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SUMMARY The lenticel is a channel‐like structure that facilitates oxygen, carbon dioxide, and water vapor exchange on secondary growth tissue, such as a tree stem. Although the structure of lenticel has been described, there is limited understanding regarding the impact of this secondary structure on secondary growth as well as the cellular and metabolic processes underlying its formation. The study reveals the essential role of the lenticel in the process of tree secondary growth and the cellular and metabolic processes that take place during its formation. Under the stomata, lenticel development occurs when cells divide and differentiate into a structure of disconnected cells with air spaces between them. During lenticel formation, specific metabolic pathways and wax biosynthesis are activated. The SERK (somatic embryogenesis receptor kinase) gene controls lenticel density, and serk1serk3serk5 triple mutants enhance lenticel initiation. The findings shed light on the cellular and metabolic processes involved in lenticel formation, laying the groundwork for further mechanistic elucidation of their development, function, and genetic regulation in trees. [ABSTRACT FROM AUTHOR]

Functional traits offer insights into plant performance. However, linking traits to individual tree performance requires considering the overall phenotypic context and utilizing traits measured at the individual level. Tree growth rates are informative metrics about performance, however how it is measured provides different information on tree or community growth dynamics and structure and can alter the relationships or their strength with functional traits and individual phenotypes. Moreover, at the community level, trees can adjust their crown shapes and sizes to optimize canopy space utilization, and a high level of canopy packing can enhance the individual to community-level growth rate. In this study, we assessed the crown area of 1144 individual trees, a simple trait measured at the individual level, and the leaf mass per area (LMA), a common functional trait, to test trait-growth relationships, considering absolute and relative growth rate. The observed total photosynthetic mass (integrating crown area and LMA) positively explained absolute tree growth rates, interacting with tree height. As higher the trees, more intense was the effect. Importantly, this effect was not solely based on LMA or crown size. This implies that LMA's predictive power could improve by integrating leaf-level traits with whole-plant allocation to leaf area. These variables, however, failed to predict the tree's relative growth rates. Additionally, our study found that increased canopy packing levels raised the community-level growth rate within our plots. This overall community growth seems be facilitated by denser tree arrangements and efficient light interception in the forest due to the higher canopy packing level. We highlight the importance of considering crown area as a critical variable to be measured during floristic inventories and in studies focused on tree performance. [ABSTRACT FROM AUTHOR]

Scale-free networks are prevalently observed in a great variety of complex systems, which triggers various researches relevant to networked models of such type. In this work, we propose a family of growth tree networks \(\mathcal{T}_{t}\) , which turn out to be scale-free, in an iterative manner. As opposed to most of published tree models with scale-free feature, our tree networks have the power-law exponent \(\gamma=1{ + }\ln 5/\ln 2\) that is obviously larger than \(3\). At the same time, "small-world" property can not be found particularly because models \(\mathcal{T}_{t}\) have an ultra-large diameter \(D_{t}\) (i.e., \(D_{t}\sim|\mathcal{T}_{t}|^{\ln 3/\ln 5}\)) and a greater average shortest path length \(\langle\mathcal{W}_{t}\rangle\) (namely, \(\langle\mathcal{W}_{t}\rangle\sim|\mathcal{T}_{t}|^{\ln 3/\ln 5}\)) where \(|\mathcal{T}_{t}|\) represents vertex number. Next, we determine Pearson correlation coefficient and verify that networks \(\mathcal{T}_{t}\) display disassortative mixing structure. In addition, we study random walks on tree networks \(\mathcal{T}_{t}\) and derive exact solution to mean hitting time \(\langle\mathcal{H}_{t}\rangle\). The results suggest that the analytic formula for quantity \(\langle\mathcal{H}_{t}\rangle\) as a function of vertex number \(|\mathcal{T}_{t}|\) shows a power-law form, i.e., \(\langle\mathcal{H}_{t}\rangle\sim|\mathcal{T}_{t}|^{1+\ln 3/\ln 5}\). Accordingly, we execute extensive experimental simulations, and demonstrate that empirical analysis is in strong agreement with theoretical results. Lastly, we provide a guide to extend the proposed iterative manner in order to generate more general scale-free tree networks with large diameter. [ABSTRACT FROM AUTHOR]

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The sensitivity of tree growth to precipitation regulates their responses to drought, and is a crucial metric for predicting ecosystem dynamics and vulnerability. Sensitivity may be changing with continuing climate change, yet a comprehensive assessment of its change is still lacking. We utilized tree ring measurements from 3,044 sites, climate data and CO2 concentrations obtained from monitoring stations, combined with dynamic global vegetation models to investigate spatiotemporal changes in the sensitivity over the past century. We observed an increasing sensitivity since around 1950. This increased sensitivity was particularly pronounced in arid biomes due to the combined effect of increased precipitation and elevated CO2. While elevated CO2 reduced the sensitivity of the humid regions, the intensified water pressure caused by decreased precipitation still increased the sensitivity. Our findings suggest an escalating vulnerability of tree growth to precipitation change, which may increase the risk of tree mortality under future intensified drought. Plain Language Summary: The sensitivity of tree growth to precipitation strongly regulates global vegetation dynamics and their responses to climate change, yet changes in sensitivity remain poorly understood. Here, we defined a sensitivity of tree radial growth to precipitation, and found that most tree species showed an increased sensitivity in the second half of the 20th century. This increased sensitivity in arid biomes could be attributed to increasing precipitation, while the increased sensitivity in humid biomes was caused by decreasing precipitation. Although elevated atmospheric CO2 have generally increased sensitivity in arid biomes and decreased it in humid biomes, these contrasting influences were ultimately overshadowed by changes in precipitation, resulting in an overall increased sensitivity across both arid and humid biomes. Key Points: The sensitivity of tree growth to precipitation is increasing since around 1950, both at the arid and humid biomesThis increased sensitivity is particularly pronounced in arid biomes due to the combined effect of increased precipitation and elevated CO2Although elevated CO2 reduce the sensitivity in humid biomes, the decreased precipitation still lead to an increased sensitivity [ABSTRACT FROM AUTHOR]

Introduction: The Congo Basin forests, a crucial global carbon sink, are expected to face increased challenges of climate change by 2027, with an expected temperature rise of 1.5°C above pre-industrial levels, accompanied by increased humidity conditions. However, studies that try to understand their functioning and untangle the species-specific responses about how weather conditions impact secondary growth dynamics are still rare. Methods: Here we present the results of a study on diel and annual stem growth in 17 trees, belonging to 11 most abundant species, both canopy and understory, in the Mayombe forest (Congo Basin) in the Democratic Republic of the Congo (DRC). We measured highly-resolved radial stem size variations and weather conditions, to comprehend the ongoing patterns of secondary growth and examine the potential influence of projected weather conditions on them. Results: We found that at the diel scale, trees probably grow mainly from 6pm to 9am, and that at the annual scale, they grow mainly during the rainy season, from October to May. Some trees grow year-round, while others stop growing for a period ranging from 1 to 4 months. This growth cessation typically occurs during the dry season from June to September. A generalized linear mixed-effect model revealed that annual radial stem growth is positively related to rainfall. Discussion: Our results suggest that trees in the study site have a significant potential to cope with the projected 1.5°C increase in global temperature and an additional 50 mm of local rainfall. Trees of the species T. superba exhibited improved growth under the projected scenarios. For the other tree species, no significant difference in growth was observed between the predicted and observed scenarios. We believe that much remains to be done to better understand the tree growth-climate interaction of the large variety of tree species in the Congo Basin. [ABSTRACT FROM AUTHOR]

The impact of nitrogen (N) and phosphorus (P) on the physiological and biochemical processes crucial for tree seedling growth is substantial. Although the study of plant hydraulic traits in response to N and P is growing, comprehensive research on their combined effects remains limited. Malus sieversii, a key ancestral species of modern apples and a dominant species in Xinjiang's Tianshan wild fruit forest, is witnessing a decline due to climate change, pests and diseases, compounded by challenges in seedling regeneration. Addressing this, a 4‐year study was conducted to determine the optimal fertilisation method for it. The experiment explored varying levels of N (N10, N20 and N40) and P (P2, P4 and P8), and their combined effects (N20Px: N20P2, N20P4, N20P8; NxP4: N10P4, N20P4 and N40P4), assessing their impact on gas exchange, hydraulic traits, and the interplay among functional traits in Tianshan Mountains' M. sieversii seedlings. Our study revealed that All N‐inclusive fertilisers slightly promoted the net photosynthetic rate. N10 significantly increasing leaf hydraulic conductivity. All P‐inclusive fertilisers adversely affected hydraulic conductivity. P8, N20P4 and N20P8 notably increased seedlings' vulnerability to embolism. Seedlings can adaptively adjust multiple functional traits in response to nutrient changes. The research suggests N10 and N20 as the most effective fertilisation treatments for M. sieversii seedlings in this region, while fertilisation involving phosphorus is less suitable. This study contributes valuable insights into the specific nutrient needs of it, vital for conservation and cultivation efforts in the Tianshan region. [ABSTRACT FROM AUTHOR]

Morocco is a leading citrus producer with a Mediterranean climate and fertile soil. The diversity of microbial communities is a subtle indicator of this fertility and lends insights into soil function and sustainability. We compare the soil microbiome under oranges in the Taroudant and Béni Mellal regions: 90 samples were analysed by genetic sequencing using Illumina MiSeq. Several groups of microorganisms play a key role in soil health, tree growth, and the production of good quality fruit. Proteobacteria dominate the bacterial phyla, Ascomycota the fungal phyla, but ANOVA reveals a highly significant difference between the two studied areas (R = 0.164, p = 0.001) in terms of bio-sustainability and microbiome. According to the Similarity Percentage Test, the Taroudant region is characterised by high biodiversity, contributing 55% to the other parameters, whereas Béni-Mellal region exhibits high resistance of microbial communities, contributing 43% to the other parameters. [ABSTRACT FROM AUTHOR]

Bristlecone pine (Pinus longaeva) (PILO) trees exhibit exceptional longevity. Their tree‐ring width (TRW) series offer valuable insights into climatic variability. Maximum latewood density (MXD) typically correlates better with temperature variations than TRW, yet PILO MXD records are non‐existent due to methodological challenges related to tree‐ring structure. Here, we used an X‐ray Computed Tomography (X‐ray CT) toolchain on 51 PILO cores from the California White Mountains to build a chronology that correlates significantly (r = 0.66, p < 0.01) with warm‐season (March‐September) temperature over a large spatial extent. This led to the first X‐ray CT‐based temperature reconstruction (1625–2005 CE). Good reconstruction skill (RE = 0.51, CE = 0.32) shows that extending MXD records across the full length of the PILO archive could yield a robust warm‐season temperature proxy for the American Southwest over millennia. This breakthrough opens avenues for measuring MXD in other challenging conifers, increasing our understanding of past climate further, particularly in lower latitudes. Plain Language Summary: Ancient Bristlecone pine trees can live for several millennia and hold invaluable climate information. Their annual rings were used to develop millennium‐length records of the Holocene climate. Maximum latewood density (MXD), which is the highest wood density value in the latewood of a tree ring, has been shown to closely follow summer temperature in different conifer species, but not yet in Bristlecone pine. The gnarly and twisted growth of these ancient trees has presented significant hurdles for MXD analysis. Here we apply an X‐ray Computed Tomography toolchain that allows us to 3D scan through the tissue of a tree ring and to map MXD variations. Using this new technique, we were able to reconstruct warm‐season temperature for the American Southwest back to 1625 CE. With these findings, we are confident that a full‐length reconstruction (back to 2575 BCE) can yield the longest annually resolved temperature reconstruction for this continent. Key Points: We present the first X‐ray Computed Tomography‐derived maximum latewood density‐based temperature reconstruction using Bristlecone pine tree coresBristlecone pine maximum latewood density is a reliable proxy for warm‐season temperature over a large part of the American SouthwestOur reconstruction (1625–2005 CE) contains low‐frequency variability and can be prolonged over a large part of the Holocene [ABSTRACT FROM AUTHOR]

We investigate the acquisition of different functions of wh-words in Czech (Slavic) - a language where wh-words are highly polyfunctional. Our working hypothesis is that the acquisition proceeds in accordance with the growth of the syntactic tree (aka the growing trees hypothesis; Friedman et al. 2021), which in turn is matched by the growth of the semantic representation. More specifically, children are expected to first acquire wh-interrogatives, then conditionals, correlatives, and free relatives, and finally (light-)headed relatives. The working hypothesis is set against the background of what could be considered the null hypothesis, namely that children’s production matches the adult input. We have examined the Czech CHILDES corpus (Chromá et al. 2024; 6 children 1;07-3;09), tagging all wh-occurrences (nearly 11 thousand tokens) for the construction they appear in. Using both descriptive and inferential statistical methods, we have found evidence either supporting or being compatible with our hypothesis. At the same time, our results are not consistent with a simple input-based account. We also discuss some limitations of a corpus-based approach for addressing our research question. The most significant hurdle is the overall low frequency of non-interrogative wh-words. [ABSTRACT FROM AUTHOR]

Individual modelling is a foundational approach to study the natural forest growth and in this paper, we develop a serial distance-depended individual tree model for some species in natural forest which would provide prediction and characteristics for natural species. The data used to develop individual model for natural mixed forests were collected from 712 remeasured 10-year periodic permanent sample plots of in Baihe Forest Bureau of Changbai Mountains, northeast China. Based on analyzing relationship between diameter increment of individual trees with tree size, competitive status, and site condition and finding out the major independent variables, the growth models for individual trees of 15 species in the natural mixed forests, that have good predicting precision, and easily applicable, were developed using stepwise regression method. The individual growth model developed in this study can reflect the tree increment of 15 species and be generally well suited for simulating tree and stand growth for natural mixed forests in Changbai Mountains. The research results for individual trees growth model of each species showed that main variable to influence on diameter increment of individual trees for natural mixed forests were tree size (D) and then competition index. The site condition was not related with diameter increment. The natural logarithm of DBH (lnD) and square diameter (D2) were included in the predicting models of diameter increment for all 15 species. The diameter increment was directly proportional to tree diameter for each species. For the competitive indexes in growth model, the relative diameter (RD), canopy closure (P), and the ratio of diameter of subject tree with maximum diameter (DDM) were related to diameter increment and the stand density measures were not significantly influenced on diameter increment. As canopy closure increase, tree increment decreases. The site conditions were performance less of factors in increment predictions in the model. [ABSTRACT FROM AUTHOR]

South American subtropical landscapes are dominated by open grasslands and mosaics of forest–grassland formations. Forests are often restricted to riverine margins with sharp forest–grassland ecotones. Understanding the mechanisms maintaining forest–grassland ecotones is important to anticipate the effects of changing climate and disturbance regimes on the extent of these biomes and the ecosystem services they provide. We used a combination of field surveys and long‐term field experiments to explore the mechanisms that explain tree cover expansion at the ecotone of riverine forests and grasslands in central Uruguay, within the South American Campos. We assessed the role of tree seed dispersal and seedling establishment limitations, and experimentally tested for the effects of cattle, nurse tree cover and grasses on the recruitment of forest and grassland tree species at the forest–grassland ecotone. We found that forest expansion depends on the interplay between cattle and nurse trees. Vachellia caven trees colonize the grassland successfully and facilitate the formation of forest patches by enhancing seed accumulation and seedling establishment of forest tree species. Surprisingly, grass cover had mostly positive effects on early seedling survival of forest tree seedlings. However, cattle limits tree seedling growth and survival, especially of forest tree species. This results in a nucleated vegetation pattern of tree patches that ultimately limits forest expansion. Synthesis and applications. Tree cover can potentially expand on the subtropical South American grasslands. Reductions in cattle densities and increases in rainfall levels associated with climate change could facilitate forest expansion in this region. [ABSTRACT FROM AUTHOR]

Chlorophyll monitoring is an important topic in phenotypic research. For fruit trees, chlorophyll content can reflect the real-time photosynthetic capacity, which is a great reference for nutrient status assessment. Traditional in situ estimation methods are labor- and time-consuming. Remote sensing spectral imagery has been widely applied in agricultural research. This study aims to explore a transferable model to estimate canopy SPAD across growth stages and tree species. Unmanned aerial vehicle (UAV) system was applied for multispectral images acquisition. The results showed that the univariate model yielded with Green Normalized Difference Vegetation Index (GNDVI) gave valuable prediction results, providing a simple and effective method for chlorophyll monitoring for single species. Reflection features (RF) and texture features (TF) were extracted for multivariate modeling. Gaussian Process Regression (GPR) models yielded better performance for mixed species research than other algorithm models, and the R² of the RF+TF+GPR model was approximately 0.7 in both single and mixed species. In addition, this method can also be used to predict canopy SPAD over various growth stages, especially in the third and fourth stages with R² higher than 0.6. This paper highlights the importance of using RF+TF for canopy feature expression and deep connection exploration between canopy features with GPR algorithm. This research provides a universal model for canopy SPAD inversion which can promote the growth status monitoring and management of fruit trees. [ABSTRACT FROM AUTHOR]

The use of individual protective covers (IPCs) to protect newly planted citrus trees from Huanglongbing (HLB) infection is being widely adopted in Florida, an HLB-endemic citrus-producing area. It is known that IPCs positively influence most horticultural traits, increasing tree growth, flush expansion, and leaf size, enabling trees to sustain balanced carbohydrate metabolism by preventing Candidatus Liberibacter asiaticus (CLas) infection, and inducing higher leaf chlorophyll levels. This may result in more productive trees. However, as the tree grows, IPCs eventually are removed, typically between 2 and 3 years after their initial installation. Once IPCs are removed, trees become exposed to the Asian citrus psyllid (ACPs) and ultimately become infected. In this work, we covered Valencia sweet orange trees with IPCs for 30 months, until the trees entered fruit-bearing age. We investigated how the IPC protection of newly planted trees for 30 months influenced the fruit quality and yield of "Valencia" trees for three consecutive seasons after IPC removal compared to non-covered trees. The use of IPCs kick-started the newly planted citrus trees, resulting in higher yields and fruits with better internal and external quality. After 30 months of IPC protection, tree canopies were larger and denser, supporting more fruit per tree than non-protected trees for three consecutive seasons, even though by the end of the first season after IPC removal, the trees were HLB-positive. Tree height, scion diameter, canopy volume, and leaf area were significantly improved compared to non-covered trees. Additionally, fruit quality was significantly improved in the three seasons following IPC removal compared to non-covered trees. However, a decline in quality was measurable in fruit from IPC trees after the second harvesting season, with trees affected by HLB. Based on the results from this study, we conclude that the benefits from IPC protection may last for at least three consecutive seasons once trees enter the productive age, despite CLas infection within 12 months after IPC removal. [ABSTRACT FROM AUTHOR]

[Objective]The effects of nutrient elements N, P, K and B on growth of 17-months-old Eucalyptus cloeziana plantation were studied in order to select well treatment to tree growth and provide fertilization. [Method]In this study, the three essential nutrients N, P, K and trace element B were used as experimental factors. Orthogonal experimental design was used to construct experimental treatment including control (no fertilization). The optimal fertilization treatment was selected according to the growth changes before and after fertilization under all treatments. [Result]The results of the experiment showed that 600 d after fertilization, the order of elements effect on growth was P, B, K, N. The order of elements effect on tree height and volume was P, K, N, B. There were significant differences in DBH, height and volume growth between fertilization treatment and control and between different fertilization treatments. The growth of DBH, tree height and volume of treatments ⑧, ⑨, ④ and ⑤ were all rank 1st, 2nd, 3rd and 4th, respectively. The growth of control was the least. According to the analysis results of fertilizer efficiency and tree growth of each treatment, treatment ④ was selected as the best fertilization treatment in this experiment, which DBH, tree height and volume were 36. 4%, 11. 7% and 54. 3% higher than control, respectively. [Conclusion]Fertilization treatment ④ can be used as a reference to topdressing young E. cloeziana that application rates of total amount of available nutrients 460. 25 g / plant(N 34. 2%, P 26. 6%, K 38. 0%, B 1. 2%), releasing in two years and once a year, and the first dose accounted for 42. 9% and the second dose accounted for 57. 1%. [ABSTRACT FROM AUTHOR]

Introduction: Citrus is one of the most important fruit crops worldwide, and the root-associated microbiota can have a profound impact on tree health and growth. Methods: In a collaborative effort, the International Citrus Microbiome Consortium investigated the global citrus root microbiota with samples collected from nine citrus-producing countries across six continents. We analyzed 16S rDNA and ITS2 amplicon sequencing data to identify predominant prokaryotic and fungal taxa in citrus root samples. Comparative analyses were conducted between root-associated microbial communities and those from the corresponding rhizosphere and bulk soil samples. Additionally, genotype-based group-wise comparisons were performed to assess the impact of citrus genotype on root microbiota composition. Results: Ten predominant prokaryotic phyla, containing nine bacterial phyla including Proteobacteria, Actinobacteria, Acidobacteria, and Bacteroidetes and one archaeal phylum (Thaumarchaeota), and multiple fungal phyla including Ascomycota and Basidiomycota were identified in the citrus root samples. Compared with the microbial communities from the corresponding rhizosphere and bulk soil samples from the same trees, the prokaryotic and fungal communities in the roots exhibited lower diversity and complexity but greater modularity compared to those in the rhizosphere. In total, 30 root-enriched and 150 root-depleted genera in bacterial community were identified, whereas 21 fungal genera were enriched, and 147 fungal genera were depleted in the root niche compared with the rhizosphere. The citrus genotype significantly affected the root prokaryotic and fungal communities. In addition, we have identified the core root prokaryotic genera comprising Acidibacter, Allorhizobium, Bradyrhizobium, Chitinophaga, Cupriavidus, Devosia, Dongia, Niastella, Pseudomonas, Sphingobium, Steroidobacter and Streptomyces, and the core fungal genera including Acrocalymma, Cladosporium, Fusarium, Gibberella, Mortierella, Neocosmospora and Volutella. The potential functions of these core genera of root microbiota were predicted. Conclusion: Overall, this study provides new insights into the assembly of microbial communities and identifies core members of citrus root microbiota across a wide geographic range. The findings offer valuable information for manipulating root microbiota to enhance plant growth and health. [ABSTRACT FROM AUTHOR]

Introduction: The almond tree is a major global nut crop, and its production has surged dramatically in recent years. Super high-density (SHD) planting systems, designed to optimize resource efficiency and enhance precocity, have gained prominence in almond cultivation. A shift in cropping systems toward sustainable intensification (SI) pathways is imperative, and so maximizing branching density within the canopies of SHD trees is crucial to establish and maintain productive potential, especially for hedge-pruned trees. This study investigates the influence of different almond cultivars grafted onto a novel growth-controlling rootstock on tree architectural and growth parameters in a SHD orchard. This open field research provided valuable insights for the development and application of new tools and methods to increase productivity and sustainability in almond growing. Methods: Three cultivars (Lauranne® Avijour, Guara Tuono, and Filippo Cea) were evaluated in Gravina in Puglia (BA) over a two-year period. Canopy growth parameters, such as canopy volume and trunk cross-sectional area, and architectural traits, like branching density, branching angle, number and length of subterminal shoots, and number of brachyblasts, were measured through qualitative and quantitative measurements. Results and discussion: Results revealed significant differences in tree height, canopy thickness, width, volume, and vigor among the cultivars. Architectural traits, including branch parameters, brachyblast parameters, and subterminal shoots, varied among the cultivars. Lauranne displayed a more compact welldistributed canopy and exhibited the lowest vigor. Filippo Cea showed the highest vigor and the greatest canopy volume. Tuono had a higher number of buds and bud density. The best ideotype for SHD orchards is a smaller tree, with high branching density and smaller trunk diameters, i.e. the vigor. Cv. Lauranne seemed to be the best cultivar, mostly with the lowest tree vigor of all the cultivars involved. These findings provide valuable insights for almond growers and breeders seeking to optimize orchard design and management for enhanced SHD orchards productivity and sustainability. Future research will explore the relationship between canopy architecture and yield parameters, considering different scion/rootstock combinations in different environmental conditions. [ABSTRACT FROM AUTHOR]

For trees originating from boreal and temperate regions, the dormancy‐to‐active transition, also known as bud dormancy release and bud break, are crucial processes that allow trees to reactive growth in the spring. The molecular mechanisms underlying these two processes remain poorly understood. Here, through integrative multiomics analysis of the transcriptome, DNA methylome, and proteome, we gained insights into the reprogrammed cellular processes associated with bud dormancy release and bud break. Our findings revealed multilayer regulatory landscapes governing bud dormancy release and bud break regulation, providing a valuable reference framework for future functional studies. Based on the multiomics analysis, we have determined a novel long intergenic noncoding RNA named Phenology Responsive Intergenic lncRNA 1 (PRIR1) plays a role in the activation of bud break. that the molecular mechanism of PRIR1 has been preliminary explored, and it may partially promote bud break by activating its neighbouring gene, EXORDIUM LIKE 5 (PtEXL5), which has also been genetically confirmed as an activator for bud break. This study has revealed a lncRNA‐mediated regulatory mechanism for the control of bud break in Populus, operating independently of known regulatory pathways. Summary statement: we report the multilayer regulatory landscapes of dormancy release and bud break regulation in hybrid poplar (Populus tremula x alba). We also identify a long intergenic noncoding RNA PRIR1 and characterise its role in dormancy release. Our study provides a useful reference framework for dormancy release and bud break regulation studies. [ABSTRACT FROM AUTHOR]

Dry spells strongly influence biomass production in forest ecosystems. Their effects may last several years following a drought event, prolonging growth reduction and therefore restricting carbon sequestration. Yet, our understanding of the impact of dry spells on the vitality of trees' above-ground biomass components (e.g., stems and leaves) at a landscape level remains limited. We analyzed the responses of Pinus sylvestris and Picea abies to the four most severe drought years in topographically complex sites. To represent stem growth and canopy greenness, we used chronologies of tree-ring width and time series of the Normalized Difference Vegetation Index (NDVI). We analyzed the responses of radial tree growth and NDVI to dry spells using superposed epoch analysis and further explored this relationship using mixed-effect models. Our results show a stronger and more persistent response of radial growth to dry spells and faster recovery of canopy greenness. Canopy greenness started to recover the year after the dry spell, whereas radial tree growth remained reduced for the two subsequent years and did not recover the pre-drought level until the fourth year after the event. Stem growth and canopy greenness were influenced by climatic conditions during and after drought events, while the effect of topography was marginal. The opposite responses of stem growth and canopy greenness following drought events suggest a different impact of dry spells on trees´ sink and source compartments. These results underscore the crucial importance of understanding the complexities of tree growth as a major sink of atmospheric carbon. [ABSTRACT FROM AUTHOR]

Chitosan is a naturally abundant biopolymer that has been studied as an alter - native means to elicit beneficial responses in plants, such as enhanced plant growth and improved defense response. Most studies focus on agriculture and horticulture, but few have investigated forest trees. Based on chitosan's success as a biostimulant, we hypothesized that trees such as pine (Pinus sylvestris L.) and alder (Alnus glutinosa L.) may also be positively affected by it. We evaluated vegetative growth parameters and secondary metabolites (phenolics, antioxidant indicators), pigments of seedlings grown in sterile in vitro and non-sterile ex vitro conditions to determine if various concentrations of chitosan solubilized in different solvents and stored in different conditions would significantly impact trees at various stages and conditions of growth. Results showed that in in vitro conditions, chitosan had a mainly positive effect on pine germination and growth, but a mainly negative effect on pine secondary metabolism (SM) indicators. In vitro grown alder's SMs were positively affected in all measured parameters, but chitosan had no effect on growth. Overall, ex vitro results indicated that chitosan has no effect on pine growth and varied impact on its SM indicators. Similarly, the effect on growth parameters and SM indicators was varied in alder. Results on how chitosan storage can affect its impact on tree growth showed that storage conditions had a significant impact on both pine and alder. Based on our data, future studies must carefully evaluate all possible variables to optimize chitosan use in silviculture. [ABSTRACT FROM AUTHOR]

Forests around the world are experiencing changes due to climate variability and human land use. How these changes interact and influence the vulnerability of forests are not well understood. In the eastern United States, well‐documented anthropogenic disturbances and land‐use decisions, such as logging and fire suppression, have influenced forest species assemblages, leading to a demographic shift from forests dominated by xeric species to those dominated by mesic species. Contemporarily, the climate has changed and is expected to continue to warm and produce higher evaporative demand, imposing stronger drought stress on forest communities. Here, we use an extensive network of tree‐ring records from common hardwood species across ~100 sites and ~1300 trees in the eastern United States to examine the magnitude of growth response to both wet and dry climate extremes. We find that growth reductions during drought exceed the positive growth response to pluvials. Mesic species such as Liriodendron tulipifera and Acer saccharum, which are becoming more dominant, are more sensitive to drought than more xeric species, such as oaks (Quercus) and hickory (Carya), especially at moderate and extreme drought intensities. Although more extreme droughts produce a larger annual growth reduction, mild droughts resulted in the largest cumulative growth decreases due to their higher frequency. When using global climate model projections, all scenarios show drought frequency increasing substantially (3–9 times more likely) by 2100. Thus, the ongoing demographic shift toward more mesic species in the eastern United States combined with drier conditions results in larger drought‐induced growth declines, suggesting that drought will have an even larger impact on aboveground carbon uptake in the future in the eastern United States. [ABSTRACT FROM AUTHOR]

Nutrient resorption (NR) is a critical ecological process in forest ecosystems. However, there is a lack of knowledge about this process in the peatlands of Indonesia, and this may be seen as a research gap. In the present study, NR in young trees of three native species (Macaranga pruinosa, Cratoxylum arborescens, and Macaranga gigantea) and one exotic species (Acacia crassicarpa) in a drained tropical peatland was investigated. This study was conducted at an experimental plot in Pelalawan-Riau, Indonesia. Nutrient resorption efficiency (RE) and proficiency (RP) were calculated and correlated with soil properties, foliar nutrients, and growth variables. Our results revealed that M. pruinosa exhibited an RE value for phosphorus (PRE) that was 64% higher than that for the second-ranked native species but still significantly (84%) lower than that for A. crassicarpa. RE values for nitrogen (NRE) and potassium (KRE) did not differ significantly among species, ranging from 39 to 42% and 41 to 56%, respectively, for native species, with figures of 45% and 66%, respectively, for A. crassicarpa. Finally, PRE exhibited strong and significant correlations with PRP and tree growth, a finding that indicated that the uptake and conservation of P nutrients are essential for the fitness of the three native species. Overall, the results of the present study may be seen as beneficial for species selection and the management of nutrients by those engaged in restoration of tropical peatland forests. [ABSTRACT FROM AUTHOR]

Climate change is a growing threat to agriculture globally, with most substantial impacts expected in tropical smallholder systems such as cocoa farms in West Africa. Cocoa agroforestry is widely believed to enhance resilience to climatic extremes due to protection and a favourable microclimate under the shade trees. Morphological traits of many locally used shade tree species and their specific contribution to microclimate for climate-resilient cocoa production remain unclear. Therefore, aboveground morphology and sub canopy microclimate of eight common shade tree species were investigated in cocoa agroforestry systems in the Ahafo region, Ghana. Additionally, the growth of cocoa trees in three different distance zones to the shade tree stem was measured. The eight different shade tree species exhibited considerable variation in their impact on microclimate and cocoa growth. M. indica and M. excelsa allowed lowest light transmission, with the highest microclimatic buffering effect, i.e., reducing vapour pressure deficit and daily fluctuations of temperature and relative humidity. Cocoa trees around M. lucida and F. capensis were the highest in growth, characterized by height and stem diameter. However, a universally superior shade tree species could not be identified implying the need for shade tree diversity allowing various microclimatic conditions within an agroforestry system to spread risk of climate extremes. Cocoa tree growth was more affected by distance to the shade tree than by shade tree species, resulting in enhanced growth with distance to the stem. These findings provide a better understanding of species-related differences on cocoa growing conditions and climate change adaptation strategies. [ABSTRACT FROM AUTHOR]

Introduction: Salinity and droughts are severe abiotic stress factors that limit plant growth and development. However, the differences and similarities of non-structural carbohydrates (NSCs) responses patterns of trees under the two stress conditions remain unclear. Methods: We determined and compared the growth, physiology, and NSCs response patterns and tested the relationships between growth and NSCs concentrations (or pool size) of Eucommia ulmoides seedlings planted in field under drought and salt stress with different intensities and durations. Results and discussion: We found that drought and salt stress can inhibit the growth of E. ulmoides, and E. ulmoides tended to enhance its stress resistance by increasing proline concentration and leaf thickness or density but decreasing investment in belowground biomass in short-term stress. During short-term drought and salt stress, the aboveground organs showed different NSCs response characteristics, while belowground organs showed similar change characteristics: the starch (ST) and NSCs concentrations in the coarse roots decreased, while the ST and soluble sugar (SS) concentrations in the fine roots increased to enhance stress resistance and maintain water absorption function. As salt and drought stress prolonged, the belowground organs represented different NSCs response patterns: the concentrations of ST and SS in fine roots decreased as salt stress prolonged; while ST in fine roots could still be converted into SS to maintain water absorption as drought prolonged, resulting in an increase of SS and a decrease of ST. Significant positive relationships were found between growth and the SS and total NSCs concentrations in leaves and branches, however, no significant correlations were found between growth and below-ground organs. Moreover, relationships between growth and NSCs pool size across organs could be contrast. Conclusion: Our results provide important insights into the mechanisms of carbon balance and carbon starvation and the relationship between tree growth and carbon storage under stress, which were of great significance in guiding for the management of artificial forest ecosystem under the context of global change. [ABSTRACT FROM AUTHOR]

Over the past few decades, increasing populations of cervid species in the Baltic region have reduced the quality and vitality of cultivated Norway spruce (Picea abies (L.) Karst.) stands. This study evaluated the effect of bark stripping on the volume growth of spruce trees in Latvia. Data collection took place in two forest stands. In each stand, 20 Norway spruce trees were sampled, 10 with visible bark damage scars and 10 control trees. Stem discs were collected from control trees at specified heights (0 m, 0.5 m, 1 m, 1.3 m, and 2 m, and then at one-metre intervals up to the top) and from damaged trees at additional specific points relative to the damage. Each disc was sanded and scanned; tree ring widths were measured in 16 radial directions using WinDendro 2012a software. Annual volume growth reconstruction was performed for each tree. Changes in relative volume growth were analysed in interaction with scar parameters, tree type (damaged/control), and pre-damage volume using linear regression models. The significance of parameter interactions was assessed using analysis of variance (ANOVA). Pairwise comparisons of estimated marginal means (EMMs) were conducted using Tukey's HSD post hoc test. No significant effect of bark stripping on the total stem volume increment was detected. However, the length of bark stripping scars had a significant impact on relative volume growth in the lower parts of the stems. These findings underscore the importance of further research examining a broader spectrum of cervid damage intensity and the effects of repeated damage on tree survival and growth. [ABSTRACT FROM AUTHOR]

The future evolution of the Amazon rainforest remains uncertain not only due to uncertain climate projections, but also owing to the intricate balance between tree growth and mortality. Many Earth System Models inadequately represent forest demography processes, especially drought‐induced tree mortality. In this study, we used ORCHIDEE‐CAN‐NHA, a land surface model featuring a mechanistic hydraulic architecture, a tree mortality sub‐model linked to a critical loss of stem conductance and a forest demography module for simulating regrowth. The model was forced by bias‐corrected climate forcing data from the ISIMIP‐2 program, considering two scenarios and four different climate models to project biomass changes in the Amazon rainforest until 2100. These climate models display diverse patterns of climate change across the Amazon region. The simulation conducted with the HadGEM climate model reveals the most significant drying trend, suggesting that the Guiana Shield and East‐central Amazon are approaching a tipping point. These two regions are projected to transition from carbon sinks to carbon sources by the mid‐21st century, with the Brazilian Shield following suit around 2060. This transition is attributed to heightened drought‐induced carbon loss in the future. This study sheds light on uncertainties in the future carbon sink in the Amazon forests, through a well‐calibrated model that incorporates tree mortality triggered by hydraulic damage and the subsequent recovery of drought‐affected forests through demographic processes. Plain Language Summary: Whether the Amazon rainforest will remain as net carbon sink or not has long been of great concern as the drought events are predicted to become more frequent and more intense in the future and such extreme events highly threaten the forest net carbon uptake capacity. Here we use a process‐based model embedding drought‐induced tree mortality scheme that can perform well regarding past drought events over Amazon basin, to predict the future drought‐induced tree mortality risk and the evolution of net biomass carbon sink. The climate models present consistent warming but different wetting/drying patterns, although most of them consistently predict a drier trend in northeastern Amazon. Simulations forced by one climate model showed a carbon sink turning to a carbon source in more than half of Amazon rainforest since the middle of the 21st century. This work can inform the forest area with high tree mortality risk in the future, which calls for more concerns on mitigation policies. Key Points: We used a land surface model forced by ISIMIP2 climate data to simulate the future drought‐induced tree mortality risk in Amazon rainforestWhile climate models differ in projections of wetting/drying patterns, many of them suggest a drying trend in the northeastern AmazonSimulations forced by HadGEM model indicate the Guiana Shield and East‐central Amazon will transition from carbon sink to source from 2050s [ABSTRACT FROM AUTHOR]

Tree radial growth is one of the most direct measures of tree performance and is also sensitive to climate. Growth performance is the consequence of the interplay between ecological and evolutionary processes. However, the effect of the evolutionary relatedness among species (i.e., phylogeny) on tree radial growth, especially under stressful conditions, remains largely unknown. Furthermore, there is still no ecological evidence for the influence of phylogeny on tree growth across different tree attributes (i.e., tree diameter variation and tree canopy height) and topographic habitat types. We used Blomberg's K to quantify the tree growth phylogenetic signal (TGPS) using two long‐term dendrometer data sets: one a continuous census of 225 tree species at 3‐month intervals in a tropical forest in southwest China from 2009 to 2017; the other, 12 tree species measured at 6‐month intervals in a temperate forest in Washington State, USA from 2013 to 2019. We found that TGPS values were higher in the temperate forest than in the tropical forest. Precipitation, tree diameter, canopy strata, and habitat types all influenced TGPS values. TGPS values were significantly (p < 0.05) and negatively related to precipitation in Xishuangbanna, and the three of four tree diameter classes in the temperate forest, respectively. Stressful growing conditions arose from either based on low precipitation or among large‐diameter trees competing with each other in the upper canopy led to phylogenetic conservatism in trees' radial growth performance. We conclude that phylogeny is pivotal to understanding the growth response differences among species and their responses to climate variability. Key Points: This study examined phylogeny‐based tree radial growth across precipitation gradients and tree attributes (i.e., tree diameter and canopy height) in tropical and temperate forestsTemperate trees showed a stronger phylogenetic growth effect than tropical treesTree radial growth phylogenetic conservatism was higher during stress events (i.e., drought) than in normal climatic situations [ABSTRACT FROM AUTHOR]

Forest site productivity estimates are crucial for making informed forest resource management decisions. These estimates are valuable both for the tree species currently growing in the stands and for those being considered for future stands. Current models are generally designed for pure stands and do not account for the influence of climate on tree growth. Consequently, site index (SI) conversion equations were developed specifically for jack pine (Pinus banksiana Lamb.) and trembling aspen (Populus tremuloides Michx.) trees grown in naturally originated mixed stands. This work involved sampling 186 trees (93 of each species) from 31 even-aged mixed stands (3 trees per species per site) across Ontario, Canada. Stem analysis data from these trees were utilized to develop stand height growth models by incorporating climate variables for each species. The models were developed using a mixed effects modelling approach. The SI of one species was correlated with that of the other species and climate variables to establish SI conversion equations. The effect of climate on site productivity was evaluated by projecting stand heights at four geographic locations (east, center, west, and far west) in Ontario from 2022 to 2100 using the derived stand height growth models. Height projections were made under three emissions scenarios reflecting varying levels of radiative forcing by the end of the century (2.6, 4.5, and 8.5 watts m−2). Climate effects were observed to vary across different regions, with the least and most pronounced effects noted in the central and far western areas, respectively, for jack pine, while effects were relatively similar across all locations for trembling aspen. Stand heights and SIs of jack pine and trembling aspen trees grown in naturally originated mixed stands can be estimated using the height growth models developed here. Similarly, SI conversion equations enable the estimation of the SI for one species based on the SI of another species and environmental variables. [ABSTRACT FROM AUTHOR]

In response to concerns that increment coring with an increment borer might contribute to the dieback of pine trees in Thailand, this research aimed to evaluate the effects of increment coring on the growth of Khasi pine (Pinus kesiya Royle ex Gordon) at Doi Khuntan National Park in northern Thailand. Increment coring is commonly used in dendrochronology, but its impact on tree growth needs to be better understood. This study involved the selection of pine trees of varying diameters, categorizing them into control (uncored) and experimental (cored) groups. Subsequently, data were collected bimonthly from September 2018 to April 2023, except for interruptions from February 2020 to December 2021 due to the COVID-19 pandemic. Tree diameters at breast height were measured, and image analysis was used to monitor the wound healing every two months. A repeated-measures ANOVA was used to compare the growth of cored and uncored groups and the wound healing rates among small-, medium-, and large-tree groups. The growth of cored and uncored Khasi pines within the same and different diameter classes showed no significant differences nor did the wound healing rates. The findings indicated that increment coring had an insignificant impact on the tree growth across all diameter classes, with wounds healing effectively within 14 months. These results support the continued and safe use of increment coring with an increment borer as a non-destructive method for collecting tree-ring and wood samples for climate research and for providing valuable insights into forest management practices. [ABSTRACT FROM AUTHOR]

Radial tree growth at high-elevation and high-latitude sites is predominantly controlled by changes in summer temperature. This relationship is, however, expected to weaken under projected global warming, which questions the reliability of tree-ring chronologies for climate reconstructions. Here, we examined the growth–climate response patterns of five tree-ring width (TRW) and maximum latewood density (MXD) chronologies of larch (Larix sibirica) from upper-treeline ecotones in the Altai Mountains, which is a key region for developing millennial-long dendroclimatic records in inner Eurasia. The TRW and MXD chronologies exhibited significant year-to-year coherency within and between the two parameters (p < 0.001). While TRW is mostly influenced by temperature changes during the first half of the growing season from June to July (r = 0.66), MXD is most strongly correlated with May–August temperatures (r = 0.73). All seasonal temperature signals are statistically significant at the 99% confidence level, temporally stable back to 1940 CE, the period with reliable instrumental measurements, and spatially representative for a vast area of inner Eurasia between northeastern Kazakhstan in the west, northern Mongolia in the east, southern Russia in the north and northwestern China in the south. Our findings demonstrate the paleoclimatic potential of TRW and especially MXD chronologies and reject any sign of the ´divergence problem´ at these high-elevation, mid-latitude larch sites. [ABSTRACT FROM AUTHOR]

Understanding the drivers of drought-induced tree mortality remains a significant scientific challenge. Here, we investigated an unexpected mortality event of Nothofagus dombeyi (Mirb.) Oerst. following the 2014–15 drought in a Valdivian rainforest, Argentina. Our focus was on long-term growth trend differences between vital and dead trees, and how the mixing of species in tree neighbourhoods drives tree growth during drought. The inter-annual variation of basal area increments of vital and 2014–15-dead N. dombeyi trees showed a similar pattern through the 1930–2015 period, while the climate–growth relationships indicated that precipitation during the growing season promoted growth in both vitality classes, regardless of whether they were in the wettest location. For the period 1990–2015, both vitality classes showed similar estimated growth regardless of competition level, whereas species mingling in the neighbourhood significantly affected the dead tree growth. Network analysis revealed that drought performance covaried positively with a neighbourhood dominated by species functionally different from the focal species only in vital trees. These findings suggest a nuanced response of N. dombeyi to drought, shaped by multifaceted interactions at both the individual tree and neighbourhood levels. This research underscores that species-specific relationships under different mixtures imply different tree responses within a stand, and add complexity to understanding drought response at the individual level. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal fungi (AMF) are widespread obligate symbionts of plants. This dynamic symbiosis plays a large role in successful plant performance, given that AMF help to ameliorate plant responses to abiotic and biotic stressors. Although the importance of this symbiosis is clear, less is known about what may be driving this symbiosis, the plant's need for nutrients or the excess of plant photosynthate being transferred to the AMF, information critical to assess the functionality of this relationship. Characterizing the AMF community along a natural plant productivity gradient is a first step in understanding how this symbiosis may vary across the landscape. We surveyed the AMF community diversity at 12 sites along a plant productivity gradient driven by soil nitrogen availability. We found that AMF diversity in soil environmental DNA significantly increased along with the growth of the host plants Acerrubrum and A. saccharum., a widespread tree genus. These increases also coincided with a natural soil inorganic N availability gradient. We hypothesize photosynthate from the increased tree growth is being allocated to the belowground AMF community, leading to an increase in diversity. These findings contribute to understanding this complex symbiosis through the lens of AMF turnover and suggest that a more diverse AMF community is associated with increased host–plant performance. [ABSTRACT FROM AUTHOR]

Plantations actively participate in the global carbon cycle and play a significant role in mitigating global climate change. However, the influence of forest management strategies, especially planting density management, on the biomass carbon storage and production value of plantations for ensuring carbon sink benefits is still unclear. In this study, we estimated the carbon sequestration and economic value of Pinus massoniana plantations with various stand densities and rotation ages using a growth model method. The results revealed that with increasing stand age, low-density plantations at 2000 trees·ha−1 (358.80 m3·ha−1), as well as high-density plantations at 4500 trees·ha−1 (359.10 m3·ha−1), exhibited nearly identical standing volumes, which indicated that reduced inter-tree competition intensity favors the growth of larger trees during later stages of development. Furthermore, an increase in planting density led to a decrease in the average carbon sequestration rate, carbon sink, and number of trees during the rapid growth period, indicating that broader spacing between trees is favorable for biomass carbon accumulation. Further, extending the rotation period from 15 to 20 years or 25 years and reducing the optimal planting density from 3000 to 2000 trees·ha−1 increased the overall benefits of combined timber and carbon sink income by 2.14 and 3.13 times, respectively. The results highlighted that optimizing the planting density positively impacts the timber productivity and carbon sink storage of Pinus massoniana plantations and boosts the expected profits of forest managers. Thus, future afforestation initiatives must consider stand age and planting density management to shift from a scale-speed pattern to a quality-benefit design. [ABSTRACT FROM AUTHOR]

Soil respiration (Rs) in forest ecosystems is an important process in the global carbon cycle. The unbalanced use of forest natural resources and deforestation in the past have resulted in changes in forest structure, tree growth, and the release of carbon dioxide (CO2) emissions from Rs. Understanding Rs in both primary and secondary forests plays a crucial role in the global carbon cycle. Therefore, the purpose of this study was to estimate and compare Rs in primary dry dipterocarp forests (PDDF) and secondary dry dipterocarp forests (SDDF) in Thailand, in relation to diurnal and seasonal variations in environmental variables (air and soil temperatures, and soil moisture). CO2 flux was measured continuously from March 2019 to February 2020 in the PDDF and SDDF sites in the Nakhon Ratchasima and Ratchaburi provinces of Thailand. Using the soil gradient method, CO2 probes were employed to measure average CO2 concentrations from Rs every minute in the both sites. Additionally, air and soil temperatures and soil moisture were measured continuously to analyze the correlation between Rs and environmental variables. The average annual soil respiration rate in PDDF and SDDF were 8.16 and 8.83 tons C ha−1 yr−1, respectively. The diurnal variation of Rs in both sites changed according to air and soil temperatures. The monthly variation of the average Rs was lower in the PDDF site than in the SDDF site. Soil moisture and soil temperature were significantly correlated with the monthly variation of Rs in both sites. Rs in the PDDF and SDDF sites exhibited high emissions during the wet season, accounting for ~61 and 56% of the total annual emissions, respectively. The results indicated that soil and air temperatures were the main drivers of diurnal variation, while the combination of soil moisture and soil and air temperatures determined the seasonal variations. Additionally, litterfall production was the main carbon substrate promoting soil respiration in the SDDF site, as litterfall production was significantly lower in the PDDF site (5.32 tons dry matter ha−1 yr−1) than in the SDDF site (10.49 tons dry matter ha−1 yr−1). [ABSTRACT FROM AUTHOR]

Background: Tree rings play an important role in reconstructing past climate. Growth differences among individual trees due to microclimatic conditions and local disturbances are averaged in developing tree-ring chronologies. Here, we addressed the problem of averaging by investigating growth synchrony in individual trees. We used tree-ring data of 1046 juniper trees from 32 sites on the Tibetan Plateau and 538 pine trees from 20 sites in the subtropical region of eastern China and calculated the tree-growth synchrony index (TGS). Results: Our results showed that both the TGS index and tree-ring index could be indicators of interannual variation of climatic factors. The TGS index identified 20% more climatic extremes than tree-ring index over the last 50 years that high synchrony indicates extreme climate forcing in controlling forest growth. Conclusions: The TGS index can identify extreme climatic events effectively than tree-ring index. This study provides a novel perspective for climate reconstruction, especially in the realm of tree growth response to extreme climate. Our findings contribute to understanding of the spatiotemporal dynamics and the causes of historical climate extremes and provide guidance for protecting trees from climate extremes in the future. [ABSTRACT FROM AUTHOR]

Dielectric materials are foundational to our modern-day communications, defense, and commerce needs. Although dielectric breakdown is a primary cause of failure of these systems, we do not fully understand this process. We analyzed the dielectric breakdown channel propagation dynamics of two distinct types of electrical trees. One type of these electrical trees has not been formally classified. We observed the propagation speed of this electrical tree type to exceed 10 million meters per second. These results identify substantial gaps in the understanding of dielectric breakdown, and filling these gaps is paramount to the design and engineering of dielectric materials that are less susceptible to electrostatic discharge failure. [ABSTRACT FROM AUTHOR]

Loblolly pine (Pinus taeda L.) grown on infertile coastal plain soils typically shows a growth response to N and P applied at mid-rotation. The objectives of this study were to determine whether less soluble poultry litter ash (PLA) provides an adequate supply of P compared to triple superphosphate (TSP), and assess effects on P mineralization and runoff loss. Effects of 56 kg P ha−1 as either PLA or TSP, and no fertilization were compared using an 11-year-old stand of two loblolly pine genotypes on a loamy sand in a completely randomized design. Tree height, diameter and foliar nutrients, soil Mehlich 3 P and phosphatase activity (A and E horizons), and P in surface runoff were monitored. Through more than two years, P fertilization had no effect on tree growth. Similar foliar P with PLA or TSP, together with increasing foliar and soil P over time, suggested that PLA is an adequate source of P for loblolly pine. Neither fertilizer suppressed P mineralization as measured by phosphatase activity. The advantage of PLA compared to TSP is potentially much less runoff P loss. [ABSTRACT FROM AUTHOR]

Summary: It is well established that solar irradiance greatly influences tree metabolism and growth through photosynthesis, but its effects acting through individual climate metrics have not yet been well quantified. Understanding these effects is crucial for assessing the impacts of climate change on forest ecosystems.To describe the effects of solar irradiance on tree growth, we installed 110 automatic dendrometers in two old‐growth mountain forest reserves in Central Europe, performed detailed terrestrial and aerial laser scanning to obtain precise tree profiles, and used these to simulate the sum of solar irradiance received by each tree on a daily basis. Generalized linear mixed‐effect models were applied to simulate the probability of growth and the growth intensity over seven growing seasons.Our results demonstrated various contrasting effects of solar irradiance on the growth of canopy trees. On the one hand, the highest daily growth rates corresponded with the highest solar irradiance potentials (i.e. the longest photoperiod). Intense solar irradiance significantly decreased tree growth, through an increase in the vapor pressure deficit. These effects were consistent for all species but had different magnitude.Tree growth is the most effective on long rainy/cloudy days with low solar irradiance. [ABSTRACT FROM AUTHOR]

Understanding the biodiversity–productivity relationship (BPR) is crucial for biodiversity conservation and ecosystem management. While it is known that diversity enhances forest productivity, the underlying mechanisms at the local neighborhood level remain poorly understood. We established a 9.6 ha dynamic forest plot to study how neighborhood diversity, intraspecific competition, and interspecific competition influence tree growth across spatial scales using linear mixed-effects models. Our analysis reveals a significant positive correlation between neighborhood species richness (NSR) and relative growth rate (RGR). Notably, intraspecific competition, measured by conspecific neighborhood density and resource competition, negatively impacts RGR at finer scales, indicating intense competition among conspecifics for limited resources. In contrast, interspecific competition, measured by heterospecific density and resource competition, has a negligible impact on RGR. The relative importance of diversity and intra/interspecific competition in influencing tree growth varies with scale. At fine scales, intraspecific competition dominates negatively, while at larger scales, the positive effect of NSR on RGR increases, contributing to a positive BPR. These findings highlight the intricate interplay between local interactions and spatial scale in modulating tree growth, emphasizing the importance of considering biotic interactions and spatial variability in studying BPR. [ABSTRACT FROM AUTHOR]

Urban street trees offer cities critical environmental and social benefits. In New York City (NYC), a decadal census of every street tree is conducted to help understand and manage the urban forest. However, it has previously been impossible to analyze growth of an individual tree because of uncertainty in tree location. This study overcomes this limitation using a three-step alignment process for identifying individual trees with ZIP Codes, address, and species instead of map coordinates. We estimated individual growth rates for 126,362 street trees (59 species and 19% of 2015 trees) using the difference between diameter at breast height (DBH) from the 2005 and 2015 tree censuses. The tree identification method was verified by locating and measuring the DBH of select trees and measuring a set of trees annually for over 5 years. We examined determinants of tree growth rates and explored their spatial distribution. In our newly created NYC tree growth database, fourteen species have over 1000 unique trees. The three most abundant tree species vary in growth rates; London Planetree (n = 32,056, 0.163 in/yr) grew the slowest compared to Honeylocust (n = 15,967, 0.356 in/yr), and Callery Pear (n = 15,902, 0.334 in/yr). Overall, Silver Linden was the fastest growing species (n = 1,149, 0.510 in/yr). Ordinary least squares regression that incorporated biological factors including size and the local urban form indicated that species was the major factor controlling growth rates, and tree stewardship had only a small effect. Furthermore, tree measurements by volunteer community scientists were as accurate as those made by NYC staff. Examining city wide patterns of tree growth indicates that areas with a higher Social Vulnerability Index have higher than expected growth rates. Continued efforts in street tree planting should utilize known growth rates while incorporating community voices to better provide long-term ecosystem services across NYC. [ABSTRACT FROM AUTHOR]

Background: Drought periods are major evolutionary triggers of wood anatomical adaptive variation in Lower Tropical Montane Cloud Forests tree species. We tested the influence of historical drought events on the effects of ecological stress memory on latewood width and xylem vessel traits in two relict hickory species (Carya palmeri and Carya myristiciformis) from central-eastern Mexico. We hypothesized that latewood width would decrease during historical drought years, establishing correlations between growth and water stress conditions, and that moisture deficit during past tree growth between successive drought events, would impact on wood anatomical features. We analyzed latewood anatomical traits that developed during historical drought and pre- and post-drought years in both species. Results: We found that repeated periods of hydric stress left climatic signatures for annual latewood growth and xylem vessel traits that are essential for hydric adaptation in tropical montane hickory species. Conclusions: Our results demonstrate the existence of cause‒effect relationships in wood anatomical architecture and highlight the ecological stress memory linked with historical drought events. Thus, combined time-series analysis of latewood width and xylem vessel traits is a powerful tool for understanding the ecological behavior of hickory species. [ABSTRACT FROM AUTHOR]

Questions: How does the grass layer affect seedlings across large environmental gradients in savannas? Location: Savanna sites in Argentina, Tanzania, and South Africa. Methods: We carried out a joint analysis of three grass removal experiments in which seedlings of various Fabaceae species were transplanted into plots with native grass and companion plots where grass had been removed. First, we estimated the effect of grasses on tree seedling mortality and seedling growth rate at each site. Then, we used the resulting coefficient estimates from site‐level models to examine the impact of two climate (monthly precipitation and aridity index) and two soil (soil organic carbon content and clay content) variables on the direction and magnitude of the grass effects. Results: Grasses increased the risk of mortality, but there was no evidence for a global effect of grasses on tree seedling rate of height growth. The best model fit indicated a high mortality risk of tree seedlings in response to grasses at intermediate aridity index values. No other climate or soil variable influenced tree seedling survival or growth (monthly precipitation, soil organic carbon content and clay content). Conclusions: Our results support the notion that the grass layer consistently creates a bottleneck to tree seedling establishment in African and South American savannas beyond climate and soil conditions, mainly by affecting tree seedling survival. The negative effect of grasses on seedling survival was lower in dry conditions compared to intermediate aridity levels. These results suggest that grass–seedling interaction is less intense in drier conditions, possibly due to reduced total grass biomass, which leads to decreased site evapotranspiration and improved soil water retention capacity. [ABSTRACT FROM AUTHOR]

Questions: To comprehensively understand ecological dynamics within a forest ecosystem, it is vital to explore how surrounding trees influence the growth of individual trees in a community. This study investigates the importance of biotic interactions on tree growth by examining several metrics of competitive interactions and community structure and considering three classes of intrinsic growth rates among the focal individuals: slower, intermediate, and faster‐growing trees. We also separated the focal trees based on their canopy position. Location: Brazilian subtropical forests. Methods: We assessed various factors related to the focal trees and their neighbors, including differences in traits, neighborhood crowding, phylogenetic distance, and overall trait composition within the community. We then ran linear mixed‐effects models to test how these different metrics influenced the growth rates of the focal trees. Results: Our results indicate that phylogenetic distance is linked to higher growth. Specific leaf area (SLA), leaf area (LA), and wood density (WD) are significantly related to tree growth. Trees surrounded by neighbors with higher SLA than themselves grow better, particularly smaller trees. Similarly, taller trees with smaller LA than their neighbors grow better. Trees in the intermediary growth class grow better when they have higher WD than their neighbors. Conversely, smaller trees benefit from greater WD difference between the focal trees and their neighbors, while height difference negatively impacts faster‐growing trees. Moreover, communities with higher SLA and WD positively impact the growth of faster‐growing trees. Conclusions: We conclude that the interactions between trees are mediated by their ecological differences, but the performance and responses to surrounding competitors vary along with their grow class and position within a community. This study has revealed that the tree's intrinsic growth rate mediates the effect of traits and phylogeny of surrounding trees on individual tree growth. [ABSTRACT FROM AUTHOR]

Summary: Ectomycorrhizal symbiosis, which involves mutually beneficial interactions between soil fungi and tree roots, is essential for promoting tree growth. To establish this symbiotic relationship, fungal symbionts must initiate and sustain mutualistic interactions with host plants while avoiding host defense responses. This study investigated the role of reactive oxygen species (ROS) generated by fungal NADPH oxidase (Nox) in the development of Laccaria bicolor/Populus tremula × alba symbiosis.Our findings revealed that L. bicolor LbNox expression was significantly higher in ectomycorrhizal roots than in free‐living mycelia. RNAi was used to silence LbNox, which resulted in decreased ROS signaling, limited formation of the Hartig net, and a lower mycorrhizal formation rate.Using Y2H library screening, BiFC and Co‐IP, we demonstrated an interaction between the mitogen‐activated protein kinase LbSakA and LbNoxR. LbSakA‐mediated phosphorylation of LbNoxR at T409, T477 and T480 positively modulates LbNox activity, ROS accumulation and upregulation of symbiosis‐related genes involved in dampening host defense reactions.These results demonstrate that regulation of fungal ROS metabolism is critical for maintaining the mutualistic interaction between L. bicolor and P. tremula × alba. Our findings also highlight a novel and complex regulatory mechanism governing the development of symbiosis, involving both transcriptional and posttranslational regulation of gene networks. [ABSTRACT FROM AUTHOR]

Individual-tree-based models (IBMs) have emerged to provide finer-scale operational simulations of stand dynamics by accommodating and/or representing tree-to-tree interactions and competition. Like stand-level growth model development, IBMs need an array of detailed data from individual trees in any stand through repeated measurement. Conventionally, these data have been collected through forest mensuration by establishing permanent sample plots or temporary measurement plots. With the evolution of remote sensing technology, it is now possible to efficiently collect more detailed information reflecting the heterogeneity of the whole forest stand than before. Among many techniques, airborne laser scanning (ALS) has proved to be reliable and has been reported to have potential to provide unparallel input data for growth models. This study utilized repeated ALS data to develop a model to project the annualized individual tree height increment (ΔHT) in a conifer plantation by considering spatially explicit competition through a mixed-effects modelling approach. The ALS data acquisition showed statistical and biological consistency over time in terms of both response and important explanatory variables, with correlation coefficients ranging from 0.65 to 0.80. The height increment model had high precision (RMSE = 0.92) and minimal bias (0.03), respectively, for model fitting. Overall, the model showed high integrity with the current biological understanding of individual tree growth in a monospecific Pinus radiata plantation. The approach used in this study provided a robust model of annualized individual tree height growth, suggesting such an approach to modelling will be useful for future forest management. [ABSTRACT FROM AUTHOR]

Twisted trunks are not uncommon in trees, but their effects on tree growth are still unclear. Among coniferous tree species, the phenomenon of trunk distortion is more prominent in Pinus yunnanensis. To expand the germplasm of genetic resources, we selected families with excellent phenotypic traits to provide material for advanced generation breeding. The progeny test containing 93 superior families (3240 trees) was used as the research material. Phenotypic measurements and estimated genetic parameters (family heritability, realistic gain and genetic gain) were performed at 9, 15, and 18 years of age, respectively. The genetic evaluation yielded the following results (1) The intra-family variance component of plant height (PH) was greater than that of the inter-family, while the inter-family variance components of other traits (diameter at breast height (DBH), crown diameter (CD), height under branches (HUB), degree of stem-straightness (DS)) were greater than that of the intra-family, indicating that there was abundant variation among families and potential for selection. (2) At half rotation period (18 years old), there was a significant correlation among the traits. The proportion of trees with twisted trunks (level 1–3 straightness) reached 48%. The DS significantly affected growth traits, among which PH and DBH were the most affected. The volume loss rate caused by twisted trunk was 18.06-56.75%, implying that trunk distortion could not be completely eliminated after an artificial selection. (3) The influence of tree shape, crown width, and trunk on volume increased, and the early-late correlation between PH, DBH and volume was extremely significant. The range of phenotypic coefficient of variation, genetic variation coefficient and family heritability of growth traits (PH, DBH, and volume) were 44.29-127.13%, 22.88-60.87%, and 0.79–0.83, respectively. (4) A total of 21 superior families were selected by the method of membership function combined with independent selection. Compared with the mid-term selection (18 years old), the accuracy of early selection (9 years old) reached 77.5%. The selected families' genetic gain and realistic gain range were 5.79-19.82% and 7.12-24.27%, respectively. This study can provide some useful reference for the breeding of coniferous species. [ABSTRACT FROM AUTHOR]

Lianas, or woody vines, are key components of many tropical forests and can have substantial impacts on the dynamics and functioning of these important ecosystems. Their competition with trees for resources, in particular light, can hamper the recovery of forests from disturbances. Yet, it is unclear how forest disturbance interacts with liana–tree ratio (LTR), topography and soil properties to shape tree dynamics and the trajectories of forest succession.Using temporal data from the Kilombero Valley and the Udzungwa Mountains of Tanzania, we demonstrate how the dynamics of tree stems and biomass vary between secondary and old‐growth forests with changes in the dominance of lianas and environmental gradients.Greater tree recruitment and mortality in secondary forests compared with old‐growth forests suggested rapid regeneration processes and faster turnover. However, no significant differences were found in the net annual changes in the number or biomass of trees between secondary and old‐growth forests.Our findings also showed that higher LTRs were positively associated with stem mortality but also with tree biomass growth, indicating a nuanced ecological role of lianas in forest ecosystems, which warrants further investigation to fully understand the causal factors at play.Net changes in tree stem numbers decreased significantly with elevation, implying climatic constraints on forest regeneration at higher elevations. Soil cation exchange capacity and organic carbon were found to significantly influence tree stem recruitment and net change in abundance, although their effects on biomass remained unclear.Synthesis: Our findings indicate that the recovery of tropical forests from disturbance in terms of the number and biomass of tree stems may be predictable along environmental gradients. These insights have the potential to broaden our capacity to develop more nuanced strategies that identify when and where tropical forests may require restoration interventions, with a focus on structural recovery. [ABSTRACT FROM AUTHOR]

Summary: This work is part of a project investigating the heartwood formation process in Scots pine. Despite the economic and ecological importance of pine heartwood (HW), the process of its formation in many respects remains poorly understood. Scientists believe that HW formation in Scots pine begins at 9–20 years, however, systematic studies of HW initiation age in this species have not previously been conducted. Samples were collected from 105 P. sylvestris trees aged 10 to 25 years, growing in the middle and northern taiga subzones, as well as on the border of the northern taiga subzone with the tundra. Samples were taken at the trunk base according to a single technique and processed using two biochemical (peroxidase activity, pinosylvin presence) and two anatomical markers (presence of extractives on the tracheid pit membranes, nuclei disappearance) characterizing different events during HW formation. Biochemical markers showed an overestimation in the number of HW annual rings compared with HW determination based on anatomical criteria by 1–3 years, on average. Attempts to detect peroxidase activity showed a negative result in the inner sapwood annual ring, while detectable pinosylvin accumulation occurred in the transition zone (TZ). We have detected for the first time true HW (without living cells) in Scots pine samples with a cambial age (CA) of 15–17 years. The number of growth rings in TZ and HW in young trees depended on growth conditions. These results are important for understanding the mechanisms of HW formation and developing realistic models of this process, including changing climate conditions. [ABSTRACT FROM AUTHOR]

Dendrochronological studies with shrubs from arid ecosystems in South America are of great importance due to the scarcity of ecological information that exists in these environments. This approach allows to evaluate the responses of plant species exposed to climate variability under arid conditions. We developed ring width chronologies and evaluated, for the first time for Argentina, the relationship between radial growth and climatic variables (precipitation, temperature and aridity index) of two shrub species characteristic of arid montane environments, Proustia cuneifolia and Hualania colletioides. The chronology of P. cuneifolia recorded a positive correlation with precipitation (May), temperature (October, July and February), and SPEI (June-October). The chronology of H. colletioides showed negative correlation with the temperature of the months of December and February. The results suggest that variations of the annual ring widths of P. cuneifolia are influenced by regional climate, mainly by aridity, while the growth of H. colletioides could be influenced by factors at the scale of microsite. A more extensive network of chronologies is necessary to explore site-climate variability under conditions of a complex topography such as that found in mountainous areas, suggesting the spatial extension of these records in order to understand in more detail the climatic imprint on the annual growth of these shrubs. [ABSTRACT FROM AUTHOR]

The functioning of a tree is shaped by the neighbouring species through the interspecific interaction and local environments. The functional trait composition of the neighbourhood could provide mechanistic insights into the effects of neighbours on the resource strategies of focal trees. In this study, we deployed an automated high‐frequency measurement of the sap flow density (SFD) and the radial growth of 48 trees of 12 species at BEF‐China, a large‐scale forest biodiversity manipulation experiment, to investigate the consequences and underlying mechanisms of the functional trait composition of the neighbourhood on the sap flow and radial growth of focal trees. We found a positive relationship between SFD and growth, reflecting the important supportive role of sap flow in tree growth. High functional diversity (FD) of the neighbourhood depressed SFD but promoted growth when considering all species, and thus promoted water‐use efficiency. Acquisitiveness of neighbouring trees positively affected growth, suggesting interspecific facilitation. Furthermore, neighbourhood FD benefits evergreen focal trees by promoting growth. However, in deciduous focal trees, neighbourhood FD reduced SFD but had no significant effects on growth. Our findings suggest that considering the functional trait composition of neighbourhood communities will support effective afforestation and forest management. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]