Abstract Aims This research investigates the variations in ecological stoichiometric characteristics of carbon (C), nitrogen (N), and phosphorus (P) between plant roots and soil at different latitudes, and explores the homeostasis of plant roots stoichiometry and analyzes its coupling relationship with climatic and environmental factors. The results contribute to elucidating the nutrient dynamics and adaptation strategies of the plant-soil system along a latitudinal gradient, thereby providing a theoretical basis for the vegetation restoration of coastal wetland ecosystems. Methods In this study, 102 plant and 102 soil samples are collected from seven coastal wetlands at different latitudes (19.87°- 41.03°N): Dongzhai Harbor, Zhangjiang Estuary, Minjiang Estuary, Hangzhou Bay, Yancheng Estuary, the Hanghe Estuary, and Liaohe Estuary, and their carbon (C), nitrogen (N), and phosphorus (P) contents are measured. The contents of carbon (C), nitrogen (N), and phosphorus (P) in the aboveground parts of plants, underground roots, and soil are measured. In addition, environmental indicators such as climatic element, soil water content, soil pondus hydrogenii, and soil electrical conductivity are also obtained. Important findings The results demonstrat the following: (1) In comparison to the aboveground parts, the content of carbon (C), nitrogen (N), and phosphorus (P) in roots, as well as their stoichiometric ratios, exhibit variation with latitude and are more responsive to environmental changes. (2) Significant interspecific differences are observed in the response of plant root stoichiometric characteristics to latitudinal changes. Specifically, with increasing latitude, the N content in mangrove roots decrease significantly, while the changes in C content, P content, and the stoichiometric ratios of C:N:P show opposing trends between the two mangrove species. Among salt marsh plants, the C content in the roots of S. alterniflora. significantly decrease, whereas the C content in the roots of ×B. mariqueter. increase. (3) As latitude increase, soil C and N contents, as well as the C:P and N:P ratios, are significantly lower than the national average in high-latitude regions. The plant root N:P ratio is generally less than 14, indicating that root growth is nitrogen-limited. (4) Based on homeostasis index analysis, the order of stoichiometric internal stability among the six plant roots is as follows: A. marina. > P. australis. > S. alterniflora. > ×B. mariqueter. > A. corniculatum. > S. salsa. Among them, the root stoichiometric homeostasis of S. salsa. is the weakest., the random forest model reveals that climatic element and soil water content significantly influence the homeostasis characteristics of root P content, C:P ratio, and N:P ratio, while the homeostasis characteristics of the root N:P ratio is primarily regulated by soil salinity.

Aims The study of plant functional traits in response to nitrogen deposition and warming is crucial for understanding plant growth and community assembly under environmental change. However, the differential effects of nitrogen deposition and warming on community traits, as well as the underlying mechanisms, remain unclear. Methods Therefore, this study was conducted in the Bayinbuluke Grassland, located in the southern Tianshan Mountains. We set up an experimental design with warming (open-top chambers, OTC) and nitrogen addition (10 g/m2), and measured the effects of nitrogen addition and warming on community species composition and five functional traits (plant height, leaf area, leaf carbon content, leaf nitrogen content, and leaf phosphorus content). The aim was to explore the impact and driving mechanisms of nitrogen addition and warming on community-level functional traits. Important findings The results indicated that: 1) Compared to the control, nitrogen addition significantly increased community-level plant height and leaf carbon content by 52.89% and 28.65%, respectively, while leaf phosphorus content decreased significantly by 32.23%. There were no significant changes in leaf area or leaf nitrogen content. For plant height, the relative contribution of species turnover to the community change was greater than that of intraspecific trait variability (ITV), whereas for leaf chemical traits (leaf carbon content, leaf nitrogen content, and leaf phosphorus content), ITV played a significantly larger role than species turnover. 2) Under warming, community-level leaf area, leaf nitrogen content, and leaf phosphorus content decreased significantly by 44.53%, 25.07%, and 42.06%, respectively, compared to the control, while plant height and leaf carbon content showed no significant changes. Changes in plant height were mainly driven by the covariation between species turnover and ITV, whereas for leaf morphology (leaf area) and leaf chemical traits (leaf carbon, nitrogen, and phosphorus contents), species turnover had a much greater impact than ITV. 3) In the warming + nitrogen addition treatment, community-level leaf phosphorus content decreased significantly by 52.19%, with no significant changes in plant height, leaf area, leaf carbon content, or leaf nitrogen content. The changes in plant height and leaf carbon, nitrogen, and phosphorus contents were primarily driven by species turnover, while leaf area was mainly influenced by ITV. This study suggests that nitrogen deposition and warming can alter the functional composition of alpine meadow communities through distinct mechanisms. Following nitrogen deposition, ITV increases functional variability among individuals, enhancing the community's responsiveness and stability to environmental changes. Under warming and warming + nitrogen addition conditions, species turnover influences the community by altering species composition, directly affecting species diversity and structure, thereby significantly impacting the community function in the alpine meadows of the Tianshan Mountains.

Aims The reabsorption of nitrogen (N) by leaves before senescence can reduce the dependence of root uptake after N release from decomposing litter. However, weather N reabsorption efficiency is dependent on the N contents in fresh leaves and in soils remains poorly understood, and weather this coupling varies with life forms is also largely unknown. Methods Here we collected fresh and senescent leaves of 92 woody plants in subtropical forests in southern China and complied a global dataset of N reabsorption efficiencies from 54 literatures to evaluate the coupling of N reabsorption efficiency with N contents in fresh leaves and in soils across various life forms. Important findings We found that: 1) In subtropical forests and on global scale, there was no significant difference in leaf N reabsorption efficiency between evergreen and deciduous and between angiosperms and gymnosperms species. On the global scale, the leaf N reabsorption efficiency of trees was significantly greater than that of shrubs, and the efficiency of ectomycorrhizal woody plants was significantly higher than that of arbuscular mycorrhizal woody plants. 2) The N reabsorption efficiency of evergreen woody plants was significantly correlated with the initial N content in fresh leaves, while this coupling was not found for angiosperms versus gymnosperms or ectomycorrhizal versus arbuscular mycorrhizal woody plants. 3) The N reabsorption efficiencies of evergreen, angiosperms and ectomycorrhizal woody plants were significantly correlated with soil N content at the sampling sites, while those of deciduous, gymnosperms and arbuscular mycorrhizal woody plants were not significantly correlated with the soil N content. Our results suggest that there are differences in N reabsorption efficiency among woody plants with different life forms. These differences are primarily influenced by nutrient acquisition strategies, which is of great significance for revealing the differentiated nutrient utilization strategies among plants.

Aims Previous studies have shown that different growing season stages and twig ages are the key factors affecting the variation of plant twig traits, however, few studies simultaneously explored the variation of twig traits and the relationship between twig traits with growing season stages and twig ages. Methods In this study, Pinus koraiensis, Picea koraiensis and Abies nephrolepis, which are typical evergreen conifers in northeast China, were studied. Seven traits including specific twig length, twig dry matter content, twig wood density, the pith proportion cross-sectional area ratio, the xylem proportion cross-sectional area ratio, the phloem proportion cross-sectional area ratio and the resin channel proportion cross-sectional area ratio of annual and perennial twigs were measured in the early growing season (July), middle growing season (September) and late growing season (November) of 135 trees. To explore the effects of different growing season stages and twig ages on twig traits and correlation among traits. Important findings In early growing season, twig dry matter content and twig wood density were significantly lower than those in middle and late growing season, while the resin channel proportion cross-sectional area ratio was significantly higher than the other two stages. The xylem proportion cross-sectional area ratio and the phloem proportion cross-sectional area ratio increased significantly with the increase of twig ages. The negative correlation between twig wood density and twig dry matter content of annual twigs was lower in early growing season. The negative correlation between specific twig length and twig dry matter content only existed in early growing season. In early growing season, annual twigs showed high specific twig length and low twig dry matter content. This proves that the early growing season of the annual twigs adopt the "quick investment - return" survival strategy. On the contrary, the late growing season and perennial twigs adopted the "slow investment-return" survival strategy. The results of this study provide insight into how plants adapt to habitat changes by regulating twig traits.

Aims Mycorrhizal fungi are closely related to the host's carbon (C), nitrogen (N), phosphorus (P), and C, N, P stoichiometric characteristics. However, whether the C, N, P stoichiometric characteristics in leaves and fine roots of different mycorrhizal tree species are significantly correlated in subtropical forests remains unclear. Therefore, this study aims to clarify the differences of the C, N, P stoichiometric characteristics in leaves and fine roots be-tween arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) tree species, and whether the C, N, P stoichio-metric ratio in leaves and fine roots of AM and ECM tree species changes consistently. Methods This study collected leaf and fine root samples of 81 AM tree species and 16 ECM tree species from the forest dynamic monitoring sample plot in Heishiding Nature Reserve, located in Guangdong Province, and meas-ured their C, N, and P concentrations. We calculated Blomberg's K statistic to test phylogenetic signals, used the linear mixed model to test the differences in C, N and P concentrations and stoichiometric ratios of leaves and fine roots among different mycorrhizal species, and used the Pearson correlation coefficient to test the correlation be-tween C, N and P concentrations and stoichiometric ratios in leaves and fine roots of different mycorrhizal species. Finally, we used standardised major axis regression to analyze the relationship of C, N and P concentrations and stoichiometric ratios between leaves and fine roots in different mycorrhizal species. Important findings The P concentration in fine roots of AM species was higher than that of ECM species, but C:P was lower than that of ECM species. There was a significant positive correlation between the N and P concentra-tions, C:N and C:P in the leaves and fine roots of AM and ECM tree species. There was a significant correlation between the concentrations of C, N and P and stoichiometric ratios of leaves and fine roots in AM species, while there was a significant correlation between N concentration, C:N and N:P of leaves and fine roots in ECM species. The results of this study confirm that the colonization of mycorrhizal fungi affected the chemical element compo-sition and stoichiometric ratio of plants, but the C, N and P stoichiometric ratios between leaves and fine roots in AM and ECM tree species were all significantly correlated.

Aims Exploring the differences in the life strategies of the “twig system” (old twigs, new twigs, and leaves) of Corylus mandshurica in different seasons can provide a theoretical basis for the protection and management of wild C. mandshurica. At the same time, it can promote the understanding of the multi-organ coordinated re-sponse of plants to climate change. Methods In this study, taking C. mandshurica, the dominant species in the shrub layer of the broad-leaved Ko-rean pine forest, as an example, the old twigs, new twigs, and leaves of C. mandshurica were collected in spring, summer, and autumn respectively. Three types of traits were measured, including chemical traits (carbon, nitro-gen, and phosphorus), non-structural carbon (soluble sugar, starch, and total non-structural carbohydrates), and defense traits (total phenols, tannins, and flavonoids), to explore the growth and defense strategies of the plant’s “twig system”. Important findings The results showed that: except that the effect of organs on starch was not significant (p >0.05, partial Eta squared value = 0.016), season, organs and their interactions had significant effects on the functional traits of C. mandshurica (p <0.05). In spring, among the six overall characteristic parameters of the trait network of leaves, five and four parameters (such as the number of nodes, the number of edges, diameter, and edge density) were higher than those of new twigs and old twigs respectively. Among the six overall charac-teristic parameters of the trait network of leaves, four parameters (such as the number of nodes, average path length, and modularity) were lower than those of new twigs and old twigs. In spring, in the “twig system” (old twigs, new twigs, and leaves) of C. mandshurica, leaves and new twigs tended towards the “growth” strategy, while old twigs tended towards the “defense” strategy. In summer, leaves tended towards the “growth” strategy, while new twigs and old twigs tended towards the “defense” strategy. In autumn, leaves tended towards the “de-fense” strategy, and new twigs and old twigs tended towards the “resource recovery” strategy. The research results revealed differences in the growth and defense strategies of the “twig system” of C. mandshurica, which is con-ducive to promoting the theoretical research on how plants respond to environmental changes in a more system-atic and refined direction.

Aims The impoundment of the Three Gorges Reservoir (TGR) has led to the transformation of a large number of natural riparian zones into reservoir drawdown zones, characterized by reverse seasonal water level fluctuations. This transformation has fundamentally altered the local habitat, significantly impacting the differentiation of plant morphological traits. This study aims to reveal the impact of habitat transformation from "riverbank to drawdown zone" as a result of the TGR backwater disturbance on the functional trait differentiation of adapted herbaceous plants as well as their adaptation strategies. Methods This study used a typical small watershed (Baijiaxi) in TGR area as a case. Four herbaceous plant species (Cynodon dactylon, Bidens tripartita, Xanthium strumarium, and Persicaria hydropiper) suitable for the local environment were selected as objects. The spatial differentiation characteristics of 17 plant functional trait indicators were analyzed across the habitat transformation from the riparian zone to the drawdown zone. Pearson correlation analysis was employed to explore the co-evolutionary relationships among functional traits, while redundancy analysis (RDA) was conducted to assess the influence of habitat factors on the differentiation of these traits. Important findings (1) The transition from natural riparian habitats into the drawdown zone can result in significant variations in the morphological traits of the four plant species. These variations are characterized by increased plant height and aboveground growth, along with decreased belowground growth. These changes are primarily attributed to the restricted growth period imposed by imposed by the water-level-fluctuating and the relatively simplified plant communities’ structure with reduced competitive pressure. Concurrently, leaf thickness increases and leaf area expands in most plants, which was mainly driven by the intensified drought stress during summer in the drawdown zone. It highlighted that the backwater effects of the TGR significantly amplifies local-scale shape variations among species. (2) The chlorophyll content and net photosynthetic rate of leaves in four plant species were significantly higher in the drawdown zone compared to those in the natural riparian zone, indicating that plants may have developed an adaptation strategy to enhance photosynthetic efficiency and accelerate growth rates as a response to the habitat limitation in the drawdown zone. (3) Under the habitat screening effect of the backwater in the TGR, four plant species have developed a trade-off strategy between between “growth” and “drought tolerance”, showing convergent adaptation. Cynodon dactylon exhibits relatively stronger phenotypic variability, especially in its photosynthetic traits, indicating stronger adaptability to habitat changes. In contrast, Bidens tripartita, Xanthium strumarium, and Persicaria hydropiper have formed more conservative adaptation strategies. (4) RDA analysis shows that the variations in functional traits of the four plant species within the upstream riparian zone are primarily associated with soil moisture. While, in the midstream and downstream drawdown zone, these variations are predominantly linked to flooding depth, soil pH temperature, suggesting that differences in the flooding environment have driven the differentiation of plant functional traits.

Aims Tropical and subtropical areas are hotspots for the distribution of artificial forests in our country. Clarifying the status and influential factors of plant biomass in typically mixed artificial forests in these areas is important. This can help to uncover the limiting factors for stand productivity and guide the management of artificial forests. Methods In this study, the conifer-broadleaf forest, being transformed from a Chinese fir plantation in Yunyong forestry station located in Foshan city, Guangdong province, was selected as the object. First, we compared the difference in biomass of each plant organ among tree species configuration models at the early recovery stage (8-16 year). Second, the shifts in soil physicochemical properties and community-level plant functional traits under changes in tree species configuration were characterized. Finally, we explored the relative contributions of tree species configuration, soil properties and plant leaf traits to plant biomass variations, and evaluated their influential pathways. Based on these analyses, we aimed to evaluate the key influential factor for plant biomass in artificial forests in south subtropical areas. Important findings Our results showed that the total plant biomass and biomass in each organ both differed significantly across tree species configuration models. Tree species configurations affected plant biomass mainly via regulating leaf functional traits and soil nutrients content. Moreover, the leaf functional traits had greater influence on foliage and branch biomass, while the variation in soil nutrients content was the main factor driving the changes in truck, roots and total biomass. More specifically, tree species configurations characterized by a higher ratio of leaf nitrogen : phosphorus (P) and a higher functional diversity also had greater biomass in plant communities. An increase in soil total P content significantly promoted the increase in plant biomass, while an excess in soil total potassium would suppress the growth in biomass. This study compared the relative effects of leaf functional traits and soil nutrients content on plant biomass in the typically mixed artificial stands in south subtropical forests, and explored the key influential factor for the biomass in total and in each organ. These results provided the theoretical bases for restoration, operation and management of the artificial forests in south subtropical areas.

Abstract Aims Pinus tabuliformis, a representative species of temperate coniferous forests in China, exhibits strong ecological adaptability. Investigating the stoichiometric characteristics of leaves, twigs and roots across different age groups and their interrelationships is essential for understanding intraspecific variation and resource allocation strategies. Methods In this study, we sampled natural P. tabuliformis forests from nine regions in China and measured the carbon (C), nitrogen (N) and phosphorus (P) content in six organ types from 81 trees: current-year leaves, perennial leaves, current-year twigs, perennial twigs, absorptive roots and transport roots. Important findings (1) N and P concentrations were higher in current-year organs than in perennial organs, whereas C:N, C:P and N:P ratios were higher in perennial organs. The stoichiometric traits of each organ exhibited varying degrees of intraspecific variation among age groups, with organ age being the primary factor driving this variation. (2) Standardized major axis regression analysis indicated that, compared to current-year leaves, P. tabuliformis allocated more P to perennial leaves; compared to perennial twigs and perennial roots, more C, N and P were allocated to current-year twigs and current-year roots. (3) The allocation of C, N and P to current-year roots was significantly higher than that to current-year leaves and twigs. (4) Mean annual temperature (MAT) and soil phosphorus content (SPC) were the primary environmental factors influencing current-year and perennial leaves, respectively. Mean annual precipitation (MAP) and SPC were the main factors affecting current-year and perennial branches, while soil moisture content (SMC) and soil nitrogen content (SNC) primarily influenced absorptive roots and transport roots. This study elucidates the nutrient allocation strategies and environmental adaptability of P. tabuliformis across different organ ages. We recommend considering organ age differences when studying the stoichiometric characteristics of evergreen species to better understand their C, N and P allocation mechanisms and environmental adaptation strategies across different age groups.