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Epoxy insulators in gas-insulated power apparatus are subjected to the combined effects of electrical and mechanical loads. In this work, a simulation model is built based on the energy theory to explore the electrical tree growth of epoxy resin under tensile and compressive stresses. With increasing AC voltage, the electrical tree growth is promoted, exhibiting a morphology with more branches. Tensile stress accelerates the electrical tree growth, while proper compressive stress has the opposite effect. However, when the compressive stress exceeds a certain value, electrical tree growth is promoted again. When the mechanical stress is vertical to the needle electrode, these effects primarily impact the length of the trees. Conversely, in parallel cases, mechanical stress mainly affects the width of the electrical trees. Filler doping play the role of obstacles as well as enhancing the electric field concentration, the electrical tree growth is firstly inhibited and then promoted as the doping content increases. The electrical tree morphologies of simulation and experiment are in good consistency, proving the reasonability of the simulation model. [ABSTRACT FROM AUTHOR]

Introduction: Groundcover management plays a crucial role in improving water retention and soil nutrition in orchard systems, thereby preventing environmental constrains by non-point source pollution. However, effectiveness of groundcover management in citrus orchards developed on sloping farmland with eroded purple soil has not been studied in detail. In particular, information on the soil nutrient losses, e.g. , nitrogen (N) and phosphorus (P), through interflow and its effects on growth and nutrition of citrus plants has not been reported. Methods: The present study evaluated the effects of different cover crops, i.e. , Lolium perenne L. (Lolium), Vicia villosa Roth (Vicia) and Orychophragmus violaceus (Ory), on nutrition and growth of citrus trees as well as water, soil and nutrient retention in an orchard developed in sloping farmland during two consecutive years. Results and discussion: The results show that the groundcover species Lolium and Vicia mediated nursing effects on nutrition and growth of citrus trees. These nursing effects included enhanced foliar levels of carbon(C), N and P as well as increased tree height, stem diameter, and crown width. Groundcover management generally reduced the annual surface runoff, interflow, soil loss, total N loss and total P loss. Among the cover crop species studied, Lolium and Vicia were overall more efficient than Ory in this context. Lolium reduced the average annual total loss of N and P by 42.53% and 49.23%, respectively, compared with clean tillage. The estimated annual reduction potentials of soil, N and P losses in Southwestern China were 16.3, 3.4 and 8.5 million tons yr-1, respectively. Obviously, Lolium and Vicia provide highly beneficial ground coverage on sloping farmland and, thus, can be used for future sustainable development of citrus orchards. [ABSTRACT FROM AUTHOR]

The simulation and modelling of tree growth is a complex subject with a long history and an important area of research in both computer graphics and botany. For more than 50 years, new approaches to this topic have been presented frequently, including several aspects to increase realism. To further improve these achievements, we present a compact and robust functional‐structural plant model (FSPM) that is consistent with botanical rules. While we show several extensions to typical approaches, we focus mainly on the distribution of light as a resource in three‐dimensional space. We therefore present four different light distribution models based on ray tracing, space colonization, voxel‐based approaches and bounding volumes. By simulating individual light sources, we were able to create a more specified scene setup for plant simulation than it has been presented in the past. By taking into account such a more accurate distribution of light in the environment, this technique is capable of modelling realistic and diverse tree models. [ABSTRACT FROM AUTHOR]

Remote sensing technology has found extensive application in agriculture, providing critical data for analysis. The advancement of semantic segmentation models significantly enhances the utilization of point cloud data, offering innovative technical support for modern horticulture in nursery environments, particularly in the area of plant cultivation. Semantic segmentation results aid in obtaining tree components, like canopies and trunks, and detailed data on tree growth environments. However, obtaining precise semantic segmentation results from large-scale areas can be challenging due to the vast number of points involved. Therefore, this paper introduces an improved model aimed at achieving superior performance for large-scale points. The model incorporates direction angles between points to improve local feature extraction and ensure rotational invariance. It also uses geometric and relative distance information for better adjustment of different neighboring point features. An external attention module extracts global spatial features, and an upsampling feature adjustment strategy integrates features from the encoder and decoder. A specialized dataset was created from real nursery environments for experiments. Results show that the improved model surpasses several point-based models, achieving a Mean Intersection over Union ( m I o U ) of 87.18%. This enhances the precision of nursery environment analysis and supports the advancement of autonomous nursery managements. [ABSTRACT FROM AUTHOR]

Land-use changes and anthropogenic disturbances are major threats to biodiversity, affecting ecosystem function and recovery. In boreal Alberta, Canada, petroleum development has led to extensive landscape fragmentation, notably through linear clearings created for seismic exploration that remove surface vegetation and microtopography. Despite partial recovery on forested seismic lines, peatland recovery is often arrested, impacting wildlife and carbon dynamics. Restoration efforts employ silviculture techniques to create microtopography and foster tree growth, but the efficacy of restoration treatments in restoring peatland plant diversity remains uncertain. We compared taxonomic, phylogenetic, and functional diversity of understory plant communities across treated and untreated seismic lines, alongside reference sites in treed bogs and fens. Treated lines generally had a twofold increase in plant height, leaf dry matter content, and foliar nitrogen and phosphorus contents compared to reference sites. In bogs, treated lines differed from reference conditions driven by increases in herbaceous taxa, while fens displayed disparities mainly in taxonomic and phylogenetic diversity. Differential responses of bogs and fens underline the necessity for tailored management strategies. Changes in plant diversity away from restoration targets have implications for ecosystem recovery, emphasizing the importance of long-term monitoring to evaluate the effectiveness of silviculture techniques in restoring boreal peatland plant communities. [ABSTRACT FROM AUTHOR]

After canopy removing disturbance, recalcitrant understory shrubs can rapidly occupy the forest understory to the detriment of tree regeneration and growth. The expansion of recalcitrant species has been documented following stand replacing disturbances, such as fire and timber harvest. However, there is little information on how these species respond to much smaller canopy gaps created by the senescence and (or) death of single or groups of canopy trees. In this study, we determined the response of Labrador tea (Rhododendron groenlandicum Oeder.), a recalcitrant ericaceous shrub, to canopy gaps in a late-successional boreal forest in northwestern Ontario, Canada. We evaluated functional traits related to the morphology and regeneration strategy of this plant to elucidate the mechanism of gap filling. We found that R. groenlandicum abundance and vigor were greater at the center of treefall gaps than in gap edges or the forest understory due to aggressive sprouting from buried clonal bud banks. Layering was higher in canopy gaps than in the understory. The composition of ground cover and rooting substrate was more influential on the adventitious rooting of the layered stems than increased light availability in gaps. We found a strong response of R. groenlandicum to small canopy openings, suggesting that the species can form recalcitrant understory layers even in the absence of stand replacing disturbance. [ABSTRACT FROM AUTHOR]

The dating of landslide movements is a unique opportunity to learn about their past in the absence of archival data. Dendrogeomorphic methods, based on the study of tree rings, offer an exceptional combination of accuracy and temporal range of dating. However, most landslide studies to date have been based on the analysis of macroscopic growth disturbances in trees. In doing so, the use of anatomical growth responses may be more advantageous in some aspects. Thus, this study aims to introduce the spectrum of anatomical growth responses in trees induced by landslide movements for their dating, substantiating their advantages and limitations, and comparing them with each other. Samples from roots and trunks of sycamore maple (Acer pseudoplatanus L.) growing on a landslide of known time of occurrence (May 2010) were used. Geophysical ERT measurements were performed to test the assumption of subsurface influence of landslide movements on tree growth. Based on the results focused on the intensity of changes in vessel lumen area (VLA) and percentage changes of VLA within the tree ring, anatomical changes identified in four different geomorphic situations on the landslide with expected different effects of landslide movements on tree growth were compared with each other. Responses in tree roots were generally significantly stronger compared to those in tree trunks. However, the short time series and difficult cross-dating of roots can be considered as a disadvantage. On the other hand, the identification of anatomical responses in trees with straight trunks (until now practically not used in landslide research) allows a significant expansion of the number of trees usable for landslide dating in the future. [ABSTRACT FROM AUTHOR]

• Wetter winters as a result of climate change increase N and S topsoil availability in forests. • Surprisingly high leaching rates of additionally available nutrients. • No short-term effects of wetter winters on decomposition and tree growth. • Groundwater N and S pollution likely increases with winter climate change. Climate models project moderate to large increases in air temperature for most temperate ecosystems with an overall increase in winter precipitation and a shift from snow towards rain. We investigated the effects of increased winter rainfall on the ecosystem functioning of European beech forests at their north-eastern distribution range. In a large-scale field experiment we manipulated winter climate at nine forest sites by increasing the amount of rainfall and excluding snow. Nutrient availability in the topsoil and leaching in 50 cm depth as well as litter decomposition and radial growth of mature European beech trees were analysed. It was hypothesized that (1) wetter winters lead to increased nutrient deposition as well as leaching, with an overall increase in net nutrient availability, (2) decomposition decreases in response to water addition containing also additional nutrients and (3) primary production during the subsequent growing season increases as presumably not all additionally available nutrients would be leached. We found an increase in topsoil nitrate and sulfate availability during winter in response to rain addition, likely as a consequence of collecting more atmospheric deposition, and surprisingly high leaching rates of the additionally available nutrients. During the subsequent early growing season, no difference in nutrient availability could be observed anymore. Enhanced nutrient availability in the topsoil and leaching do not seem to have a strong short-term influence on forest ecosystem processes in ecosystems which are close to their critical load of N deposition. Decomposition rates during winter and early growing season as well as stem diameter growth during the following growing season were not influenced. This indicates that additional nutrients in the topsoil in response to wetter winters are not available for plant growth but pollute ground- and surface waters. [ABSTRACT FROM AUTHOR]

[Objective] This study investigated the growth conditions and fruit traits of different jujube varieties introduced to southern Xinjiang and selected the best varieties suitable for local jujube production. [Method] One-year-old branches of 17 excellent fresh jujube varieties in China were selected as scions, and 5-year-old gray jujube was selected as rootstock for introduction tests in Aksu, Xinjiang. By comparing the phenological period, tree growth potential (grafting survival rate, tree growth amount and dendritic force), fruit results (fruit lifting rate, fruit cracking rate, fruit mass, fruit uniformity and edible rate) and fruit quality (appearance color, flesh taste and flavor and main nutrient contents), 9 varieties with good taste, flavor and nutrient contents were initially screened. According to contents of soluble solid, VC, titrable acid and soluble sugar, single fruit mass, edible rate, fruit shape index and fruit uniformity, these varieties were scored by grey correlation method. [Result] After the introduction to southern Xinjiang, the phenological periods were quite different among varieties, which included 2 very early maturing varieties, 5 early maturing varieties, 9 medium maturing varieties and 1 medium late maturing variety. The graft survival rates of all varieties were higher than 65%. Jinggudazao, Fucuimi, Lengbaiyu and Yujiao trees had large growth amounts, strong branching force and prosperous growth. In the second and third years of grafting, fruit lif-ting rates of all varieties were relatively stable and consistent, and Zaocuimi and Luzao 5 had higher rate. Fruit cracking rates of Jingzao 28 and Jingzao 60 were 20. 57% and 23. 83%, respectively. Single fruit mass was very different among verities, ranging from 4. 22 to 26. 18 g, and the single fruit masses of most varieties were higher in the third year than in the second year. The fruit uniformity was 46. 63% to 79. 41%, and the edible rates were 91. 67% to 98. 76%. The fruit appearance was different among varieties, mainly in oval, oblong and inverted oval shapes. The fruit size was also greatly different with light red or red color. In the second year (2021), Jinsi 4 had the highest content of soluble solids of 38. 33%. The soluble sugar contents of Zaocuimi, Fucuimi and Jinsi 4 were higher than 29%. The titrable acid contents of Jingzao 18 and Yulu were above 1. 41%. The VC contents of Yujiao, Luzao 5 and Jinggudazao were higher than 400 mg/hg. According to the taste and flavor, 9 varieties with crisp, delicate and juicy flesh were initially screened, including Zaocuimi, Zaoqiuhong, Fucuimi, Yingbailu, Yueguang, Jingzao 28, Jingzao 60, Luzao 5 and Yulu. Three varieties of Jingzao 60, Jingzao 28 and Yueguang with good comprehensive fruit quality were selected by the comprehensive score of grey correlation degree. [Conclusion] Jingzao 60, Jingzao 28 and Yueguang can be promoted and cultivated as the main fresh jujube varieties in southern Xinjiang as they well adapted to the climate and site conditions and showed good yield and fruit quality. [ABSTRACT FROM AUTHOR]

New forests on former agricultural land originate either from natural regeneration or active restoration. Previous research has compared biodiversity of naturally regenerated stands (NR) and plantations (PL), however, whether understory succession towards natural forests depends on stand type remains unknown. In this study, we used data from two monitorings on permanent plots (2011 and 2019) in PL (n = 11) and NR (n = 11) birch stands in Estonia to highlight successional changes in herb and bryophyte communities together with environmental changes. We further evaluated whether stand type influenced the recovery of forest specialists. We found an increase in tree growth characteristics, soil phosphorus and nitrogen content, no change in light conditions and a decrease in soil pH in both stand types. The amount of litter and deadwood was higher in NR in 2011. Herb richness increased from 123 to 130 and the number of bryophytes from 43 to 62. Stand types shared 50% of herb species in 2011 and 2019, while the fraction of shared bryophytes increased from 37.2 to 56.5%. We observed an increase of forest specialists and a decrease in light-demanding species (based on indicator value for light) in both stand types. Bryophyte cover and richness increased and species compositions of stand types converged. However, the number of bryophytes was significantly higher in NR plots indicating the significance of deadwood as growth substrate. We conclude that the recovery of forest understory followed similar successional pathways in PL and NR. [ABSTRACT FROM AUTHOR]

Phonolite rock powder is an alternative to potassium fertilizer, having applicable K and Na content among rocks, as well as others nutrients (e.g. Ca, S and Si). The study tested the effects of replacing KCl with phonolite rock powder on tree growth, nutrition, and nutrient cycling in a Eucalyptus stand. We compared four top dressing fertilization treatments: PHO (91.7 kg ha− 1 of K and 47.5 kg ha− 1 of Na, applied via phonolite); SOD (54.2 kg ha− 1 Na, applied via NaCl); KCl (91.7 kg ha− 1 of K), and Control (no top dressing fertilization); where KCl and SOD present equivalent molar amount (2.33 kmol). Leaf K concentrations were elevated in the KCl treatment and leaf Na concentrations were elevated in the SOD treatment. Leaf K and Na concentrations in the phonolite rock powder treatment were similar to or lower than those in the KCl and SOD treatments. There were no differences among treatments in tree growth, volume, and aboveground biomass, probably due to a prolonged drought, during which precipitation was 27% below and the average temperature was 2.3ºC above the local historical average. Trees fertilized with KCl had the highest K deposition in litterfall, those fertilized with NaCl had the highest Na deposition, and phonolite rock powder fertilization was intermediate for both elements. We conclude that despite the use of phonolite did not significantly enhance the growth of eucalyptus plants, its application as a fertilizer yielded comparable leaf concentration, stem volume, and aerial biomass to that achieved with KCl, and in certain instances, even surpassed the results obtained with NaCl fertilization proving it applicability when compared to traditional sources, such as KCl. [ABSTRACT FROM AUTHOR]

Coastal wetlands surrounding urban environments provide many important ecosystem services including protection from coastal erosion, soil carbon sequestration and habitat for marine and terrestrial fauna. Their persistence with sea-level rise depends upon their capacity to increase their soil surface elevation at a rate comparable to the rate of sea-level rise. Both sediment and organic matter from plant growth contribute to gains in soil surface elevation, but the importance of these components varies among sites and with variation in climate over long time scales, for which monitoring is seldom available. Here, we analysed variation in surface elevation, surface accretion and mangrove tree growth over 15 years in Moreton Bay, Queensland, Australia, a period that spans variation in the El Niño/La Niña (ENSO) cycle, which strongly influences rainfall and sea level in the region. Piecewise structural equation models were used to assess the effects of biotic (tree growth, plant cover and bioturbation by invertebrates) and environmental factors on annual surface elevation increments throughout this period. Our model for mangroves identified that surface accretion and tree growth were both positively influenced by rainfall, but surface elevation was not, and thus, higher levels of compaction of the soil profile in high rainfall/high sea level years were inferred. In contrast, our saltmarsh model found that rainfall positively influenced surface accretion and elevation gains. Declines in surface elevation in the mangroves were influenced by the species composition of the mangrove, with higher levels of elevation loss occurring in mangrove forests dominated by Avicennia marina compared to those with a higher proportion of Rhizophora stylosa. Decadal-scale variation in ENSO affected mangrove tree growth, but surface elevation trends were more strongly influenced by variation in environmental conditions than by tree growth, although effects of biotic factors (mangrove species composition and bioturbation) on surface elevation trends were observed. Further research into tipping points with extreme ENSO events (either La Niña with high rainfall and high sea level or El Niño with low rainfall and low sea levels) will help clarify the future of mangrove and saltmarsh distribution within Moreton Bay. [ABSTRACT FROM AUTHOR]

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Background: The genus Robinsonia DC. (tribe Senecioneae, Asteraceae) endemic to the Juan Fernández Islands in Chile is one of the most conspicuous insular plant groups in the world. Unlike typical herbaceous Asteraceae plants, these plants demonstrate spectacular and unusual rosette tree growth forms as shown by the alpine giant senecios (genus Dendrosenecio, tribe Senecioneae) endemic to the East African mountains. However, monophyly of the genus and phylogenetic relationships among species of Robinsonia as well as their plastome evolution remain elusive. This study aims to explore their phylogeny, species diversification, and molecular evolution based on the complete plastome sequences in the context of adaptive radiation on oceanic islands. Results: The insular Robinsonia plastomes are highly conserved in their structures and organization of contents. Five divergence hotspots as potential chloroplast markers and five positively selected coding genes (accD, ndhF, rpoA, ycf1, and ycf2) are identified. Robinsonia plastomes has an overall nucleotide diversity higher than that of the sky island Dendrosenecio, but much lower than herbaceous Senecio. Phylogenetic analysis demonstrates the monophyly of Robinsonia and identifies two major infrageneric lineages. Both Robinsonia and Dendrosenecio are deeply nested within large genus Senecio. Conclusions: While plastid genomes of Robinsonia are highly conserved, their sequences strongly demonstrated the monophyly of the genus and inferred robust interspecific relationships, including herbaceous Senecio and woody Dendrosenecio. Different sets of positively selected chloroplast genes, five for Robinsonia and two for Dendrosenecio, may play an important role in the adaptation strategies of these fascinating woody species in insular and continental sky island habitats. Overall phylogenetic positions and sister lineages of Robinsonia and Dendrosenecio require additional study based on broader sampling of Senecio. [ABSTRACT FROM AUTHOR]

Tree‐growth stability is crucial in upholding forest ecosystem services. Despite extensive research on the correlation between tree growth and climate, the influence of forest understorey on tree‐growth stability remains understudied. We surveyed forest plots and collected tree‐ring samples along two elevational gradients, ranging from 3600 to 4400 m a.s.l., in the southeastern Tibetan Plateau. An index was developed to quantify individualistic growth stability of trees, and its linkage with the complexity of forest understorey structure was examined. We found that tree‐growth stability is more pronounced in complex forest communities. In forests with higher understorey complexity, the proportion of trees experiencing growth release increased during wet years, while those with growth suppression augmented during dry years. Interestingly, a subset of trees exhibits abnormal growth increases even during the driest years, whereas another subset shows abnormal growth reductions during the wettest years. Furthermore, forests with more complex understorey structures exhibited a higher proportion of trees showcasing these two types of ‘anti‐phase’ growth statuses. Synthesis. Our study underscores the linkage between individualistic growth stability of trees and the complexity of understorey structures. The growth stability of the overstorey layer is conveyed at the expense of individual‐level growth stability and synchrony in forests with complex understorey structures. These findings emphasize the necessity for attention to the interplay between tree growth and understorey community structures when assessing the impacts of future climate change on forest dynamics. [ABSTRACT FROM AUTHOR]

Freeze events govern the distribution and structure of mangrove ecosystems, especially in tropical‐temperate transitional zones. Understanding mangrove responses to freezing is crucial for predicting their poleward expansion under climate change. However, there is a need for field‐based measurements of mangrove freeze resistance and resilience. After an extreme winter storm in December 2022, we measured mangrove post‐freeze damage and recovery (January and November 2023), building on a pre‐freeze baseline assessment conducted in July 2022 across 12 sites along the temperature gradient of Florida's Gulf of Mexico coast (USA). Low‐temperature thresholds for leaf damage to Avicennia germinans, Rhizophora mangle and Laguncularia racemosa were quantified near −6, −4 and − 4°C, respectively. Thresholds for mortality were found to be near −6 to −7°C for A. germinans and −4 to −5°C for R. mangle. A threshold for loss of reproductivity in A. germinans was identified near −6 to −7°C. Resprouting was observed in all three species but limited to just one individual for R. mangle. Surviving A. germinans resprouted vigorously and had the greatest number of resprout branches, which was proportional to leaf damage. Tall A. germinans had a higher resprout percentage than short trees. Strata‐specific differences in freeze damage were most pronounced for R. mangle, with higher damage in tall versus short trees, while no difference was found between A. germinans strata. These results suggest that R. mangle population recovery may depend on the growth of short trees, while A. germinans can recover from all strata. Minimum air temperature was strongly correlated with mangrove height and above‐ground biomass. Projections of future minimum temperature and species‐specific freeze degree days predict warming winters, suggesting further mangrove development and range expansion under climate change. Synthesis: Collectively, our study advances understanding of mangrove responses to freezing and identifies low‐temperature thresholds for each species, aiding predictions of mangrove range expansion. [ABSTRACT FROM AUTHOR]

ABSTRACT Traditional photosynthesis‐driven growth models have considerable uncertainties in predicting tree growth under changing climates, partially because sink activities are directly affected by the environment but not adequately addressed in growth modelling. Therefore, we developed a semi‐mechanistic model coupling stomatal optimality, temperature control of enzymatic activities and phenology of cambial growth. Parameterized using Bayesian inference and measured data on Picea abies and Pinus sylvestris in peatland and mineral soils in Finland, the coupled model simulates transpiration and assimilation rates and stem radial dimension (SRD) simultaneously at 30 min resolution. The results suggest that both the sink and phenological formulations with environmental effects are indispensable for capturing SRD dynamics across hourly to seasonal scales. Simulated using the model, growth was more sensitive than assimilation to temperature and soil water, suggesting carbon gain is not driving growth at the current temporal scale. Also, leaf‐specific production was occasionally positively correlated with growth duration but not with growth onset timing or annual cambial area increment. Thus, as it is hardly explained by carbon gain, phenology itself should be included in sink‐driven growth models of the trees in the boreal zone and possibly other environments where sink activities and photosynthesis are both restrained by harsh conditions. [ABSTRACT FROM AUTHOR]

Summary Wood of broad‐leaf tree species is a valued source of renewable biomass for biorefinery and a target for genetic improvement efforts to reduce its recalcitrance. Glucuronoxylan (GX) plays a key role in recalcitrance through its interactions with cellulose and lignin. To reduce recalcitrance, we modified wood GX by expressing GH10 and GH11 endoxylanases from Aspergillus nidulans in hybrid aspen (Populus tremula L. × tremuloides Michx.) and targeting the enzymes to cell wall. The xylanases reduced tree height, modified cambial activity by increasing phloem and reducing xylem production, and reduced secondary wall deposition. Xylan molecular weight was decreased, and the spacing between acetyl and MeGlcA side chains was reduced in transgenic lines. The transgenic trees produced hypolignified xylem having thin secondary walls and deformed vessels. Glucose yields of enzymatic saccharification without pretreatment almost doubled indicating decreased recalcitrance. The transcriptomics, hormonomics and metabolomics data provided evidence for activation of cytokinin and ethylene signalling pathways, decrease in ABA levels, transcriptional suppression of lignification and a subset of secondary wall biosynthetic program, including xylan glucuronidation and acetylation machinery. Several candidate genes for perception of impairment in xylan integrity were detected. These candidates could provide a new target for uncoupling negative growth effects from reduced recalcitrance. In conclusion, our study supports the hypothesis that xylan modification generates intrinsic signals and evokes novel pathways regulating tree growth and secondary wall biosynthesis. [ABSTRACT FROM AUTHOR]

Resilience to drought represents an important focus for trees during climate change, with the aim of predicting the resistance and recovery of species worldwide. Previous studies mainly linked tree growth resilience to plant functional traits that are related to resource acquisition and investment. Here, we investigate a potential link between resilience and the amount of parenchyma tissue in wood, a multifunctional tissue that may provide various physiological benefits to drought‐related mechanisms. We compiled a global tree‐ring data set to evaluate the relationship between growth resistance, resilience or recovery from drought and xylem parenchyma tissue fractions of 50 angiosperms, which was complemented with a local study of nine species from Mt. Tiantong in China. We also assessed the influence of climate and phylogeny on these relationships. We found that growth recovery after drought was positively related to the fractions of total parenchyma locally and globally. This association remained statistically significant when accounting for the effects of climate and phylogeny. No other associations between parenchyma fractions and growth resilience metrics were statistically significant. Our results suggest that drought recovery of angiosperm trees is affected by the amount of parenchyma. Incorporating xylem parenchyma fraction with other traits, such as hydraulic traits, could therefore enhance our comprehension of how various angiosperm tree species will respond to future droughts. Further studies should focus on unravelling the physiological roles of xylem parenchyma fraction. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Based on the need to protect previous ancient trees and the development of dendroclimatology, the use of non-destructive technologies in tree-ring research has gained increasing attention. This study focuses on the ancient Pinus tabulaeformis in Yu Xiang Forest Farm in Henan Province. Firstly, samples were collected using the traditional Increment borers and the Resistograph, a non-destructive method. Subsequently, the peak-valley analysis was used to filter the data obtained by the Resistograph to extract the tree ring width sequence, and the data's accuracy was verified by correlation analysis with tree ring width sequence by the Increment borers. Then, the optimal filtering method and an appropriate comprehensive threshold were determined, and tree ring width and density sequences were successfully extracted. Following that, the growth trend and residual resistance in the measurement process were corrected using linear fitting and Ensemble Empirical Mode Decomposition (EEMD) technology, thereby establishing the tree-ring width and density index series, which were further validated through correlation analysis and t-tests. Finally, analysis of the correlation with climatic factors, identified the main limiting factors for tree growth, and the accuracy of the tree-ring information extracted by the Resistograph was further verified. The results showed that spite of certain differences between the tree-ring width indices extracted by the Resistograph and the Increment borer, they were generally reliable. The radial growth of the ancient P. tabulaeformis in Yu Xiang Forest Farm is primarily influenced by temperature, with the maximum density of the tree rings responding more significantly to the mean maximum temperature, while the minimum density of the tree rings responded more significantly to the mean minimum temperature. These results not only provide a scientific and accurate age for the protection of ancient trees and verify the reliability of the data obtained by the Resistograph, but also facilitate the use of non-destructive technology for in-depth study of ancient trees, therefore enhancing our understanding of how climate change affects tree growth and provide valuable insights for the future protection and management of these ancient trees. [ABSTRACT FROM AUTHOR]

Late spring frosts, occurring after spring phenological events, pose a dire threat to tree growth and forest productivity. With climate warming, earlier spring phenological events have become increasingly common and led to plants experiencing more frequent and severe frost damage. However, the effect of late spring frosts after leaf-out on subsequent flowering phenology in woody species remains unknown. Utilizing 572,734 phenological records of 640 species at 5024 sites from four long-term and large-scale in situ phenological networks across the Northern Hemisphere, we show that late spring frosts following leaf-out significantly delay the onset of the subsequent flowering by approximately 6.0 days. Late-leafing species exhibit greater sensitivity to the frosts than early-leafing species, resulting in a longer delay of 2.5 days in flowering. Trees in warm regions and periods exhibit a more pronounced frost-induced flowering delay compared to those in cold regions and periods. A significant increase in the frequency of late spring frost occurrence is observed in recent decades. Our findings elucidate the intricate relationships among leaf-out, frost, and flowering but also emphasize that the sequential progression of phenological events, rather than individual phenological stages, should be considered when assessing the phenological responses to climate change. Climate warming causes earlier spring phenological events and higher risk of late spring frost damage. Here, the authors investigate the impact of late spring frosts on phenological events, finding that they delayed flowering by an average of 6 days across 640 species. [ABSTRACT FROM AUTHOR]

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. Significance Statement: The lenticel is a porous, channel‐like structure that forms during plant secondary growth. Despite the description of the general structure of lenticels, their impact on plant growth and the specific cellular and molecular processes involved in their development remain incompletely understood. The study elucidates the critical role of the lenticel in tree growth and delineates the cellular process and metabolic specialization involved in its development. [ABSTRACT FROM AUTHOR]

We present new climate field reconstructions (CFR) of tropical Pacific ENSO sea surface temperatures (HadISST) for the boreal winter season using a circum‐Pacific tree‐ring network from known El Niño rainfall impact regions. We use two different CFR methods: Point‐by‐Point Regression (PPR) and reduced‐space Orthogonal Spatial Regression (OSR). Both methods produce reconstructions with high validation skill, but OSR is preferred because it has less spatial noise and is more efficient. Only the leading EOF of the SST field (EOF1) can be skillfully reconstructed by either method; EOF2 does not validate. The success of EOF1 reflects its importance for ENSO rainfall impacts over land; the failure with EOF2 is from the lack of these impacts. EOF1 allows for the reconstruction of many ENSO indices, including the ENSO Longitudinal Index (ELI). We also find evidence in our reconstructions for a recent increase in ENSO activity. Plain Language Summary: Earth's climate is strongly affected by how warm the tropical Pacific Ocean "El Niño" region is. This is especially true for the delivery of rainfall over many parts of the globe. Tree growth can thus be strongly affected by El Niño impacts on rainfall. We use this relationship to reconstruct tropical Pacific sea surface temperatures associated with El Niño over most of the past millennium from a network of annual tree‐ring chronologies located in regions known to be impacted by El Niño rainfall. Only the leading mode of variability in Pacific sea surface temperatures associated with El Niño can be reconstructed well, but it reflects most of the long‐term variability of El Niño exceptionally well. The reconstruction extends back to 1500 with exceptional skill and back to 1100 with acceptable skill. We can thus compare recent El Niño variability, perhaps affected by global warming, with what happened over the previous centuries unaffected by human activity. We find evidence for an increase in El Niño activity, and for an overall warming in recent decades. Key Points: Tree‐ring series from ENSO rainfall impact regions reconstruct tropical Pacific SSTs with high degrees of skill back to 1500 CE and 1100 CETwo very different reconstruction methods produce similar results and each can only reconstruct the leading EOF mode of SST variabilityReconstructions extending back 1100 CE indicate a recent increase in El Niño variability, and overall SST warming in the equatorial Pacific [ABSTRACT FROM AUTHOR]

Iron (Fe) plays a fundamental role in the nutrition of plants, yet its role in oil palm remains understudied. This study aims to unlock the role of Fe by analyzing its cycling and export different stages of oil palm tree growth. The experiment was conducted in Thailand, Pará State (Brazil), in a dystrophic Yellow Ferralsol, in a split-block, with four replications and seven treatments (plant age; 2, 3, 4, 5, 6, 7, and 8). The concentration, accumulation, recycling, immobilization, and export of Fe were evaluated, in addition to Fe use efficiency, in all plant organs. Analysis of variance (p < 0.05) was carried out on the results and regression model adjustments. The concentration and accumulation of Fe in the stem was greatest at the eighth year of the plants, and the fruit had higher Fe export values in the eighth year of the oil palm as well. As plants aged, the Fe concentration, accumulation, export, and use efficiency increased. Oil palm accumulates and immobilizes more Fe in its organs than it exports, a fact that contributes to the cycling and nutrition of the Fe in the plant. This research paves the way for future studies to explore how Fe can be optimized in oil palm trees to unlock their full potential. [ABSTRACT FROM AUTHOR]

Pilgerodendron uviferum is an endemic Cupressaceae of Patagonia (Argentina) that is restricted to a small group of individual trees, growing in isolated populations (relicts) along its distribution. The main objective was to evaluate the habitat, forest structure, leaf traits, leaf nutrient reabsorption and growth of four relicts (area between 0.3 and 0.86 ha) in the Santa Cruz province (Argentina) to improve the available information for forest conservation purposes. Principal components analysis was conducted to determine the separation between relict populations based on their ecological characteristics (individual and habitat levels). We found contrasting environmental and forest structure conditions among the four studied relicts. For example, two relicts associated with Nothofagus antarctica showed higher values of P. uviferum tree density, DBH and dominant height at the stand level. Alongside that, these relicts presented a higher sapling density (1950–3167 ind ha−1) and understory plant diversity compared to pure P. uviferum relicts growing near the ecotone with the steppe grassland. Specific leaf area, carbon and nutrient concentrations in P. univerum leaves varied depending on the relict conditions and tree age of the individuals. The mean nutrient resorption efficiency varied according to relicts and particular nutrients, ranging from 18.1% to 49.5% for Ca and P, respectively. The diameter growth of the dominant P. univerum trees ranged from 0.33 to 0.46 mm yr−1, indicating that the species follows a stress-tolerant strategy. The information of this work may assist in the conservation of marginal P. uviferum forest communities spatially disconnected with continuous forests, growing in relicts. [ABSTRACT FROM AUTHOR]

AbstractAn accurate investigation is needed to determine if the selected location, the tree species, and the applied treatments can support a successful seedling establishment and outplanting performance to ensure the success of large-scale tree-planting initiatives. To shed light on the growth pattern of the trees used in the Green Belt Project plantations in the Mongolian steppe, we analysed the biomass allocation in the stem and roots of Ulmus pumila in terms of ring width, considering different management techniques involving irrigation and fertilisation. We found that the root and shoot ring width of U. pumila followed a bell-shaped curve and reached maximum values after three or four years from seedling outplanting. Moreover, our data confirm that increasing watering regimes may enhance plant growth, especially the root system, while fertilisation did not show a positive effect independently of the fertilisation type (i.e. NPK and compost). Our data allowed us to develop a predictive regression model that could be used with other species and in different environmental conditions to forecast stem and root tree growth and to simulate afforestation performances in different climatic conditions. [ABSTRACT FROM AUTHOR]

One of the key challenges in robotics is the motion planning problem. This paper presents a local trajectory planning and obstacle avoidance strategy based on a novel sampling-based path-finding algorithm designed for autonomous vehicles navigating complex environments. Although sampling-based algorithms have been extensively employed for motion planning, they have notable limitations, such as sluggish convergence rate, significant search time volatility, a vast, dense sample space, and unsmooth search routes. To overcome the limitations, including slow convergence, high computational complexity, and unnecessary search while sampling the whole space, we have proposed the RE-RRT* (Robust and Efficient RRT*) algorithm. This algorithm adapts a new sampling-based path-finding algorithm based on sampling along the displacement from the initial point to the goal point. The sample space is constrained during each stage of the random tree's growth, reducing the number of redundant searches. The RE-RRT* algorithm can converge to a shorter path with fewer iterations. Furthermore, the Choose Parent and Rewire processes are used by RE-RRT* to improve the path in succeeding cycles continuously. Extensive experiments under diverse obstacle settings are performed to validate the effectiveness of the proposed approach. The results demonstrate that the proposed approach outperforms existing methods in terms of computational time, sampling space efficiency, speed, and stability. [ABSTRACT FROM AUTHOR]

Studying tree growth processes helps us evaluate the success of restoration efforts in recovering ecosystem processes such as carbon accumulation. Here, we study aboveground biomass dynamics in four common‐endemic tree species from the tropical Andes (Quercus humboldtii, Retrophyllum rospigliosii, Citharexylum subflavescens, and Croton magdalenensis), established in the main water supply basins of Medellín, Colombia. We use measurements from 19 permanent plots from five censuses between 2010 and 2023 to develop biomass equations as a function of t for each species (B = f[t]) by combining tree growth models of diameter (D) as a function of time (t) and pre‐existing allometric equations of biomass (B) developed in the same site as a function of D and wood density (ρ). We found that, because of initially higher growth rates characteristic of species belonging to the fast‐growing end of the fast‐slow growth economic spectrum, C. magdalenensis and C. subflavescens were the species with higher biomass accumulation at 13 years (142 and 132 kg, respectively). However, the potential of the slow‐growing species (Q. humboldtii and R. rospigliosii) for carbon sequestration initiatives in the long term was highlighted. To our knowledge, this is the first study in the region examining the dynamics of aboveground biomass in Andean restoration programs. It combines growth models and allometric equations, which can be useful for measuring the success of the implementation of ecological restoration programs and evaluating the need to apply adaptive management strategies. [ABSTRACT FROM AUTHOR]

Phyllosphere microorganisms are essential for plant growth and health. Although there are an increasing number of studies showing that the composition of phyllosphere communities varies among different plant species, it remains unclear whether and how their bacterial and fungal community composition predictably varies with plant traits and leaf age. In this study, we used high-throughput sequencing to explore the diversity and composition of phyllosphere communities in needles of different ages (originating from different cohorts) for three evergreen coniferous species (Pinus koraiensis, Picea koraiensis, and Abies nephrolepis). Our results indicated that Gammaproteobacteria (bacteria) and Dothideomycetes (fungi) were dominant in newly formed needles, whereas Actinobacteria (bacteria) and Eurotiomycetes (fungi) were dominant in perennial needles. Tree species identity and needle age were the main factors explaining the variations of the α diversity (species richness of phyllosphere communities) and β diversity (dissimilarity among phyllosphere communities). In particular, we found that leaf dry matter content, leaf mass per area, and total phosphorus content emerged as key predictors of composition and diversity of phyllosphere microbial communities, underscoring the major influence of tree species identity and needle age on phyllosphere communities through changes in plant functional traits. Finally, we found that the interaction between tree species identity and needle age also contributed significantly to explaining the diversity and composition of phyllosphere communities, probably because differences in plant functional traits or environmental conditions between new and perennial needles depend on tree growth rates and resource acquisition strategies. These findings provide new insights into the mechanisms of community assembly among different evergreen tree species and offer a better understanding of the interactions between plant traits and phyllosphere microorganisms during needle aging. [ABSTRACT FROM AUTHOR]

The Democratic Republic of the Congo (DRC) is facing a shortage of local scientists, particularly in the field of environmental research, which is hindering the study and preservation of the Congo River Basin rainforest. The lack of researchers is seen as a threat to the long-term survival of the rainforest, which is the second largest in the world. While foreign researchers contribute to the study of the rainforest, local scientists offer language skills, knowledge of local cultures, and a better understanding of the landscape. However, training and retaining researchers in the DRC is challenging due to limited funding, outdated science curricula, poor infrastructure, and low salaries. Efforts are being made to boost local scientific capacity, but more support and investment are needed to address these obstacles and ensure the preservation of the rainforest. [Extracted from the article]

Light is essential for tree growth and development, yet some species are able, or prefer, to tolerate shady conditions without adversely affecting their development. This ecological preference prompts different strategies in these species, often involving a trade-off between performance and safety in terms of mechanical support, conductivity, and pest and disease protection. Studies on the ecological strategies of trees and their associated functional traits are essential to gain further insight into biodiversity and the processes that shape wood quality from the standpoint of technological properties useful to humans. This literature review showcases current links between ecological preferences and the main functional traits of tree species, with particular emphasis on wood properties. [ABSTRACT FROM AUTHOR]

Climate change is a major global concern that has increased the frequency and intensity of extreme drought. Severe drought stress negatively affected tree survival and growth. Poplars are fast-growing trees that can effectively sequester atmospheric carbon dioxide, the most important greenhouse gas. Recently, poplar has attracted attention as a bioenergy fuel source, owing to its fast-growing traits and abiotic stress tolerance. However, the molecular mechanisms underlying drought tolerance in poplars remain uncertain. Therefore, we compared the transcriptomes of P. davidiana and its hybrid with Populus alba grown under drought stress. Before drought stress, genes related to root development processes were up-regulated, and aboveground tissue development genes were down-regulated in P. davidiana compared to P. alba × P. davidiana. After 6 days of drought treatment, P. alba × P. davidiana showed susceptibility to drought stress, whereas P. davidiana exhibited a resistant phenotype. At the transcriptional level, cell wall and lignin biosynthesis genes were up-regulated on day 6 of drought treatment. We concluded that P. davidiana showed more resistance to drought stress than its hybrid and that cell wall biosynthetic processes contributed to drought tolerance by preventing xylem damage. These results could provide valuable information for poplar breeding to improve drought stress tolerance. [ABSTRACT FROM AUTHOR]

Fine roots play a crucial role in soil nutrient and water acquisition, significantly contributing to tree growth. Fine roots with a high specific root length (SRL) and small diameter are often considered to help trees grow fast. However, inconsistencies in the literature do not provide a clear basis on the effect of root functional traits, such as SRL or root mass density (RMD), on tree growth rate in phylogenetically related trees. Our aim was to examine relationships between tree growth rate and root functional traits, using clones displaying different growth rates in a hybrid poplar plantation located in New Liskeard, ON, Canada. Fine roots (diameter < 2 mm) samples were collected using soil cores at depths of 0–20, 20–40 and 40–60 cm, and analyzed for morphological, chemical and architectural traits. High SRL and thin fine roots were associated with the least productive clones, which is not consistent with the root economics spectrum (RES) theory. However, the most productive clone had larger fine root diameter and higher root lignin concentrations, probably reducing root construction and maintenance costs and carbon losses. Therefore, at the 0–20 and 20–40 cm depths, tree growth rates showed positive correlations with root diameter and root lignin concentrations, but negative correlations with SRL and root soluble compounds concentration. Increasing RMD at the 0–20 cm depth promoted tree growth rates, showing the importance of soil exploration in the topsoil for tree growth. We conclude that fine root variation does not always follow the RES hypothesis and argue that the rapid growth rate of trees may also be driven by fine root growth in diameter and mass in phylogenetically related trees. [ABSTRACT FROM AUTHOR]

Lowland northern white-cedar (Thuja occidentalis L.) forests are increasingly exposed to extreme droughts and floods that cause tree mortality. However, it is not clear the extent to which these events may differentially affect regeneration of cedar and its increasingly common associate, balsam fir (Abies balsamea (L.) Mill.). To test this, we measured how seedlings of cedar and fir were able to avoid, resist and recover from experimental drought and flood treatments of different lengths (8 to 66 days). Overall, we found that cedar exhibited a strategy of stress resistance and growth recovery (resilience) from moderate drought and flood stress. Fir, on the other hand, appears to be adapted to avoid drought and flood stress and exhibited overall lower growth resilience. In drought treatments, we found evidence of different stomatal behaviors. Cedar used available water quickly and therefore experienced more drought stress than fir, but cedar was able to survive at water potentials > 3 MPa below key hydraulic thresholds. On the other hand, fir employed a more conservative water-use strategy and therefore avoided extremely low water potential. In response to flood treatments, cedar survival was higher and only reached 50% if exposed to 23.1 days of flooding in contrast to only 7.4 days to reach 50% mortality for fir. In both droughts and floods, many stressed cedar were able to maintain partially brown canopies and often survived the stress, albeit with reduced growth, suggesting a strategy of resistance and resilience. In contrast, fir that experienced drought or flood stress had a threshold-type responses and they either had full live canopies with little effect on growth or they died suggesting reliance on a strategy of drought avoidance. Combined with increasingly variable precipitation regimes, seasonal flooding and complex microtopography that can provide safe sites in these forests, these results inform conservation and management of lowland cedar stands. [ABSTRACT FROM AUTHOR]

Summary: Forest fires play a significant role in the growth and development of trees because they can damage the phloem and cambium. Fire injury induces the formation of fire scars that can cause xylem dysfunction. The study area is located in Taşköprü, Kastamonu (Western Black Sea of Turkiye), where two forest fires occurred in 1957 and 2020. In this study, the effect of the 1957 fire on the tree-ring widths and tracheid dimensions of Pinus nigra trees was investigated. We measured tree-ring widths and tracheid dimensions of fire-scarred (FS) and unscarred (UF) trees during four different periods: the pre-fire period (1947–1956), fire event year (1957), and post–fire periods (1958–1967 and 2011–2020). In this study, UF trees showed almost 2.5–3 times wider tree–ring widths (TRWs) than FS trees. FS and UF trees also showed great variation in tracheid dimensions in the four different periods; the average tracheid diameter (TD), lumen area (TLA), and wall thickness (TWT) values increased significantly in UF trees compared to FS trees during the fire event and post-fire periods. The average TD, TLA, and average tracheid lumen diameter (TLD) decreased during the fire and post-fire years in the FS trees. In this study, we suggest that fire injury significantly affects the tracheid dimensional traits of FS Pinus nigra trees. Our results also suggest that although Pinus nigra trees experienced serious fire damage, they continued to grow but with a decrease in tracheid size. [ABSTRACT FROM AUTHOR]

In the current context of climate change, this paper provides a brief overview of climate-vegetation interactions in the Mediterranean basin, where global warming and aridification trends are predicted to intensify. Rising temperatures coupled with extreme drought events have notable impacts on forest ecosystems, triggering dieback and mortality phenomena worldwide. The health status of forest vegetation may be assessed by either ground surveys or remote sensing. Several investigations of declining oak forests in the Apennine region have shown that the drought vulnerability of Mediterranean oaks is dependent on differences in access to deep soil water pools, which can be related to differences in rooting depth, tree size and growth rate. Forest dieback is widely reported in Italy, but the extent and overall distribution of this phenomenon have not yet been well defined. Thus, understanding the future dynamics of forest stands has several key objectives: inventorying declining forest stands to gain insight into the phenomenon and create a nationallevel database; locating these stands to allow monitoring of their evolution over time; and monitoring to allow planning of mitigation measures, as well as recovery and adaptation strategies. This background led to the implementation of SilvaCuore, the first web application designed in Italy to report forest health status. Silvacuore is a web application developed with the aim of improving the link between citizens and the scientific community by contributing to the development of a valuable scientific database. The direct involvement of citizens in forest preservation offers an interesting perspective because the innovative use of technology can tap into citizens' growing enthusiasm for environmental topics. Thus, SilvaCuore may be viewed from a dual perspective as a resource for the scientific community and as a unique opportunity for citizens to take an active role in research activities (Citizen Science project). [ABSTRACT FROM AUTHOR]

With ongoing global warming, increasing water deficits promote physiological stress on forest ecosystems with negative impacts on tree growth, vitality, and survival. How individual tree species will react to increased drought stress is therefore a key research question to address for carbon accounting and the development of climate change mitigation strategies. Recent tree‐ring studies have shown that trees at higher latitudes will benefit from warmer temperatures, yet this is likely highly species‐dependent and less well‐known for more temperate tree species. Using a unique pan‐European tree‐ring network of 26,430 European beech (Fagus sylvatica L.) trees from 2118 sites, we applied a linear mixed‐effects modeling framework to (i) explain variation in climate‐dependent growth and (ii) project growth for the near future (2021–2050) across the entire distribution of beech. We modeled the spatial pattern of radial growth responses to annually varying climate as a function of mean climate conditions (mean annual temperature, mean annual climatic water balance, and continentality). Over the calibration period (1952–2011), the model yielded high regional explanatory power (R2 = 0.38–0.72). Considering a moderate climate change scenario (CMIP6 SSP2‐4.5), beech growth is projected to decrease in the future across most of its distribution range. In particular, projected growth decreases by 12%–18% (interquartile range) in northwestern Central Europe and by 11%–21% in the Mediterranean region. In contrast, climate‐driven growth increases are limited to around 13% of the current occurrence, where the historical mean annual temperature was below ~6°C. More specifically, the model predicts a 3%–24% growth increase in the high‐elevation clusters of the Alps and Carpathian Arc. Notably, we find little potential for future growth increases (−10 to +2%) at the poleward leading edge in southern Scandinavia. Because in this region beech growth is found to be primarily water‐limited, a northward shift in its distributional range will be constrained by water availability. [ABSTRACT FROM AUTHOR]

The Qinling Mountains, serving as a natural geographical and climatic boundary in China, require comprehensive climatic records to elucidate the trends in climate changes across the country. While stable isotopes in tree rings are widely employed to indicate historical environmental changes, investigations into tree ring isotopes in the Qinling Mountains, particularly within the widespread broad-leaf oaks, remain limited. In this study, we investigated both intra- and inter-annual variations in the δ13C values of tree rings and their correlations with climatic signals over the past two decades for Quercus aliena var. acuteserrata, a dominant species among oak trees on the main peak of the Qinling Mountains. Our results reveal that responses to climate differ among altitudes and individual trees, with trees at higher altitudes exhibiting higher sensitivity to extreme climate, which is low temperatures and rainfall fluctuations during the growth period in intra-annual δ13C variations. Furthermore, the positive correlations are observed between temperature during growing season and both tree growth and the inter-annual δ13C variations. However, the climate signal appears to be hampered by oak-specific factors, such as intense competition among individuals and the age of trees. Therefore, we suggest a more rigorous selection of sampling and propose further investigations into isotopic fractionation processes in oaks for future studies. [ABSTRACT FROM AUTHOR]

An infinite homogeneous tree is a special type of graph that has a completely symmetrical structure in all directions. For an infinite homogeneous tree T = (V , E) with the natural distance d defined on graphs and a weighted measure μ of exponential growth, the authors introduce the variable Lebesgue space L p (·) (μ) over (V , d , μ) and investigate it under the global Hölder continuity condition for p (·) . As an application, the strong and weak boundedness of the maximal operator relevant to admissible trapezoids on L p (·) (μ) is obtained, and an unbounded example is presented. [ABSTRACT FROM AUTHOR]

In commercial Pinus taeda stands, the appearance of needle chlorosis has intensified in slow growth areas. This study aimed to verify if Visible Atmospherically Resistant Index (VARI) captures heterogeneity of Pinus taeda development and to determine what specific factors are associated with occurrence of chlorotic symptoms. We evaluated a 14 year-old reforested P. taeda stand that had already undergone two thinnings; the study area encompassed 18.42 ha on soil derived from acidic igneous parent material. A VARI map was used to delineate the area into four classes: Very Low, Low, Medium, and High. In each class, tree growth was evaluated, and samples of tree tissue (needles, trunk cross sections, and fine roots), litter, and soil were collected for evaluation. There were no differences in soil classification and fertility between classes for this acidic low fertility soil. However, compared to the lower VARI classes (Low and Very Low), tree wood volume (without bark) of the High class was 0.20 m3 higher per tree. Higher VARI classes showed greater concentrations of Ca and Mg in needles, bark, and fine roots. The High class also showed higher concentrations of Ca and Mg in litter, but with less litter accumulation. Therefore, VARI efficiently captured tree growth heterogeneity with a direct relationship noted between VARI and tree growth (height, DBH, volume, and trunk mass). In addition, chlorosis symptoms (yellowing) at needle tips and tree crown loss were more likely indicative of Mg deficiency, which probably caused reduced tree development. [ABSTRACT FROM AUTHOR]

Crown profile has been the key indicator for assessing tree vigor and has many potential applications in forest growth modelling and forest management. Based on the measurement of the branches for a total of 156 Larix kaempferi individual trees from Liaoning province, Hubei province and Gansu provinces, we developed a nonlinear mixed effects outer-and inner-crown profile model, which included tree variables, climate variables, competition indices, and site quality. The effects of dominant tree height (Hdom), competition indices and climate variables on crown modelling were analyzed. The results showed that climate, competition and Hdom all had significant effects on the outer-and inner-crown profile. Among them, the ratio of DBH of the subject tree to the DBH of the largest individual tree in the stand (DDM) is the most significant competition index. The outer-crown radius increased with the increasing of DDM, and the inner-crown radius decreased with the increasing of DDM. Hdom also showed significant effect on outer-and inner-crown radius. Mean warmest month temperature (MWMT) were selected as the best climate variable to incorporate into the outer-crown profile model, and mean coldest month temperature (MCMT) for the inner-crown profile model. The regularity for the difference of outer-crown radius among three regions was Gansu > Liaoning > Hubei and Liaoning > Hubei for the inner-crown radius. Compared with base model, mean square error reduction (MSER) of the nonlinear mixed effect outer-crown profile model was 22.3% and the nonlinear mixed effect inner-crown profile model was 37.5% compared to the base model. The relative contributions of each variable to the outer-crown profile were DBH (40.05%), site quality (31.11%), CR (16.16%), competition (5.83%), HD (5.47%), and MWMT (1.38%), and the relative contributions to the inner-crown profile were MCMT (40.79%), DBH (32.32%), site quality (25.68%), and competition (1.21%). [ABSTRACT FROM AUTHOR]

Understanding the growth efficiency of individual trees, or growth per unit of resource utilization, can inform silvicultural management strategies to maximize tree and stand growth. Stand structure—the size and spatial distributions of trees within the stand—strongly influences water, light, and nutrient availability, as well as the resource-use efficiency of each tree. Key silvicultural tools for stand management include manipulating tree density, size distribution, and arrangement by controlling natural regeneration, artificial seeding, planting seedlings, and/or subsequent thinning of established trees. We analyzed two sets of plots from even-aged stands of common coniferous species in central Spain, 106 pure Scots pine (Pinus sylvestris) and 92 pure Mediterranean pine (Pinus pinaster), to examine the dynamics of the dominance hypothesis, the relationship between stand structure and growth, and the relationship between structure and growth efficiency. Our main findings revealed a negative impact of size-class uniformity on stand growth in both Scots pine and Mediterranean pine, while the positive effect of tree size on growth efficiency was supported for Mediterranean pine stands but uncertain for Scots pine. At the operational level, our results highlight how thinning intensity is more important than the thinning method in Mediterranean pinewoods and how thinning can benefit the provision of multiple ecosystem services. We also recommend integrating dominance effects on growth into individual tree modelling. [ABSTRACT FROM AUTHOR]

The Himalayas are undergoing significant changes in temperature and moisture availability due to global climate change. Understanding how these changes affect tree growth is critical for conserving and managing this biodiverse region. To investigate the growth-limiting climatic factors, we collected tree-ring data from Abies pindrow old-growth mountain forests across 3190 to 3700 m a.s.l. in the inner valleys of the Garhwal Himalayas. This area faces significant temperature increases, reduced summer monsoon activity, and decreased winter precipitation. We found that over the past century, tree growth suffered from warm and dry springs and benefited from cool and moist springs, particularly at lower elevations (< 3400 m a.s.l.). Conversely, summer climate dynamics had minimal impact on radial growth. The sensitivity of Abies growth to spring climate can be attributed to the inner valleys' continental climate, marked by spring water deficit. Additionally, higher elevation trees (> 3400 m a.s.l.) showed positive correlations with dormant period temperatures in prior October and January, with the positive effect of October warmth strengthening over time. A dynamic analysis of the impact of spring (March–May) temperature, precipitation and Standardized Precipitation-Evapotranspiration Index revealed a recent unification (the 1980–2010s) of the climate–growth relationship across elevations. Specifically, the low-elevation trees have become less sensitive to warm springs, while the high-elevation trees have only recently become sensitive to warm and dry springs. The varying growth responses along the elevation gradient highlight the necessity of site-dependent differentiation when assessing the impacts of global climate change on species performance and geographic range shifts. [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]

Wood ash fertilization remarkably increases tree growth and hence, carbon sequestration in drained boreal peatland forests, particularly in nitrogen (N)-rich Scots pine sites with limited phosphorus (P) and potassium (K). Because ash lacks N, N-deficient ombrotrophic and poor oligotrophic sites are generally considered unsuitable for ash fertilization. In this study, timber production was investigated in six field experiments in N-poor, drained Scots pine dominated peatlands in central Finland, where ash fertilization was applied 15–85 years earlier. Ash significantly increased tree growth in all the study sites. Unfertilized plots showed long-term average mean annual increment (MAI) of 2.01 m3·ha−1·a−1, whereas in fertilized plots MAI was 4.46 m3·ha−1·a−1. An analysis with nonlinear mixed effects model revealed a faster volume yield development and higher asymptote of the mean curve in fertilized plots. Higher amount of K in the ash significantly increased the response. Fertilizations were financially lucrative: on average, the break-even cost surpassed the ash fertilization cost (390 € ha−1) more than two-fold at 5% interest rate. The current nutrient status of fertilized trees was rather balanced. The results proved that the long-term growth response to ash fertilization in poor drained peatland sites is comparable to N-rich sites, but the response time is distinctively longer. [ABSTRACT FROM AUTHOR]

Leaf‐cutting ants (LCA) are one of the most important pests in the Neotropics region. To estimate the potential biomass consumption by LCA on Salicaceae plantations in the lower delta of the Paraná River, we studied the foraging activity and harvesting patterns of Acromyrmex lundii (Guérin‐Méneville, 1838) and Acromyrmex ambiguus (Emery, 1888) (Hymenoptera: Formicidae) in a 14‐year‐old poplar plantation in Argentina. Foraging activity (workers/time), harvested vegetal biomass (dry weight/time) and climatic conditions (temperature and relative humidity) were monitored daily and seasonally in nests from autumn 2016 to summer 2017. The two sympatric species harvested a similar quantity of dry biomass throughout the year (4.9–6.0 kg/colony). Although both species were active in all seasons, their foraging activity was higher in spring and summer, but they avoided extreme temperatures. The accumulated biomass harvested for both species was higher in summer (28.8 and 25.7 g/colony/day, for Ac. ambiguus and Ac. lundii, respectively). However, Ac. lundii harvested three times more biomass than Ac. ambiguus in spring (30.3 and 13.1 g/colony/day, respectively). Although the highest consumption on the vegetation occurred in summer, control tasks should be started during spring (sprouting phase), the most vulnerable period for Salicaceaes. The consumption of new leaves in spring is critical for tree growth, survival and wood production, especially by Ac. lundii, the most detrimental species during this season. [ABSTRACT FROM AUTHOR]

Growth curve models are popular tools for studying the development of a response variable within subjects over time. Heterogeneity between subjects is common in such models, and researchers are typically interested in explaining or predicting this heterogeneity. We show how generalized linear mixed-effects model (GLMM) trees can be used to identify subgroups with different trajectories in linear growth curve models. Originally developed for clustered cross-sectional data, GLMM trees are extended here to longitudinal data. The resulting extended GLMM trees are directly applicable to growth curve models as an important special case. In simulated and real-world data, we assess performance of the extensions and compare against other partitioning methods for growth curve models. Extended GLMM trees perform more accurately than the original algorithm and LongCART, and similarly accurate compared to structural equation model (SEM) trees. In addition, GLMM trees allow for modeling both discrete and continuous time series, are less sensitive to (mis-)specification of the random-effects structure and are much faster to compute. [ABSTRACT FROM AUTHOR]

Mangrove‐saltmarsh ecotones are experiencing rapid alterations due to climate change and human activities, however, the ecological and morphological implications of these shifts remain largely unknown. This study systematically explores how interspecific interactions and herbivory influence the dominant wetland species, as well as the resultant morphological evolution and landscape configuration. To achieve this, we develop a new eco‐morphodynamic model that integrates hydrodynamics, sediment transport, bed‐level change, and vegetation dynamics. The novelty of the current model lies in newly incorporated modules to simulate biotic interactions between mangroves and saltmarshes, enabling exploration of eco‐morphodynamic feedback in mangrove‐saltmarsh ecotones in response to tidal flows and species interactions. Our results show that vertical growth rates of coexisting vegetation species are dominant factors in determining wetland dominance. When mangroves and saltmarshes exhibit comparable growth rates, mangroves typically become the dominant wetland species. Conversely, if mangroves grow more slowly than saltmarshes, they are unable to outcompete saltmarshes. Additionally, herbivory can fundamentally alter wetland dominance depending on herbivore food preferences. Our simulations further underline that saltmarsh‐dominated wetlands develop channel networks more extensively and rapidly than mangrove‐dominated systems. This pattern is also observed during species invasions, with invading saltmarshes extending channel networks, while invading mangroves inhibit ongoing network expansion. This study highlights the pivotal roles of relative growth properties and herbivory in driving ecotone development in respect to wetland dominance and channel network development at the intertidal scale. Plain Language Summary: In coastal areas where mangrove trees and saltmarsh grasses exist together, climate change and human activities significantly impact wetland development. This study uses a novel computer model to explore how different plants interact, how plant‐eating animals influence plant distribution and how these factors affect the shape of coastal landscapes. Our findings reveal that mangrove trees with growth rates similar to saltmarsh grasses can outcompete saltmarshes and become the dominant wetland species. Additionally, animals that eat plants play a crucial role in determining which plants survive, with their effects highly dependent on their feeding preferences. Wetlands dominated by saltmarshes tend to develop deeper channels. This occurs because saltmarshes spread slowly and grow in patches, which changes water flow and promotes erosion in areas without vegetation. Conversely, wetlands where mangroves are taking over typically feature fewer and shallower channels. Overall, our study suggests that the growth rates of different plants and the presence of plant‐eating animals are essential in shaping these coastal environments. Key Points: A new eco‐morphodynamic model is developed accounting for facilitation, competition and predation in mangrove‐saltmarsh ecotonesEcotone dynamics at intertidal scale are determined by herbivory and the relative growth properties between mangroves and saltmarshesTidal networks in saltmarsh‐dominant ecotones are formed more rapidly and extensively with deeper channels [ABSTRACT FROM AUTHOR]

Nitrogen (N) addition can stimulate tree growth; however, the strength of this growth effect usually changes over time and the factors underlying these responses are not fully understood. Based on a decade‐long N addition experiment (by adding 0, 20, 50, and 100 kg N ha−1 yr−1) in a boreal forest, we studied responses of tree growth to N addition over time and explored the potential role of temporal precipitation variation and plant stoichiometric changes in mediating this. We found positive growth responses to N addition but this effect changed nonlinearly over time. Annual precipitation was positively related to growth under high‐level N addition; hence, a hump‐shape temporal pattern in precipitation contributed to the nonlinear tree growth responses. After precipitation effects were accounted for, the positive growth responses to N addition peaked in the seventh year and then declined for all levels of N. Later reductions in growth responses could partly be attributed to increased leaf N:phosphorus (P) ratio over time, especially at higher N addition rates. We also found an increase in soil acid phosphatase, the ratio of labile to occluded soil P fraction, and a decreased ratio in leaf N to P resorption efficiency with increasing N addition rates during the late stage of this experiment, suggesting increased P demand. Collectively, our results imply that changes in plant nutrient stoichiometry with cumulative N input may limit the N stimulation on tree growth over time, while temporal precipitation variation appears unlikely to modulate this effect under the atmospheric N deposition. Plain Language Summary: Tree growth can be limited by the availability of nitrogen (N), while the stimulation effects of increased N input on growth can change over time due to constraints by the availability of either water or other nutrients such as phosphorus (P). We investigated the temporal dynamics of tree growth to decade‐long N addition in a boreal forest and assessed how growth was mediated by temporal precipitation variation and plant tissue N:P. The rate of tree growth was enhanced by N addition, but the positive effect first increased but then decreased over time. Annual precipitation variation mediated the growth response to the highest N addition (100 kg N ha−1 yr−1) only, whereas an increase in leaf N:P ratio over time under N addition explained the changes in tree growth response to N addition. We also found evidence for the acceleration of ecosystem P cycling. Our findings suggest that the relative P limitation may constrain tree growth responses to increased N availability over time, and these should be considered in predicting forest carbon sequestration with N deposition. Key Points: Effects of N addition on tree growth changed nonlinearly over timeInterannual precipitation enhanced the stimulation effect of N addition on tree growth under the highest N level onlyThe increase in leaf N:P ratio over time mediated the temporal dynamics of tree growth responses to N addition [ABSTRACT FROM AUTHOR]

In mountainous tea plantations, which are the primary mode of tea cultivation in China, issues such as soil erosion and declining soil fertility are particularly severe. Although green manure cover is an effective agricultural measure for restoring soil fertility, its application in mountainous tea plantations has been relatively understudied. Methods: This study investigated the effects of continuous green manure cover using the slope-protecting plant Ophiopogon japonicus on tea plant growth and soil microbial community structure. We implemented three treatments: 1 year of green manure coverage, 2 years of coverage, and a control, to study their effects on tea plant growth, soil physicochemical properties, and soil bacterial and fungal communities. Results: Results demonstrate that green manure coverage significantly promote the growth of tea plants, enhanced organic matter and pH levels in soil, and various enzyme activities, including peroxidases and cellulases. Further functional prediction results indicate that green manure coverage markedly promoted several carbon cycling functions in soil microbes, including xylanolysis, cellulolysis, degradation of aromatic compounds, and saprotrophic processes. LEfSe analysis indicated that under green manure cover, the soil tends to enrich more beneficial microbial communities with degradation functions, such as Sphingomonas, Sinomonas, and Haliangium (bacteria), and Penicillium, Apiotrichum, and Talaromyce (fungi). In addition. Random forest and structural equation models indicated that carbon cycling, as a significant differentiating factor, has a significant promoting effect on tea plant growth. Discussion: In the management practices of mountainous tea plantations, further utilizing slope-protecting plants as green manure can significantly influence the soil microbial community structure and function, enriching microbes involved in the degradation of organic matter and aromatic compounds, thereby positively impacting tea tree growth and soil nutrient levels. [ABSTRACT FROM AUTHOR]