Biology subjects

Messier, C.

Publications and source records attributed to Messier, C..

9 recordsLinked to original sources

bioRxiv2026

A crown story: How tree architecture drives maple syrup yields

Maple syrup production is strongly influenced by spring weather conditions, particularly the frequency and intensity of freeze-thaw cycles. However, marked individual differences in sap and sugar yields persist among trees growing under similar stand conditions, indicating additional tree-level sources of variation. This study aimed to explain inter-individual variability in maple yields in commercial high-vacuum syrup production using structural, morphological, and growth characteristics. We used terrestrial light detection and ranging to derive variables describing crown, stem, and whole-tree size, biomass, and structure in 38 mature sugar maples. We related these variables to individual yields, including sap volume, sugar content, and syrup production. Our models explained substantial inter-individual variability: 52% in sap sugar content, 44% in sap volume, and 47% in syrup production. Laterally expanded crowns were associated with higher sap sugar content, as were lower growth rates in the first 25 mm of wood. Sap volume was highest in large, heavily branched trees with crowns extending vertically along the stem. Projected crown surface area was the strongest predictor of syrup yield, with an estimated increase of 250 mL per 5.6 m2. These findings highlight the importance of multidimensional crown development in maximizing individual yields in maple syrup production.

ecology↗

bioRxiv2025

Intraspecific variability rivals interspecific differences in root traits of temperate tree seedlings

AbstractGlobal change and associated disturbances are increasing the risk of regeneration failure for tree species in temperate forests. Seedlings are particularly vulnerable to water stress due to their shallow root systems, making belowground plasticity a potentially key component of species adaptive capacity. Quantifying root trait variability and its drivers can improve our understanding of regeneration success under increasingly warm and dry conditions. We quantified between species variation (BTV) and intraspecific variation (ITV) in seven root traits linked to water uptake--root-to-shoot ratio, maximum rooting depth, proportion of absorptive roots, specific root length, root tissue density, average absorptive root diameter, and root branching density--for seedlings of seven common, co-occurring tree species in forests of northeastern North America. We sampled seedlings under contrasting climate and light conditions, and assessed the influence of abiotic (climate, light conditions, soil properties) and biotic drivers (neighboring vegetation) as well as seedling characteristics (species identity, age, spermatophyte type) on root ITV at local and regional scales. Species differed significantly for some traits but differed even more strongly in multivariate trait syndromes, suggesting distinct belowground strategies. ITV was substantial but trait-dependent, with maximum rooting depth and root to shoot ratio being the most variable (coefficient of variation > 45%) and branching density the least variable. BTV was the primary driver of overall trait variation for three traits, explaining more than 60% of variation, whereas within-plot ITV accounted for more than 50% of variation in the remaining four traits. Local drivers did not outweigh regional factors, and the overall explanatory power of measured drivers was limited, suggesting that fine-scale heterogeneity, not captured in our study, may strongly influence root ITV. High ITV in most traits suggests substantial plasticity in roots, which may contribute to the adaptive capacity of seedlings facing climate change. Integrating this plasticity into mechanistic models is critical for predicting regeneration dynamics or root-mediated ecosystem processes. We propose a set of guidelines for integrating root traits into comparative studies and models based on trait measurability and extent of ITV. We further highlight the need to account for the scale- and gradient-intensity dependence of ITV-environment relationships.

ecology↗

bioRxiv2024

Self-pruning in tree crowns is influenced by functional strategies and neighborhood interactions

As canopy closure causes forest stands to face increasing light limitation, trees lower branches begin to die back. This process, called self-pruning, defines a crowns base and depth and shapes the structure of entire stands. Self-pruning is often thought to occur after shading causes individual branches to transition from net carbon sources to sinks. Under this explanation, we would expect resource-conservative and shade-tolerant species to initiate self-pruning under deeper shade because their branches need less light to maintain a positive carbon balance. However, the notion that branches are fully autonomous may be complicated by correlative inhibition, in which plants preferentially allocate resources towards sunlit branches. Consistent with this idea, we predicted that within species, trees with sunlit tops would initiate self-pruning at a higher light threshold. Lastly, we predicted that plot-level diversity in self-pruning strategies would correlate with productivity and total crown volume. We tested these predictions in an experiment where 12 temperate tree species were planted in plots of varying diversity and composition. We measured characteristics of crown size and position as well as the light level at the crown base (denoted Lbase), which we took as an estimate of the light threshold of self-pruning. As we predicted, more shade-tolerant and resource-conservative species self-pruned at a deeper level of shade (lower Lbase). In addition, most species had higher Lbase when they had more light at the crown top, suggestive of correlative inhibition. With respect to their neighbors traits, though, conservative and acquisitive species showed contrary patterns of plasticity: conservative species had lower Lbase around conservative neighbors, while acquisitive species had lower Lbase around acquisitive neighbors. However, all species declined in crown depth when they grew alongside larger, more acquisitive neighbors. As predicted, plots with a greater interspecific diversity of Lbase had greater basal area and crown volume. Using simulations, we showed that plasticity in crown depth between monocultures and mixtures strengthened the relationship with crown volume, primarily due to competitive release experienced by acquisitive species. By placing shade-induced self-pruning in a comparative context, we clarify how forest function emerges from competition for light between individual trees.

ecology↗

bioRxiv2024

Orthosteric STING inhibition elucidates molecular correction of SAVI STING

STING is broadly implicated in diseases ranging from cancer, autoimmune disease, neurodegeneration to rare, monogenic diseases.1 Early drug discovery campaigns focused on STING activation as a promising platform for cancer immunotherapy yet failed in multiple clinical trials due to lack of efficacy thus far.2 Current research and development activities concentrate on STING inhibition for treating autoimmune disease and neuroinflammation. While the progression of STING activators into the clinic has been successful, the discovery and clinical progression of STING inhibitors remain elusive. Questions persist about the molecular properties needed to distinguish between a STING activator and inhibitor, particularly within SAVI disease, a monogenic autoinflammatory disease that renders STING constitutively active.3 Here we leverage an orthosteric STING activator and inhibitor from the same chemical series to discover that STING M271 is a critical residue for molecular activation. The M271CH3 NMR chemical shifts reveal a unique molecular signature for pharmacological or genetically driven activation and inhibition that is not captured by x-ray crystallography. Additionally, M271 directly interacts with the most common SAVI mutation, V155M, and using an orthosteric STING inhibitor, we show partial rescue and molecular correction of STING V155M. Finally, these data present insights into therapeutic STING molecular correction for treating SAVI patients. Our results elucidate an unappreciated structural interaction critical for STING modulation that could be utilized as a molecular diagnostic tool for drug discovery. Furthermore, we demonstrate for the first time how the therapeutic requirements of a molecular corrector differ from an orthosteric STING inhibitor, and why this is important for the SAVI disease population.

molecular biology↗

bioRxiv2023

Resident memory T cell precursors in tumor draining lymph nodes require type-1 IFN for optimal differentiation

Resident memory (Trm) cells play an essential role in anti-tumor immunity. However, little is known about the precursors that differentiate into protective Trm populations against cancer. Here we employed an established model of B16 melanoma neoadjuvant anti-CD4 therapy, to track tumor antigen-specific CD8+ T cells through tissues and across time; from their priming as effectors to their differentiation into Trm. We show that tumor-draining lymph nodes (TDLNs) contain Teff cells that begin to express canonical Trm markers CD103 and CD69. These tumor-specific Teff cells seeded skin and tumor during the effector phase of the response, although egress from these tissues was not required Trm development in LNs. Paired scRNAseq/scTCRseq was used to identify Teff clonotypes in TDLNs and trace their differentiation, in real-time, into Trm populations. We found that expanded clonotypes favored the Trm fate and were unlikely to co-differentiate into other lineages. Precursors of Trm (pre-Trm) clonotypes that subsequently seeded populations throughout tumors, LNs, and skin, were characterized by early expression of tissue residency, stemness, and type-1 IFN sensing genes. These multipotent pre-Trm cells sensed plasmacytoid dendritic cell-derived type-1 interferons in TDLNs, and their expression of interferon alpha receptor was required for their formation of Trm populations in LNs but not in skin. These findings reveal the defining features of pre-Trm cells in response to tumor antigens, and reveal a previously unappreciated role for type-1 IFNs in programming regional Trm immunity to cancer. One Sentence SummaryAnti-tumor effector CD8 T cells adopt early characteristics of tissue residency and stemness, and rely on the sensing of type-1 interferons for their local differentiation into resident memory T cells.

immunology↗

bioRxiv2022

Higher aboveground carbon stocks in mixed-species planted forests than monocultures - a meta-analysis

Natural forest is declining globally as the area of planted forest increases. Planted forests are often monocultures, despite results suggesting that higher species richness improves ecosystem functioning and stability. To test if this is generally the case, we performed a meta-analysis of available results. We assessed aboveground carbon stocks in mixed-species planted forests vs (a) the average of constituent species monocultures, (b) the best constituent species monoculture, and (c) commercial species monocultures. We investigated whether any advantage of mixtures over monocultures was positively related to species richness, as well as potential mechanisms driving differences in carbon stocks between mixtures and monocultures. The meta-analysis dataset included 79 comparisons from 21 sites. Carbon stocks in mixed planted forests were higher than the average of stocks in monocultures of their constituent species, containing on average 70% more carbon. Mixed planted forests also out-performed commercial monocultures, containing on average 77% more carbon. There was c.25% more carbon in mixed planted forests relative to the best performing monocultures, although this difference was not statistically significant. Overyielding was highest in four-species mixtures (richness range 2-6 species). More data providing better coverage of richness and age gradients (study sites aged 3.5-28 years) is needed to increase confidence in these results. None of the potential mechanisms we examined (nitrogen-fixer present vs absent; native vs non-native/mixed origin; tree diversity experiment vs forestry plantation) consistently explained variation in the diversity effects. This suggests that our findings are driven by a combination of small (statistically insignificant) effects from these sources or further unidentified mechanisms or some combination of the two. We conclude that increasing tree species richness in planted forests can increase carbon stocks while bringing other potential benefits associated with diversification. However, implementation will depend on the balance of these benefits relative to the operational challenges and costs of diversification.

ecology↗

bioRxiv2021

Non-structural carbohydrate concentrations in woody organs, but not leaves, of temperate and tropical tree angiosperms are independent of the "fast-slow" plant economic spectrum

Background and AimsCarbohydrate reserves play a vital role in plant survival during periods of negative carbon balance. Considering active storage of reserves, there is a trade-off between carbon allocation to growth and to reserves and defense. A resulting hypothesis is that allocation to reserves exhibits a coordinated variation with functional traits associated with the fast-slow plant economics spectrum. MethodsWe tested the relationship between non-structural carbohydrates (NSC) of tree organs and functional traits using 61 angiosperm tree species from temperate and tropical forests with phylogenetic hierarchical Bayesian models. Key ResultsOur results provide evidence that NSC concentrations in woody organs and plant functional traits are largely decoupled, meaning that species resilience is unrelated to their position on the fast-slow plant economics spectrum. In contrast, we found that variation between NSC concentrations in leaves and the fast-slow continuum was coordinated, as species with higher leaf NSC had traits values associated with resource conservative species such as lower SLA, lower Amax, and high wood density. We did not detect an influence of leaf habit on the variation of NSC concentrations in tree organs. ConclusionsEfforts to predict the response of ecosystems to global change will need to integrate a suite of plant traits, such as NSC concentrations in woody organs, that are independent of the fast-slow spectrum and that capture how species respond to a broad range of global change factors.

plant biology↗

bioRxiv2020

Mutually inclusive mechanisms of drought-induced tree mortality

An extreme summer drought caused unprecedented tree dieback across Central Europe in 2018, highlighting the need for a better mechanistic understanding of drought-induced tree mortality. While numerous physiological risk factors have been identified, the principal mechanisms, hydraulic failure and carbon starvation, are still debated. We studied 9,435 trees from 12 temperate species planted in a diversity experiment in 2013 to assess how hydraulic traits, carbon dynamics, pest infestation, tree height and neighbourhood competition influence individual mortality risk. We observed a reduced mortality risk for trees with wider hydraulic safety margins, while a rising sugar fraction of the non-structural carbohydrate pool and bark beetle infestation were associated with higher risk. Taller trees had a lower mortality risk. The sign and magnitude of neighbourhood effects on mortality risk depended on the species-identity of the involved trees, with most species having beneficial and some having deleterious effects on their neighbours. While severe tissue dehydration causing hydraulic failure precedes drought-induced tree mortality, we show that the probability of this event depends on a series of mutually inclusive processes including pest infestation and starch depletion for osmotic adjustment, and is modulated by the size and species identity of a tree and its neighbours.

ecology↗

bioRxiv2020

Biotic and abiotic drivers of soil microbial functions across tree diversity experiments

AimSoil microorganisms are essential for the functioning of terrestrial ecosystems. Although soil microbial communities and functions may be linked to the tree species composition and diversity of forests, there has been no comprehensive study of how general potential relationships are and if these are context-dependent. A global network of tree diversity experiments (TreeDivNet) allows for a first examination of tree diversity-soil microbial function relationships across environmental gradients. LocationGlobal Major Taxa StudiedSoil microorganisms MethodsSoil samples collected from eleven tree diversity experiments in four biomes across four continents were used to measure soil basal respiration, microbial biomass, and carbon use efficiency using the substrate-induced respiration method. All samples were measured using the same analytical device in the same laboratory to prevent measurement bias. We used linear mixed-effects models to examine the effects of tree species diversity, environmental conditions, and their interactions on soil microbial functions. ResultsAcross biodiversity experiments, abiotic drivers, mainly soil water content, significantly increased soil microbial functions. Potential evapotranspiration (PET) increased, whereas soil C-to-N ratio (CN) decreased soil microbial functions under dry soil conditions, but high soil water content reduced the importance of other abiotic drivers. Tree species richness and phylogenetic diversity had overall similar, but weak and context-dependent (climate, soil abiotic variables) effects on soil microbial respiration. Positive tree diversity effects on soil microbial respiration were most pronounced at low PET, low soil CN, and high tree density. Soil microbial functions increased with the age of the experiment. Main conclusionsOur results point at the importance of soil water content for maintaining high levels of soil microbial functions and modulating effects of other environmental drivers. Moreover, overall tree diversity effects on soil microbial functions seem to be negligible in the short term (experiments were 1-18 years old). However, context-dependent tree diversity effects (climate, soil abiotic variables) have greater importance at high tree density, and significant effects of experimental age call for longer-term studies. Such systematic insights are key to better integrate soil carbon dynamics into the management of afforestation projects across environmental contexts, as todays reforestation efforts remain focused largely on aboveground carbon storage and are still dominated by less diverse forests stands of commercial species.

ecology↗