Tree Growth Research Articles

Morphological and genetic characterization of jackfruit (Artocarpus heterophyllus) in the Kayunga and Luwero districts of Uganda

BackgroundJackfruit (Artocarpus heterophyllus) is an economically valuable fruit tree in Uganda. However, the production of jackfruit in Uganda is low. Additionally, because of deforestation, genetic erosion of the resource is predicted before its exploitation for crop improvement and conservation. As a prerequisite for crop improvement and conservation, 100 A. heterophyllus tree isolates from the Kayunga and Luwero districts in Uganda were characterized using 16 morphological and 10 microsatellite markers.ResultsThe results from the morphological analysis revealed variations in tree height, diameter at breast height (DBH), and crown diameter, with coefficient of variation (CV) values of 20%, 41%, and 33%, respectively. Apart from the pulp taste, variation was also observed in qualitative traits, including tree vigor, trunk surface, branching density, tree growth habit, crown shape, leaf blade shape, fruit shape, fruit surface, flake shape, flake color, flake flavor and pulp consistency/texture. Genotyping revealed that the number of alleles amplified per microsatellite locus ranged from 2 to 5, with an average of 2.90 and a total of 29. The mean observed (Ho) and expected (He) heterozygosity were 0.71 and 0.57, respectively. Analysis of molecular variance (AMOVA) indicated that 81% of the variation occurred within individual trees, 19% among trees within populations and 0% between the two populations. The gene flow (Nm) in the two populations was 88.72. The results from the ‘partitioning around medoids’ (PAM), principal coordinate analysis (PCoA) and genetic cluster analysis further revealed no differentiation of the jackfruit populations. The Mantel test revealed a negligible correlation between the morphological and genetic distances.ConclusionsBoth morphological and genetic analyses revealed variation in jackfruit within a single interbreeding population. This diversity can be exploited to establish breeding and conservation strategies to increase the production of jackfruit and hence boost farmers’ incomes. However, selecting germplasm based on morphology alone may be misleading.

Effects of Aviation Mutagenesis on Soil Chemical Indexes, Enzyme Activities, and Metabolites of Dahongpao (Camellia sinensis) Tea Trees.

Aviation mutagenesis is a breeding method for the rapid selection of superior plant varieties. In this study, rhizosphere soil chemical indexes, soil enzyme activities, and soil metabolites were measured in Dahongpao tea trees with aviation mutagenesis (TM) and without aviation mutagenesis (CK). The main soil metabolites distinguishing TM and CK and their relationships with soil chemical indexes and soil enzyme activities were analyzed and obtained. The results showed that there was no significant change in the rhizosphere soils' pH of TM tea trees compared to CK (p = 0.91), while all other chemical indexes of TM were significantly higher than CK (p < 0.05). In addition, the activities of enzymes related to soil nutrient cycling such as urease, protease, sucrase, acid phosphatase and cellulase, and enzymes related to soil antioxidants such as superoxide dismutase, catalase, peroxidase, and polyphenol oxidase were significantly increased (p < 0.05) in the rhizosphere soils of TM tea trees compared to CK. Soil metabolite analysis showed that the main soil metabolites distinguishing CK from TM were carbohydrates, nitrogen compounds, and amines. Of these, carbohydrates and nitrogen compounds were significantly positively correlated with soil chemical indexes and soil enzymes, whereas amine was significantly negatively correlated with soil chemical indexes such as organic matter, total nitrogen, total potassium, available nitrogen, available phosphorus; amine showed significant negative correlation with soil enzymes such as catalase, peroxidase, polyphenol oxidase, and urease. It can be seen that aviation mutagenesis is conducive to improving the ability of tea tree rhizosphere aggregation and transformation of soil nutrients, increasing the total amount of soil nutrients and the content of available nutrients, which is more conducive to promoting the uptake of nutrients by the tea tree, and thus promoting the growth of the tea tree.

Influence of Leaf Area Index Inversion and the Light Transmittance Mechanism in the Apple Tree Canopy

Light plays a crucial role in the growth of fruit trees, influencing not only nutrient absorption but also fruit appearance. Therefore, understanding fruit tree canopy light transmittance is essential for agricultural and forestry practices. However, traditional measurement methods, such as using a canopy analyzer, are time-consuming, labor-intensive, and susceptible to external influences, lacking convenience and automation. To address this issue, we propose a novel method based on point clouds to estimate light transmittance, with the Leaf Area Index (LAI) serving as the central link. Focusing on apple trees, we utilized handheld LiDAR for three-dimensional scanning of the canopy, acquiring point cloud data. Determining the optimal voxel size at 0.015 m via standardized point cloud mean spacing, we applied the Voxel-based Canopy Profile method (VCP) to estimate LAI. Subsequently, we established a function model between LAI and canopy light transmittance using a deep neural network (DNN), achieving an overall correlation coefficient R2 of 0.94. This model was then employed to estimate canopy light transmittance in dwarfed and densely planted apple trees. This approach not only provides an evaluation standard for pruning effects in apple trees but also represents a critical step towards visualizing and intelligentizing light transmittance.

Inoculation with arbuscular mycorrhiza did not affect growth, root traits or gas exchange of grafted almond saplings when exposed to drought stress

Very little is known about potential benefits of using AM inoculation as a tool to alleviate drought stress of trees grown under nursery conditions. There is some evidence that benefits of mycorrhiza on gas exchange parameters and growth of trees are proportionally greater when trees are subjected to drought stress. We hypothesized that inoculation with mycorrhiza would increase growth, nutrition, stem water potential and gas exchange of containerized almond (Prunus dulcis (Mill.) D.A. Webb) when young trees are grown under low water availability.In the spring of 2015 and 2016, forty containerized almond trees (Nonpareil scion grafted on Hansen 536, a peach/almond hybrid rootstock) were either inoculated or not with a commercially available arbuscular mycorrhizal inoculum and kept well-watered for 60 days in 2015 and 54 days in 2016, after which half of the plants were exposed to gradually reduced water availability over 38 days in 2015 and 61 days in 2016. Measurements included growth metrics, stem water potential, stomatal density, leaf NPK concentration, light saturated photosynthesis, and parameters calculated from CO2 response curves (Vcmax, J, TPU, Rd, gm, and stomatal limitation).The low-water treatment decreased stem water potential and reduced trunk diameter growth, light saturated photosynthesis (A), stomatal conductance (gs), Vcmax, J, TPU, gm, specific root length, leaf N and K concentration and total leaf N, P, and K content. Inoculation decreased root mass, increased leaf mass fraction, and decreased root mass fraction in 2015, but not in 2016. Neither stem water potential nor gas exchange were significantly altered by inoculation. Inoculation decreased leaf stomatal density, and slightly elevated leaf N and P concentrations in the low water treatments, although not consistently across years. Contrary to expectations we did not find substantially greater benefits from mycorrhizal inoculation in young drought stressed almond trees and conclude that the potential for mycorrhizal inoculant to alleviate drought stress in containerized trees is minimal.

Combined effects of border irrigation and super-absorbent polymers on enzyme activity and microbial diversity of poplar rhizosphere soil.

Fast-growing poplar plantations are considered a great benefit to timber production, but water availability is a key factor limiting their growth and development, especially in arid and semi-arid ecosystems. Super-absorbent polymers facilitate more water retention in soil after rain or irrigation, and they are able to release water gradually during plant growth. This study aimed to examine the effects of reduced irrigation (60% and 30% of conventional border irrigation) co-applied with super-absorbent polymers (0, 40 kg/ha) on root exudates, enzyme activities, microbial functional diversity in rhizosphere soil, and volume increments in poplar (Populus euramericana cv. 'Neva'). The results showed that 60% border irrigation co-applied with super-absorbent polymers significantly increased the content of organic acids, amino acids and total sugars in the root exudates, and the activities of invertase, urease, dehydrogenase, and catalase in the rhizosphere soil in comparison to conventional border irrigation without super-absorbent polymers. Meanwhile, this treatment also enhanced the average well-color development, Shannon index, and McIntosh index, but decreased the Simpson index. Additionally, the average volume growth rate and relative water content of leaves reached their maximum using 60% irrigation with super-absorbent polymers, which was significantly higher than other treatments. However, using 30% irrigation with super-absorbent polymers, had a smaller effect on rhizosphere soil and volume growth than 60% irrigation with super-absorbent polymers. Therefore, using an appropriate water-saving irrigation measure (60% conventional border irrigation with super-absorbent polymers) can help to improve enzyme activities and microbial diversity in the rhizosphere soil while promoting the growth of poplar trees.

Major axes of variation in tree demography across global forests

The future trajectory of global forests is closely intertwined with tree demography, and a major fundamental goal in ecology is to understand the key mechanisms governing spatio‐temporal patterns in tree population dynamics. While previous research has made substantial progress in identifying the mechanisms individually, their relative importance among forests remains unclear mainly due to practical limitations. One approach to overcome these limitations is to group mechanisms according to their shared effects on the variability of tree vital rates and quantify patterns therein. We developed a conceptual and statistical framework (variance partitioning of Bayesian multilevel models) that attributes the variability in tree growth, mortality, and recruitment to variation in species, space, and time, and their interactions – categories we refer to as organising principles (OPs). We applied the framework to data from 21 forest plots covering more than 2.9 million trees of approximately 6500 species. We found that differences among species, the species OP, proved a major source of variability in tree vital rates, explaining 28–33% of demographic variance alone, and 14–17% in interaction with space, totalling 40–43%. Our results support the hypothesis that the range of vital rates is similar across global forests. However, the average variability among species declined with species richness, indicating that diverse forests featured smaller interspecific differences in vital rates. Moreover, decomposing the variance in vital rates into the proposed OPs showed the importance of unexplained variability, which includes individual variation, in tree demography. A focus on how demographic variance is organized in forests can facilitate the construction of more targeted models with clearer expectations of which covariates might drive a vital rate. This study therefore highlights the most promising avenues for future research, both in terms of understanding the relative contributions of groups of mechanisms to forest demography and diversity, and for improving projections of forest ecosystems.

Precocity of fruiting in Pinus yunnanensis revealed by common garden experiment and association analysis with molecular markers

Shortening the growth cycle and maintaining high yields are the goals pursued by all breeders. Under the distinct ecological conditions of tropical and rainy and dry seasons, many plants experience the phenomenon of early flowering and fruiting under adverse conditions. However, there is still no clear conclusion as to whether early flowering and fruiting will affect the vegetative growth of plants. In this study, the vegetative and reproductive growth traits of 270 families of Pinus yunnanensis of 6 years old in common garden were analyzed. There were significant differences in phenotypic traits of different populations, indicating that the trait differences were genetically stable. The variation of vegetative growth traits mainly comes from within populations, and the variation of reproductive growth traits mainly comes among populations. The average coefficient of variation of reproductive growth traits was significantly higher than that of vegetative growth traits. There was a positive correlation between vegetative growth traits and precocity of fruiting. Ecological environment factors have impact on phenotypic variation, among which the temperature of the wettest season has the greatest impact. According to cluster analysis, the nine populations could be divided into three categories. These cluster results were not due to geographic distances, indicating the discontinuity of phenotypic variation. By association analysis, 9 and 3 SSR loci were found to be significantly associated with the trait of precocity of fruiting, respectively. Among them, PK840 locus had the highest interpretation rate for the trait of precocity of fruiting. There were 10 and 7 unique haplotypes in precocity and non-precocity of fruiting individuals, with 179 bp and 183 bp bands, respectively. According to the breeding goal of high productivity and precocity of fruiting, 54 superior families and 200 superior individuals were selected. This study explored the adaptation strategies of tree growth traits to environmental changes.

Exploring the molecular mechanisms of melatonin-induced tolerance to salt-alkali stress in Populus cathayana × canadansis 'Xinlin 1′

Melatonin is widely recognized as involved in a wide range of plant growth and development functions. Research has primarily focused on herbaceous plants, with few findings on the function of melatonin in supporting tree growth. In this study, it was demonstrated that melatonin, as an endogenous hormone, considerably contributed towards the increased tolerance of poplar to salt-alkali stress. Transcriptome and metabolome analysis revealed that melatonin may enhance the cellular protection and antioxidant mechanisms of poplar and improve salt-alkali tolerance by regulating genes and metabolites involved in photosynthesis, antioxidant enzyme systems, plant hormone signal transduction pathways, and in the flavonoid as well as the melatonin biosynthesis pathway. The results of this study not only aid our increased understanding of the potential roles of melatonin in salt-alkali stress but also shed light on the potential mechanisms of the economically important woody model plant, poplar, involved in resisting abiotic stress.

Pre-Commercial Thinning Increases Tree Size and Reduces Western Gall Rust Infections in Lodgepole Pine

Alberta’s forest industry is predicted to be impacted by a medium-term decline in timber supply. Intensive silviculture tools, such as pre-commercial thinning, have been shown to increase individual tree growth, shorten rotation lengths, and improve stand merchantability in important commercial species such as lodgepole pine. However, lodgepole pine stands are susceptible to western gall rust infections, and thinning at an early stage may increase infection rates. This study collected tree and stand level data from 33 operational harvest origin lodgepole pine stands consisting of 11 stands thinned at age 17–19 years (PCT_18), 11 stands thinned at age 23–25 (PCT_24), and 11 unthinned stands. Approximately 40 years after pre-commercial thinning, merchantable volume is similar in all stands but thinned stands, regardless of timing, had greater individual tree size (~15% higher) compared to unthinned stands. Pre-commercially thinned stands also had a higher potential for commercial thinning since they have lower variability in tree size and longer live crown lengths. In addition, delayed thinning (PCT_24) reduced western gall rust infections and the severity of infections compared to both PCT_18 and unthinned stands. In conclusion, pre-commercial thinning should be considered for lodgepole pine stands in order to address timber supply issues in Alberta.

How do soil and topographic drivers determine tree diameter spatial distribution in even aged cork oak stands installed in average to high productivity areas

AbstractLocal terrain or microsite conditions influence the development of trees, particularly at early ages. These conditions might be described by edaphic or topographic variables. We mapped soil and topographic variables from four even-aged and even-spaced cork oak plantations located in two climatically distinct Portuguese regions. The major goal of this research was to understand the relation between soil and topographic fine-scale conditions and tree growth expressed by diameter without cork annual growth (idu). The methodology consisted in (1) analysing the spatial variability and autocorrelation of idu; (2) modelling idu with ordinary least squares (OLS) regressions; (3) comparing with spatial modelling of idu, incorporating spatial autocorrelation. The driest stands A and B, exhibited weaker spatial autocorrelation, distributed in smaller clusters (R2 &lt; 0.03, OLS models), while stands C (R2 = 0.18, OLS models) and D (R2 = 0.11, OLS models) showed higher predictive capacity. Spatial models increased R2 scores, keeping most variables from OLS models and accounting for spatial autocorrelation. A + B + C + D OLS model obtained an R2 = 0.34 and respective spatial model R2 = 0.58. Apparent electrical conductivity at 0.5 (ECa0.5) and 1 m of soil depth, slope, elevation and topography position index were included as predictors (OLS), but only ECa0.5, slope and elevation were selected in the spatial model. Models were fitted using average to high productivity stands and should be used cautiously outside this range. Local terrain conditions determine the growth of young cork oak trees. Mapping soil and topographic variables before establishing new plantations may identify limiting microsite conditions where using cork oak species is not suitable due to low growth rates expectations.

Parametrization of biological assumptions to simulate growth of tree branching architectures.

Modeling and simulating the growth of the branching of tree species remains a challenge. With existing approaches, we can reconstruct or rebuild the branching architectures of real tree species, but the simulation of the growth process remains unresolved. First, we present a tree growth model to generate branching architectures that resemble real tree species. Secondly, we use a quantitative morphometric approach to infer the shape similarity of the generated simulations and real tree species. Within a functional-structural plant model, we implement a set of biological parameters that affect the branching architecture of trees. By modifying the parameter values, we aim to generate basic shapes of spruce, pine, oak and poplar. Tree shapes are compared using geometric morphometrics of landmarks that capture crown and stem outline shapes. Five biological parameters, namely xylem flow, shedding rate, proprioception, gravitysense and lightsense, most influenced the generated tree branching patterns. Adjusting these five parameters resulted in the different tree shapes of spruce, pine, oak, and poplar. The largest effect was attributed to gravity, as phenotypic responses to this effect resulted in different growth directions of gymnosperm and angiosperm branching architectures. Since we were able to obtain branching architectures that resemble real tree species by adjusting only a few biological parameters, our model is extendable to other tree species. Furthermore, the model will also allow the simulation of structural tree-environment interactions. Our simplifying approach to shape comparison between tree species, landmark geometric morphometrics, showed that even the crown-trunk outlines capture species differences based on their contrasting branching architectures.

DeepAVP-TPPred: identification of antiviral peptides using transformed image-based localized descriptors and binary tree growth algorithm.

Despite the extensive manufacturing of antiviral drugs and vaccination, viral infections continue to be a major human ailment. Antiviral peptides (AVPs) have emerged as potential candidates in the pursuit of novel antiviral drugs. These peptides show vigorous antiviral activity against a diverse range of viruses by targeting different phases of the viral life cycle. Therefore, the accurate prediction of AVPs is an essential yet challenging task. Lately, many machine learning-based approaches have developed for this purpose; however, their limited capabilities in terms of feature engineering, accuracy, and generalization make these methods restricted. In the present study, we aim to develop an efficient machine learning-based approach for the identification of AVPs, referred to as DeepAVP-TPPred, to address the aforementioned problems. First, we extract two new transformed feature sets using our designed image-based feature extraction algorithms and integrate them with an evolutionary information-based feature. Next, these feature sets were optimized using a novel feature selection approach called binary tree growth Algorithm. Finally, the optimal feature space from the training dataset was fed to the deep neural network to build the final classification model. The proposed model DeepAVP-TPPred was tested using stringent 5-fold cross-validation and two independent dataset testing methods, which achieved the maximum performance and showed enhanced efficiency over existing predictors in terms of both accuracy and generalization capabilities. https://github.com/MateeullahKhan/DeepAVP-TPPred.

Different drought recovery strategy between Larix spp. and Quercus mongolica in temperate forests

Forests are experiencing increasingly severe drought stress worldwide. Although most studies have quantified how tree growth was affected by extreme droughts, how trees recover from different drought intensities are still poorly understood for different species. We used a network of tree-ring data comprising 731 Quercus mongolica trees across 29 sites, 312 Larix olgensis Henry trees from 13 sites, and 818 Larix principis-rupprechtii trees from 34 sites, covering most of their distribution range in northern China, to compare the influences of drought intensity on post-drought recovery. The results showed that summer droughts had strong negative influences on tree growth. Post-drought growth varied with drought intensity for the three species. Larix species exhibited strong legacy effects after severe droughts, which is related to the lack of compensatory growth. In contrast, the compensatory growth of Q. mongolica reduced drought legacy effect. However, the compensatory growth of Q. mongolica gradually weaken with increasing drought intensity and disappeared during severe drought. Our findings indicated that influence of drought on Q. mongolica growth mainly shown in drought years, but Larix species suffered from long-term drought legacy effects, implying Q. mongolica rapidly recovered from droughts but Larix species need several years to recover from droughts, thus the two genera have different recovery strategy.

Identification of macrofungal Ganodermataceae in Martelu Purba Nature Reserve

Fungi are organisms that enrich the diversity of living things in the plant world. Macroscopic fungi significantly affect the forest food web, the survival or germination of saplings, tree growth, and the overall health of the forest. Ganoderma has been widely cultivated in various countries due to its benefits as a medicine which is known to have the ability to treat hypertension, hyperglycemia, acute bronchitis, hepatitis, leukopenia, and arteriosclerosis. Research on mushrooms is still very minimally documented, so this research needs to be done. This study aims to identify the types of macroscopic fungi of the ganodermataceae that exist in Martelu Purba Nature Reserve. This study uses a direct survey method in the field. This method can be done by exploring in an area. Based on the research results, 6 types of macroscopic fungi from the Ganoderma family were obtained, namely Amauroderma rude, Cymatoderma elegans, Ganoderma applanatum, Ganoderma adspersum, Ganoderma pfeifferi, and Ganoderma boninense. The six types of mushrooms come from 3 genera, namely Amauroderma, Cymatoderma, and Ganoderma. Each type has different morphological characteristics which are the basis for distinguishing them. The potential utilization of Ganoderma has now been widely developed in the medical world

Growth decline characteristics of Picea schrenkiana at different altitudes in Yili River Basin, western Tian-shan Mountains, Xinjiang, China

Picea schrenkiana is the dominant tree species in Ili River Basin located in the western Tianshan Mountains of Xinjiang. We investigated the growth decline characteristics of P. schrenkiana at different altitudes (1800, 2300 and 2800 m) based on tree-ring index (TRI) and percentage growth change (GC), aiming to understand the growth response of P. schrenkiana to drought events at different altitudes and the impacts of altitude on tree growth decline in this region. The results showed that P. schrenkiana experienced multiple decline events at low-altitude (1800 m). TRI and GC identified inconsistent occurrence time of the decline events. The variations of TRI indicated that P. schrenkiana at low-altitude experienced two large-scale declines during 1927-1933 and 2017-2014, respectively. The variations of GC identified four decline events, including 1891-1893, 1924-1926, 1973-1975, and 2004-2009. The radial growth of P. schrenkiana across altitudes from low to high was significantly affected by the Palmer drought severity index (PDSI) of the previous growing season. The impact of current PDSI on P. schrenkiana during the growing season initially enhanced but later decreased with increasing altitude. In the extreme drought year 1917, the magnitude of growth decline increased with altitude. At low-altitude (1800 m), the TRI was 0.65, which was 35% lower than the normal level. At mid-altitude (2300 m) and high-altitude (2800 m), it was 0.56 and 0.54, respectively, being 40% lower than the average level. The drought event in 1917 had a 2-year legacy effect on the growth of P. schrenkiana at all the altitudes, with the TRI in 1920 recovered to exceeding 0.9, being close to the normal level. The impact of altitude on drought-induced forest decline was significant. Tree growth in low-altitude areas was more vulnerable to drought events due to the relatively poorer water and temperature conditions at low-altitude, which could lead to multiple large-scale decline events. In mid- and high-altitude areas, where hydrothermal conditions were more favorable, trees could experience even more severe decline during extreme droughts.

Enhanced interannual drought resilience in mixed stands: unveiling possible complementarity effects between tree species of the Spanish Northern Plateau

AbstractClimate change is expected to intensify drought in the Mediterranean region. Previous studies indicate that tree species mixing may reduce the water stress. Our study investigates the response to past drought events of four co-occurring Mediterranean species: Pinus pinea L. (stone pine), Pinus pinaster Ait. (maritime pine), Juniperus thurifera L. (Spanish juniper) and Quercus ilex L (holm oak). The study was performed at an interannual scale, both in monospecific and mixed stands. Annual tree ring widths data measured on increment cores and stem discs obtained from 281 trees were used to quantify the responses to drought events using complementary resilience indices. Additionally, we assessed tree intra- and inter-specific competition impact over the past 25 years. We fitted and compared generalised linear mixed models to determine the influence of species identity, stand composition as intra-specific and inter-specific competition on complementary resilience indices and annual basal area increment. The co-existence with other species enhanced the resistance to drought of the stone pine as the resilience capacity of the Spanish juniper. Conversely, maritime pine’s drought resistance declined considerably in mixed stands. Notably, only the anisohydric species Spanish juniper and holm oak were able to return to pre-disturbance growth rates after the drought. The influence of competition on tree growth was found to differ according to the hydrological conditions of each year and varied based on the specific source of competition. Our study showed that mixed stands in the Spanish Northern Plateau, especially with holm oak and Spanish juniper, are more resilient to prolonged droughts due to spatio-temporal complementarity and subsequent competition reduction. That is another reason for which such composed mixed stands should be promoted in the arid conditions of the Spanish Northern Plateau.

Root System Reductions of Grafted ‘Valencia’ Orange Trees Are More Extensive Than Aboveground Reductions after Natural Infection with Candidatus Liberibacter Asiaticus

Huanglongbing (HLB), which is associated with the phloem-limited bacteria Candidatus Liberibacter asiaticus (CLas), is a devastating disease that affects citrus trees worldwide. Because of the pervasiveness of the bacteria and psyllid vector, the disease is considered endemic in Florida. Although the effects of CLas on tree growth and physiology have been investigated for decades, most studies compared infected and noninfected trees under greenhouse conditions. This study used newly planted field-grown ‘Valencia’ sweet orange (Citrus sinensis) trees on two different rootstocks to monitor the distribution and accumulation of CLas in aboveground and belowground tissues following natural psyllid colonization and assess tree physiological responses and biomass reductions under HLB-endemic conditions. Trees were transplanted into the field with individual protective covers (IPCs), which are used to exclude psyllids and prevent infection. Openings were cut in the IPCs of half of the trees; to promote infection, these IPCs were temporarily removed during the main vegetative flushing period when psyllid populations were high. All trees that were exposed to psyllids became infected and displayed the symptoms typically associated with HLB. Throughout the study, higher levels of CLas were detected in the leaves compared with those in the fibrous roots. Trees that were not exposed to psyllids remained noninfected and healthy. After 18 months, a subset of trees was excavated to assess biomass differences between infected and noninfected trees. Infected trees had root system reductions of 37% and shoot system reductions of 20%, thereby significantly reducing the belowground-to-aboveground biomass ratio. Fibrous root loss was 49% and more severe than the loss of the rest of the root tissue. This study is the first to demonstrate the full extent of damage caused by CLas infection under natural HLB-endemic conditions. The results confirm previous observations that suggested fibrous root loss as one of the major consequences of infection and colonization with CLas. They also reinforce the benefits of using IPCs to prevent infection of young citrus trees during the first years of growth in the field.

Obstacle avoidance motion planning for space redundant manipulator based on improved RRT algorithm

In addressing the challenge of obstacle-avoidance motion planning for space redundant manipulators operating in environments with obstacles, an improved method based on a rapidly exploring random tree (RRT) algorithm is proposed. The method first adopts a target probabilistic sampling strategy to enhance the target orientation. Secondly, an artificial potential field is constructed to steer the growth of the node tree in joint space. Subsequently, a collision detection model between the manipulator and obstacles is established based on the bounding capsule and bounding sphere in Cartesian space. Finally, the paths are pruned and smoothed with a cubic Bezier curve. The simulation results validate the method’s capacity to effectively plan a collision-free path for the space redundant manipulator and the joint motion trajectory is smooth.

Stress-tolerant trees for resilient cities: Tree-ring analysis reveals species suitable for a future climate

Cities are vulnerable to droughts and heatwaves due to the decline in permeable green spaces and the emergence of heat islands. To tackle these environmental challenges, many cities adopted ambitious tree-planting initiatives. However, tree tolerance to climate extremes is overlooked even though physiological and growth limitations jeopardize ecosystem services provision. We assessed the responses of Tipuana tipu to the 2013/2014 summer drought in São Paulo, Brazil. We sampled trees in a park and streets and assessed how tree-ring δ13C and growth responses to drought differ. The Regression Tree shows that microhabitats exert the strongest control on tree-ring δ13C seconded by drought. δ13C is on average 1.0‰ higher in streets where growth rate is 60% higher than in the park. Similarly, δ13C increased by up to 0.9‰ during the drought when growth increased by up to 45% in both sites. This positive association between δ13C and growth rate (R2 = 0.78) indicates that growth is limited by assimilation rate. Assimilation is up to 15% higher in streets and increased by up to 10% during the drought because of higher incident sunlight and air temperature. Thus, T. tipu is a drought-tolerant species with potential to contribute to (sub)tropical cities, thriving in a warming climate.

The timing of wood formation in peatland trees as obtained with different approaches

Dendrometers offer valuable insights into how tree growth responds to climatic variables and physiological processes over the course of a year. Yet, their applicability to extremely slow-growing trees, such as those in peatlands, has been limited due to the intricate and slow nature of growth, therefore rendering interpretation of results complex. In this study, we conducted a comprehensive monitoring of tree wood formation in both peatland and mineral soil ecosystems in southern Sweden (58.37 N, 12.17 E, 75 m asl) in 2021 and 2022, using both band and point dendrometers. To verify and validate the dendrometer data, we also sampled microcores every two weeks during both growing seasons. We find that peatland trees grow at approximately 30 % the rate of their neighbors on mineral soils. The onset of growth among peatland trees typically occurs between mid-May and early June, consistently lagging the start of the growing season in trees on mineral soils by one to three weeks. Notably, growth peaks are synchronized across peatland trees and coincide with the summer solstice. Both types of dendrometers exhibit varying degrees of accuracy depending on the phenological stages measured. They perform well in identifying growth onset and peak but are less effective at detecting growth cessation. Point dendrometers demonstrate superior accuracy as they better capture daily irreversible growth increments. In the case of band dendrometers, growth increments are obscured by greater reversible fluctuations in dead bark tissues. However, they remain valuable for tracking the wood phenology of trees with growth rates exceeding 2 mm/year. Based on our results, for an effective tree monitoring in peatlands, we strongly recommend (1) using point dendrometers and (2) removing the dead bark tissues on monitored trees.