drought and heat tolerance (low root–shoot ratio and high flavonoids). The development of above- and below-ground tissues responded mainly to acorn mass, whereas leaf physiology variations were associated with the populations’ climate. Conclusions: Surprisingly, dry-origin seedlings display a more acquisitive strategy at the whole-plant level compared with seedlings from mesic provenances. This allows greater water and carbon uptake capacities following germination, which is critical for their survival during their first summer. Leaf physiology adjustments to populations’ climate contrasts with observations by other studies addressing juvenile trees, highlighting the use by Q. suber of varying adaptive strategies at different ontogenic stages.

Background and Aims: Assessing intra-specific trait covariation across populations is essential to understand species’ adaptive responses to climatic variation. However, in tree species, this is understudied for early-life stages despite they are more vulnerable to environmental changes and that climatic adaptations can differ between tree ages. In this paper, we studied the integrated phenotype of Quercus suber during the months following germination. For that, we studied the covariation of key traits involved in seedlings’ water and C economies along a gradient of aridity at seed origin. Methods: We performed a provenance trial with 157 Q. suber seedlings originating from 7 different populations across the species distribution. The seedlings were germinated and grown during 4 months under common conditions. Acorn mass along with 11 above- and below-ground traits involved in water and C use were measured. Their covariation in response to aridity at seed origin was analyzed using structural equation modelling (SEM). The variation of individual traits to increasing aridity and the mediation of acorn mass was also tested. Key Results: Seedlings from arid populations displayed higher leaf evaporative demand coupled with a greater root water uptake capacity. Their leaf physiology also depicted a greater C acquisition capacity, strongly linked to traits conferring drought and heat tolerance. The development of above- and below-ground tissues responded mainly to acorn mass, whereas leaf physiology variations were associated to populations’ aridity. Conclusions: Dry-origin seedlings display a more acquisitive strategy at the whole-plant level compared with seedlings from mesic provenances. This allows a greater water and carbon uptake capacities following germination, which is critical for their survival during their first summer. Leaf physiology adjustments to populations’ climate contrasts with its plasticity observed by other studies addressing juvenile trees, highlighting Q. suber varying adaptive strategies at different life stages.

Remote sensing satellites allow large-scale and fast detections of forest loss. Operational forest loss detection systems have been mainly developed over tropical forests, however, it is increasingly important to have access to accurate and up-to-date information on temperate forests. In this study, we adapted a Sentinel-1 based near real-time tropical forest loss detection method, based on the radar change ratio, to detect French temperate forests clear-cuts. Using ancillary data, annual and sub-monthly clear-cuts were assessed for broadleaf and conifer forests, for various tree species, over public and private forests. Using 967 validation plots, the maps exhibited recall and precision of 80.9% and 99.4% respectively. The clear-cuts area shows remarkable stability over time from 2020. We found seven times more clear-cuts in private forests than in public forests, although the surface area of private forests is only three times that of public forests. It was also demonstrated that only 1.6% out of 4,530 dieback reference plots, and 6.2% of maps of forest bark beetle attacks, were confused with clear-cuts before clear-cuts actually occurred, which makes our maps complementary with forest dieback maps. Collectively, the findings of this study could have significant implications for the implementation of a radar-satellite-based system designed for the real-time detection of large-scale clear-cuts in European temperate forests. The data are available via https://ee-sufosatclearcuts.projects.earthengine.app/view/sufosat-clearcuts.