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The intensive use of chemical fertilizers in China to maintain high crop yields has led to significant environmental degradation and destabilized crop production. Returning straw to soil presents a potential alternative to reduce chemical fertilizer requirements and enhance soil fertility. This study investigates the effects of different nitrogen (N) input levels and straw additions on crop phosphorus (P) uptake and soil P availability based on a long-term N-fertilizer trial. The treatments included no fertilizer input (CK), conventional (NPK), reduced NPK (0.75NPK), and straw-amended (SNPK) treatments. Results indicate that SNPK significantly enhances shoot P uptake and crop yields by 43.7–61.9% and 29.3–39.6%, respectively. The SNPK treatment improved rhizosphere P availability and increased the phosphorus activation coefficient (PAC) by 1.72-fold compared to NPK alone. The enhanced soil P availability under SNPK was primarily attributed to an abundance of functional microbes, leading to higher P storage in the microbial biomass P pool and its turnover. Additionally, SNPK promoted root exudate and phosphate-mobilizing microbes, enhancing P mobilization and uptake. Nitrogen fertilization primarily influenced root functional traits related to P acquisition. These findings provide valuable insights for developing effective fertilizer management strategies in maize–oilseed rape rotation systems, emphasizing the benefits of integrating straw with chemical fertilizers. [ABSTRACT FROM AUTHOR]

Plants adapt to the limitation of soil phosphorus (P) induced by nitrogen (N) deposition through a complex interaction of various root and leaf functional traits. In this study, a pot experiment was conducted to explore the effects of different levels of N addition (control, low N [LN]: 25 kg N ha−1 yr−1, high N [HN]: 50 kg N ha−1 yr−1) on tree growth, leaf nutrient content, foliar P fractions and root characteristics of two dominant tree species, the pioneer species Salix rehderiana Schneid and the climax species Abies fabri (Mast.) Craib, in a subalpine forest in southwestern China. The results demonstrated that LN addition had a minimal impact on leaf N and P contents. Conversely, HN addition significantly decreased the leaf P content in both species. Salix rehderiana exhibited more pronounced increases in specific root length and specific root area under P deficiency triggered by HN addition when compared with A. fabri. In contrast, A. fabri showed weaker morphological responses to N addition but had a higher proportion of foliar P to metabolic P, as well as higher root exudates rate and root phosphatase activity in response to HN addition. Abies fabri employs a synergistic approach by allocating a greater amount of leaf P to metabolite P and extracting P from the soil through P-mobilizing exudates and root phosphatase activity, while S. rehderiana exhibits higher flexibility in modifying its root morphology in response to P limitation induced by HN addition. This study provides insights into subalpine tree species adaptation to N-induced P limitation, emphasizing its significance for guiding forest management and conservation in the context of global climate change. [ABSTRACT FROM AUTHOR]

Hard limestone substrates, which are extensively distributed, are believed to exacerbate drought and increase the difficulty of restoration in vulnerable karst regions. Fissures in such substrates may alleviate the negative effect of drought on plants, but the underlying mechanisms remain poorly understood. In a two-way factorial block design, the growth and photosynthesis of 2-year-old Phoebe zhennan seedlings were investigated in two water availabilities (high versus low) and three stimulated fissure habitat groups (soil, soil-filled fissure and non-soil-filled fissure). Moreover, the fissure treatments included both small and big fissures. Compared to the soil group, the non-soil-filled fissure group had decreased the total biomass, root biomass, total root length, and the root length of fine roots in the soil layer at both water availabilities, but increased net photosynthetic rate (Pn) and retained stable water use efficiency (WUE) at low water availability. However, there were no significant differences between the soil-filled fissure group and soil group in the biomass accumulation and allocation as well as Pn. Nevertheless, the SF group decreased the root distribution in total and in the soil layer, and also increased WUE at low water availability. Across all treatments, fissure size had no effect on plant growth or photosynthesis. Karst fissures filled with soil can alleviate drought impacts on plant root growth, which involves adjusting root distribution strategies and increasing water use efficiency. These results suggest that rock fissures can be involved in long-term plant responses to drought stress and vegetation restoration in rocky mountain environments under global climate change. [ABSTRACT FROM AUTHOR]

Root respiration is a critical physiological trait that significantly influences root system activity. Recent studies have associated root respiration with the economic functioning of roots; however, research on root respiration in tropical plants remains limited. This study examined the fine root respiration and the relationship between root respiration and root chemical and morphological traits in 16 tropical plant species, including both evergreen and deciduous species. Findings revealed that deciduous species exhibited higher root respiration compared to evergreen species. Root respiration positively correlated with root nitrogen concentration and specific root length and correlated negatively with root diameter and root tissue density across all species. The root respiration patterns in evergreen species aligned with those seen in all tree species, while deciduous species showed a distinct negative correlation with root tissue density and no significant correlations with other root traits. Principal component analysis revealed that the patterns of root variation in both evergreen and deciduous trees were multidimensional, with deciduous trees exhibiting acquisitive traits and evergreen trees displaying conservative traits. Random forest and multiple regression analysis showed that specific root length exerted the most significant influence on root respiration in both evergreen and deciduous trees. These findings are ecologically significant, enhancing our understanding of root respiration in tropical plants and its impact on ecosystem functions. They contribute valuable insights and support the conservation and management of tropical vegetation. [ABSTRACT FROM AUTHOR]

An increasing number of studies have shown how feedback interactions between plants and soil can influence primary and secondary succession. However, very little is known about the patterns and mechanisms of such plant–soil feedbacks on stressed mine tailings ecosystem, which can be severely contaminated by a range of toxic elements.In a two‐phase plant–soil feedback experiment based on the rare earth element (REE) mine tailing soil, we investigated biotic (changes in bacterial and fungal communities) and abiotic (changes in chemical properties) legacies of three pioneer grass species, and examined feedback effects of three grasses, two legumes and two woody plants with different root traits.Positive plant–soil feedbacks were found in Miscanthus sinensis, Paspalum thunbergii and Tephrosia candida, and neutral feedbacks were observed in the other four plants. These effects corresponded with an increase in nutrients and total organic carbon, as well as a decrease in acidity and extractable aluminium and REEs. There were less signs of biotic changes in the conditioned tailings.The correlation analysis suggested a relationship between plants' responses to soil legacies and root traits, as well as root economics spectrum. On the mine tailings, acquisitive species with higher specific root length appeared to have greater potential for positive feedback.Synthesis and application. Our study shows that early succession on contaminated rare earth element mine tailings may lead to more positive plant–soil feedback than predicted based on results of non‐contaminated soils, mainly due to the alleviation of abiotic stress in tailings. Therefore, the improvement of specific abiotic soil stress and the trait‐based selection of acquisitive plants should be preferentially considered to promote the primary restoration of degraded land. [ABSTRACT FROM AUTHOR]

The intensive use of chemical fertilizers in China to maintain high crop yields has led to significant environmental degradation and destabilized crop production. Returning straw to soil presents a potential alternative to reduce chemical fertilizer requirements and enhance soil fertility. This study investigates the effects of different nitrogen (N) input levels and straw additions on crop phosphorus (P) uptake and soil P availability based on a long-term N-fertilizer trial. The treatments included no fertilizer input (CK), conventional (NPK), reduced NPK (0.75NPK), and straw-amended (SNPK) treatments. Results indicate that SNPK significantly enhances shoot P uptake and crop yields by 43.7–61.9% and 29.3–39.6%, respectively. The SNPK treatment improved rhizosphere P availability and increased the phosphorus activation coefficient (PAC) by 1.72-fold compared to NPK alone. The enhanced soil P availability under SNPK was primarily attributed to an abundance of functional microbes, leading to higher P storage in the microbial biomass P pool and its turnover. Additionally, SNPK promoted root exudate and phosphate-mobilizing microbes, enhancing P mobilization and uptake. Nitrogen fertilization primarily influenced root functional traits related to P acquisition. These findings provide valuable insights for developing effective fertilizer management strategies in maize–oilseed rape rotation systems, emphasizing the benefits of integrating straw with chemical fertilizers.

Plants allocate a substantial amount of C belowground for root exudates and for the construction and adjustment of root morphological and architectural traits. What relationships exist between root exudates and other root traits and these relationships change with growing season, however, remain unclear. We quantified the root exudation rate and root morphological traits, including total root length (RL), total root surface area (RS), root diameter (RD), specific root length (SRL), specific root area (SRA) and root tissue density (RTD), and architectural traits, such as branching intensity (BI), and investigated their associations during the rapidly growing season (April and August) and the slowly growing season (December) of three common native tree species, Liquidambar formosana , Michelia maudiae and Schima superba , in subtropical China. We found that the linkages of RD, SRL, SRA, RTD and BI did not change with the growing season, reflecting their highly conservative relationships. The root exudation rate varied significantly with growing season (P  < 0.05) and produced various associations with other root traits at different growing seasons. During the rapidly growing season (i.e. April), the exudation rate was the highest and was positively correlated with RL. The exudation rate was the lowest during the slowly growing season (i.e. December) and was negatively associated with RL, RS and RTD. Our findings demonstrate the seasonality of the linkages of root exudation rate with other root traits, which highlights the highly plastic and complex associations of belowground root traits. These findings help to deepen our understanding of plant nutrient acquisition strategies. [ABSTRACT FROM AUTHOR]

Background and aims: It is unclear how atmospheric nitrogen (N) deposition influences CO2 release from grassland by affecting heterotrophic respiration of bulk and rhizosphere soils and how the heterotrophic rhizosphere respiration of different grass species responds to N deposition. Methods: In this study, we investigated the effects of N addition on heterotrophic respiration of bulk and rhizosphere soils associated with the dominant species (Bothriochloa ischaemum) and subdominant species (Artemisia sacrorum and Stipa capillata) in the grassland treated with N fertilizer (0,3,9 g N m−2 y−1) for eight years. Results: Low-N addition significantly increased cumulative CO2-C emissions of bulk soil by 22.91% and rhizosphere soil of A. sacrorum by 72.26%, while high-N addition significantly increased that of rhizosphere soil of (A) sacrorum by 37.38% and S. capillata by 13.71%. There was no clear response to N addition for (B) ischaemum. Heterotrophic rhizosphere respiration of B. ischaemum was most strongly related to stable-C-degrading functional genes, whereas that of A. sacrorum and S. capillata was most strongly related to labile-C-degrading functional genes. C-degrading functional genes in rhizosphere soil were significantly related to root morphological characteristics, especially specific root length, specific root surface area, and root average diameter rather than root exudation rates. Conclusion: The present study revealed that N addition could affect heterotrophic soil respiration by changing labile-C and stable-C degrading functional genes, which in the rhizosphere of different plant species were regulated by their root functional traits. [ABSTRACT FROM AUTHOR]

Rubber tree plantations (Hevea brasiliensis) are expanding into the tropical regions of southwest China to ensure production to meet the growing demand for latex. The effects of long-term plantations on soil carbon processes are still unclear. Also, the effects of the plant's rhizosphere on the decomposition of soil organic matter (SOM) play a crucial role in predicting soil carbon dynamics. The rhizosphere and soils corresponding to a chronosequence of ages (4, 15 and 30 years) of rubber plantations were collected and incubated to determine the effect of the rhizosphere (RE) on SOM decomposition. We also examined the soil physicochemical properties; bacterial community structure; and root morphological, chemical, and physiological traits to further explore the underlying mechanisms of the RE on SOM decomposition. The REs on SOM decomposition varied significantly in the different age classes of the rubber plantations, and the higher the REs on SOM decomposition in an older plantation might limit the accumulation of organic carbon in the soil. Root traits, including the specific root length, root nitrogen content, and root carbon/nitrogen ratio, varied significantly in response to the plantation age and explained more of the variance in the RE on SOM decomposition than the soil and microbial properties. Due to the changing root morphological and chemical traits along the age chronosequence, the rhizosphere bacterial community composition tended to shift the carbon utilisation strategy and the bulk soil nitrogen content decreased. These variations also affected the RE on SOM decomposition. Our results indicate that the development of rubber plantations would prevent soil carbon accumulation, especially in the rhizosphere, by increasing the RE on SOM decomposition, which would be predicated by root morphological and chemical traits. [ABSTRACT FROM AUTHOR]

Root‐based functional traits are relatively overlooked as drivers of savanna plant community dynamics, an important gap in water‐limited ecosystems. Recent work has shed light on patterns of trait coordination in roots, but less is known about the relationship between root functional traits, water acquisition, and plant demographic rates. Here, we investigated how fine‐root vascular and morphological traits are related in two dominant PFTs (C3 trees and C4 grasses from the savanna biome), whether root traits can predict plant relative growth rate (RGR), and whether root trait multivariate relationships differ in trees and grasses. We used root data from 21 tree and 18 grass species grown under greenhouse conditions, and quantified a suite of vascular and morphological root traits. We used a principal components analysis (PCA) to identify common axes of trait variation, compared trait correlation matrices between the two PFTs, and investigated the relationship between PCA axes and individual traits and RGR. We found that there was no clear single axis integrating vascular and morphological traits, but found that vascular anatomy predicted RGR in both trees and grasses. Trait correlation matrices differed in trees and grasses, suggesting potentially divergent patterns of trait coordination between the two functional types. Our results suggested that, despite differences in trait relationships between trees and grasses, root conductivity may constrain maximum growth rate in both PFTs, highlighting the critical role that water relations play in savanna vegetation dynamics and suggesting that root water transport capacity is an important predictor of plant performance in the savanna biome. [ABSTRACT FROM AUTHOR]

Root respiration is a critical physiological trait that significantly influences root system activity. Recent studies have associated root respiration with the economic functioning of roots; however, research on root respiration in tropical plants remains limited. This study examined the fine root respiration and the relationship between root respiration and root chemical and morphological traits in 16 tropical plant species, including both evergreen and deciduous species. Findings revealed that deciduous species exhibited higher root respiration compared to evergreen species. Root respiration positively correlated with root nitrogen concentration and specific root length and correlated negatively with root diameter and root tissue density across all species. The root respiration patterns in evergreen species aligned with those seen in all tree species, while deciduous species showed a distinct negative correlation with root tissue density and no significant correlations with other root traits. Principal component analysis revealed that the patterns of root variation in both evergreen and deciduous trees were multidimensional, with deciduous trees exhibiting acquisitive traits and evergreen trees displaying conservative traits. Random forest and multiple regression analysis showed that specific root length exerted the most significant influence on root respiration in both evergreen and deciduous trees. These findings are ecologically significant, enhancing our understanding of root respiration in tropical plants and its impact on ecosystem functions. They contribute valuable insights and support the conservation and management of tropical vegetation.

Summary: Phosphorus (P) fertilization can alleviate a soil P deficiency in grassland ecosystems. Understanding plant functional traits that enhance P uptake can improve grassland management.We measured impacts of P addition on soil chemical and microbial properties, net photosynthetic rate (Pn) and nonstructural carbohydrate concentrations ([NSC]), and root P‐uptake rate (PUR), morphology, anatomy, and exudation of two dominant grass species: Leymus chinensis (C3) and Cleistogenes squarrosa (C4).For L. chinensis, PUR and Pn showed a nonlinear correlation. Growing more adventitious roots compensated for the decrease in P transport per unit root length, so that it maintained a high PUR. For C. squarrosa, PUR and Pn presented a linear correlation. Increased Pn was associated with modifications in root morphology, which further enhanced its PUR and a greater surplus of photosynthate and significantly stimulated root exudation (proxied by leaf [Mn]), which had a greater impact on rhizosheath micro‐environment and microbial PLFAs.Our results present correlations between the PUR and the Pn of L. chinensis and C. squarrosa and reveal that NSC appeared to drive the modifications of root morphology and exudation; they provide more objective basis for more efficient P‐input in grasslands to address the urgent problem of P deficiency. [ABSTRACT FROM AUTHOR]

Plant nutrient acquisition strategies range along a spectrum from autonomous foraging to investment in cooperative foraging through mycorrhizal associations. However, in temperate ecosystems, many plant species encounter contrasted levels of symbiont availability in open fields versus closed forests. Little is known about how fungal partner availability may be associated with intraspecific variation in other root foraging traits in natural settings.Here, we addressed this issue by sampling saplings from two tree species: the arbuscular mycorrhizal (AM) Acer rubrum and the ectomycorrhizal (ECM) Quercus rubra from open fields (AM dominated) and adjacent forest plots (ECM dominated). For each species and environment, we measured morphological, architectural and symbiotic root traits.For the open field, Quercus had greater specific root length (SRL) while Acer had higher AM colonization and root diameter. In the closed forest, the opposite pattern was observed, namely Quercus had higher ECM colonization and Acer greater SRL.Both species showed evidence of a shift towards autonomous root foraging in the habitat with low expected symbiont abundance (open field for Quercus and forest for Acer). Although the confounding effects of site abiotic properties could not be strictly controlled in this study, these results suggest that plants might adjust root foraging traits according to local habitat conditions.Synthesis: Our results shed new light on the intraspecific variation in plant position along the so‐called 'collaboration gradient', and suggest that mycorrhizal symbiont availability, along with other factors such as competition and site properties, may contribute to this variation. [ABSTRACT FROM AUTHOR]

Understanding the effects of nitrogen (N) deposition on plant functional traits can provide insights into their adaptation strategies. We conducted an N application experiment (0, 5, 10, 15 g N m−2) with potted saplings of the endangered species Davidia involucrata and examined 24 functional traits of both leaves and roots. We found that N application increased the leaf morphological traits, except for a significant decrease (by 19.2%–27.0%) in specific leaf area (SLA). Compared to the control treatment, N application significantly increased the specific root surface area (SRA), specific root length (SRL), and root tissue density (RTD) by 9.2%–20.1%, 20.2%–47.9%, and 30.8%–46.4%, respectively, while root diameter was conservative and insensitive to N application. Additionally, N application had contrasting effects between leaf and root carbon, N, and phosphorus contents and their stoichiometry. SRL, SRA, and RTD were positively correlated with most leaf photosynthetic traits, but negatively correlated with SLA. Moreover, root biomass and root chemical traits were also tightly correlated with leaf photosynthetic traits and chemical traits. These results suggest that N application may trigger a resource-conservative strategy for leaves but a nutrient-acquisitive strategy for roots. Future N deposition combined with other practices, such as simultaneous P fertilizer application, can be effective for the scientific conservation of D. involucrata populations in their natural habitats. [ABSTRACT FROM AUTHOR]

The mycorrhizal type affects the structure and functions of tree roots. Therefore, the mechanical traits of the roots of tree species with different types of mycorrhizal fungi may be linked to different root functional traits. Fine roots, in particular, are closely related to the root structure and are also important for slope protection. However, the relationship among the mycorrhizal types of trees, root mechanical traits, and root structure remains unclear. This study aims to investigate the link between fine root tensile strength (Tr) and root morphological and/or structural traits in temperate trees with different mycorrhizal types. We investigated the seedlings of 15 dominant tree species in the cool temperate forests of northern Japan. For each species, fine root Tr and other five common root morphological and structural traits were measured. There was a significant positive correlation between total fine root biomass and fine root Tr consistently, even in the analysis of mycorrhizal types (arbuscular mycorrhizal (AM), and ectomycorrhizae (EM)). Our findings indicate that the root structural trait is an important driver of fine root Tr, especially for AM and EM species, and suggest that including a plant-mycorrhizal framework in future work offers great potential to improve our understanding of forest restoration. [ABSTRACT FROM AUTHOR]

Living roots and their rhizodeposits can accelerate or decelerate the decomposition of soil organic matter which refers to the rhizosphere priming effect (RPE). However, whereas plant traits are thought to be key factors controlling the RPE, little is known about how root traits representative of plant biomass allocation, morphology, architecture, or physiology influence the magnitude of the RPE. Using a natural abundance 13C tracer method allowing partitioning of native soil organic carbon (SOC) decomposition and plant rhizosphere respiration, we studied here the effects of eight C3 tree species featuring contrasting functional traits on C4 soil respiration over a 204‐day period in a microcosm experiment. All tree species enhanced the rate of SOC decomposition, by 82% on average, but the strength of the rhizosphere priming significantly differed among species. Mean diameter of first‐order roots and root exudate‐derived respiration were positively correlated with the RPE, together explaining a large part of observed variation in the RPE (R2 = 0.72), whereas root branching density was negatively associated with the RPE. Path analyses further suggested that mean diameter of first‐order roots was the main driver of the RPE owing to its positive direct effect on the RPE and its indirect effects via root exudate‐derived respiration and root branching density. Our study demonstrates that the magnitude of the RPE is regulated by complementary aspects of root morphology, architecture and physiology, implying that comprehensive approaches are needed to reveal the multiple mechanisms driving plant effects on the RPE. Overall, our results emphasize the relevance of integrating root traits in biogeochemical cycling models to improve model performance for predicting soil C dynamics. [ABSTRACT FROM AUTHOR]

Summary: Forest fungal communities are shaped by the interactions between host tree root systems and the associated soil conditions. We investigated how the soil environment, root morphological traits, and root chemistry influence root‐inhabiting fungal communities in three tropical forest sites of varying successional status in Xishuangbanna, China.For 150 trees of 66 species, we measured root morphology and tissue chemistry. Tree species identity was confirmed by sequencing rbcL, and root‐associated fungal (RAF) communities were determined using high‐throughput ITS2 sequencing.Using distance‐based redundancy analysis and hierarchical variation partitioning, we quantified the relative importance of two soil variables (site average total phosphorus and available phosphorus), four root traits (dry matter content, tissue density, specific tip abundance, and forks), and three root tissue elemental concentrations (nitrogen, calcium, and manganese) on RAF community dissimilarity. The root and soil environment collectively explained 23% of RAF compositional variation. Soil phosphorus explained 76% of that variation. Twenty fungal taxa differentiated RAF communities among the three sites.Soil phosphorus most strongly affects RAF assemblages in this tropical forest. Variation in root calcium and manganese concentrations and root morphology among tree hosts, principally an architectural trade‐off between dense, highly branched vs less‐dense, herringbone‐type root systems, are important secondary determinants. [ABSTRACT FROM AUTHOR]

Some invasive ants have worldwide distributions and impose substantial impacts on human society and native biodiversity. Yet we know little about how ants impact soil ecosystems in general, much less how soil ecosystems shift when invasive ants move in. We excavated the coarse roots of a monodominant savanna tree in invaded and uninvaded areas to test the hypothesis that the presence of invasive ants would be associated with changes in root distribution and biomass across the landscape. We found that in the presence of invasive ants, trees had a shifted distribution of lateral coarse roots, with proportionally less root biomass near the surface and far from tree stems. In addition, the density of lateral coarse-root biomass was ~ 20% lower for trees within invaded landscapes. Our results suggest that soil-nesting invasive ants can drive important changes in rooting strategy for a tree species that serves a foundational role in the biogeochemical cycles of vertisol savannas. [ABSTRACT FROM AUTHOR]

Trait plasticity and integration mediate vegetable adaptive strategies. However, it is unclear how patterns of vegetables in root traits influence vegetable adaptation to different phosphorus (P) levels. Nine root traits and six shoot traits were investigated in 12 vegetable species cultivated in a greenhouse with low and high P supplies to identify distinct adaptive mechanisms in relation to P acquisition (40 and 200 Pmg kg-1 as KH2PO4). At the low P level, a series of negative correlations among root morphology, exudates and mycorrhizal colonization, and different types of root functional properties (root morphology, exudates and mycorrhizal colonization) respond differently to soil P levels among vegetable species. nonmycorrhizal plants showed relatively stable root traits as compared to solanaceae plants that showed more altered root morphologies and structural traits. At the low P level, the correlation between root traits of vegetable crops was enhanced. It was also found in vegetables that low P supply enhances the correlation of morphological structure while high P supply enhances the root exudation and the correlation between mycorrhizal colonization and root traits. Root exudation combined with root morphology and mycorrhizal symbiosis to observe P acquisition strategies in different root functions. Vegetables respond highly under different P conditions by enhancing the correlation of root traits. Low P supply could significantly improve the direct and indirect ways of mycorrhizal vegetable crops' root traits axis on shoot biomass, and enhance the direct way of non-mycorrhizal vegetable crops' root traits axis and reduce the indirect way of root exudates. [ABSTRACT FROM AUTHOR]

Summary: Unravelling belowground strategies is critical for understanding species coexistence and successional dynamics; yet, our knowledge of nutrient acquisition strategies of forest species at different successional stages remains limited.We measured morphological (diameter, specific root length, and root tissue density), architectural (branching ratio), physiological (ammonium, nitrate, and glycine uptake rates) root traits, and mycorrhizal colonisation rates of eight coexisting woody species in an early successional plantation forest in subtropical China.By incorporating physiological uptake efficiency, we revealed a bi‐dimensional root economics space comprising of an 'amount‐efficiency' dimension represented by morphological and physiological traits, and a 'self‐symbiosis' dimension dominated by architectural and mycorrhizal traits. The early pioneer species relied on root–fungal symbiosis, developing densely branched roots with high mycorrhizal colonisation rates for foraging mobile soil nitrate. The late pioneer species invested in roots themselves and allocated effort towards improving uptake efficiency of less‐mobile ammonium. Within the root economics space, the covariation of axes with soil phosphorus availability also distinguished the strategy preference of the two successional groups.These results demonstrate the importance of incorporating physiological uptake efficiency into root economics space, and reveal a trade‐off between expanding soil physical space exploration and improving physiological uptake efficiency for successional species coexistence in forests. [ABSTRACT FROM AUTHOR]

How crop domestication mediates root functional traits and trait plasticity in response to neighboring plants is unclear, but it is important for selecting potential species to be grown together to facilitate P uptake. We grew two barley accessions representing a two-stage domestication process as a sole crop or mixed with faba bean under low and high P inputs. We analyzed six root functional traits associated with P acquisition and plant P uptake in five cropping treatments in two pot experiments. The spatial and temporal patterns of root acid phosphatase activity were characterized in situ with zymography at 7, 14, 21, and 28 days after sowing in a rhizobox. Under low P supply, wild barley had higher total root length (TRL), specific root length (SRL), and root branching intensity (RootBr) as well as higher activity of acid phosphatase (APase) in the rhizosphere, but lower root exudation of carboxylates and mycorrhizal colonization (MC), relative to domesticated barley. In response to neighboring faba bean, wild barley exhibited larger plasticity in all root morphological traits (TRL, SRL, and RootBr), while domesticated barley showed greater plasticity in root exudates of carboxylates and colonization by mycorrhiza. Wild barley with greater root morphology-related trait plasticity was a better match with faba bean than domesticated barley, indicated by higher P uptake benefits in wild barley/faba bean than domesticated barley/faba bean mixtures under low P supply. Our findings indicated that the domestication of barley disrupts the intercropping benefits with faba bean through the shifts of root morphological traits and their plasticity in barley. Such findings provide valuable information for barley genotype breeding and the selection of species combinations to enhance P uptake. [ABSTRACT FROM AUTHOR]

The competitive advantage of lianas over trees has been widely documented in studies of their leaf functional traits across diverse habitats; however, the relative contribution of root functional traits to the competitive superiority of lianas over trees has not yet been evaluated. The aim of this study was to explore the root functional traits, phylogenetic structure of these traits and root trait dimensions of lianas to clarify why lianas can outperform trees.We sampled 69 liana species from tropical and temperate forests in China and measured nine key functional traits of first‐order roots of each species, including morphological, architectural, anatomical and chemical traits, as well as the percentage of mycorrhizal colonization. Data on these traits were then compared with similar data of 127 tree species from the same biome obtained from the Global Root Traits (GRooT) database and our previous studies.Liana roots had lower construction costs and could acquire resources more rapidly compared with tree roots. Significant differences were observed in most tree root traits between tropical and temperate sites. However, no significant differences were observed in any of the liana root traits between tropical and temperate sites, apart from the root branching ratio.Lianas showed much weaker phylogenetic conservatism in their root traits than trees when species were pooled across sites. Phylogenetic constraint was lower for nearly all root traits of both temperate lianas and trees compared with those of tropical lianas and trees.The root economics space of lianas and trees had two orthogonal dimensions with 'conservation' and 'collaboration' axes. However, lianas occupied the trait space with higher root nitrogen concentration and greater specific root length, showing 'fast' resource acquisition strategy, while trees placed opposite space and exhibited relatively 'slow' strategy.Synthesis. The ability of lianas to outcompete trees in harsh environments might be explained by their faster resource acquisition strategy and the lower phylogenetic constraint in root traits. Generally, lianas might play an increasingly important role in the structure and function of forest ecosystems in the future with ongoing habitat fragmentation and climate change. [ABSTRACT FROM AUTHOR]

Trait plasticity and integration mediate vegetable adaptive strategies. However, it is unclear how patterns of vegetables in root traits influence vegetable adaptation to different phosphorus (P) levels. Nine root traits and six shoot traits were investigated in 12 vegetable species cultivated in a greenhouse with low and high P supplies to identify distinct adaptive mechanisms in relation to P acquisition (40 and 200 P mg kg-1 as KH2PO4). At the low P level, a series of negative correlations among root morphology, exudates and mycorrhizal colonization, and different types of root functional properties (root morphology, exudates and mycorrhizal colonization) respond differently to soil P levels among vegetable species. non-mycorrhizal plants showed relatively stable root traits as compared to solanaceae plants that showed more altered root morphologies and structural traits. At the low P level, the correlation between root traits of vegetable crops was enhanced. It was also found in vegetables that low P supply enhances the correlation of morphological structure while high P supply enhances the root exudation and the correlation between mycorrhizal colonization and root traits. Root exudation combined with root morphology and mycorrhizal symbiosis to observe P acquisition strategies in different root functions. Vegetables respond highly under different P conditions by enhancing the correlation of root traits. Low P supply could significantly improve the direct and indirect ways of mycorrhizal vegetable crops’ root traits axis on shoot biomass, and enhance the direct way of non-mycorrhizal vegetable crops’ root traits axis and reduce the indirect way of root exudates.

Rubber tree plantations (Hevea brasiliensis) are expanding into the tropical regions of southwest China to ensure production to meet the growing demand for latex. The effects of long-term plantations on soil carbon processes are still unclear. Also, the effects of the plant’s rhizosphere on the decomposition of soil organic matter (SOM) play a crucial role in predicting soil carbon dynamics. The rhizosphere and soils corresponding to a chronosequence of ages (4, 15 and 30 years) of rubber plantations were collected and incubated to determine the effect of the rhizosphere (RE) on SOM decomposition. We also examined the soil physicochemical properties; bacterial community structure; and root morphological, chemical, and physiological traits to further explore the underlying mechanisms of the RE on SOM decomposition. The REs on SOM decomposition varied significantly in the different age classes of the rubber plantations, and the higher the REs on SOM decomposition in an older plantation might limit the accumulation of organic carbon in the soil. Root traits, including the specific root length, root nitrogen content, and root carbon/nitrogen ratio, varied significantly in response to the plantation age and explained more of the variance in the RE on SOM decomposition than the soil and microbial properties. Due to the changing root morphological and chemical traits along the age chronosequence, the rhizosphere bacterial community composition tended to shift the carbon utilisation strategy and the bulk soil nitrogen content decreased. These variations also affected the RE on SOM decomposition. Our results indicate that the development of rubber plantations would prevent soil carbon accumulation, especially in the rhizosphere, by increasing the RE on SOM decomposition, which would be predicated by root morphological and chemical traits.

The complex interactions between plant roots and soil microorganisms are, broadly, well described. Yet the patterns of microbe–microbe interaction and their association with the root functional traits are less known especially in plant communities at the edges of agricultural landscapes. To address this gap, we measured the active soil microbial communities with and without the presence of plant roots, using in situ root exclusions, in four plant communities at the edges of agricultural fields: undisturbed natural deciduous forests (FOREST1), coniferous forests (FOREST2), rehabilitated agroforests (AGROFOREST) and perennial herbaceous grass buffers (GRASS). Amplicon‐based analysis of 16S rRNA and ITS transcripts was used to evaluate soil bacterial, archaeal and fungal communities, and their interactions, with 'roots' and with 'no roots'. Plants roots were measured for a suite of functional traits and explored in association with microbial community composition. Significant differences in bacterial and archaeal but not fungal diversity were observed between soil plots with 'roots' and with 'no roots'. Network analysis illustrated intra and inter kingdoms co‐occurrence patterns respond to the presence of plant roots, with GRASS exhibiting distinct patterns in comparison to tree‐dominated soils. A shift in microbial hub from bacterial to fungal was observed with the exclusion of roots; Planctomycetes (OM190)_10 was replaced by Archaeorhizomyces in AGROFOREST site. Microbial taxa strongly correlate with root traits especially specific root length, root diameter and root tissue density indicating root traits are predictors of microbial community composition. This study validates the vital role of root traits in predicting plant–microbe interactions and highlights the key role of fungi in microbial interkingdom interactions when roots are absent. These findings have significant ecosystem level implications, with the rising interest in associated biodiversity in and at the edges of agricultural landscapes, this work suggests that plant community selection for specific root traits may drive microbial community structure and ecosystem services. [ABSTRACT FROM AUTHOR]

Global climate change is increasing pest and pathogen pressures on plant communities, deteriorating optimal plant functioning. In plant communities, root functional trait expression and microbial communities are important indicators of plant functioning belowground, and, when confronted with pathogens aboveground, can simultaneously reflect plant defence strategies. Yet, while research is continuing to emerge on the response of root functional traits and microbial processes to pathogens aboveground, little work has investigated these interactions in tree‐crops, or the role organic amendments play in moderating these relationships. The main objective of this study is to disentangle the dynamic effects of pathogens and amendments on root functional traits (i.e. specific root length and area, root diameter, root length density, root nitrogen and root carbon to nitrogen ratio) and root endophytic fungal communities. As a model, we use Coffea arabica (coffee) variety Caturra along a gradient of coffee leaf rust – a foliar disease prominent in coffee systems – under contrasting but widespread amendment regimes in biodiverse agroforestry systems. We found that root trait expression varies along established conservation and collaboration gradients, where fungal endophyte community composition varies significantly as a function of root traits. Belowground resource acquisition strategies do not change with foliar disease incidence, suggesting they may be decoupled. Rather, amendment regimes differentially shape root trait expression and microbial communities, where coffee plants under organic amendments, regardless of foliar disease incidence, expressed greater acquisitive traits and enhanced collaboration with symbiotic fungi. This is an important first step in disentangling the dynamic inter‐relationships between plant traits, endophytes and pathogens, generating new questions on the role of amendments in sustainable pathogen management in biodiverse agroecosystems. [ABSTRACT FROM AUTHOR]

Purpose: In agroforestry systems, the root distributions and properties of the annual and perennial vegetation are poorly known, although they are recognized for fostering soil carbon (C) stocks through annual root-derived C inputs and by altering microbial activity. This study aimed to evaluate the potential contribution of roots from the understory vegetation strip (UVS) and the crop to top- and subsoil C stocks (0–100 cm) to a 3-year-old agroforestry system of the alley-cropping type. Methods: Root biomass, chemical composition, functional traits and anatomical structure were assessed in parallel to a characterization of soil physicochemical and microbiological properties, including enzymatic activity, at different depths and locations perpendicular to the tree line. Results: The root biomass and properties were heterogeneous in the young alley-cropping system due to the presence of different plant communities and the heterogeneity of the soil mineral N content according to the location perpendicular to the tree line. The soil microbiological properties and organic C stocks did not vary horizontally at this stage of agroforestry but should be monitored through multiple-time samples to confirm a differentiation in subsequent years suggested by the tight link between root stoichiometry and microbial extracellular enzymatic activities that we found. Conclusions: Altogether, our results suggested that increasing the root biomass in topsoil in agroforestry systems positively contributes to increasing soil organic C stocks, but in deeper soil layers, an increase in litter inputs with a high C:N ratio might accentuate microbial N limitations and limit soil C storage. [ABSTRACT FROM AUTHOR]

When it comes to root and mycorrhizal associations that define resource acquisition strategy, there is a need to identify the leading dimension across root physiology, morphology, architecture and whole plant biomass allocation to better predict the plant's responses to multiple environmental constraints. Here, we developed a new framework for understanding the variation in roots and symbiotic fungi by quantifying multiple-scale characteristics, ranging from anatomy to the whole plant. We chose the rubber (Hevea brasiliensis) grown at three elevations to test our framework and to identify the key dimensions for resource acquisition. Results showed that the quantities of absorptive roots and root system architecture, rather than single root traits, played the leading role in belowground resource acquisition. As the elevation increased from the low to high elevation, root length growth, productivity and root mass fraction (RMF) increased by 2.9-, 2.3- and 13.8-fold, respectively. The contribution of RMF to the changes in total root length was 3.6-fold that of specific root length (SRL). Root architecture exhibited higher plasticity than anatomy and morphology. Further, mycorrhizal colonization was highly sensitive to rising elevations with a non-monotonic pattern. By contrast, both leaf biomass and specific leaf area (traits) co-varied with increasing elevation. In summary, rubber trees changed root system architecture by allocating more biomass and lowering the reliance on mycorrhizal fungi rather than improving single root efficiency in adapting to high elevation. Our framework is instructive for traits-based ecology; accurate assessments of forest carbon cycling in response to resource gradient should account for the leading dimension of root system architecture. [ABSTRACT FROM AUTHOR]

Plants and microbes are the primary drivers in affecting the formation and accrual of soil organic carbon (SOC) for natural ecosystems. However, experimental evidence elucidating their underlying mechanisms for SOC accumulation remains elusive. Here, we quantified plant and microbial contributions to SOC accrual in successional subtropical forests by measuring leaf-, root-, and microbial biomarkers, root and leaf litter inputs, and microbial C decomposition. The long-term monitoring results showed that SOC accumulated rapidly at the early-successional stage, but changed little at the mid- and late-successional stages. SOC accrual rate was positively correlated with fine-root production and microbial C turnover, but negatively with annual litterfall. Biomarker data exhibited that the rapid SOC accumulation was jointly driven by root- and microbe-derived C inputs from the early- to mid-successional stages. In contrast, aboveground litterfall considerably contributed to soil C accrual from the mid- to late-successional stages compared to belowground processes, although SOC accumulation is low. Our study revealed the importance of root production and microbial anabolism in SOC accrual at the early stages of forest succession. Incorporating these effects of belowground C inputs on SOC formation and accumulation into earth system models might improve model performance and projection of long-term soil C dynamics. [ABSTRACT FROM AUTHOR]

Climate forecasts show that in many regions the temporal distribution of precipitation events will become less predictable. Root traits may play key roles in dealing with changes in precipitation predictability, but their functional plastic responses, including transgenerational processes, are scarcely known. We investigated root trait plasticity of Papaver rhoeas with respect to higher versus lower intra-seasonal and inter-seasonal precipitation predictability (i.e., the degree of temporal autocorrelation among precipitation events) during a four-year outdoor multi-generation experiment. We first tested how the simulated predictability regimes affected intra-generational plasticity of root traits and allocation strategies of the ancestors, and investigated the selective forces acting on them. Second, we exposed three descendant generations to the same predictability regime experienced by their mothers or to a different one. We then investigated whether high inter-generational predictability causes root trait differentiation, whether transgenerational root plasticity existed and whether it was affected by the different predictability treatments. We found that the number of secondary roots, root biomass and root allocation strategies of ancestors were affected by changes in precipitation predictability, in line with intra-generational plasticity. Lower predictability induced a root response, possibly reflecting a fast-acquisitive strategy that increases water absorbance from shallow soil layers. Ancestors’ root traits were generally under selection, and the predictability treatments did neither affect the strength nor the direction of selection. Transgenerational effects were detected in root biomass and root weight ratio (RWR). In presence of lower predictability, descendants significantly reduced RWR compared to ancestors, leading to an increase in performance. This points to a change in root allocation in order to maintain or increase the descendants’ fitness. Moreover, transgenerational plasticity existed in maximum rooting depth and root biomass, and the less predictable treatment promoted the lowest coefficient of variation among descendants’ treatments in five out of six root traits. This shows that the level of maternal predictability determines the variation in the descendants’ responses, and suggests that lower phenotypic plasticity evolves in less predictable environments. Overall, our findings show that roots are functional plastic traits that rapidly respond to differences in precipitation predictability, and that the plasticity and adaptation of root traits may crucially determine how climate change will affect plants. [ABSTRACT FROM AUTHOR]

Understanding the effects of nitrogen (N) deposition on plant functional traits can provide insights into their adaptation strategies. We conducted an N application experiment (0, 5, 10, 15 g N m−2) with potted saplings of the endangered species Davidia involucrata and examined 24 functional traits of both leaves and roots. We found that N application increased the leaf morphological traits, except for a significant decrease (by 19.2%–27.0%) in specific leaf area (SLA). Compared to the control treatment, N application significantly increased the specific root surface area (SRA), specific root length (SRL), and root tissue density (RTD) by 9.2%–20.1%, 20.2%–47.9%, and 30.8%–46.4%, respectively, while root diameter was conservative and insensitive to N application. Additionally, N application had contrasting effects between leaf and root carbon, N, and phosphorus contents and their stoichiometry. SRL, SRA, and RTD were positively correlated with most leaf photosynthetic traits, but negatively correlated with SLA. Moreover, root biomass and root chemical traits were also tightly correlated with leaf photosynthetic traits and chemical traits. These results suggest that N application may trigger a resource-conservative strategy for leaves but a nutrient-acquisitive strategy for roots. Future N deposition combined with other practices, such as simultaneous P fertilizer application, can be effective for the scientific conservation of D. involucrata populations in their natural habitats.

Fine roots play crucial roles in terrestrial biogeochemical cycles. Although biodiversity loss and changes in precipitation are two major drivers of global change, our understanding of their effects on fine root biomass (FRB), root functional traits, and fine root decay (FRD) remains incomplete. We manipulated precipitation in young boreal forests dominated by Populus tremuloides, Pinus banksiana, and their relatively even mixtures using 25 % addition, ambient, and 25 % reduction in throughfall during the growing season. We collected root samples using soil core and trunk-traced methods to quantify FRB and root traits, and we simulated fine root decay using an in-situ experiment over 531 days. We found that compared to the average of single-species-dominated stands, species mixtures increased FRB by 41 % under ambient throughfall, by 89 % under throughfall reduction and by 71 % under throughfall addition. Root surface area, fine root volume, and root length density responded to species mixtures similarly to FRB. Meanwhile, species mixtures reduced FRD across all water treatments. There was a positive relationship between the effect of species mixtures on the FRD of absorptive roots and those on the FRB. Our results highlight that species mixtures could modify carbon cycling by enhancing fine root biomass accumulation and reducing its decomposition of young boreal forests under changing precipitation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Belowground responses are critical in understanding how plants cope with the predicted increase in drought intensity and frequency in the Mediterranean region, because plant root systems compete with each other and interact with soil microbial communities under limiting water availability. However, the combined responses of plant roots and soil microorganisms to drought are not well understood. Using an experimental approach, we addressed the question of how recurrent drought and different combinations of two individuals from three common Mediterranean plant species (Quercus coccifera, Cistus albidus, and Brachypodium retusum) affect root characteristics and soil microbial activity. We hypothesized that drought effects on root characteristics and associated soil microbial communities are stronger when plant individuals of the same species compete for limiting water compared to inter-specific competition. Root morphological traits were more affected by the species identity of the neighbor individual than by recurrent severe drought, particularly in B. retusum, which may in part explain the higher survival previously observed for this species. On the other hand, drought and plant composition had little effect on root-associated soil microbes’ ability to use a wide range of different carbon substrates. Overall, our results did not confirm stronger effects of intra- compared to interspecific competition on the root and microbial responses, but showed strong species identity effects.

The mycorrhizal type affects the structure and functions of tree roots. Therefore, the mechanical traits of the roots of tree species with different types of mycorrhizal fungi may be linked to different root functional traits. Fine roots, in particular, are closely related to the root structure and are also important for slope protection. However, the relationship among the mycorrhizal types of trees, root mechanical traits, and root structure remains unclear. This study aims to investigate the link between fine root tensile strength (Tr) and root morphological and/or structural traits in temperate trees with different mycorrhizal types. We investigated the seedlings of 15 dominant tree species in the cool temperate forests of northern Japan. For each species, fine root Tr and other five common root morphological and structural traits were measured. There was a significant positive correlation between total fine root biomass and fine root Tr consistently, even in the analysis of mycorrhizal types (arbuscular mycorrhizal (AM), and ectomycorrhizae (EM)). Our findings indicate that the root structural trait is an important driver of fine root Tr, especially for AM and EM species, and suggest that including a plant-mycorrhizal framework in future work offers great potential to improve our understanding of forest restoration.

In southern Taiwan, mudstone badland accounts for over 1000 km2 of the upstream region of watersheds. Rainstorms often induce interrill and surface erosion on the mudstone slopes. Furthermore, the large quantity of soils detached by surface runoff result in severe sedimentation in reservoirs. Thus, soil erosion control of mudstone badlands represents one of the most pressing problems in reservoir watershed management. Cynodon dactylon (L.) Pers. (Bermuda grass) and Eremochloa ophiuroides (Munro) Hack. (Centipedegrass) are two native predominant C4 grass species appearing on mudstone badlands. They play a key role in erosion control and the revegetation of mudstone slopes. Nevertheless, their root functional traits and water erosion-reducing potential have not been investigated. In this study, the root traits were examined. Vertical pullout and tensile tests were conducted to measure root pullout resistance and root tensile strength. Hydraulic flume tests were also performed to evaluate their water erosion-reducing potentials. The results demonstrated that the root systems of C. dactylon and E. ophiuroides grasses all belonged to the fibrous M-type. C. dactylon had remarkably better root traits compared to those of E. ophiuroides. Furthermore, the root tensile resistance of C. dactylon was remarkably higher than that of E. ophiuroides. In addition, hydraulic flume tests showed that C. dactylon has remarkably smaller soil detachment rates than that of E. ophiuroides. Altogether, our data clearly show that C. dactylon has better root traits, root pullout resistance, root tensile resistance and water erosion-reducing potential than E. ophiuroides and is more suitable for erosion control of mudstone badland. Further studies on large-scale implementation techniques of these species for efficient vegetation restoration are needed. [ABSTRACT FROM AUTHOR]

Aim: Diversity may increase the resistance of ecosystem productivity to environmental stress, such as warming, via compensatory processes associated with adjustments of species interactions. However, experimental evidence of compensatory processes that buffer productivity declines in relation to environmental stress is limited, especially in below‐ground settings. We asked whether species richness could stabilize productivity under warming via compensatory responses in root biomass and root functional traits. Methods: Using three herbaceous species, we created plant communities composed of four individuals in either monocultures or two‐ and three‐species assemblages. We grew them at three temperatures, simulating current climate conditions, moderate warming and severe warming, respectively. We built mixed‐linear mixed models to model plant productivity by species richness and warming and we also analyzed the interactive roles of species richness and warming in species interaction and root functional traits. Results: We found that warming reduced both above‐ and below‐ground productivity and shifted the biodiversity–productivity relationship from negative to positive. Productivity reductions were weaker in richer species combinations. Warming ameliorated the strength of interspecific competition below‐ground in mixed‐species communities by reducing the root biomass of strong competitors, which benefitted root growth of weaker competitors. Conclusions: Our results suggest warming can facilitate compensatory responses in herbaceous root productivity across species competition hierarchies. These compensatory processes by which species richness stabilizes plant community functioning emphasize the importance that plant functional diversity has in maintaining ecosystem functioning with climate change. [ABSTRACT FROM AUTHOR]

Aims: Plant roots show various functional strategies in soil phosphorus (P) acquisition. Under limited soil phosphatase activity, P deficiency is the main concern, and roots either invest carbon (C) to produce higher levels of phosphatase or establish more symbioses with mycorrhizal fungi. However, these strategies and their interactions are not clear. Furthermore, few studies have investigated trade-offs of functional traits in woody species associated with different types of mycorrhizal partners. Methods: Here we examined the abilities to release acid phosphatase (AP) and the colonization ratio by arbuscular and ectomycorrhizal fungi for fine roots of 15 woody species growing in a tropical common garden in Xishuangbanna, China. We also measured acid phosphatase activities of bulk soils under the canopy of target trees. Results: Soil and root AP activities exhibited a positive correlation, indicating that roots actively produced AP to acquire P even bulk soil AP was increasing. We found a significantly negative correlation (P ¼ 0.02) between mycorrhizal colonization ratio and root-released AP activity across target species, reflecting a trade-off between these two P acquisition strategies. Conclusions: Our findings suggest a trade-off of resource allocation between these two strategies at both species and individual levels, and provide information on the overall mechanism of P acquisition by fine roots that they either ‘do it by themselves’ or ‘rely on mycorrhizal partners’. These two strategies might be integrated into the collaboration gradient of the root economics space. [ABSTRACT FROM AUTHOR]

Plants and microbes are the primary drivers in affecting the formation and accrual of soil organic carbon (SOC) for natural ecosystems. However, experimental evidence elucidating their underlying mechanisms for SOC accumulation remains elusive. Here, we quantified plant and microbial contributions to SOC accrual in successional subtropical forests by measuring leaf-, root-, and microbial biomarkers, root and leaf litter inputs, and microbial C decomposition. The long-term monitoring results showed that SOC accumulated rapidly at the early-successional stage, but changed little at the mid- and late-successional stages. SOC accrual rate was positively correlated with fine-root production and microbial C turnover, but negatively with annual litterfall. Biomarker data exhibited that the rapid SOC accumulation was jointly driven by root- and microbe-derived C inputs from the early- to mid-successional stages. In contrast, aboveground litterfall considerably contributed to soil C accrual from the mid- to late-successional stages compared to belowground processes, although SOC accumulation is low. Our study revealed the importance of root production and microbial anabolism in SOC accrual at the early stages of forest succession. Incorporating these effects of belowground C inputs on SOC formation and accumulation into earth system models might improve model performance and projection of long-term soil C dynamics.

The interactions among soil microbiota can be indicated by co-occurrence network analysis. The root-associated and soil-associated fungal networks are likely to be influenced by aboveground energy and belowground resources supplies. Most studies have focused on the role of soil nutrients in driving the network, yet the root's role remains elusive. Here, we chose a pure larch forest plantation to control the tree species, age, and soil nitrogen, collected more than 8000 root tips, quantified six root traits, and investigated the compositions of root and rhizosphere soil fungal communities, and network modules across 27 plots. We found that each root tip harboured distinctive fungal species interactions, even in the same tree with a similar age and soil nitrogen. Root-associated fungal OTUs accounted for 14% of soil-associated fungal OTUs, and they only formed a few functional modules, which correlated with three key resource-related root traits: root branching intensity, specific root length, and root diameter. Forest age, linked with root traits, exerts a greater role than nitrogen addition in constraining the complexity and stability of fungal interactions. In contrast, the rhizosphere soil fungi showed complex interactions and formed nearly 120 modules, and several of the key soil fungal modules (higher relative abundance) were influenced by soil nitrogen and phosphorous availability. These results demonstrated that root acquisitive traits are the central factors influencing the root-associated fungal interactions, with a systematic co-varied phenomenon in the root acquisitive traits-microbe functional modules across a wide range of soil nitrogen levels. • Root acquisitive traits were strongly correlated with root-associated fungi modules. • Middle-aged forests showed the most complexities in network. • Each root tip has its own unique fungal species composition and interactions. [ABSTRACT FROM AUTHOR]

We investigated the variation in tree fine root traits and their functional diversity along a local topographic gradient in a Neotropical montane forest to test if fine root trait variation along the gradient is consistent with the predictions of the root economics spectrum on a shift from acquisitive to conservative traits with decreasing resource supply.We measured five fine root functional traits in 179 randomly selected tree individuals of 100 species and analysed the variation of single traits (using Bayesian phylogenetic multilevel models) and of functional trait diversity with small‐scale topography.Fine roots exhibited more conservative traits (thicker diameters, lower specific root length and nitrogen concentration) at upper slope compared with lower slope positions, but the largest proportion of variation (40–80%) was explained by species identity and phylogeny. Fine root functional diversity decreased towards the upper slopes.Our results suggest that local topography and the related soil fertility and moisture gradients cause considerable small‐scale variation in fine root traits and functional diversity along tropical mountain slopes, with conservative root traits and greater trait convergence being associated with less favourable soil conditions due to environmental filtering. We provide evidence of a high degree of phylogenetic conservation in fine root traits. [ABSTRACT FROM AUTHOR]

In southern Taiwan, mudstone badland accounts for over 1000 km2 of the upstream region of watersheds. Rainstorms often induce interrill and surface erosion on the mudstone slopes. Furthermore, the large quantity of soils detached by surface runoff result in severe sedimentation in reservoirs. Thus, soil erosion control of mudstone badlands represents one of the most pressing problems in reservoir watershed management. Cynodon dactylon (L.) Pers. (Bermuda grass) and Eremochloa ophiuroides (Munro) Hack. (Centipedegrass) are two native predominant C4 grass species appearing on mudstone badlands. They play a key role in erosion control and the revegetation of mudstone slopes. Nevertheless, their root functional traits and water erosion-reducing potential have not been investigated. In this study, the root traits were examined. Vertical pullout and tensile tests were conducted to measure root pullout resistance and root tensile strength. Hydraulic flume tests were also performed to evaluate their water erosion-reducing potentials. The results demonstrated that the root systems of C. dactylon and E. ophiuroides grasses all belonged to the fibrous M-type. C. dactylon had remarkably better root traits compared to those of E. ophiuroides. Furthermore, the root tensile resistance of C. dactylon was remarkably higher than that of E. ophiuroides. In addition, hydraulic flume tests showed that C. dactylon has remarkably smaller soil detachment rates than that of E. ophiuroides. Altogether, our data clearly show that C. dactylon has better root traits, root pullout resistance, root tensile resistance and water erosion-reducing potential than E. ophiuroides and is more suitable for erosion control of mudstone badland. Further studies on large-scale implementation techniques of these species for efficient vegetation restoration are needed.

This article is a Commentary on Colombi et al. (2022), 233: 1542–1547. [ABSTRACT FROM AUTHOR]

Summary: Root exudation stimulates microbial decomposition and enhances nutrient availability to plants. It remains difficult to measure and predict this carbon flux in natural conditions, especially for mature woody plants. Based on a known conceptual framework of root functional traits coordination, we proposed that root functional traits may predict root exudation.We measured root exudation and other seven root morphological/chemical/physiological traits for 18 coexisting woody species in a deciduous‐evergreen mixed forest in subtropical China.Root exudation, respiration, diameter and nitrogen (N) concentration all exhibited significant phylogenetic signals. We found that root exudation positively correlated with competitive traits (root respiration, N concentration) and negatively with a conservative trait (root tissue density). Furthermore, these relationships were independent of phylogenetic signals. A principal component analysis showed that root exudation and morphological traits loaded on two perpendicular axes.Root exudation is a competitive trait in a multidimensional fine‐root functional coordination. The metabolic dimension on which root exudation loaded was relatively independent of the morphological dimension, indicating that increasing nutrient availability by root exudation might be a complementary strategy for plant nutrient acquisition. The positive relationship between root exudation and root respiration and N concentration is a promising approach for the future prediction of root exudation. [ABSTRACT FROM AUTHOR]

Summary: Dimensions of tree root systems in savannas are poorly understood, despite being essential in resource acquisition and post‐disturbance recovery. We studied tree rooting patterns in Southern African savannas to ask: how tree rooting strategies affected species responses to severe drought; and how potential rooting depths varied across gradients in soil texture and rainfall.First, detailed excavations of eight species in Kruger National Park suggest that the ratio of deep to shallow taproot diameters provides a reasonable proxy for potential rooting depth, facilitating extensive interspecific comparison. Detailed excavations also suggest that allocation to deep roots traded off with shallow lateral root investment, and that drought‐sensitive species rooted more shallowly than drought‐resistant ones.More broadly across 57 species in Southern Africa, potential rooting depths were phylogenetically constrained, with investment to deep roots evident among miombo Detarioids, consistent with results suggesting they green up before onset of seasonal rains. Soil substrate explained variation, with deeper roots on sandy, nutrient‐poor soils relative to clayey, nutrient‐rich ones. Although potential rooting depth decreased with increasing wet season length, mean annual rainfall had no systematic effect on rooting depth.Overall, our results suggest that rooting depth systematically structures the ecology of savanna trees. Further work examining other anatomical and physiological root traits should be a priority for understanding savanna responses to changing climate and disturbances. [ABSTRACT FROM AUTHOR]

Background: Disentangling nutrient acquisition strategies between trees and crops is central to understanding positive nutrient interactions in agroforestry systems for improved low-input agriculture. However, as plants are responsive to a complex soil matrix at multiple scales, generalizable diagnostics across diverse agroforests remains challenging. Scope: We synthesize research at various scales of the tree-crop interface that are cumulatively hypothesized to underpin nutrient acquisition strategies in agroforestry systems. These scales span the whole root system to fine-scale sites of acquisition actively engaged in biological and chemical interactions with soil. We target vertical and horizontal dimensions of acquisition patterns; localized root-soil dynamics including biological associations; root-scale plasticity for higher acquisition; and nutrient additions via biological nitrogen fixation and deep soil nutrient uplift. We consolidate methodological advances and the effects of environmental change on well-established nutrient interactions. Conclusions: Root distribution patterns remain one of the most universal indicators of nutrient acquisition strategies in a range of agroforestry systems, while root functional traits are emerging as an effective root-scale indicator of nutrient acquisition strategy. We validate that in agroforestry systems crop root functional traits reveal bivariate trade-offs similar to, but weaker than, crops in monoculture, with mechanistic links to nutrient acquisition strategies. While interspecific root overlap may be associated with nutrient competition, clear cases of enhanced chemically and microbially meditated processes result in species- and management-specific nutrient facilitation. We argue for agroforestry science to use distinct and standardized nutrient acquisition indicators and processes at multiple scales to generate more nuanced, while also generalizable, diagnostics of tree-crop interactions. And extensive research is needed on how agroforestry practices stabilize key nutrient acquisition patterns in the face of environmental change. [ABSTRACT FROM AUTHOR]