Plant resource uptake depends on the interplay between the quantity and quality of roots, yet their coordination at the community level remains poorly understood. Using standardized root cores across 20 diverse grassland sites on the Inner Mongolian Plateau and the Tibetan Plateau, we quantified community-level root quantity traits (mass, length, and nitrogen density per soil volume) and quality traits (specific root length (SRL), nitrogen concentration, and root tissue density (RTD)). The two regions differ markedly in soil, climate, and species composition. Community-level root traits clustered into three orthogonal dimensions. The root quantity dimension, reflecting carbon investment in roots for soil exploration, was correlated with soil nitrate concentration. Two root quality dimensions captured contrasting strategies: a foraging-efficiency dimension represented by a negative correlation between RTD and SRL, and an uptake-efficiency dimension related to root nitrogen concentration. Different from the quantity dimension, the efficiency dimensions were regulated by distinct environmental factors within each region, highlighting the context-dependency of root trait-environment interactions. Collectively, our findings show that community-level root strategies can be captured by a tri-dimensional root quantity-quality trait matrix, which represents a novel understanding of the community-level plant assemblies and their responses and adaptation to climate change.

Abstract Seed mass is a key trait influencing plant form and function. It reflects parental resource investment and influences seedling growth as well as the construction of root and leaf organs. However, how seed mass regulates root and leaf functional traits in legume species remains unclear. In this study, we selected 16 common herbaceous legume species growing in pots. The results showed that seed mass exhibited a U-shaped quadratic relationship with both fine root diameter and fine root biomass. Seed mass was significantly positively correlated with single leaf area, specific leaf area, and stomatal length. However, it showed no significant correlation with leaf nitrogen concentration, leaf vein traits, or stomatal density. Meanwhile, the relationships between seed and root traits and between seed and leaf traits in these legume species were markedly different from those reported for global non-nitrogen-fixing plants. In summary, seed mass may selectively regulate certain root and leaf traits. These findings provide a new perspective for understanding the formation of life history strategies in legumes and their responses and adaptations to environmental change.

Mycorrhizal fungi play a functional role in nutrient absorption and transfer in ecosystems, influencing plant survival and interspecific interactions. However, it is unclear how different types of mycorrhizae affect symbiotic tree species in subtropical regions. To investigate the patterns of tree species diversity and the driving factors across different mycorrhizal-dominated communities in the Wuyi Mountains of China, we established four plots (20 m & times; 20 m) at each interval along a gradient of increasing arbuscular mycorrhizal (AM) tree dominance (10% to 90%), corresponding to a concurrent decline in ectomycorrhizal (EcM) tree dominance. Partial least squares path modeling (PLS-PM) was applied to quantify the direct and indirect effects of environmental variables on woody plant species diversity along a gradient of relative density of AM-associated tree species. Our results demonstrated that (1) species diversity significantly increased with the rising relative density of AM-associated trees; (2) increasing relative density of AM-associated trees was accompanied by distinct variations in community phylogenetic structure, spatial aggregation, competition intensity, conspecific negative density dependence (CNDD) strength, stand structural diversity, and soil chemical properties among plots; (3) the partial least squares path model revealed that the relative abundance of AM-associated trees promoted woody plant diversity through two indirect mechanisms: first, by enhancing community phylogenetic diversity, thereby reducing competitive exclusion and facilitating species coexistence; and second, by intensifying CNDD among AM trees, which decreased community aggregation and further mitigated the negative effects of competition, ultimately enhancing species diversity. These findings highlight the pivotal role of AM tree dominance in shaping diversity patterns, offering key insights for forest management and biodiversity conservation in subtropical ecosystems.

Abstract Arbuscular mycorrhizal (AM) fungi are pivotal mediators of plant nutrient acquisition and depend on host‐derived carbon (C). However, how plant C allocation to AM fungi responds to below‐ground (e.g. soil nutrient availability) and above‐ground drivers (e.g. plant C availability) remains poorly understood. We used a long‐term (2015–2023) factorial field experiment in a meadow steppe in northern China, with six N addition rates (0, 2, 5, 10, 20 and 50 g N m −2 yr. −1 ) crossed with mowing (mown vs. unmown) to test how N enrichment and mowing alter plant–fungus C allocation strategies. In 2023, plant and fungal biomass, C content and AM fungal community composition were quantified. In unmown plots, plants preferentially allocated C to roots while maintaining relatively stable C allocation to mycelium, although mycelium biomass declined with N addition. By contrast, mowing intensified plant P limitation and altered C allocation strategies, with declines in mycelium biomass becoming evident only under relatively high‐N levels (above 10 g N m −2 yr. −1 ). In mown plots, receiving low‐N inputs increased C allocation to mycelium, whereas at higher N inputs, soil acidification sharply reduced C transfer to fungi. Changes in C allocation were tightly associated with the abundance of the dominant taxon Glomus VT387. Synthesis . Together, our findings demonstrate that mowing mediates N addition effects on plant C allocation to AM fungi, thereby providing mechanistic insight into plant–microbial interactions in grassland subject to global change and management.

Root exudates are central to plant-soil-microbe interactions, yet their seasonal chemical dynamics and variation among tree types remain poorly understood in tropical forests with abundant nitrogen (N)-fixing plants. Here, we applied spectroscopic analysis combined with ultra-high-resolution mass spectrometry to characterize root exudates from four tropical tree species, including two N-fixers (Albizia lucidior and Erythrina subumbrans) and two non-N-fixers (Betula alnoides and Castanopsis echinocarpa), across four time points spanning the dry-to-wet season transition. Exudates contained both protein-like and humic-like fluorescent components, with abundant highly unsaturated and phenolic molecules. N-fixers, compared with non-N-fixers, released exudates with lower aromaticity and higher proportions of amino acids and peptides, reflecting enhanced N metabolism linked to the ability of the plants to acquire N directly through fixation. All species exhibited marked seasonal variability in exudate chemistry, with the greatest interspecific dissimilarity occurring during the rapid-growing period in the rainy season (July), likely resulting from the increased nutrient demand. Our findings highlight the significant roles of plant N acquisition strategies and phenological stages in shaping the molecular composition of root exudates in tropical forests. Such interspecific and seasonal variations likely influence rhizosphere microbial dynamics and nutrient cycling, underscoring the ecological significance of root exudate plasticity in forest ecosystems.

1. The amount and frequency of atmospheric nitrogen (N) deposition have dramatically increased, profoundly influencing population regeneration, community composition and productivity in grasslands. Perennial species in grasslands primarily grow and expand clonally, yet it remains unclear how their below-ground buds and above-ground shoots respond to the amount and frequency of N deposition. 2. We conducted a long-term (2008-2022) N addition experiment in a semiarid grassland. The experiment included nine addition amounts (0, 1, 2, 3, 5, 10, 15, 20 and 50gN m(-2)year(-1)) and two addition frequencies: low frequency (twice per year) and high frequency (once per month). This allowed us to assess the interactive effects of N addition amount and frequency on bud density, shoot density and the ratio of bud to shoot density (meristem limitation index, MLI) in semiarid grasslands. 3. We found a significant interaction between N addition amount and frequency on community bud and shoot densities. Community bud and shoot densities declined with increasing N amount under low addition frequency but remained stable under high addition frequency. However, community MLI was unchanged under low addition frequency but increased with increasing N amount under high addition frequency. Both N addition amount and frequency significantly altered the composition of community buds and shoots, with more pronounced effects under low versus high addition frequency. Bud and shoot densities and MLI declined with N amount under both addition frequencies for bunchgrasses. In contrast, rhizomatous grasses exhibited increased bud density and MLI under high N addition frequency, while shoot density remained unchanged regardless of addition frequency. These demographic responses did not alter above-ground net primary productivity (ANPP) but shifted community composition toward greater dominance of rhizomatous grasses under N addition. 4. Synthesis. These results suggest that grassland bud and shoot responses to N deposition depend on both the deposition amount and frequency. Commonly used low frequency N addition experiments may lead to inaccurate plant demographic and community responses to chronic N deposition.

Ectomycorrhizal (EcM) tree species often dominate temperate and warm-temperate forests, yet how their mycorrhizal dominance reshapes the species diversity–aboveground biomass relationship (DBR) remains unclear. In this study, we examined 6-ha permanent monitoring forest plots across the temperate–subtropical transition zone of China. Based on bivariate regression, generalized linear mixed models (GLMM), and structural equation modeling (SEM), we quantified the contribution and mechanistic pathways of the mycorrhizal dominance to aboveground biomass (AGB) accumulation. Our findings reveal that i) Ectomycorrhizal tree dominance is the key determinant of AGB accumulation in temperate-subtropical transition forests; ii) EcM tree dominance enhances AGB by reducing stand structural heterogeneity rather than increasing it. iii) Although EcM tree dominance reduces arbuscular mycorrhizal (AM) tree abundance and species richness through competitive exclusion, the positive biodiversity–ecosystem function (BEF) relationship persists. These results elucidate the interplay between selection and complementarity effects, offering new insights into the ecological drivers of DBR and providing a scientific foundation for the sustainable management of temperate forests.

Soil nitrogen-fixing microorganisms naturally fertilize terrestrial ecosystems, but the primary driver of their diversity across the globe and the underlying mechanisms remain unclear. We analyzed the nifH gene in 1257 (1137 publicly available + 120 self-generated) soil metagenomes from 318 terrestrial ecosystems globally. Mean annual precipitation was identified as the key factor influencing the relative abundance, richness, and composition of the potential nitrogen-fixers. Precipitation was directly associated with nitrogen-fixers (e.g., water availability) rather than indirectly via other soil variables (e.g., pH). Lower precipitation increased the contribution of deterministic processes (e.g., interspecific competition) in driving their community assembly and selected species with larger genomes, while higher precipitation increased the contribution of stochastic processes (e.g., random birth/death) and favored smaller-genome species. A multifactorial experiment further demonstrated that precipitation increase had a larger regulatory effect on the stochastic processes than other factors (e.g., climate warming). eXtreme Gradient Boosting (XGBoost) projections under future global change scenarios indicate a general increase in their relative abundance across most regions worldwide, with declines only in specific areas. These findings reveal distinct patterns and mechanisms governing the global biodiversity and biogeography of soil nitrogen-fixers, providing valuable insights for developing region-specific management strategies aimed at maintaining ecosystem productivity.

Knowledge about the variation patterns of plant traits along environmental gradients is valuable for the mechanistic understanding of community assembly and ecosystem functions under environmental changes. In wetlands, aboveground plant traits are commonly studied, however, little is known about the responses of belowground plant traits and their coordination with aboveground traits to environmental changes. Samples of four dominant species and soil were collected from wetland sites of varying degradation along the Yellow River. Key leaf and root traits were measured to determine variations of community functional composition (i.e., community-weighted trait means and functional diversity) and their environmental drivers. Intensified degradation of riparian wetlands shifted community-level leaf and root traits towards more conservative values, characterized by denser leaves and roots (i.e., greater leaf dry matter content and root tissue density) and lower nutrient contents. However, the functional diversity of leaf and root traits did not show a consistent increase or decrease with the degradation of riparian wetlands. Moreover, degradation-induced changes in soil nutrients were the main factors driving leaves and roots within the plant community to become denser and lower in nutrient content toward severely degraded habitats. These results demonstrate that leaf and root traits are coordinated in adapting to changes in wetland habitats, and highlight that filtering mechanisms for plant adaptive traits within the community are trait-specific. This is insightful for understanding the adaptation of wetland plants to environmental change, and could contribute to plant functional restoration of riparian wetlands in disturbed landscapes.

The plant rhizosphere, a region interconnecting roots, soil, and microorganisms, is critical for plant resource acquisition, community structure, and the functional stability of ecosystems. Most studies focus primarily on root traits, while overlooking the covariation within the rhizosphere root-soil-microbe continuum and its ecological implications under environmental change. Here, we highlight the necessity of integrating rhizosphere function into a broader theoretical framework encompassing belowground traits, such as the core functional modules of roots, rhizosphere microorganisms (including mycorrhizal fungi), and soil. We further identify critical knowledge gaps and future directions for research on rhizosphere function traits. This framework expands current perspectives on plant belowground functional traits, plant adaptation, and ecosystem stability under changing environments.

Soil compaction often imposes stress on root development and plant survival. However, root anatomical responses that enable persistent root growth and functioning under soil compaction remain unclear. We grew 10 herbaceous species differing substantially in lateral root diameter, in soils with low (1.0 g cm-3) and high (1.4 g cm-3) bulk density, and assessed root traits including root biomass, anatomical structures, and respiration rates. Greater root thickening upon soil compaction was found in species with thicker first-order lateral roots, mainly due to larger cortical cell size. Both xylem vessel diameter and wall thickness increased more in compacted soils in these species. Despite these anatomical shifts, root respiration rate responded little to soil compaction across most species, likely due to the opposite investment in cortical cells and xylem vessels. Notably, root biomass, independent of root respiration rate and anatomical structures, determined whole-plant growth under soil compaction. Our study reveals two independent strategies of root response to soil compaction: anatomical remodeling for mechanical and metabolic maintenance, and root biomass investment for resource acquisition. These findings offer new insights for breeding and selecting species tolerant to soil compaction and highlight multidimensional strategies of plant adaptation to physical stress.

Terrestrial plants exhibit immense variation in their form and function among species. Coordination between resource acquisition by roots and reproduction through seeds could promote the fitness of plant populations. How root and seed traits covary has remained unclear until our analysis of the largest-ever compiled joint global dataset of root traits and seed mass. Here we demonstrate that seed mass and seed phosphorus mass scale positively with root diameter in arbuscular mycorrhizal (AM) plants, depending on variation in root cortical thickness instead of root vessel size. These findings suggest a dual role of AM association in phosphorus uptake and pathogen resistance which drives the global root–seed coordination, instead of initially expected resource transport via root vessels as the main driver. In contrast, we found no relationship between root traits and seed mass in ectomycorrhizal plants. Overall, our study reveals coordination between roots and seeds in AM plants, which is probably regulated by root–mycorrhizal symbiosis, and may be crucial in shaping global plant diversity and species distributions. In this study, Yang et al. compile a global dataset to uncover the degree to which plants coordinate root and seed traits. They report a global positive correlation between root diameter and seed size, driven by dual roles of arbuscular mycorrhiza in phosphorus uptake and pathogen defence.

Root traits, particularly anatomical traits, underpin root functions necessary for plant survival and adaptation. However, the coordination of root traits in extreme environments remains unresolved. We linked root functions that encompass foraging, uptake, and mining to anatomical traits of absorptive roots of typical and common species on the Tibetan Plateau and compared them with those in other regions globally. Our results showed that in alpine grasslands of the Tibetan Plateau, root functions were governed by root diameter and associated anatomical traits, rather than by specific root length (SRL, an indicator of root foraging) as observed globally. Specific root respiration (an indicator of active nutrient uptake) scaled with tube size and number within the root vascular system, whereas root exudation rate and acid phosphatase activity (indicators of nutrient mining) were linked to cortex cell size and layer number. These anatomical adaptations contrast with global patterns, where higher SRL supports nutrient acquisition through reduced construction costs. Our findings reveal unique root forms and functions in the alpine environments, highlighting the importance of cellular anatomy in shaping plant function in extreme environments.

Nutrient acquisition through symbiotic ectomycorrhizal fungi is carbon (C) costly but fundamental for plant growth, community, and ecosystem functioning. Here, we examined the functions of roots and mycorrhiza with respect to nutrient uptake after artificially inducing C limitation-seven months after girdling of an ectomycorrhizal tree, Pinus taeda. Root physiological activity (measured as root nitrogen content and root exudation) declined after girdling and was accompanied with 110% and 340% increases in mycorrhizal colonization and extramatrical hyphal length, respectively. Fungi colonizing roots switched to a community characterized by higher C efficiency (lower C cost) of nutrient acquisition (CENA, the amount of nutrient acquisition per unit C cost) and lower network complexity, indicating a tradeoff between CENA and stability of the fungal community. Root transcriptome analysis suggested a shift in metabolic pathways from a tricarboxylic acid cycle decomposition of carbohydrate to lipid biosynthesis to maintain closer associations with mycorrhiza for nutrient cycling after the girdling. By integrating multi-level evidence, including root transcriptome, fungal composition, and network complexity data, we demonstrate an increased dependence on mycorrhiza for nutrient acquisition under the C limitation condition, which is likely due to a shift to fungal community with higher CENA at the cost of lower stability.

Interactions among roots and leaves are fundamental for plant growth and survival, yet there remains a knowledge gap in mangrove plants that experience saline stress distinct from most other vascular plants hereafter the non-mangroves. Here, we explored the coordination of above- and below-ground trait relationships among mangrove species in tropical China and compared it with those of non-mangroves. Our results show that root stele, the water-conducting tissue, was coupled with leaf water use traits and tissues outside the stele (ToS), the carbon-consuming tissues in roots, were independent of leaf economics traits in non-mangroves. However, in mangroves, root stele is independent of leaf water use traits and root ToS is coupled with leaf economics traits. The contrasting root-leaf coordination between mangroves and non-mangroves potentially arises from the existence of leaf water storage tissues in mangroves and the universal allometric relationship between root stele and ToS in both plant groups. Our findings pave a new way for understanding the ecology and vegetation dynamics of mangrove and non-mangrove plants under global environmental change. (sic)(sic) (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)-(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic) (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)-(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)-(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)((sic)(sic)(sic)(sic)(sic))(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).

This study identified root architecture optimization as the core mechanism by which Arbuscular mycorrhizal fungi (AMF) promote root development, revealing a complete promotion chain from root architecture to nutrient accumulation and plant growth. The analysis also discovered a threshold effect based on colonization rates with distinct root regulatory patterns and explored how biological factors influence AMF‐root interactions, advancing our understanding of plant‐AMF symbiotic mechanisms.

Plants form mycorrhizal symbioses to enhance nutrient acquisition, yet the biophysical principles governing carbon and nutrient exchange remain unclear. Here, we develop a theory of bi-directional carbon-nutrient transfer that integrates root anatomy, energetic costs, and mycorrhizal positioning. We show that nutrient uptake per unit carbon or energy investment declines with increasing root diameter due to higher carbon demands across thicker cortical tissues. Mycorrhizal fungi mitigate this constraint by enabling more carbon-efficient nutrient uptake, particularly when arbuscules are positioned in inner cortical layers. This spatial optimization minimizes the carbon cost of transporting nutrients to the stele. Our framework reconciles anatomical variation, symbiotic structure, and functional efficiency across root types and mycorrhizal strategies and offers a new lens for understanding the coevolution between roots and mycorrhizal fungi.

The stability mechanisms of ecosystem functions have been a hot topic in ecology. However, in wetland ecosystems, the mechanisms by which biotic and abiotic factors interact to affect ecosystem stability in changing environments remain largely unclear. This study investigated the key factors and underlying mechanisms that regulate the spatial variability of wetland productivity by measuring community productivity, multiple components of biodiversity (i.e., species diversity, community functional composition and diversity), and environmental factors along a well-characterized gradient of wetland degradation in the lower reaches of the Yellow River. The results showed that the spatial variability of productivity in wetlands increased with intensified degradation. The spatial variability of wetland productivity was not related to species richness, but was mainly affected by changes in community functional composition and diversity. Furthermore, degradation-induced changes in soil nutrients drove the spatial variability of productivity to increase with shifts in functional composition towards more conservative traits (i.e., higher leaf dry matter content and root tissue density), and to decrease with higher functional trait diversity. These findings reveal the driving mechanism of spatial variability in wetland productivity under degradation, and suggest that reduced nutrient availability, by altering plant resource strategies, can affect the spatial reliability of key ecosystem functions in wetlands.

The transformation of litter-derived dissolved organic matter (DOM) in soils is important for carbon cycling in terrestrial ecosystems. However, the linkage between root litter- and rhizosphere soil-derived DOM remains unclear. In this study, using ultrahigh-resolution mass spectrometry and metagenomics, we evaluated the DOM in paired roots and rhizosphere soils for herbaceous plants in a semiarid grassland and their biogeochemical processes. Analyses revealed a decoupling between root- and rhizosphere soil-derived DOM despite being directly attached, with a considerable loss of root-derived aliphatics and proteins, and production of highly unsaturated, aromatic, and carboxyl-rich compounds. From roots to rhizosphere soils, DOM shifted toward a more uniform molecular composition, which was likely the result of a more "specialized" utilization of root-derived DOM and a more "generalized" utilization of rhizosphere soil-derived DOM by the rhizosphere microbial community. Overall, DOM transformation at the root-soil interface occurred along two principal dimensions: 1) the dimension of "root-to-soil variation" with "lability" and "aromaticity" as two end members, and 2) the dimension of "interspecies variation" dominated by bulk and optical DOM components. These findings suggest that root- and rhizosphere soil-derived DOM constitute two distinct carbon sources for rhizosphere microbial communities and provide a framework for future investigations into DOM dynamics and ecosystem functioning at the plant-soil interface.