Abstract Plants adapt to the changes of nitrogen and water availability by balancing nitrogen use efficiency (NUE) and water use efficiency (WUE) especially in grasslands, where water and nitrogen are limiting plant growth. While NUE-WUE relationship has received considerable attention, the plasticity bias between them remains unexplored. Here, we define this plasticity bias as the asymmetry in plasticity magnitude between NUE and WUE. In an experiment simulating nitrogen deposition and drought in a temperate grassland in northern China, we measured NUE, WUE and ten functional traits of six common plant species, evaluated the NUE-WUE plasticity bias, and identified the underlying key traits. Under either nitrogen addition or drought, the NUE-WUE plasticity bias in most species consistently exhibited a WUE-favoring direction, with an increased intensity. The relationships between the NUE-WUE plasticity bias and functional traits were strengthened under nitrogen addition but became non-significant under drought. Among the traits investigated, leaf nitrogen content (LNC) was identified as the key driver influencing the NUE-WUE plasticity bias. This study captures the dynamic imbalance of resource use by quantifying plasticity bias, moving beyond static correlation analysis. We emphasize the critical role of above-ground traits (such as LNC) in driving plant adaptive strategies, and suggest that future predictive models should incorporate both above- and below-ground traits to comprehensively capture whole-plant resource coordination under environmental change.
Abstract Understanding how multidimensional biodiversity influences forest biomass carbon storage is crucial for sustainable forest management. However, empirical evidence on the mechanisms and relative contributions of three dimensions of tree diversity (species, functional, and structural) to forest biomass stocks across varying environmental gradients remains limited. This study used forest inventory data from 94 subtropical natural forest plots with an area of 0.6 hectares, and analyzed the impacts of multidimensional diversity, climate, soil, and topography on above-ground biomass across wider geographical gradients. We found that species, functional, and structural diversity significantly promoted aboveground biomass. Structural diversity showed a better association with above-ground biomass relative to other single variables and was linked to the species richness-aboveground biomass relationship. These findings support the niche complementarity effect and selection effect simultaneously. High water availability and soil fertility promoted species richness, functional diversity, and above-ground biomass. Three dimensions of tree diversity and biomass displayed either no trend, a linear increase, or a hump-shaped pattern with rising elevation, failing to support the species-energy hypothesis. Our findings highlight that structural diversity is a critical driver promoting forest biomass stocks across broad spatial ecogeographical gradients. Moreover, adequate water availability and favorable soil resource conditions are essential for maintaining biodiversity and ecosystem functioning.
Abstract Arbuscular mycorrhizal fungi (AMF) are key mutualists in plant invasions, but their availability may constrain range expansion if plant spread outpaces fungal dispersal. In this study, we tested whether core and edge populations of an invasive plant differ in their AMF associations and how this affects expansion-related traits. Using a combination of field surveys and a greenhouse experiment, we investigated the effects of AMF on the growth, competitive ability, and reproduction of the invasive plant Galinsoga quadriradiata in its core and edge populations. Field data confirmed that core populations had significantly higher root AMF colonization than edge populations. In the greenhouse, edge populations exhibited greater mycorrhizal dependency; AMF inoculation significantly shortened their duration of vegetative growth phase (DVGP) and enhanced both growth and reproductive output in the edge populations but generally had no such effects on the core populations. However, the presence of competitors, particularly intraspecific ones, weakened these plant-AMF interactions. The results of piecewise structural equation models revealed distinct plant-AMF interaction pathways for the core versus edge populations of G. quadriradiata. Our findings demonstrate that plant-AMF interactions differentiate during range expansion, with edge populations suffering from an AMF deficit that can limit their growth and delay reproduction. AMF not only promotes invader performance but also adjusts its temporal niche by accelerating life history. Consequently, AMF availability acts as a critical ecological filter at the expansion front, serving as both a potential promoter and a limiter of invasive spread, with population-level variation in symbiosis shaping invasion dynamics.
Abstract Phragmites australis is a dominant species in estuaries. It can reproduce sexually and clonally. Understanding the latitudinal patterns of the traits can help in predicting adaptive strategies across environmental gradients. However, changes in growth and reproductive traits of P. australis, as well as growth-reproduction relationships along latitudinal gradients remain unclear. We sampled P. australis from five estuaries along latitudinal gradients in China and analyzed changes in growth, reproductive, and biomass allocation. The results revealed that with increasing latitude, the ramet height, flowering frequency, inflorescence biomass per flowering ramet, and weight of 100 seeds increased, whereas the ramet density generally decreased. The latitudinal growth and reproduction patterns were primarily influenced by variations in the temperature, precipitation, and light intensity. These results suggest that high-latitude P. australis populations may reduce their flowering and seed production under climate warming.
Abstract Arbuscular mycorrhizal (AM) fungi are well documented to alleviate physiological stress in plants. While AM fungal benefits under low-water conditions are well studied, AM fungal benefits under high-water conditions are far less understood. Previously, direct experimentation on AM fungal effects on plant performance has largely focused on agricultural crop species, frequently using categorical ambient and drought condition treatments rather than leveraging gradients appropriate for detecting non-linear responses. Thus, there is little understanding about how AM fungi may mediate native, terrestrial plant responses across gradients of water availability. Here, we tested the effects of AM fungi on a common, ruderal plants species (Solidago altissima) across a wide range of water availability in a greenhouse experiment. AM fungi improved plant performance at moderate and high levels of water availability, but surprisingly AM fungi did not improve plant performance in the lowest water availability treatment groups. Most importantly, without AM fungi, S. altissima was unable to take advantage of increasing water availability, indicating that even for a ruderal plant species, mycorrhizal associations may be a critical component to plastic responses in plant performance under climate-driven changes in water availability.
Abstract Genetically based trait covariances are critical for invasive plant adaptation. Clonal growth can facilitate local expansion; however, the evolutionary relationship between clonal timing and performance remains underexplored. Particularly, it is unclear how these traits covary to affect adaptation across latitudes. Here, we investigated variation and covariance in two clonal traits (the timing of the first ramet emergence and peak number of ramets within a growing season) of Spartina alterniflora, an aggressive coastal invader in China. We sampled eight populations spanning the entire latitudinal range of S. alterniflora along the Chinese coast (21° N–38° N). These seeds were cultivated in three common gardens at low (21° N), mid (28° N), and high (38° N) latitudes. Plants from low-latitude garden exhibited significantly earlier ramet emergence and greater ramet production than those in mid- and high-latitude gardens across the growing season, highlighting substantial phenotypic plasticity. The timing of the first ramet emergence showed a provenance-by-environment interaction, and was driven by abiotic factors at original sites. Furthermore, we found a generally negative covariance between ramet emergence time and ramet production, populations originating from low-latitudes consistently exhibited earlier ramet emergence with more ramets. Our findings suggest that clonal traits covariances were likely to benefit the local adaptation of S. alterniflora at low latitudes, and such covariances appeared to be driven by genetic admixture. Our study advances the understanding of how variable life-history strategies enable invasion success across environmental gradients in the introduced range, and highlights the need for region-specific management strategies tailored to local phenology.
Abstract Population stability (PS) of functionally important species underpins ecosystem resilience, yet the mechanisms that maintain PS under heterogeneous nitrogen (N) conditions remain elusive, particularly for legumes in (sub)tropical forests. Legumes can stabilize their population performance through high abundance or symbiotic N2 fixation, but how soil N “chooses” between these strategies is unknown. In a 20-ha subtropical forest plot, the sole dominant legume Ormosia glaberrima, with >2,500 individuals recorded over 15 years, provides an ideal system to test these pathways. We quantified PS from long-term demography as the inverse of inter-period variation in basal area growth, and assessed biological N fixation (BNF) ability using the N stable isotope natural abundance method. Structural equation modeling (SEM) was applied to disentangle the direct and indirect effects of soil N, abundance, and BNF ability on PS. Results showed no significant direct effect of soil N on the PS of O. glaberrima. Instead, it was positively correlated with abundance (R2adj =0.22, P < 0.001) and negatively related to BNF ability (R2adj =0.26, P < 0.001). SEM explained 34% of the variation in PS and revealed opposing mediating pathways. Elevated soil N indirectly enhanced PS by increasing abundance (β = 0.27) but reduced PS by suppressing BNF ability (β = -0.15). These findings reveal a context-dependent “abundance-fixation trade-off” as a novel mechanism regulating long-term legume population performance, with important implications for forest management aimed at maintaining ecosystem stability under global N deposition.
Abstract Plant-herbivore interactions play a critical role in shaping plant performance and community dynamics. The strength of herbivory is expected to be associated with plant functional traits and environmental conditions. However, it remains unclear how these relationships differ between plant growth forms, particularly woody and herbaceous species at the global scale. By collecting global plant leaf herbivory data from 1,651 sites, including 2,594 species belonging to 1,060 genera and 204 families, we analyzed the variation in leaf herbivory and its relationships with plant functional traits and environments for woody and herbaceous species. We found that most variation of herbivory occurred among species and across ecoregion. The relationships between herbivory and plant traits and soil differed for woody and herbaceous plants: conservative leaf traits were associated with higher herbivory in woody plants but lower herbivory in herbaceous plants, while sandier soils increased herbivory in herbaceous plants but had weaker effects on woody species. In woody species, higher temperatures and infertile soils enhance herbivory both directly and indirectly through increased plant height. Conversely, in herbaceous species, while higher temperatures and sandier soils directly promote herbivory, higher temperatures and infertile soils indirectly suppress it via increased leaf dry matter content. These findings suggest distinct ecological processes control the variation of herbivory in woody versus herbaceous plants. We highlight the importance of integrating plant growth form to understand the trait-environment-herbivory relationships across terrestrial ecosystems.
Abstract Plant−herbivory interactions are traditionally expected to strengthen along warming temperature gradients. However, little is known about the impact of long−term warming on the forest leaf−level effects associated with herbivory. To address this gap, we simulated ecosystem warming by utilizing natural temperature variation along an altitudinal gradient using open-top chambers (OTCs), in which native forest tree species (Schima superba, Syzygium rehderianum, Machilas breviflora, and Itea chinensis) and soil were translocated from cooler high−elevation ecosystems (600 m) to warmer low−elevation ecosystems (300 and 30 m; +1℃ and +2℃, respectively), to investigate the effects of warming on leaf herbivory. After 12 years of ecosystem warming, +1℃ and +2℃ lead up to 10 % and 48 % increment in herbivory, respectively. Warming reduced leaf toughness and thickness while increasing leaf area, potentially weakening structural defenses. Warming also decreased lignin content and was associated with significant increases in herbivory, while changes in leaf chemistry were minor and had no detectable influence on herbivory. During the herbivory study period (Mar−Nov 2023) and relative to the control, a +2°C warming combined with +6% precipitation collectively enhanced herbivory. Our findings show that plants from higher elevation exhibit stronger leaf physical protective structures; however, these traits are reduced under long−term warming, thereby weaken leaf structural integrity and potentially influencing plant−herbivore dynamics. These findings enhance our understanding how warming could modify leaf structure and its relationship with herbivory in a subtropical forest ecosystem, thereby may improve predictions of potential ecological responses to future warming scenarios.
Abstract Intraspecific trait variation (ITV) is a critical mechanism for species adaptation to heterogeneous environments, yet its relative contribution and variation patterns across different ecosystems remain poorly understood. This study investigated 28 dominant species and 910 individuals in three climatically distinct ecosystems of Yunnan Province, China: tropical rainforest (Xishuangbanna), subtropical evergreen broad-leaved forest (Ailaoshan), and savanna (Yuanjiang). We measured leaf thickness (LT), leaf area (LA), specific leaf area (SLA), leaf dry matter content (LDMC), and leaf chlorophyll content (LCC), combining phylogenetic signal testing and variation partitioning to quantify the effects of site, species, and individual scales on leaf trait variation. We detected significant phylogenetic signals among those leaf traits. Plants in the tropical rainforest exhibited resource-acquisitive strategies (high LA and SLA, but low LDMC), whereas species in the subtropical evergreen broad-leaved forest and savanna showed more resource-conservative strategies. ITV accounted for 9%–47% of the total trait variation at the regional scale. At local scale, the relative contribution of ITV to total community trait variance was highest in the resource-rich forest and negligible in the savanna. Our findings demonstrate that the variance of functional traits is highly context-dependent and scale-dependent across ecosystems. Given that intraspecific variation contributes substantially to total community-level trait variance, explicitly incorporating ITV into predictive models is critical for accurately shifting our understanding from static trait means to dynamic mechanisms of community assembly and ecosystem responses to global climate change.
Abstract Fire-resistant tree species are vital for reducing fire ignition and spread, thus playing a key role in maintaining forest biodiversity and ecosystem functions. However, understanding how these species respond to environmental change and human activities across latitudinal gradients in China remains unclear. Here, we integrated four species distribution models to identify the most effective approach for predicting current and future habitat shifts of eight typical fire-resistant tree species (Salix koreensis Andersson, Ulmus pumila L., Acer truncatum Bunge, Juglans mandshurica Maxim, Toona sinensis (Juss.) Roem., Michelia macclurei Dandy, Schima superba Gardner & Champ, and Castanopsis hystrix Hook. f. & Thomson ex A. DC.) in China under two emissions scenarios (SSP1-2.6 and SSP5-8.5). We found a distinct latitudinal divergence in habitat distributions: S. koreensis, U. pumila, A. truncatum and J. mandshurica were predominantly found in northern and northeastern China, while T. sinensis, M. macclurei, S. superba, and C. hystrix dominated in southern China. Low-latitude species exhibited consistently higher habitat suitability than their high-latitude counterparts. Importantly, human activities primarily shaped the distributions of high-latitude species, whereas low-latitude species were more sensitive to climate, especially precipitation. Under future climate scenarios, low-latitude species are expected to expand northward, exhibiting greater range-expansion potential, whereas high-latitude species may shift north but lose habitat in the south, especially U. pumila and J. mandshurica face substantial contraction. These findings highlight the divergent responses of fire-resistant tree species to climate and anthropogenic pressures and provide a scientific basis for strengthening forest resilience and region-specific forest-fire prevention strategies.
Abstract Global climate change has markedly increased compound drought frequency and intensity worldwide, severely threatening ecosystem function and sustainable socio-economic development. As a climate-vulnerable region with high drought susceptibility, China requires a deeper understanding of the spatiotemporal evolution of compound droughts, along with their ecosystem resilience impacts. “Compound drought novelty” is introduced to quantify the degree of deviation of compound drought characteristics from their historical state. Based on national-scale meteorological observations and remote-sensing data, methods were developed for identifying compound drought events and analyzing their novelty. Ecosystem resilience was then computed, and the mechanisms by which compound drought influences resilience were examined. Results indicate pronounced regional differences in compound drought across China, the spatial centroid of compound drought frequency showed an overall westward shift. Regarding ecosystem resilience, 42.5% of the area experienced a significant decline, 32.6% showed a significant increase. Partial Least Squares Structural Equation Modeling (PLS-SEM) further showed that compound drought was overall significantly negatively correlated with AR1, whereas compound drought novelty was significantly positively correlated with AR1. These results suggest that regions with long-term exposure to stronger compound drought characteristics may possess higher resilience, whereas when combinations of drought characteristics deviate from their historically experienced range, ecosystem recovery tends to slow and resilience correspondingly declines. The proposed concept of compound drought novelty and its mapped spatial patterns reveal new risk features for ecosystems under an increasingly frequent drought regime. These findings contribute scientific insights for regional drought management and strategies aimed at enhancing ecological resilience.
Abstract Dioecious species play a pivotal role in terrestrial ecosystems. However, the physiological and growth responses of widely distributed dioecious plants to environmental changes remain poorly understood from an integrated perspective. The studies about sexual differences in dioecious plants (64 valid literature references and 256 independent studies) under environmental changes were evaluated through a meta-analysis. Across all measured functional traits, the weighted response ratios to environmental stress ranged from -0.30 to -0.03, indicating an overall negative but variable effect on dioecious plants. Plant biomass and photosynthetic performance of both sexes were considerably affected by various stressors. Specifically, drought, salt, and heavy metal stress significantly reduced net photosynthetic rate (Pn) and total biomass, with drought being the most inhibitory. Moreover, this meta-analysis revealed that the inhibition effect was more pronounced in females than in males, and females exhibited a broader range of variation to environmental fluctuations. In addition, combined environmental stressors mitigated sexual differences in plant responses relative to single-factor stresses, with the effects varing by stress combination. Drought combined with high temperature or salt stress significantly reduced Pn and transpiration rate (E), whereas elevated CO2 and temperature interactively increased total biomass. This meta-analysis revealed that males generally exhibited stronger stress tolerance than females in terms of photosynthetic performance and biomass accumulation, with sex-specific differences varying by species, stress type, and environmental interactions. Collectively, these findings provide valuable insights for understanding adaptation of dioecious plants to global environmental changes, and guidance for future research and ecological management involving dioecious species.
Abstract Climate change, characterized by rising CO2 concentrations and warming, impacts soil microbial processes regulating nitrogen (N) availability for crops. This study aimed to elucidate the responses to elevated CO2 and warming of rhizosphere microbial communities involved in N mineralization under major cereal crops. A controlled pot experiment was conducted in open-top chambers with four treatments: ambient conditions (Control), elevated CO2 (700 ppm), warming (2°C above ambient), and their combination. Maize, wheat, and rice were grown in a Mollisol for 92 days. Functional microbial communities were characterized by sequencing of the chiA and pepA genes, which encode key enzymes involved in chitin and peptide degradation, respectively. Principal coordinate and network analyses revealed distinct, crop-specific microbial assemblages and responses to climate factors. Rice rhizosphere communities exhibited significantly greater functional resilience under elevated CO2 and warming compared with those of maize and wheat. This resilience may be attributed to anaerobic conditions of flooded rice paddies, which buffer temperature and moisture fluctuations and promote microbial functional redundancy, enabling species replacement as a primary adaptive response. In contrast, dryland systems (maize and wheat) showed higher sensitivity, with disrupted microbial networks, lower abundance of key taxa, and greater variability in predicted N mineralization potential. These findings highlight that crop-specific rhizosphere environments shape the resilience of N-cycling microbiomes under climate change. The study provides practical implications for N-fertilizer management and the design of climate-resilient cropping systems that maintain soil N supply in a warming and CO2-enriched climate.
Abstract Different mycorrhizal types in plants exhibit distinct strategies for resource acquisition and environmental adaptation. Elevation integrates multiple environmental factors and influences community structure and species diversity in mountain ecosystems. However, how tree species with different mycorrhizal types vary in diversity-elevation patterns remains poorly understood. A 3210 m continuous elevational transect (636–1928 m a.s.l.) was established in Baishanzu National Park, China, and we surveyed adult trees and saplings of three mycorrhizal types: arbuscular mycorrhizal (AM), ectomycorrhizal (EcM), and ericoid mycorrhizal (ErM). We calculated Hill indices (q = 0, 1, 2) to compare diversity-elevation patterns among mycorrhizal types and life stages. Bray-Curtis and Sørensen indices were used to quantify elevational changes in species composition dissimilarity between adults and saplings. Results showed that AM trees consistently exhibited higher species diversity than EcM and ErM trees. Elevation was the primary driver of diversity across all mycorrhizal types. AM diversity showed a hump-shaped relationship with elevation, whereas EcM and ErM declined monotonically with increasing elevation. Across all mycorrhizal types, adults showed a consistent hump-shaped elevation pattern, while saplings shifted from hump-shaped to monotonically decreasing patterns as q increased with abundant species weighted. Species composition dissimilarity between adults and saplings increased with elevation for AM trees, declined for EcM trees, and showed an inverse hump-shaped pattern for ErM trees. Overall, our findings reveal elevational diversity trajectories and regeneration dynamics among mycorrhizal types, highlighting the crucial role of mycorrhizal associations in shaping diversity-elevation relationships by mediating species abundance and regeneration across life stages in mountainous forests.
Abstract Plant‒soil microbe interactions play a significant role in community dynamics. While bacteria play important roles in driving plant‒soil feedback (PSF), which regulates grassland succession, it remains unclear how bacteria-mediated PSF influences tree seedling establishment during forest succession. A pot experiment of four tree seedlings (fast-growing broadleaf Betula platyphylla and Betula albosinensis, and slow-growing coniferous Picea asperata and Abies faxoniana), using sterilized soil inoculated with rooting zone soils from dominant plant species at the early, mid- and late-successional stages in a subalpine forest, was conducted in a greenhouse. Plant biomass, soil bacterial communities, and soil chemical properties were measured. Broadleaf experienced stronger negative biotic feedbacks, while coniferous generated more positive biotic feedbacks, especially in mid- and late-successional inoculated soils. Controlled pot experiments demonstrate that broadleaf biomass was correlated positively with the relative abundance of oligotrophic bacteria but negatively with copiotrophic bacteria, while this trend was opposite in coniferous. Oligotrophs, namely, Alphaproteobacteria (nitrogen-fixing bacteria) and Chloroflexi (nitrite oxidizing bacteria), were the dominant influential factors of the variations in broadleaf and coniferous biomass, respectively. These results indicate that the benefit of bacteria on tree seedling establishment is species specific. It can be inferred that plant nutritional requirements and pathogen resistance among plants with different life-history strategies may alter the composition and function of bacteria, thus alleviating soil nutrient limitation and plant‒soil microbe nutrient competition. Our findings provide new insights into the potential role of bacterial functional groups in shaping the PSFs of late-successional tree seedlings.
Abstract Climate-change-driven drought intensification increasingly threatens forest ecosystems, highlighting an urgent need for accurate monitoring of forest water stress. Leaf water potential (Ψleaf) is a key integrative indicator, yet conventional measurements are destructive and unsuitable for large-scale or high-frequency monitoring. Hyperspectral remote sensing offers a promising alternative, but robust canopy-level Ψleaf estimation remains constrained by limited labeled data and heterogeneous environmental conditions. Here, we develop a cross-scale framework integrating supervised contrastive learning with deep transfer learning to translate robust leaf-scale pretraining into canopy-scale Ψleaf estimation from hyperspectral data in a Populus × euramericana ‘I-214’ plantation. Hyperspectral imagery was captured at the leaf scale under controlled laboratory conditions (n = 229) and at the canopy scale using a UAV-based platform (n = 200), together with paired Ψleaf measurements. Reflectance consistently increased with declining Ψleaf at both scales, supporting the feasibility of cross-scale modeling. At the leaf scale, physics-consistent spectral augmentation coupled with contrastive learning enhanced feature discrimination and predictive stability under small-sample conditions (R2 = 0.8030). Transfer learning via progressive fine-tuning enabled efficient scaling of the leaf-level pretrained model to canopy-level prediction despite structural and environmental complexity and restricted field data ranges, achieving R2 = 0.7605 and RMSE = 0.1056 MPa. Coupling with individual-tree crown segmentation further enabled spatially explicit mapping of canopy Ψleaf and plot-level forest water stress dynamics. These results demonstrate that combining contrastive representation learning with cross-scale transfer provides a practical pathway for physiological monitoring and scalable, climate-smart forest phenotyping in data-constrained forested environments.
Abstract The 15N tracer technique is pivotal for quantifying nitrogen (N) dynamics in intercropping, but the assumption that results are independent of the tracer’s chemical form remains untested. We demonstrated that the choice of tracer form (NO3– vs. NH4+) systematically affected quantitative estimates of both symbiotic N2 fixation (SNF) and interspecific N transfer. In a pot experiment with maize and three leguminous green manures, the 15N-dilution technique revealed that the use of 15NH4+ as a tracer resulted in higher estimates of the proportion of N derived from the atmosphere (%Ndfa) by an average of 18.0% compared to 15NO3–. Concurrently, a 15N foliar labeling experiment showed that the tracer form assimilated by the donor plant strongly altered the observed interspecific transfer pattern: legumes transferred 2.2 times more N derived from 15NO3– than from 15NH4+ to maize, while maize transferred 1.6 times more N derived from 15NH4+ than from 15NO3– to legumes. This bidirectional transfer pattern can be best explained by the distinct biogeochemical behaviors of the two N forms and their divergent metabolic assimilation pathways within plants. Our findings exposed a critical, yet previously unquantified, methodological effect. We contend that the chemical identity of the tracer should be reported as a mandatory methodological parameter, as estimates are not absolute but represent methodology-dependent perspectives. This necessitates a critical reevaluation of data across studies, cautioning against direct comparisons of results obtained with different tracer forms.
Abstract Sexual differences in floral traits are widespread in gynodioecious plants, yet few studies have focused on floral dimorphism at the plant level. Floral display size—defined as the number of flowers blooming simultaneously on a plant—is one of the most important plant traits influencing reproductive success in animal-pollinated angiosperms. We hypothesized that in hermaphrodite plants, a large floral display size enhances pollinator attraction and seed production but incurs a cost of low-quality offspring because of self-pollination, whereas female plants can avoid this dilemma and benefit from a large floral display size. Such sex-specific differences in female reproductive success might explain the sexual dimorphism in floral display size in gynodioecious species. We tested this hypothesis in the gynodioecious species Cyananthus delavayi by investigating the effects of floral display size on pollinator attraction, seed production, and seed quality. Compared with hermaphrodite plants, female plants had larger floral display size, which was attributable to higher intra-plant flowering synchrony. Larger flower displays increased pollinator visitation and seed number per flower in both sexes. In hermaphrodites, floral display size did not significantly affect the germination rate or outcrossing rate; however, seedling survival decreased with floral display size, and compared with selfed seeds, outcrossed seeds exhibited significantly higher survival. Our findings suggest that sex-specific differences in reproductive success may drive the sexual dimorphism in terms of floral display size in gynodioecious species, providing novel insights into the evolution of sexual dimorphism in plants.
Abstract The spatiotemporal distribution of individual tree age within a forest community is important for understanding ecological processes, such as competition, succession, and function, at different scales. However, traditional methods are expensive and inefficient, particularly at large scales. This study proposes a novel conceptual framework to obtain the Forest Community Age Spectrum (FCAS) and evaluates its feasibility by integrating an explainable machine learning model with high-resolution hyperspectral remote sensing of leaves. Focusing on Larix gmelinii, we used hyperspectral data to rapidly estimate tree age. The results showed that the hyperspectral model of mature leaves could accurately estimate tree age (best model performance: R2 = 0.78, RMSE = 6.13, RPD = 2.12). The model performed best in the 400–1000 nm wavelength band because of leaf structure-sensitive wavelength (near 644.88 nm) band and Photosynthetic pigment wavelength bands (701–724 nm), and captured the entire age gradient within the 900–1700 nm wavelength band due to the presence of phenolic aldehyde and other secondary metabolite-sensitive wavelength bands (1460–1517 nm and 1600–1700 nm). Overall, this study successfully established a key methodological foundation for estimating tree age and, ultimately, constructing the FCAS. The framework provides a potential pathway for future FCAS-based research to quantify spatial age patterns and investigate mechanisms driving competition, succession, functional optimization, and carbon sequestration. These findings offer both an empirical basis and an operational tool for quantitatively linking forest age structure with core ecological processes through FCAS, representing a critical first step toward its realization.
