Leaf Trait Networks Based on Global Data: Representing Variation and Adaptation in Plants

Functional trait response to aridity based on leaf trait network analysis in the Hexi Corridor, China

BACKGROUND

Aridity acts as a strong environmental filter for plants and is predicted to intensify in the future, resulting in changes to leaf functional traits. However, few studies explore how interactions of multiple traits result in leaf trait tradeoff strategies along an aridity gradient, and whether trait separation occurs with increasing aridity intensity. This study examines the impact of long-term aridity on 14 plant leaf traits in two arid areas (arid and hyper-arid) in the Hexi Corridor, China. A leaf trait network (LTN) was constructed to study how leaf trait tradeoff strategies differ between the two areas. Structural equation modeling (SEM) was used to identify the direct and indirect effects of aridity and functional diversity (as measured by community weighted means and functional dispersion) on leaf nutrient concentration.

RESULTS

LTN shows trait separation, poor synergy among traits, and low resource utilization. Correlation analyses showed that the mass ratio hypothesis is dominant, and aridity is positively correlated with leaf relative water content (RWC) and leaf phosphorus content, and negatively correlated with leaf nitrogen content (LNC). SEM results indicated that LNC is directly affected by aridity, RWC, leaf carbon content, and plant height. Aridity and functional dispersion directly affects leaf phosphorus content.

CONCLUSIONS

Results indicate that increasing drought weakens plant coordination among specific traits, and the main change in plant trait tradeoff strategies is reflected in the separation of nutrient traits. Exploring the change of the tradeoff among traits along the aridity gradient can better understand the adaptation process of plants to aridity and the process of community function change.

Climate: The dominant factor influencing the spatial distribution pattern of the leaf trait network of Populus euphratica along the main stream of the Tarim River

Leaves are the primary interface through which plants interact with the environment, their functional traits (morphology, anatomy, physiology) directly reflecting ecological strategies that mediate species-environment interactions. These traits link plant performance to ecosystem processes, shaping species distributions and coexistence via their complex relationships with climatic and edaphic factors. Based on previous work, we selected 20 P. euphratica trees along the desert riparian forest of the main stream of the Tarim River for leaf sample collection and habitat survey. We used 27 leaf traits of P. euphratica to visualize the leaf trait network (LTN). Through network structure parameters, such as edge density, diameter, average path length, and average clustering coefficient, the spatial pattern of the LTN and its relationships with 19 climatic factors and 11 soil factors were discussed using principal component analysis and correlation analysis. The results showed that: (1) there were significant differences in the parameters of the leaf trait network of P. euphratica along the main stream of the Tarim River. The variation coefficients of the diameter and average path length were the largest, respectively, whereas that of the average clustering coefficient was the smallest. (2) Among the parameters, only Modularity was significantly correlated with STK and SOM. But Average clustering coefficient was significantly positively correlated with Isothermality, Average path length and Diameter were significantly positively correlated with Min temperature of coldest month and the Average clustering coefficient was significantly negatively correlated with Min temperature of coldest month, the Diameter was significantly positively correlated with Precipitation of wettest month. In general, the correlation between climate factors and LTNs was stronger than soil factors. (3) The explanatory power of climatic factors alone on the leaf traits of P. euphratica was generally higher than that of soil factors, indicating that climatic conditions play a more decisive role in shaping the network structure of leaf traits of P. euphratica. However, the influence of soil conditions on some LTNs parameters cannot be ignored.The spatial variability of leaf trait networks is driven by climate and soil factors, with climate dominating along the Tarim River's main course.

Network-informed analysis of a multivariate trait-space reveals optimal trait selection

Trait-based analyses have shown great potential to advance our understanding of terrestrial ecosystem processes and functions. However, challenges remain in adequately synthesising a multidimensional and covarying trait space. Reducing the number of studied traits while identifying the most informative ones is increasingly recognized as a priority in functional ecology. Here, we develop a trait reduction procedure based on network analysis of a global dataset comprising 27 traits in three steps. We first construct all possible reduced networks and identify optimal reduced networks that capture the structure of the full 27-trait network. Then we apply the constraints on trait consistency to identified optimal reduced networks and establish consistent network series across ecoregions. We find the best performing networks that capture the three main dimensions of the full network (hydrological safety, leaf economic strategy, and plant reproduction and competition) and the global variance of network metrics. Finally, we find a parsimonious representation of trait covariation strategies is achieved by a 10-trait network which preserves 60% of all the original information while costing only 20.1% of the full suite of traits. Our results show the network reduction approach can improve our understanding on the main plant strategies and facilitate the future trait-based research.

Leaf trait networks of subtropical woody plants weaken along an elevation gradient

The leaf economic spectrum (LES) captures key leaf functional trait relationships, defining a conservative-acquisitive axis of plant resource utilization strategies. Examining the leaf trait network (LTN) is useful for understanding resource utilization strategies but also more broadly, the ecological strategies of plants. However, the relationship between the LES conservation-acquisition axis and LTN correlations across environmental gradients is unclear. To address this knowledge gap, we measured physiological, chemical, and structural traits in 52 broad-leaved tree species spanning an elevation gradient (1400 m, 1600 m, 1800 m) in Wuyi Mountain, China. A total of 12 leaf traits were selected, including: photosynthetic rate (A25), respiration rate (R25), optimum photosynthetic temperature (Topt), rate of photosynthesis at optimum temperature (Aopt), mean temperature at which 90 % of Aopt is reached (T90), temperature sensitivity of respiration (Q10), N and P content, N/P, leaf mass per area (LMA), photosynthetic nitrogen use efficiency (PNUE) and photosynthetic phosphorus use efficiency (PPUE). We found that leaf physiological traits exhibited signs of thermal acclimation along the elevation gradient. We also observed significant changes in leaf N and P content, N/P, photosynthetic phosphorus utilization efficiency (PPUE) and LMA with elevation. The resource utilization strategies of plants changed from conservative to acquisitive as elevation increased. The LTN analysis showed that as elevation increased, the links among traits weakened and modularity (modularity is used to describe the degree of separation between networks) increased. Collectively, our results indicate that elevation changes can trigger moderate shifts in the resource utilization and ecological strategies of plants via leaf functional traits.

Trade-off strategies between growth and defense of spring ephemeral plants in early spring

Introduction

Spring ephemeral plants represent a unique ecological category of herbaceous plants, characterized by early blooming and vivid flowers with significant ornamental value. Understanding the adaptive strategies of spring ephemerals is crucial for the introduction and cultivation of early spring plants, as well as for optimizing light energy utilization and nutrient cycling within ecosystems.

Methods

We evaluated 26 functional traits across four spring ephemerals and four spring non-ephemeral plants along an elevation gradient. By establishing a plant functional trait network, we examined the adaptation strategies of early spring plants at different elevations and compared the differences in adaptation strategies between two types of plants.

Results

Spring ephemerals exhibited higher concentrations of carbon and nitrogen, lower concentrations of carbohydrates, higher edge density and modularity in trait networks, and stronger linkages between defense traits. Plants at higher elevations demonstrated higher leaf dry matter content and leaf total flavonoid concentration, and lower nitrogen concentration, influenced by temperature, precipitation, and soil nutrients.

Discussion

These results demonstrated that spring ephemerals have a strong nutrient uptake capacity, and adopt resource competition strategies to rapidly accumulate nutrients and reproduce. The plants at higher elevations adopt more conservative strategies, with trait networks showing increased modularity, edge density, and closer correlations among traits to enhance resource utilization. This study provides new insights into the adaptive strategies of spring ephemerals by demonstrating how plants allocate resources for growth and defense through the regulation of trait variation and correlations among traits.

Leaf nutrient traits exhibit greater environmental plasticity compared to resource utilization traits along an elevational gradient

Studying key leaf functional traits is crucial for understanding plant resource utilization strategies and growth. To explore the patterns and driving factors of key leaf functional traits in forests along elevational gradients under global change, we collected survey data from 697 forests across China from 2008 to 2020. This study examined the elevational patterns of Specific Leaf Area (SLA, m²/kg), Leaf Dry Matter Content (LDMC, g/g), Leaf Nitrogen (LN, mg/g), and Leaf Phosphorus (LP, mg/g), and their responses to climate, soil nutrients, and stand factors. The results showed distinct differences in these key leaf traits at different elevational gradients. Generally, as elevation increased, SLA decreased, while LDMC significantly increased (P < 0.001), and LN first increase and then decreased (P < 0.001). The direct influence of elevation on the spatial variation of key leaf traits was greater than its indirect effects (through environmental and stand factors). The elevational patterns of leaf traits related to resource utilization strategies (SLA and LDMC) were mainly influenced by climate (temperature and precipitation) and soil nutrient factors, showing opposite trends in response to environmental changes. The patterns of leaf nutrient traits (LN and LP) along elevational gradients were primarily influenced by climatic factors, with LN exhibiting greater environmental plasticity. Compared to other stand factors, forest age predominantly influenced the spatial variation of key leaf traits, especially SLA. These findings have significant theoretical implications for revealing how plants adapt to global change.

Innovations and prospectives of multidimensional trait integration

This article is a Commentary on Ye et al. (2024), 244: 436–450.

Leaf Functional Traits and Their Influencing Factors in Six Typical Vegetation Communities

Leaf functional traits (LFTs) have become a popular topic in ecological research in recent years. Here, we measured eight LFTs, namely leaf area (LA), specific leaf area (SLA), leaf thickness (LT), leaf dry matter content (LDMC), leaf carbon content (LCC), leaf nitrogen content (LNC), leaf phosphorus content (LPC), and leaf potassium content (LKC), in six typical vegetation communities (sclerophyllous evergreen broad-leaved forests, temperate evergreen coniferous forests, cold-temperate evergreen coniferous forests, alpine deciduous broad-leaved shrubs, alpine meadows, and alpine scree sparse vegetation) in the Chayu River Basin, southeastern Qinghai-Tibet Plateau. Our aim was to explore their relationships with evolutionary history and environmental factors by combining the RLQ and the fourth-corner method, and the method of testing phylogenetic signal. The results showed that (i) there were significant differences in the eight LFTs among the six vegetation communities; (ii) the K values of the eight LFTs were less than 1; and (iii) except for LCC, all other LFTs were more sensitive to environmental changes. Among these traits, LA was the most affected by the environmental factors, followed by LNC. It showed that the LFTs in the study were minimally influenced by phylogenetic development but significantly by environmental changes. This study further verified the ecological adaptability of plants to changes in environmental factors and provides a scientific basis for predicting the distribution and diffusion direction of plants under global change conditions.

Assessing leaf physiological traits in response to flooding among dominant riparian herbs along the Three Gorges Dam in China

Dams worldwide have significantly altered the composition of riparian forests. However, research on the functional traits of dominant herbs experiencing flooding stress due to dam impoundment remains limited. Given the high plasticity of leaf traits and their susceptibility to environmental influences, this study focuses on riparian herbs along the Three Gorges Hydro-Fluctuation Zone (TGHFZ). Specifically, it investigates how six leaf physiological traits of leading herbs-carbon, nitrogen, phosphorus, and their stoichiometric ratios-adapt to periodic flooding in the TGHFZ using cluster analysis, one-way analysis of variance (ANOVA), multiple comparisons, Pearson correlation analysis, and principal component analysis (PCA). We categorized 25 dominant herb species into three plant functional types (PFTs), noting that species from the same family tended to fall into the same PFT. Notably, leaf carbon content (LCC) exhibited no significant differences across various PFTs or altitudes. Within riparian forests, different PFTs employ distinct adaptation strategies: PFT-I herbs invest in structural components to enhance stress resistance; PFT-II, mostly comprising gramineous plants, responds to prolonged flooding by rapid growth above the water; and PFT-III, encompassing nearly all Compositae and annual plants, responds to prolonged flooding with vigorous rhizome growth and seed production. Soil water content (SWC) emerges as the primary environmental factor influencing dominant herb growth in the TGHFZ. By studying the response of leaf physiological traits in dominant plants to artificial flooding, we intend to reveal the survival mechanisms of plants under adverse conditions and lay the foundation for vegetation restoration in the TGHFZ.

Variations and trade-offs in leaf and culm functional traits among 77 woody bamboo species

BACKGROUND

Woody bamboos are the only diverse large perennial grasses in mesic-wet forests and are widely distributed in the understory and canopy. The functional trait variations and trade-offs in this taxon remain unclear due to woody bamboo syndromes (represented by lignified culm of composed internodes and nodes). Here, we examined the effects of heritable legacy and occurrence site climates on functional trait variations in leaf and culm across 77 woody bamboo species in a common garden. We explored the trade-offs among leaf functional traits, the connection between leaf nitrogen (N), phosphorus (P) concentrations and functional niche traits, and the correlation of functional traits between leaves and culms.

RESULTS

The Bayesian mixed models reveal that the combined effects of heritable legacy (phylogenetic distances and other evolutionary processes) and occurrence site climates accounted for 55.10-90.89% of the total variation among species for each studied trait. The standardized major axis analysis identified trade-offs among leaf functional traits in woody bamboo consistent with the global leaf economics spectrum; however, compared to non-bamboo species, the woody bamboo exhibited lower leaf mass per area but higher N, P concentrations and assimilation, dark respiration rates. The canonical correlation analysis demonstrated a positive correlation (ρ = 0.57, P-value < 0.001) between leaf N, P concentrations and morphophysiology traits. The phylogenetic principal components and trait network analyses indicated that leaf and culm traits were clustered separately, with leaf assimilation and respiration rates associated with culm ground diameter.

CONCLUSION

Our study confirms the applicability of the leaf economics spectrum and the biogeochemical niche in woody bamboo taxa, improves the understanding of woody bamboo leaf and culm functional trait variations and trade-offs, and broadens the taxonomic units considered in plant functional trait studies, which contributes to our comprehensive understanding of terrestrial forest ecosystems.

Exploring Intraspecific Trait Variation in a Xerophytic Moss Species Indusiella thianschanica (Ptychomitriaceae) across Environmental Gradients on the Tibetan Plateau

Investigating intraspecific trait variability is crucial for understanding plant adaptation to various environments, yet research on lithophytic mosses in extreme environments remains scarce. This study focuses on Indusiella thianschanica Broth. Hal., a unique lithophytic moss species in the extreme environments of the Tibetan Plateau, aiming to uncover its adaptation and response mechanisms to environmental changes. Specimens were collected from 26 sites across elevations ranging from 3642 m to 5528 m, and the relationships between 23 morphological traits and 15 environmental factors were analyzed. Results indicated that coefficients of variation (CV) ranged from 5.91% to 36.11%, with gametophyte height (GH) and basal cell transverse wall thickness (STW) showing the highest and lowest variations, respectively. Temperature, elevation, and potential evapo-transpiration (PET) emerged as primary environmental drivers. Leaf traits, especially those of the leaf sheath, exhibited a more pronounced response to the environment. The traits exhibited apparent covariation in response to environmental challenges and indicated flexible adaptive strategies. This study revealed the adaptation and response patterns of different morphological traits of I. thianschanica to environmental changes on the Tibetan Plateau, emphasizing the significant effect of temperature on trait variation. Our findings deepen the understanding of the ecology and adaptive strategies of lithophytic mosses.

Similarities and differences in the physiological adaptation to water salinity between two life forms of aquatic plants in alpine and arid wetlands

Aquatic plants play a crucial role in freshwater ecosystems as primary producers, but their survival is threatened by salinization. Understanding the physiological responses of aquatic plants to increasing water salinity is important for predicting their adaptive strategies under future climate change scenarios. In this study, we measured 15 physiological traits of 49 aquatic plant species along a large environmental gradient in alpine and arid regions of western China to explore their physiological adaptations and compare the similarities and differences in adaptive strategies between emergent and submerged life forms. We found that water salinity and low temperature were key factors affecting aquatic plants in these regions. Aquatic plants adapted to saline habitats by accumulating proline and sulfur (S) concentrations, and to cold habitats by increasing ascorbate peroxidase activity. Plant trait network analysis revealed that S was the hub trait in emergent plants, while proline was the hub trait in submerged plants, indicating that emergent plants balanced osmoregulation and reactive oxygen metabolism through S-containing compounds, while submerged plants prioritized the regulation of osmotic balance through proline.

Intraspecific trait variation and adaptability of Stipa krylovii: Insight from a common garden experiment with two soil moisture treatments

Understanding patterns of intraspecific trait variation can help us understand plant adaptability to environmental changes. To explore the underlying adaptation mechanisms of zonal plant species, we selected seven populations of Stipa krylovii, a dominant species in the Inner Mongolia Steppe of China, and evaluated the effects of phenotypic plasticity and genetic differentiation, the effects of climate variables on population trait differentiation, and traits coordinated patterns under each soil moisture treatment. We selected seeds from seven populations of S. krylovii in the Inner Mongolia Steppe, China, and carried out a soil moisture (2) × population origin (7) common garden experiment at Tianjin City, China, and measured ten plant traits of S. krylovii. General linear analyses were used to analyze how soil moisture and population origin affected each trait variation, Mantel tests were used to analyze population trait differentiation-geographic distance (or climatic difference) relationships, regression analyses were used to evaluate trait-climatic variable relationships, and plant trait networks (PTNs) were used to evaluate traits coordinated patterns. Both soil moisture and population origin showed significant effects on most of traits. Aboveground biomass, root-shoot ratio, leaf width, specific leaf area, and leaf nitrogen (N) content were significantly correlated with climate variables under the control condition. Specific leaf area and leaf N content were significantly correlated with climate variables under the drought condition. By PTNs, the hub trait(s) was plant height under the control condition and were aboveground biomass, root length, and specific leaf area under the drought condition. This study indicates that both phenotypic plasticity and genetic differentiation can significantly affect the adaptability of S. krylovii. In addition, soil moisture treatments show significant effects on trait-climate relationships and traits coordinated patterns. These findings provide new insights into the adaptive mechanisms of zonal species in the semiarid grassland region.

Plant diversity increases above- and below-ground biomass by regulating multidimensional functional trait characteristics

BACKGROUND AND AIMS

Nitrogen enrichment affects biodiversity, plant functional traits and ecosystem functions. However, the direct and indirect effects of nitrogen addition and biodiversity on the links between plant traits and ecosystem functions have been largely overlooked, even though multidimensional characteristics of plant functional traits are probably critical predictors of ecosystem functions.

METHODS

To investigate the mechanism underlying the links between plant trait identity, diversity, network topology and above- and below-ground biomass along a plant species richness gradient under different nitrogen addition levels, a common garden experiment was conducted in which those driving factors were manipulated.

KEY RESULTS

The study found that nitrogen addition increased above-ground biomass but not below-ground biomass, while species richness was positively associated with above- and below-ground biomass. Nitrogen addition had minor effects on plant trait identity and diversity, and on the connectivity and complexity of the trait networks. However, species richness increased above-ground biomass mainly by increasing leaf trait diversity and network modularity, and enhanced below-ground biomass through an increase in root nitrogen concentration and network modularity.

CONCLUSIONS

The results demonstrate the mechanistic links between community biomass and plant trait identity, diversity and network topology, and show that the trait network architecture could be an indicator of the effects of global changes on ecosystem functions as importantly as trait identity and diversity.

Plant trait networks reveal adaptation strategies in the drylands of China

BACKGROUND

Plants accomplish multiple functions by the interrelationships between functional traits. Clarifying the complex relationships between plant traits would enable us to better understand how plants employ different strategies to adapt to the environment. Although increasing attention is being paid to plant traits, few studies focused on the adaptation to aridity through the relationship among multiple traits. We established plant trait networks (PTNs) to explore the interdependence of sixteen plant traits across drylands.

RESULTS

Our results revealed significant differences in PTNs among different plant life-forms and different levels of aridity. Trait relationships for woody plants were weaker, but were more modularized than for herbs. Woody plants were more connected in economic traits, whereas herbs were more connected in structural traits to reduce damage caused by drought. Furthermore, the correlations between traits were tighter with higher edge density in semi-arid than in arid regions, suggesting that resource sharing and trait coordination are more advantageous under low drought conditions. Importantly, our results demonstrated that stem phosphorus concentration (SPC) was a hub trait correlated with other traits across drylands.

CONCLUSIONS

The results demonstrate that plants exhibited adaptations to the arid environment by adjusting trait modules through alternative strategies. PTNs provide a new insight into understanding the adaptation strategies of plants to drought stress based on the interdependence among plant functional traits.

Characteristics of plant trait network and its influencing factors in impounded lakes and channel rivers of South-to-North Water Transfer Project, China

Trait-based approaches have been widely used to evaluate the effects of variable environments on submerged macrophytes communities. However, little research focused on the response of submerged macrophytes to variable environmental factors in impounded lakes and channel rivers of water transfer project, especially from a whole plant trait network (PTN) perspective. Here, we conducted a field survey designed to clarify the characteristic of PTN topology among impounded lakes and channel rivers of the East Route of South-to-North Water Transfer Project (ERSNWTP) and to unravel the effects of determining factors on the PTN topology structure. Overall, our results showed that leaf-related traits and organ mass allocation traits were the hub traits of PTNs in impounded lakes and channel rivers of the ERSNWTP, which traits with high variability were more likely to be the hub traits. Moreover, PTNs showed different structures among impounded lakes and channel rivers, and PTNs topologies were related to the mean functional variation coefficients of lakes and channel rivers. Specially, higher mean functional variation coefficients represented tight PTN, and lower mean functional variation coefficients indicated loose PTN. The PTN structure was significantly affected by water total phosphorus and dissolved oxygen. Edge density increased, while average path length decreased with increasing total phosphorus. Edge density and average clustering coefficient showed significant decreases with increasing dissolved oxygen, while average path length and modularity exhibited significant increases with increasing dissolved oxygen. This study explores the changing patterns and determinants of trait networks along environmental gradients to improve our understanding of ecological rules regulating trait correlations.