Branch Traits Research Articles

L1-Tree: A novel algorithm for constructing 3D tree models and estimating branch architectural traits using terrestrial laser scanning data

Branch architecture provides crucial information for the understanding of plant trait variability and the adaptive strategies employed by trees in response to their environment. High-fidelity terrestrial laser scanning (TLS) data provide an accurate, efficient, and non-destructive means for constructing three-dimensional (3D) tree models and estimating architectural traits. However, the complex canopy structure of trees in natural forests and the presence of occlusion in TLS data pose significant challenges to achieving this goal. In this study, we present a novel algorithm, L1-Tree, for the construction of 3D tree models and the estimation of architectural traits from TLS data. This algorithm is grounded in the L1-Median algorithm and integrates a tree skeleton optimization procedure that considers the structural characteristics of tree branches. By comparing modeling results and manually derived branch traits for 24 trees of 24 species, we found that the L1-Tree algorithm achieved precision, recall, and F-score values of 0.94 for branch identification, coefficient of determination, root-mean-squared error, and normalized root-mean-squared error of 0.998, 0.068 m, and 0.3 % for branch length estimation, and a respective value of 0.958, 0.257 cm and 0.9 % for branch radius estimation. Additionally, the branch identification accuracy and accuracy in branch architectural trait estimation remained satisfactory across branch orders. Compared to established 3D tree model construction algorithms (e.g., TreeQSM), our L1-Tree algorithm demonstrated a superior capability in handling noisy environments and data gaps, making it a robust tool for TLS data-based tree architecture studies. Leaf-wood separation emerged as a crucial step influencing the performance of the L1-Tree algorithm. We observed significant drop in branch identification accuracy when using an automatic leaf-wood separation algorithm as input, highlighting the urgent need to develop effective leaf-wood separation algorithms to generate high-quality wood point clouds for tree architecture studies.

Disentangling how the opportunistic parasitic fungus Armillaria affects the flammability of coarse deadwood in exotic pine plantations

Parasitic wood fungi are important to forest carbon cycles globally. However, whether or how they affect the flammability of coarse deadwood is poorly understood. Given the predicted climate-driven increase in wildfires and associated carbon emissions into the atmosphere, potentially amplifying climate warming, filling this knowledge gap should have high priority. We thereto investigated coastal plantations of the exotic black pine, Pinus nigra J.F. Arnold, in the Netherlands, which are widely suffering from Armillaria infection. We hypothesized that branches from forest stands with a visible Armillaria infection will burn differently compared with branches from stands without a visible Armillaria infection, due to Armillaria infection having an additional effect on the branch traits. We tested this hypothesis by burning coarse Pinus nigra branches across a range of densities from infected and uninfected forest patches under standardized conditions in a fire lab and by measuring Armillaria biomass (via ddPCR), deadwood traits and key flammability parameters. Armillaria infection did enhance the flammability of Pinus nigra branches (e.g. more ignitable, longer flame duration and higher percentage mass loss). This higher flammability originated from both direct Armillaria influences, e.g. via changing wood structure (before and/or after wood death), and indirect influences, e.g. by facilitating nitrogen fixation in wood, thereby increasing wood decomposability and consequently reducing wood density. Our findings also have important implications for understanding the role of pathogens in fire regimes more broadly.

Adaptability of Swiss Stone Pine (Pinus cembra) in Two Different Environmental Conditions of Romanian Carpathians

Swiss stone pine (Pinus cembra) is a feasible solution for increasing the resistance of future mixed spruce–pine stands to windfall at the upper altitudinal limit of Romanian forests. This study aims to analyze the adaptability of ten full-sib families in two different environmental conditions and their evolution in time for predicting forward selection. At a seedling age of 33, evaluations were carried out for survival rate (Sr), growth (diameter at breast height—Dbh, and trees’ height), and branch traits, as well as for stem straightness. The high level of genetic variability, inheritance rate, and trait–trait correlations, registered in both trials, ensure the success of the breeding program. The Swiss stone pine shows a very good adaptation on high-sloping lands from the upper altitudinal limit of Romania’s forests, with the cross-pollinated (CP) families registering a 28.5% better survival in the Rodna trial (34° slope) compared to the Păltiniș experiment (7° slope). The consanguineous families registered only an 11% Sr in Păltiniș, while in the Rodna trial, the Sr was four times higher (in both trials, consanguineous trees were dominated). The juvenile–adult correlations of growth traits were significant, indicating that early selection could be efficient. The forward selection of the best 10% of CP families for Dbh could be applied, ensuring a 9% to 15% genetic gain.

Hydraulic vulnerability difference between branches and roots increases with environmental aridity.

The vulnerability of plant xylem to embolism can be described as the water potential at which xylem conductivity is lost by 50% (P50). According to the traditional hypothesis of hydraulic vulnerability segmentation, the difference in vulnerability to embolism between branches and roots is positive (P50 root-branch > 0). It is not clear whether this occurs broadly across species or how segmentation might vary across aridity gradients. We compiled hydraulic and anatomical datasets from branches and roots across 104 woody species (including new measurements from 10 species) in four biomes to investigate the relationships between P50 root-branch and environmental factors associated with aridity. We found a positive P50 root-branch relationship across species, and evidence that P50 root-branch increases with aridity. Branch xylem hydraulic conductivity transitioned from more efficient (e.g., wider conduit, higher hydraulic conductivity) to safer (e.g., narrower conduit, more negative P50) in response to the increase of aridity, while root xylem hydraulic conductivity remained unchanged across aridity gradients. Our results demonstrate that the hydraulic vulnerability difference between branches and roots is more positive in species from arid regions, largely driven by modifications to branch traits.

Identification of candidate genes related to two economic traits using GWAS in Gracilariopsis lemaneiformis (Rhodophyta)

The lack of systematic methods to measure traits and phenotypic data, along with limited research on genes regulating economic traits, has slowed down the variety improvement and breeding process of industrialized alga Gracilariopsis lemaneiformis (Gp. lemaneiformis). Here, we developed a unified, reliable and stable method for linear growth rate (VL) and branch measurement based on tip culture in Gp. lemaneiformis. Genome-wide association study (GWAS) including 174 haploid strains based on the phenotypic data measured by this trait assessment method was conducted, and 483,670 single nucleotide polymorphisms (SNPs) were identified through re-sequencing. There were 68 and 12 SNPs significantly associated with VL and branch respectively, and 79 and 16 genes related to VL and branch respectively within the flanking 20 kb region of these SNPs were screened. Validation of SNPs loci Chr3–969,142 and Chr13–2,948,547 confirmed their polymorphism and potential involvement in regulating VL and branch traits, respectively. Further analysis revealed a positive correlation between VL and genes LXC001292 (cell division cycle protein 20-like), LXC001293 (transcription factor-like protein DPB), and LXC001294 (unnamed protein product), indicating their potential role in VL regulation through cell cycle, ubiquitin, and RB-E2F regulatory pathways. Additionally, LXC004673 (Auxin transport protein BIG) was associated with Branch, suggesting that the gene and polar auxin transport might play a role on branch morphology of Gp. lemaneiformis. This study provides fundamental data and important gene resources for genetic and breeding studies of Gp. lemaneiformis.

Differences and allometric relationships among assimilative branch traits of four shrubs in Central Asia.

Shrubs play a major role in maintaining ecosystem stability in the arid deserts of Central Asia. During the long-term adaptation to extreme arid environments, shrubs have developed special assimilative branches that replace leaves for photosynthesis. In this study, four dominant shrubs with assimilative branches, namely Haloxylon ammodendron, Haloxylon persicum, Calligonum mongolicum, and Ephedra przewalskii, were selected as the research objects, and the dry mass, total length, node number, and basal diameter of their assimilative branches and the average length of the first three nodes were carefully measured, and the allometric relationships among five traits of four species were systematically compared. The results indicated that: (1) Four desert shrubs have different assimilative branches traits. Compared with H. persicum and H. ammodendron, C. mongolicum and E. przewalskii have longer internodes and fewer nodes. The dry mass of H. ammodendron and the basal diameter of H. persicum were the smallest; (2) Significant allometric scaling relationships were found between dry mass, total length, basal diameter, and each trait of assimilative branches, all of which were significantly less than 1; (3) The scaling exponents of the allometric relationship between four traits and the dry mass of assimilative branches of H. persicum were greater or significantly greater than those of H. ammodendron. The scaling exponents of the relationships between the basal diameter, dry mass, and total length of E. przewalskii were higher than those of the other three shrubs. Therefore, although different species have adapted to drought and high temperatures by convergence, there was great variability in morphological characteristics of assimilative branches, as well as in the scaling exponents of relationships among traits. The results of this study will provide valuable insights into the ecological functions of assimilative branches and survival strategies of these shrubs to cope with aridity and drought in desert environments.

Impact of Selected Environmental Factors on Variation in Leaf and Branch Traits on Endangered Karst Woody Plants of Southwest China

We explored the adaptability of endangered plants in degraded karst habitats through functional trait variation, using three endangered woody plants (E. cavaleriei, H. bodinieri and K. septentrionalis) in karst peak-cluster depression. We investigated the variation decomposition and correlation analysis of 13 branch and leaf functional traits using a mixed linear model, variance decomposition, Pearson’s correlation analysis, random forest regression, and generalized linear regression. The degree of variation in phosphorus concentration in the branches was the highest, while that in the carbon concentration in the leaves was the smallest. The variation in the carbon concentration in the branches and leaves, and the dry matter concentration in the leaves was mainly within species, while the variation in other functional traits was mainly between species. We found significant correlations among leaf traits, branch traits, and leaf–branch traits to different degrees; however, there were no significant correlations among branch traits in H. bodinieri. The significant correlations were higher in E. cavaleriei and K. septentrionalis than in H. bodinieri. Plant functional traits were influenced by soil and topographic factors, and the relationship between them varied by species. Our findings will enhance our understanding of the variation in leaf and branch traits in karst endangered plants and the adaptative strategies of endangered plants in degraded habitat, and will provide a scientific basis for vegetation conservation in the karst region of southwest China.

Architectural plasticity in response to population density in Abutilon theophrasti (Malvaceae)

AbstractAn increase in population density may result in the spatial and temporal heterogeneity of resources at scales smaller than an individual, inducing different modular responses at different positions of a plant, or architectural plasticity. To better understand how plants respond to density via architectural plasticity, we conducted a field experiment on an annual species, Abutilon theophrasti. Plants were subjected to three densities and harvested at 50 and 70 days, when each individual plant was separated into different layers vertically from bottom to top with an inter‐layer distance of 10 or 20 cm, before we measured a series of traits per layer and analyzed variations in them among layers, densities, and stages. Increased density reduced variation of traits among layers and had different effects on different layers of modular traits: it increased stem mass in the third to fifth layers (L3–L5) and increased stem diameter in the top layer, leading to an increase in stem density in lower layers and a decrease in stem density in the top layer. In addition, there was an increase in petiole length and mass, lamina size, and leaf number in upper layers, while they decreased in lower layers. Results suggested trade‐offs between upper and lower layers in stem density and leaf traits for plants in a dense population, which were important for keeping most leaves at higher positions to acquire light resources, while saving energy, in concert with the effort of extra stem elongation and the complex plasticity in branch traits.

Genetic diversity analysis of phenotypic traits among 37 Xanthoceras sorbifolium elite germplasms

ABSTRACT Xanthoceras sorbifolium is one of the most economically important species cultivated in northern China. To analyze the phenotypic variation within X. sorbifolium, 35 phenotypic traits among 37 elite germplasms were analyzed using nested analysis of variance, coefficient of variation (CVs), principal component analysis (PCA), correlation analysis, and cluster analysis. Large variation and rich phenotypic diversity were found among and within germplasms of X. sorbifolium. The mean of coefficient of variation for 35 traits among 37 germplasms was 25.49%. It varied from 12.80% to 63.25%, and ranked as follows: branch traits (45.51%) > inflorescence traits (31.01%) > fruit traits (24.67%) > flower traits (24.35%) > seed traits (21.82%) > leaf traits (21.45%). The mean heritability (H2) of 35 phenotypic traits was 75.94%. Significant correlations were observed within and among most branch, leaf, inflorescence, flower, fruit, and seed traits. The cumulative contribution rate of the first nine main principle components reached 80.333%. The 35 phenotypic traits were classified into two main categories and five subcategories by clustering analysis of phenotypic traits. Combined result of correlation, PCA, and clustering of phenotypic traits, 18 representative traits were selected. The 37 elite germplasms were classified into two main groups and six subgroups according to their characteristics by Ward’s method and reasonable utilization of each subgroup were suggested. These results provide useful information for genetic improvement, preservation, and evaluation of X. sorbifolium germplasms.

The importance of proleptic branch traits in biomass production of poplar in high-density plantations

The importance of proleptic branch traits in biomass production of poplar in high-density plantations

The effect of plant size and branch traits on rainfall interception of 10 temperate tree species

AbstractRainfall interception by vegetation plays an important role in the hydrological cycle. Next to rainfall characteristics, interception is influenced by tree size, crown structure and bark morphology. How tree traits determine interception across functionally and morphologically wide‐ranging tree species is poorly understood. We determined interception ratios (interception:gross precipitation) and canopy storage capacities of seven temperate deciduous broadleaved (Acer pseudoplatanus L., Betula pendula Roth, Carpinus betulus L., Fagus sylvatica L., Populus tremula L., Sorbus aucuparia L.) and three evergreen coniferous tree species (Picea abies (L.) Karsten, Pinus sylvestris L., Pseudotsuga menziesii (Mirb.) Franco) as well as the influence of various tree traits on interception parameters. Interception was measured directly with natural rainfall by means of gravimetry on potted trees, 2–8 m tall, for seven consecutive months. Our results show that (a) the coniferous species had larger canopy storage capacities and larger interception ratios than the broadleaved species both during (summer) and outside the growing season (winter); (b) the absolute tree interception (in kg) of the broadleaved species was positively related to stem diameter at breast height, tree and crown height, maximum branch length, the total branch surface area and above ground dry weight; and (c) interception per unit crown projected area (in mm) of all species was positively related to branch length and branch surface area per unit crown projected area. These results can be used to estimate interception parameters from plant traits and to simulate interception losses of trees in a more reliable manner.

Functional traits shape tree species distribution in the Himalayas

Abstract Plant functional traits determine plant performance and have therefore the potential to shape and predict species distributions along environmental gradients. This study analyses how traits affect tree species distribution along an elevational gradient in the Himalayas, Nepal. We addressed three questions: (a) what plant strategies can be distinguished among tree species? (b) how are plant traits and strategies associated with elevation? and (c) what plant traits are the best predictors of species positions along elevational gradient? We quantified for 31 tree species a set of 39 plant traits related to resource uptake, use and conservation. We analysed how traits cluster into separate functions using a cluster analysis, and how traits and clusters associate into distinct plant strategies using a principal component analysis. The cluster analysis showed five clusters of traits, reflecting (a) efficiency in vertical expansion, (b) efficiency in horizontal expansion, (c) efficiency in metabolism, (d) physical defence and (e) tree functional groups (conifers vs. broadleaf species). The first PCA axis reflects trade‐offs in traits and clusters linked to elevation: highland species had trait values that increase safety against freezing induced cavitation, high solar radiation and strong wind, and that increase resource conservation. In contrast, lowland species had trait values that increase efficiency of resource acquisition, metabolism and expansion. Additionally, a bivariate analysis showed that the first PCA axis is more strongly related to elevation than the individual traits, indicating that the combination of traits is more important than the individual traits. An all subsets regression analysis showed that a small set of traits best explain species distribution: highland species had smaller size (low basal area), safer hydraulics (low conduit diameter) and lower leaf and branch display efficiency (low leaf area per xylem area, specific branch length) that increase persistence under harsh conditions. Remarkably, leaf traits were poor predictors of species' elevational positions. Synthesis. Multiple trade‐offs in plant size, hydraulics and light competitiveness shape species distribution along the elevational gradient. Along this extreme environmental gradient, stem and branch traits that integrate multiple plant organs and functions are better predictors of species' elevational distributions than leaf traits.

Linking functional traits with tree growth and forest productivity in Quercus ilex forests along a climatic gradient

Plant functional traits are highly plastic to changes in climatic factors and nutrient availability. However, the intraspecific plant response to abiotic factors and the overall effect on tree growth and productivity is still under debate. We studied forest productivity for 30 Quercus ilex subsp. ballota forests in Spain along a broad climatic gradient of aridity (mean annual precipitation from 321 to 858 mm). We used linear mixed models to quantify the effect of climatic and edaphic (soil nutrients, topography, and texture) factors on tree functional traits (leaf and branch traits), and subsequently, the effect of such functional traits and abiotic factors on the relative growth rate (RGR) of adult trees. We used piecewise structural equation models (SEMs) to determine the causal effect of intrinsic and extrinsic factors on forest productivity. Our results showed that tree functional traits were mainly explained by climatic and edaphic factors. Functional traits and tree biomass explained forest biomass and RGR, respectively, which ultimately explained forest productivity. In conclusion, intraspecific variability of functional traits has a significant effect on plant biomass and growth, which ultimately may explain forest productivity in Quercus ilex forests.

Reprint of: Tree-tree interactions and crown complementarity: the role of functional diversity and branch traits for canopy packing

Previous studies have shown that tree species richness increases forest productivity by allowing for greater spatial complementarity of tree crowns (crown complementarity), which in turn results in more densely packed canopies. However, the mechanisms driving crown complementarity in tree species mixtures remain unclear. Here, we take advantage of a high-resolution, three-dimensional terrestrial laser scanning approach in the context of a large-scale biodiversity-ecosystem functioning experiment in subtropical China (BEF-China) to quantify the extent to which functional dissimilarity and divergences in branch traits between neighbouring trees affect crown complementarity at the scale of tree species pairs (i.e., two adjacent trees). Overall, we found no support that functional dissimilarity (divergence in morphological flexibility, specific leaf area and wood density) promotes crown complementarity. However, we show that the effects of functional dissimilarity (the plasticity of the outer crown structure) on crown complementarity vary in their magnitude and importance depending on branch trait divergences. Firstly, crown complementarity tended to be highest for tree species pairs that strongly differed in their functional traits, but were similar in branch density. In contrast, heterospecific pairs with a low functional trait divergence benefitted the most from a large difference in branch density compared with pairs characterised by a large functional dissimilarity. Secondly, the positive effects of increasing divergence in branching intensity (the plasticity of the inner crown structure) on crown complementarity became most important at low levels of functional dissimilarity, i.e. when species pairs were similar in their branch packing and vice versa. This suggests that species mixing allows trees to occupy canopy space more efficiently mainly due to phenotypic changes associated with crown morphology and branch plasticity. Our findings highlight the importance of considering outer and inner crown structures (e.g. branching architecture) to deepen our understanding of tree-tree interactions in mixed-species communities.

Various distances and orientations influenced the branching traits of Dendrocalamus minor var. amoenus in Dongshan Island, China

Branch patterns play a key role in assessing plant architecture and are adapted to forest ecosystems. The study aimed to reveal the pattern of branch traits at various distances and orientations from the seashore. For that reason, four sites with various distances from the seashore (SP1: 50–60 m, SP2: 60–100 m, SP3: 100–200 m, and SP4: 200–800 m) were selected and branch traits of Dendrocalamus minor var. amoenus were determined in Dongshan Island, China. The results showed that there were differences in the branch traits between both the 1st-order and 2nd-order branches, and distance from seashore had a significant impact on branch angle, length, diameter, and the number of leaves of 1st-order branches, whereas branch diameter, length, and the number of leaves of 2nd-order branches. In different orientations, the branch angle, length, number, and diameters of the 1st-order and 2nd-order branches showed no significant differences. Nonetheless, the number of leaves of the 1st-order branches were significantly influenced by different orientations. D. minor var. amoenus exhibited strong phenotypic plasticity with longer branches and formed a sparse crown shape. It adjusted the fractal dimension of the crown and branches by modulating the allometric growth relationships among branching traits to adapt to harsh coastal pressure. This study would provide valuable recommendations for D. minor var. amoenus as windbreaks in the coastal climate.

Tree-tree interactions and crown complementarity: The role of functional diversity and branch traits for canopy packing

Previous studies have shown that tree species richness increases forest productivity by allowing for greater spatial complementarity of tree crowns (crown complementarity), which in turn results in more densely packed canopies. However, the mechanisms driving crown complementarity in tree species mixtures remain unclear. Here, we take advantage of a high-resolution, three-dimensional terrestrial laser scanning approach in the context of a large-scale biodiversity-ecosystem functioning experiment in subtropical China (BEF-China) to quantify the extent to which functional dissimilarity and divergences in branch traits between neighbouring trees affect crown complementarity at the scale of tree species pairs (i.e., two adjacent trees). Overall, we found no support that functional dissimilarity (divergence in morphological flexibility, specific leaf area and wood density) promotes crown complementarity. However, we show that the effects of functional dissimilarity (the plasticity of the outer crown structure) on crown complementarity vary in their magnitude and importance depending on branch trait divergences. Firstly, crown complementarity tended to be highest for tree species pairs that strongly differed in their functional traits, but were similar in branch density. In contrast, heterospecific pairs with a low functional trait divergence benefitted the most from a large difference in branch density compared with pairs characterised by a large functional dissimilarity. Secondly, the positive effects of increasing divergence in branching intensity (the plasticity of the inner crown structure) on crown complementarity became most important at low levels of functional dissimilarity, i.e. when species pairs were similar in their branch packing and vice versa. This suggests that species mixing allows trees to occupy canopy space more efficiently mainly due to phenotypic changes associated with crown morphology and branch plasticity. Our findings highlight the importance of considering outer and inner crown structures (e.g. branching architecture) to deepen our understanding of tree-tree interactions in mixed-species communities.

Effects of maturity group and stem growth habit on the branching plasticity of soybean cultivars grown at various planting densities

ABSTRACT To elucidate the effects of maturity and the stem growth habit on the planting density-dependent branching plasticity of soybean cultivars, we studied the branch traits of 12 cultivars or lines planted at different densities (8.3, 16.7, and 22.2 plants m−2) in Sapporo (2012) and Ebetsu (2013). The 12 cultivars and lines consisted of three determinate cultivars from Hokkaido, three indeterminate cultivars from the northern US, and near-isogenic lines with the backgrounds of Canadian, US, and Japanese cultivars exhibiting diverse stem growth habits. We investigated the relationship between the maturity or stem growth habit and branching plasticity, which was calculated based on the ratios of different branch traits under sparse and dense planting conditions. The use of the ratios of the total branch length and the number of nodes per branch under sparse and dense planting conditions as a measure of branching plasticity revealed varietal differences across years. For the determinate and indeterminate cultivars in both years, branching plasticity was positively correlated with the number of days until stage R5 (onset of seed filling), which is when branches cease to elongate. Comparisons of Japanese and US cultivars and near-isogenic lines for the Dt1 gene (mediating the stem growth habit) indicated that the branching plasticity of indeterminate cultivars and lines is greater than that of determinate cultivars, with a large variation among backgrounds and cultivars. The results of this study imply that branching plasticity is greater in late-maturing soybean cultivars. Moreover, the indeterminate growth habit substantially enhances branching plasticity.

Epiphyte associations and canopy soil volume: nutrient capital and factors influencing soil retention in the canopy.

Canopy soil (CS) volume reflect epiphyte community maturity, but little is known about the factors that retain CS or species succession within it. Humus fern species (e.g. Phlebodium areolatum) appear capable of retaining CS. In ten Quercus spp. we sampled 987 epiphyte mats to examine the role of the common epiphyte species and crown traits determining CS volume, in order to infer successional stages and identify pioneer and late successional species. Branch traits (height, diameter and slope), CS volume and cover of the epiphyte species were determined for each mat. Nutrient content was determined in CS random samples of 12 epiphyte associations and sizes (one sample from each size quintile). A total of 60% of the mats lack CS. Cover of P.areolatum was the main variable explaining CS volume, and this species was present in 46.8% of those with CS. Epiphyte composition was highly variable, but pioneer (species appearing in monospecific mats, without CS) and late successional species could be identified. Canopy soil nutrient content was similar among the associations of epiphytes. Magnesium, Ca and pH decreased with CS volume, while P and N increased. Phlebodium areolatum is associated with high CS volumes and could act as a key species in its retention. Monospecific mats of pioneer species lack CS or have low volumes, while CS is much higher in mats with late successional species, but the mechanisms of CS formation and nutrient retention in response to interactions between epiphyte species remain to be tested.

Temporal and spatial responses of the branch and leaf growth relationship to human water flow regulation: a case study on remnant Myricaria laxiflora populations

Regulation of water flow by dams for flood control and power generation has changed the patterns of water level fluctuation in the lower Yangtze River. By investigating the branch and leaf traits of M. laxiflora plants at various growth recovery stages along the water fluctuation gradient, this study uncovered the spatiotemporal response in the relationships among branch and leaf traits during growth to the regulated water level fluctuations. Results indicated leaf number (LN) and leaf-and-branch volume (LV) rapidly increased during the first 30 d of growth recovery. Afterwards, the increase in LN gradually slowed, while LV continued to increase steadily and was isometric to the increase in leaf-and-branch dry mass (LM). The investment strategy of this plant species changed from ‘fast return’ to ‘slow return’ as plant growth was restored. In the upper hydro-fluctuation zone, the LN vs. LM and leaf-and-branch water content (LWC) vs. LM comparisons exhibited negative allometric growth, while the LV vs. LM comparison exhibited positive allometric growth. In the middle hydro-fluctuation zone, the LN vs. LM and LV vs. LM comparisons exhibited isometric growth patterns, while the LWC vs. LM comparison exhibited positive allometric growth. In the lower hydro-fluctuation zone, the LN vs. LM comparison exhibited positive allometric growth, while the LWC vs. LM comparison exhibited negative allometric growth. As water level decreased, the investment strategies of the plants switched from prioritizing LV and LWC to LN, and shifted from ‘slow return’ to ‘fast return’. The above results indicate that changes in water level fluctuation patterns have greatly affected branch and leaf growth, as well as the growth relationships among branch and leaf traits in the remnant populations of M. laxiflora. Growth of these remnant populations, especially those at the lower hydro-fluctuation zone, was seriously affected and exhibited signs of degradation as a result. HIGHLIGHTS Regulation of water flow by dams for flood control and power generation has changed the patterns of water level fluctuation in the lower Yangtze River. The human water flow regulation impacts the allometric growth of M. laxiflora in terms of branch and leaf traits, as well as the investment strategies during growth. Clear differences were observed in the growth patterns of branches and leaves at different levels along the water fluctuation gradient.

Plant size, branch age and environment factors co-drive variations of branch traits of <i>Pinus koraiensis</i>

Plant size, branch age and environment factors co-drive variations of branch traits of <i>Pinus koraiensis</i>