Etienne Laliberté

• PhD
• Professor (Associate) at Université de Montréal

1. The classical model of long‐term ecosystem development suggests that primary productivity is limited by nitrogen (N) on young substrates and phosphorus (P) on older substrates. Measurements of foliar and soil nutrients along soil chronosequences support this model, but direct tests through nutrient‐addition experiments are rare. 2. We conducted...

Some of the most species-rich plant communities occur on ancient, strongly weathered soils, whereas those on recently developed soils tend to be less diverse. Mechanisms underlying this well-known pattern, however, remain unresolved. Here, we present a conceptual model describing alternative mechanisms by which pedogenesis (the process of soil form...

There is much concern that the functioning of ecosystems will be affected by human-induced changes in biodiversity, of which land-use change is the most important driver. However, changes in biodiversity may be only one of many pathways through which land use alters ecosystem functioning, and its importance relative to other pathways remains unclea...

A new framework for measuring functional diversity (FD) from multiple traits has recently been proposed. This framework was mostly limited to quantitative traits without missing values and to situations in which there are more species than traits, although the authors had suggested a way to extend their framework to other trait types. The main purp...

Ecosystem resilience depends on functional redundancy (the number of species contributing similarly to an ecosystem function) and response diversity (how functionally similar species respond differently to disturbance). Here, we explore how land-use change impacts these attributes in plant communities, using data from 18 land-use intensity gradient...

Information on trees at the individual level is crucial for monitoring forest ecosystems and planning forest management. Current monitoring methods involve ground measurements, requiring extensive cost, time and labor. Advances in drone remote sensing and computer vision offer great potential for mapping individual trees from aerial imagery at broa...

Insect and pathogen outbreaks have a major impact on northern forest ecosystems. Even for pathogens that have been present in a region for decades, such as beech bark disease (BBD), new waves of tree mortality are expected. Hence, there is a need for innovative approaches to monitor disease advancement in real time. Here, we test whether airborne h...

The large-scale mapping of plant biophysical and biochemical traits is essential for ecological and environmental applications. Given its finer spectral resolution and unprecedented data availability, hyperspectral data has emerged as a promising, non-destructive tool for accurately retrieving these traits. Machine and particularly deep learning mo...

The potential of tree planting as a natural climate solution is often undermined by inadequate monitoring of tree planting projects. Current monitoring methods involve measuring trees by hand for each species, requiring extensive cost, time, and labour. Advances in drone remote sensing and computer vision offer great potential for mapping and chara...

Forests play a crucial role in the Earth’s system processes and provide a suite of social and economic ecosystem services, but are significantly impacted by human activities, leading to a pronounced disruption of the equilibrium within ecosystems. Advancing forest monitoring worldwide offers advantages in mitigating human impacts and enhancing our...

Foliar functional traits are key drivers of ecological processes in forests. Despite progress in forest foliar trait mapping from imaging spectroscopy, there is a need to build environment-specific, spectra-trait models trained from tree-level measurements to improve the accuracy of local trait maps. We mapped 12 foliar functional traits in a mixed...

Background & aims Mycorrhizal fungi are well known to enhance nutrient acquisition through hyphal foraging beyond the root depletion zone. However, plant species vary widely in the degree to which they rely on mycorrhizal fungi for nutrient acquisition. Species which rely more on mycorrhizal colonization are expected to perform poorly in soils with...

Insect and pathogen outbreaks have a major impact on northern forest ecosystems. Even for pathogens that have been present in a region for decades, such as beech bark disease (BBD), new waves of mortality are expected in host populations. Hence, there is a need for innovative approaches to monitor their advancement extensively in real-time. Here we...

Background & aims Tree seedling establishment in herbaceous plant communities can be influenced by belowground interactions via both roots and mycorrhizal fungi. The interplay between these mechanisms may shift according to the mycorrhizal guild of the tree, which could lead to morphological adjustments in the seedling root traits, but little is kn...

In collaboration with the International Union for the Conservation of Nature (IUCN) Taskforce on Biodiversity and Protected Areas, countries worldwide are working to develop a new systematic approach to inform the Key Biodiversity Areas (KBAs) initiative. The goal is to map KBAs from the national to global scales with a baseline international stand...

Background and aims Unravelling how fundamental axes of leaf and fine-root trait variation correlate and relate to nutrient availability is crucial for understanding plant distribution across edaphic gradients. While leaf traits vary consistently along soil nutrient availability gradients, the response of fine-root traits to the same gradients has...

Airborne hyperspectral imaging holds great promise for estimating plant diversity and composition, given its unprecedented combination of aerial coverage, spatial resolution, and spectral detail. Recently, there has been renewed attention toward the spectral variation hypothesis (SVH), which predicts that higher spectral variation is correlated wit...

Imaging spectroscopy is emerging as a leading remote sensing method for quantifying plant biodiversity. The spectral variation hypothesis predicts that variation in plant hyperspectral reflectance is related to variation in taxonomic and functional identity. While most studies report some correlation between spectral and field‐based (i.e., taxonomi...

Premise Spectroscopy is a powerful remote sensing tool for monitoring plant biodiversity over broad geographic areas. Increasing evidence suggests that foliar spectral reflectance can be used to identify trees at the species level. However, most studies have focused on only a limited number of species at a time, and few studies have explored the un...

Soil phosphorus (P) is a growth‐limiting nutrient in tropical ecosystems, driving diverse P‐acquisition strategies among plants. Particularly, mining for inorganic P through phosphomonoesterase (PME) activity is essential, given the substantial proportion of organic P in soils. Yet, the relationship between PME activity and other nutrient‐acquisiti...

Unravelling how fundamental axes of trait variation correlate among leaves and roots and relate to nutrient availability is crucial for understanding plant distribution. While the leaf trait variation axis is linked to nutrient availability gradients, the response of root trait variation to the same gradients yields inconsistent results. We studied...

Soil phosphorus (P) is a growth-limiting nutrient in tropical ecosystems, driving diverse P-acquisition strategies among plants. Particularly, mining for inorganic P through phosphomonoesterase (PME) activity is essential, given the substantial proportion of organic P in soils. Yet the relationship between PME activity and other P-acquisition root...

The advent of new spaceborne imaging spectrometers offers new opportunities for ecologists to map vegetation traits at global scales. However, to date most imaging spectroscopy studies exploiting satellite spectrometers have been constrained to the landscape scale. In this paper we present a new method to map vegetation traits at the landscape scal...

Plant nutrient acquisition strategies range along a spectrum from autonomous foraging to investment in cooperative foraging through mycorrhizal associations. However, in temperate ecosystems, many plant species encounter contrasted levels of symbiont availability in open fields versus closed forests. Little is known about how fungal partner availab...

Leaf spectra are integrated foliar phenotypes that capture a range of traits and can provide insight into ecological processes. Leaf traits, and therefore leaf spectra, may reflect belowground processes such as mycorrhizal associations. However, evidence for the relationship between leaf traits and mycorrhizal association is mixed, and few studies...

Plant ecologists use functional traits to describe how plants respond to and influence their environment. Reflectance spectroscopy can provide rapid, non‐destructive estimates of leaf traits, but it remains unclear whether general trait‐spectra models can yield accurate estimates across functional groups and ecosystems. We measured leaf spectra and...

Optical remote sensing permits modeling of variables related to forest biomass, which is a critical determinant of carbon (C) stocks and fluxes. Plant functional characteristics can be captured by (hyper)spectral data, but it remains unclear whether the links between spectral information and C content are driven largely by tree composition, tree di...

More than ever, ecologists seek to employ herbarium collections to estimate plant functional traits from the past and across biomes. However, many trait measurements are destructive, which may preclude their use on valuable specimens. Researchers increasingly use reflectance spectroscopy to estimate traits from fresh or ground leaves, and to delimi...

Plant ecologists use functional traits to describe how plants respond to and influence their environment. Reflectance spectroscopy can provide rapid, non-destructive estimates of leaf traits, but it remains unclear whether general trait-spectra models can yield accurate estimates across functional groups and ecosystems. We measured leaf spectra and...

Monitoring the rapid and extensive changes in plant species distributions occurring worldwide requires large-scale, continuous and repeated biodiversity assessments. Imaging spectrometers are at the core of novel spaceborne sensor fleets designed for this task, but the degree to which they can capture plant species composition and diversity across...

Ectomycorrhizas and arbuscular mycorrhizas, the two most widespread plant–fungal symbioses, are thought to differentially influence tree species diversity, with positive plant–soil feedbacks favouring locally abundant ectomycorrhizal tree species and negative feedbacks promoting species coexistence and diversity in arbuscular mycorrhizal forests. W...

Associations between leaf chemicals and reflectance values using spectroscopy enables the modelling, and prediction of, individual functional traits. Prediction accuracy is generally high when reflectance values are acquired from a single individual or species, however when the spectroscopy field of view is extended to include multiple species, the...

Recent studies demonstrate a strong influence of soil age on long-term silicon (Si) dynamics in terrestrial ecosystems, but how variation in ecosystem water balance and soil parent material impact this trajectory is unknown. We addressed this by studying a 2-million-year dune chronosequence in southwestern Australia characterized by a positive wate...

The Janzen‐Connell (JC) hypothesis predicts that conspecific negative density dependence contributes to the maintenance of plant diversity by lowering the recruitment of locally abundant plant species. The JC hypothesis is a widely evoked explanation for the high species diversity in tropical forests, but remains poorly tested in other species‐rich...

It has been proposed that ectomycorrhizal (EcM) fungi slow down decomposition by competing with free-living saprotrophs for organic nutrients and other soil resources (known as the “Gadgil effect”), thereby increasing soil carbon sequestration. As such, this Gadgil effect should depend on soil organic matter age and quality, but this remains unstud...

Development of soil microbial communities is driven by local abiotic and biotic conditions, yet our current understanding of their ecology is limited to studies in modified or young and relatively fertile ecosystems. In nutrient-impoverished soils, microbial communities may be predominantly structured by availability of key elements such as phospho...

In temperate and boreal forests, competition for soil resources between free-living saprotrophs and ectomycorrhizal (EcM) fungi has been suggested to restrict saprotrophic fungal dominance to the most superficial organic soil horizons in forests dominated by EcM trees. By contrast, lower niche overlap with arbuscular mycorrhizal (AM) fungi could al...

Silicon (Si) is widely recognized as an important regulator of the global carbon (C) cycle via its effect on diatom productivity in oceans and the weathering of silicate minerals on continents. Si is also a beneficial plant nutrient, improving resistance to herbivory and pathogens and mitigating the negative effects of several abiotic stresses, inc...

The resource availability hypothesis predicts that plants adapted to infertile soils have high levels of anti‐herbivore leaf defences. This hypothesis has been mostly explored for secondary metabolites such as phenolics, whereas it remains underexplored for silica‐based defences. We determined leaf concentrations of total phenols and silicon (Si) i...

It has been proposed that ectomycorrhizal (EcM) fungi slow down decomposition by competing with free-living saprotrophs for organic nutrients and other soil resources (known as the "Gadgil effect"), thereby increasing soil carbon sequestration. As such, this Gadgil effect should depend on soil organic matter age and quality, but this remains unstud...

Ectomycorrhizas and arbuscular mycorrhizas, the two most widespread plant-fungal symbioses, are thought to differentially influence tree species diversity, with positive plant-soil feedbacks favoring locally abundant ectomycorrhizal tree species and negative feedbacks promoting species coexistence and diversity in arbuscular mycorrhizal forests. Wh...

We introduce the AusTraits database - a compilation of measurements of plant traits for taxa in the Australian flora (hereafter AusTraits). AusTraits synthesises data on 375 traits across 29230 taxa from field campaigns, published literature, taxonomic monographs, and individual taxa descriptions. Traits vary in scope from physiological measures of...

Silicon (Si) in plants confers a number of benefits, including resistance to herbivores and water or nutrient stress. However, the dynamics of Si during long-term ecosystem development remain poorly documented, especially the changes in soils in terms of plant availability. We studied a 2-million-year soil chronosequence to examine how long-term ch...

Terrestrial biogeochemistry of silicon Silicon is an important element in plant tissues and contributes to structural defenses against herbivores and other stresses. However, the terrestrial biogeochemical cycling of silicon is poorly understood, particularly the relative importance of geochemical and biological mechanisms in its regulation. de Tom...

Bogs, as nutrient-poor ecosystems, are particularly sensitive to atmospheric nitrogen (N) deposition. Nitrogen deposition alters bog plant community composition and can limit their ability to sequester carbon (C). Spectroscopy is a promising approach for studying how N deposition affects bogs because of its ability to remotely determine changes in...

Imaging spectroscopy is currently the best approach for continuously mapping forest canopy traits, which is important for ecosystem and biodiversity assessments. Ideally, models are trained with trait data from fully sunlit leaves from the top of the canopy. However, sampling leaves at the top of the canopy is often difficult, and sunlit foliage fr...

Soil phosphorus (P) availability in lowland tropical rainforests influences the distribution and growth of tropical tree species. Determining the P‐acquisition strategies of tropical tree species could therefore yield insight into patterns of tree β‐diversity across edaphic gradients. In particular, the synthesis of root phosphatases is likely to b...

The rapid increase of low-cost consumer-grade to enterprise-level unmanned aerial systems (UASs) has resulted in the exponential use of these systems in many applications. Structure from motion with multiview stereo (SfM-MVS) photogrammetry is now the baseline for the development of orthoimages and 3D surfaces (e.g., digital elevation models). The...

Soils on the Lower Pleistocene Bassendean sands of the Swan Coastal Plain of Western Australia are among the most infertile in the world, but support plant communities of remarkable diversity. Following detailed studies of soil chronosequences in the Perth region, the current Bassendean reference soil near Yalgorup National Park appears to be on a...

Climate warming is expected to cause the poleward and upward elevational expansion of temperate plant species, but non‐climatic factors such as soils could constrain this range expansion. However, the extent to which edaphic constraints on range expansion have an abiotic (e.g. soil chemistry) or biotic (e.g. micro‐organisms) origin remains undeterm...

Plant spectral diversity – how plants differentially interact with solar radiation – is an integrator of plant chemical, structural, and taxonomic diversity that can be remotely sensed. We propose to measure spectral diversity as spectral variance, which allows the partitioning of the spectral diversity of a region, called spectral gamma (γ) divers...

Plant spectral diversity - how plants differentially interact with solar radiation - is a powerful integrator of plant functional and phylogenetic diversity that can be remotely sensed. We propose to measure spectral diversity as spectral variance, which allows the partitioning of the spectral diversity of a region, called spectral gamma γ diversit...

Here we describe the standardised protocol used by the Canadian Airborne Biodiversity Observatory (CABO) to measure chlorophylls and carotenoids in leaf samples, using a plate reader.

Silicon (Si) in plants confers a number of ecophysiological benefits, including resistance to herbivory, diseases, water stress and nutrient imbalances. However, the processes controlling Si availability to plants remain poorly understood. In this regard, numerous studies assume that phytogenic amorphous silicates (phytoliths) replenish Si in soil...

Here we describe the standardized protocol used by the Canadian Airborne Biodiversity Observatory (CABO) to measure carbon fractions in leaf samples, using the ANKOM2000 Fiber Analyzer. Prior to the analysis, leaf samples are oven-dried, and then ground with a cyclone mill (2-mm screen). Then, carbon fractions are measured using a sequential digest...

Long‐term ecosystem development involves changes in plant community composition and diversity associated with pedogenesis and nutrient availability, but comparable changes in soil microbial communities remain poorly understood. In particular, it is unclear whether the diversity of plants and microbes respond to similar abiotic drivers, or become de...

The vast majority of terrestrial plants form root symbioses with arbuscular mycorrhizal (AM) fungi to enhance nutrient (particularly phosphorus, P) acquisition. However, some plant species also form dual symbioses involving ectomycorrhizal (ECM) fungi, with a subset of those also forming triple symbioses also involving dinitrogen (N2)‐fixing bacter...

Long-term soil age gradients are useful model systems to study how changes in nutrient limitation shape communities of plant root mutualists because they represent strong natural gradients of nutrient availability, particularly of nitrogen (N) and phosphorus (P). Here, we investigated changes in the dinitrogen (N2)-fixing bacterial community compos...

Here we describe the standardised protocol used by the Canadian Airborne Biodiversity Observatory (CABO) to measure CN content in leaf samples, using the Elementar Vario MICRO Cube.

Feedback between plants and soil is an important driver of plant community structure, but it remains unclear whether plant–soil feedback (PSF): (i) reflects changes in biotic or abiotic properties, (ii) depends on environmental context in terms of soil nutrient availability, and (iii) varies among plant functional groups. As soil nutrient availabil...

Background Mycorrhizal strategies are very effective in enhancing plant acquisition of poorly-mobile nutrients, particularly phosphorus (P) from infertile soil. However, on very old and severely P-impoverished soils, a carboxylate-releasing and P-mobilising cluster-root strategy is more effective at acquiring this growth-limiting resource. Carboxyl...

Background and aimsWe sought to describe the species and functional composition of Brazilian campos rupestres plant communities on severely nutrient-impoverished white sands, to test hypotheses relating plant communities and physiological adaptations to infertile soils. Based on recently-published information on a south-western Australian dune chro...

During long-term ecosystem development and its associated decline in soil phosphorus (P) availability, the abundance of mycorrhizal plant species declines at the expense of non-mycorrhizal species with root specialisations for P-acquisition, such as massive exudation of carboxylates. Leaf manganese (Mn) concentration has been suggested as a proxy f...

Questions How do plant functional trait abundance and diversity in urban remnants of a rapidly urbanizing city change with fragmentation? Is there a delayed functional response to fragmentation? Location Thirty remnant Banksia woodlands, Perth, Australia. Methods We used GLMM to examine the effects of remnant age and area, and their interaction,...

To examine how climate affects soil development and nutrient availability over long timescales, we studied a series of four long‐term chronosequences along a climate gradient in southwestern Australia. Annual rainfall ranged from 533 to 1185 mm (water balance from −900 to +52 mm) and each chronosequence included Holocene (≤ 6.5 ka), Middle Pleistoc...

Changes in soil fertility during pedogenesis affect the quantity and quality of resources entering the belowground subsystem. Climate governs pedogenesis, yet how climate modulates responses of soil food webs to soil ageing remains unexplored because of the paucity of appropriate model systems. We characterised soil food webs along each of four ret...

To examine how climate affects soil development and nutrient availability over long timescales, we studied a series of four long-term chronosequences along a climate gradient in southwestern Australia. Annual rainfall ranged from 533 mm to 1185 mm (water balance from –900 mm to +52 mm) and each chronosequence included Holocene (≤6.5 ka), Middle Ple...

The abundance of nitrogen (N)‐fixing plants in ecosystems where phosphorus (P) limits plant productivity poses a paradox because N fixation entails a high P cost. One explanation for this paradox is that the N‐fixing strategy allows greater root phosphatase activity to enhance P acquisition from organic sources, but evidence to support this content...

Soil biota and plant diversity Soil biota, including symbionts such as mycorrhizal fungi and nitrogen-fixing bacteria, as well as fungal and bacterial pathogens, affect terrestrial plant diversity and growth patterns (see the Perspective by van der Putten). Teste et al. monitored growth and survival in Australian shrubland plant species paired with...

Summary' I. 'The promise of trait-based plant ecology' II. 'Redefining fine roots' III. 'Quantifying trait dimensionality' IV. 'Integrating mycorrhizas' V. 'Broadening the suite of below-ground traits' VI. 'Determining trait–environment linkages' VII. 'Understanding ecosystem-level consequences' VIII. 'Conclusions' 'Acknowledgements' References Tra...

Ectomycorrhizal (ECM) fungal communities co-vary with host plant communities along soil fertility gradients, yet it is unclear whether this reflects changes in host composition, fungal edaphic specialisation, or priority effects during fungal community establishment. We grew two co-occurring ECM plant species (to control for host identity) in soils...

Complex interactions existing between plants and soil microorganisms drive key ecosystem and community properties such as productivity and diversity. In nutrient-poor systems such as sand dunes, plant traits and fungal symbioses related to nutrient-acquisition can strongly influence vegetation dynamics. We investigated plant and fungal communities...

Soilborne pathogens can contribute to the maintenance of local plant diversity by reducing differences in competitive ability between co‐occurring plant species. It has been hypothesized that efficient phosphorus (P) acquisition by plants in P‐impoverished ecosystems might trade off against resistance to root pathogens. This could help explain high...

Long‐term soil chronosequences provide natural soil fertility gradients that can be used to explore linkages between soils and plant community composition and diversity. Well‐studied forested soil chronosequences have revealed that local (α) plant diversity increases with greater soil age and declining fertility, but corresponding changes in specie...

The promise of “trait-based” plant ecology is one of generalized prediction across organizational and spatial scales, independent of taxonomy. This promise is a major reason for the increased popularity of this approach. Here, we argue that some important foundational assumptions of trait-based ecology have not received sufficient empirical evaluat...

Table S1. Comparison of mycorrhizal root colonization between fresh and rehydrated roots. Values shown as mean ± SE based on paired t‐test

Table S3. Data file used in this study with plant biomass, N and P concentration, AM and ECM root colonization, and nodule biomass.

Table S2. Summary of statistical outputs. Values shown are degrees of freedom (DF), F‐test and p‐value of individual mixed‐effect models of two factors (Stage and Species), and their interaction for each variable.

Changes in soil nutrient availability during long-term ecosystem development influence the relative abundances of plant species with different nutrient-acquisition strategies. These changes in strategies are observed at the community level, but whether they also occur within individual species remains unknown. Plant species forming multiple root sy...

Table S1. List of EM fungal OTUs detected in roots or bulk soil of the four host species. Table S2. Mean and standard error of number of reads, richness and coverage of EM fungal OTUs with ANOVA testing. Table S3. Total relative abundance of the different EM fungal families encountered in roots and bulk soil samples in terms of number of OTUs and...