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BACKGROUND: Root systems are key contributors to plant health, resilience, and, ultimately, yield of agricultural crops. To optimize plant performance, phenotyping trials are conducted to breed plants with diverse root traits. However, traditional analysis methods are often labour-intensive and invasive to the root system, therefore limiting high-throughput phenotyping. Spectral electrical impedance tomography (sEIT) could help as a non-invasive and cost-efficient alternative to optical root analysis, potentially providing 2D or 3D spatio-temporal information on root development and activity. Although impedance measurements have been shown to be sensitive to root biomass, nutrient status, and diurnal activity, only few attempts have been made to employ tomographic algorithms to recover spatially resolved information on root systems. In this study, we aim to establish relationships between tomographic electrical polarization signatures and root traits of different fine root systems (maize, pinto bean, black bean, and soy bean) under hydroponic conditions. RESULTS: Our results show that, with the use of an optimized data acquisition scheme, sEIT is capable of providing spatially resolved information on root biomass and root surface area for all investigated root systems. We found strong correlations between the total polarization strength and the root biomass ( R 2 = 0.82 ) and root surface area ( R 2 = 0.8 ). Our findings suggest that the captured polarization signature is dominated by cell-scale polarization processes. Additionally, we demonstrate that the resolution characteristics of the measurement scheme can have a significant impact on the tomographic reconstruction of root traits. CONCLUSION: Our findings showcase that sEIT is a promising tool for the tomographic reconstruction of root traits in high-throughput root phenotyping trials and should be evaluated as a substitute for traditional, often time-consuming, root characterization methods.

Cover crops have many simultaneous roles that enhance the sustainability of agriculture compared to leaving land fallow in arable systems. In high rainfall climates, an important role of cover crops is to sequester nutrients, protecting them from loss to the environment. In many livestock intensive regions, organic manures are applied in autumn with land left fallow over winter and then a cash crop is planted in the spring. This practice of extended fallow, combined with the poorly synchronised application of nutrients to cash crop nutrient demand, further adds to the potential for large losses of nutrients specifically nitrogen (N) to the environment through leaching and volatilization. Therefore, if cover crops could respond to these nutrients through increased biomass growth and nutrient uptake, they could reduce these losses. Therefore, it is important to choose the correct species which grows adequately to deliver these potential benefits. In the region this study is conducted, Northern Ireland, there has been little research to investigate not only what optimum cover crop species are but also what species could respond to additional nutrients in the slurry. This study comprises two experiments, in consecutive years, including a combination of three factors: cover crop species (five species; a mixture and a control representing fallow); pig slurry. Consequently, it was found that with good growing conditions, in the trial year of 2018/19, species such as forage rape and tillage radish could significantly (p < 0.05) increase the amount of N contained in their biomass and the soil (to 15 cm) by 70 and 63%, respectively, in response to slurry. Alternatively, when slurry was applied to fallow land (conventional practice), low amounts (14 and 0% in the two trial years, respectively) of the N from the slurry were detected in weed biomass or retained in the soil. This demonstrates a large loss of N from the system. Thus, the integration of responsive cover crops with slurry is a better practice to abate N loss than conventional practice, if slurry applications can not be delayed. [ABSTRACT FROM AUTHOR]

In Brazil due to the establishment of new orchards, olive seedling production is growing strongly, while the use of biostimulants in agriculture has been gaining attention due to their benefits in root formation and nutrient absorption. This study evaluated the use of biostimulants for promoting the growth of 3-month-old rooted olive seedlings in pots and to assess the nursery quality of the seedlings. Rooted cuttings of Arbequina, Maria da Fé, and Ascolano 315 cultivars were treated with Azospirillum brasilense (Az) and humic substances (HS), alone and in combination. Growth parameters, such as height and stem diameter, were measured every month and after 150 days, seedlings per treatment were also analysed for aerial and root fresh and dry biomasses. Arbequina exhibited the highest growth rate with Az and best absolute growth rate with Az + HS treatment. The total dry matter of the olive seedlings, comprising both the aerial and root part, was influenced by both Azospirillum brasilense and humic substances, enhancing nitrogen availability. The three treatments showed their positive effects on aboveground growth and overall plant vigour. Despite increased biomass, treated olive seedlings showed no significant height advantage over controls, suggesting that the effects may appear in later developmental stages. [ABSTRACT FROM AUTHOR]

Abstract Buckwheat is an important nutritional and nutraceutical crop; however, owing to its low yield and productivity, its potential has not been harnessed on account of its cultivation in low-input marginal farming systems, where its productivity is limited by various abiotic stresses, including water stress. Roots play a critical role in plant growth, development, and tolerance to drought stress. The present study was the first comprehensive attempt to understand the root system architecture (RSA) of buckwheat using root morphology and in-depth features of RSA through root scanning. A total of 117 diverse genotypes of buckwheat, comprising both common and Tartary buckwheat, were cultivated in polyvinyl chloride columns in the greenhouse. The study revealed substantial variability for all the root and shoot traits of buckwheat. Comparative analysis indicated that Tartary buckwheat has better root features compared to common buckwheat. The correlation analysis showed the surface area, medium root length, and medium root volume were positively correlated and branching frequency and root shoot ratio were negatively correlated. The study identified potential genotypes with robust RSA that can be used for the development of climate-resilient buckwheat varieties.

Societal Impact Statement Free‐air CO2 enrichment (FACE) experiments provide essential data on forest responses to increasing atmospheric CO2 for evaluations of climate change impacts on humanity. Understanding and reducing the uncertainty in the experimental results is critical to ensure scientific and public confidence in the models and policy initiatives that derive therefrom. One source of uncertainty is the estimation of tree biomass using mathematical relationships between biomass and easily obtained and non‐destructive measurements (allometry). We evaluated the robustness of the allometric relationships established at the beginning of a FACE experiment and discuss the challenges and opportunities for the new generation of FACE experiments. Summary Long‐term field experiments to elucidate forest responses to rising atmospheric CO2 concentration require allometric equations to estimate tree biomass from non‐destructive measurements of tree size. We analyzed whether the allometric equations established at the beginning of a free‐air CO2 enrichment (FACE) experiment in a Liquidambar styraciflua plantation were still valid at the end of the 12 year experiment. Aboveground woody biomass was initially predicted by an equation that included bole diameter, taper, and height, assuming that including taper and height as predictors would accommodate changes in tree structure that might occur over time and in response to elevated CO2. At the conclusion of the FACE experiment, we harvested 23 trees, measured dimensions and dry mass of boles and branches, and extracted and measured the woody root mass of 10 trees. Although 10 of the harvested trees were larger than the trees used to establish the allometric relationship, measured aboveground woody biomass was well predicted by the original allometry. The initial linear equation between bole basal area and woody root biomass underestimated final root biomass by 28%, but root biomass was just 21% of total wood mass, and errors in aboveground and belowground estimates were offsetting. The allometry established at the beginning of the experiment provided valid predictions of tree biomass throughout the experiment. New allometric approaches using terrestrial laser scanning should reduce an important source of uncertainty in decade‐long forest experiments and in assessments of centuries‐long forest biomass accretion used in evaluating carbon offsets and climate mitigation.

This study highlights the potential of grass–legume intercropping systems in enhancing soil carbon sequestration and cycling nutrients, providing ecological support for sustainable agriculture. This study evaluated the chemical composition and root biomass of signal grass (Urochloa decumbens cv. Basilisk) pasture grown in monoculture or intercropped with forage peanut (Arachis pintoi cv. Belmonte) under different row spacings (40, 50, 60, 70, and 80 cm), 4–5 years after establishment. The experiment was conducted in a randomized block design with four replicates under intermittent sheep grazing. Results (p < 0.05) indicated that root biomass was higher in the intercropped pastures (6752 to 11,167 kg OM ha−1) than in the monoculture (3696 kg OM ha−1). Carbon (C) and N stored in root biomass were also influenced by the row spacings, with narrower spacings, particularly 40 cm (1282 kg C ha−1) and 50 cm (1424 kg C ha−1), showing higher C storage than in the monoculture (509 kg C ha−1). Similarly, the 40 cm (122 kg N ha−1) and 50 cm (138 kg N ha−1) spacings showed higher N accumulation in root biomass than the monoculture (38.9 kg N ha−1). These spacing also reduced C/N and lignin/ADIN ratios, which enhanced nitrogen cycling efficiency. Based on these results, 40 and 50 cm spacings are recommended for intercropped pastures, as they optimize C and N accumulation and nutrient cycling, and support sustainable pasture management. [ABSTRACT FROM AUTHOR]

Soil respiration is an important pathway of carbon release from the terrestrial biosphere to the atmosphere, which plays a key role in ecosystem carbon cycling. However, the response and mechanism of soil respiration to nitrogen and phosphorus addition in legume plants are still unclear. Here, a pot experiment planted with soybean (Glycine max (L.) Merr.) was conducted to investigate the effects of nitrogen (N) and phosphorus (P) addition on soil respiration. Four treatments were designed: control, N addition, P addition, and both N and P addition. Soil respiration was measured twice a month from June to September in 2022. Our results showed that nutrient addition treatments presented significantly negative effects on soil respiration. In particular, nitrogen addition not only directly affected soil respiration, but also indirectly impacted soil respiration by altering soil nitrate nitrogen content. Elevated soil nitrate nitrogen content could inhibit soybean root nodule number and reduce biomass allocation to roots, thereby decreasing soil respiration. Furthermore, phosphorus addition and nitrogen–phosphorus co-addition strongly inhibited soybean nodulation by changing soil pH value, thus inhibiting soil respiration of soybean. The findings provide baseline information for optimizing nutrient management in legume crops. [ABSTRACT FROM AUTHOR]

Buckwheat is an important nutritional and nutraceutical crop; however, owing to its low yield and productivity, its potential has not been harnessed on account of its cultivation in low-input marginal farming systems, where its productivity is limited by various abiotic stresses, including water stress. Roots play a critical role in plant growth, development, and tolerance to drought stress. The present study was the first comprehensive attempt to understand the root system architecture (RSA) of buckwheat using root morphology and in-depth features of RSA through root scanning. A total of 117 diverse genotypes of buckwheat, comprising both common and Tartary buckwheat, were cultivated in polyvinyl chloride columns in the greenhouse. The study revealed substantial variability for all the root and shoot traits of buckwheat. Comparative analysis indicated that Tartary buckwheat has better root features compared to common buckwheat. The correlation analysis showed the surface area, medium root length, and medium root volume were positively correlated and branching frequency and root shoot ratio were negatively correlated. The study identified potential genotypes with robust RSA that can be used for the development of climate-resilient buckwheat varieties. [ABSTRACT FROM AUTHOR]

Societal Impact Statement: Free‐air CO2 enrichment (FACE) experiments provide essential data on forest responses to increasing atmospheric CO2 for evaluations of climate change impacts on humanity. Understanding and reducing the uncertainty in the experimental results is critical to ensure scientific and public confidence in the models and policy initiatives that derive therefrom. One source of uncertainty is the estimation of tree biomass using mathematical relationships between biomass and easily obtained and non‐destructive measurements (allometry). We evaluated the robustness of the allometric relationships established at the beginning of a FACE experiment and discuss the challenges and opportunities for the new generation of FACE experiments. Summary: Long‐term field experiments to elucidate forest responses to rising atmospheric CO2 concentration require allometric equations to estimate tree biomass from non‐destructive measurements of tree size. We analyzed whether the allometric equations established at the beginning of a free‐air CO2 enrichment (FACE) experiment in a Liquidambar styraciflua plantation were still valid at the end of the 12 year experiment.Aboveground woody biomass was initially predicted by an equation that included bole diameter, taper, and height, assuming that including taper and height as predictors would accommodate changes in tree structure that might occur over time and in response to elevated CO2. At the conclusion of the FACE experiment, we harvested 23 trees, measured dimensions and dry mass of boles and branches, and extracted and measured the woody root mass of 10 trees.Although 10 of the harvested trees were larger than the trees used to establish the allometric relationship, measured aboveground woody biomass was well predicted by the original allometry. The initial linear equation between bole basal area and woody root biomass underestimated final root biomass by 28%, but root biomass was just 21% of total wood mass, and errors in aboveground and belowground estimates were offsetting.The allometry established at the beginning of the experiment provided valid predictions of tree biomass throughout the experiment. New allometric approaches using terrestrial laser scanning should reduce an important source of uncertainty in decade‐long forest experiments and in assessments of centuries‐long forest biomass accretion used in evaluating carbon offsets and climate mitigation. [ABSTRACT FROM AUTHOR]

Optimal root system architecture (RSA) is critical for efficient resource capture in soils, hence being an interest in crop breeding. Seminal root angle (SRA) at the seedling stage in durum wheat has been suggested to be a good indicator of RSA. However, research on correlating such laboratory‐based seedling root phenotyping to RSA at later phases of plant growth is limited, resulting in the importance of root trait variation seen in seedlings often being overstated. To explore the role of SRA in modifying RSA at later phases of plant growth, we assessed 11 genotypes contrasting in SRA (wide and narrow), grown in a rhizobox designed for phenotyping root systems of plants during late‐tillering. Aboveground traits and root dry mass in different soil depths and across the entire soil volume were measured manually, while root architectural traits were extracted using image analysis and summarised by multiple factor analysis to describe RSA. When comparing the wide and narrow genotypes, no differences were detected for aboveground traits and total root dry mass. However, differences were observed in the allocation of root dry mass at different depths. The wide and narrow genotypes showed distinct RSAs, particularly in the upper soil (0–30 cm). The wide genotypes exhibited a 'spread‐out' root system with dense and thin roots, whereas the narrow genotypes had a compact root system with fewer but thicker roots. Our study demonstrated a clear difference in RSA between the wide and narrow genotypes, highlighting the association between SRA on the direction and distribution of root growth in plants at later growth stages. [ABSTRACT FROM AUTHOR]

In Brazil due to the establishment of new orchards, olive seedling production is growing strongly, while the use of biostimulants in agriculture has been gaining attention due to their benefits in root formation and nutrient absorption. This study evaluated the use of biostimulants for promoting the growth of 3-month-old rooted olive seedlings in pots and to assess the nursery quality of the seedlings. Rooted cuttings of Arbequina, Maria da Fé, and Ascolano 315 cultivars were treated with Azospirillum brasilense (Az) and humic substances (HS), alone and in combination. Growth parameters, such as height and stem diameter, were measured every month and after 150 days, seedlings per treatment were also analysed for aerial and root fresh and dry biomasses. Arbequina exhibited the highest growth rate with Az and best absolute growth rate with Az + HS treatment. The total dry matter of the olive seedlings, comprising both the aerial and root part, was influenced by both Azospirillum brasilense and humic substances, enhancing nitrogen availability. The three treatments showed their positive effects on aboveground growth and overall plant vigour. Despite increased biomass, treated olive seedlings showed no significant height advantage over controls, suggesting that the effects may appear in later developmental stages.

Cover crops have many simultaneous roles that enhance the sustainability of agriculture compared to leaving land fallow in arable systems. In high rainfall climates, an important role of cover crops is to sequester nutrients, protecting them from loss to the environment. In many livestock intensive regions, organic manures are applied in autumn with land left fallow over winter and then a cash crop is planted in the spring. This practice of extended fallow, combined with the poorly synchronised application of nutrients to cash crop nutrient demand, further adds to the potential for large losses of nutrients specifically nitrogen (N) to the environment through leaching and volatilization. Therefore, if cover crops could respond to these nutrients through increased biomass growth and nutrient uptake, they could reduce these losses. Therefore, it is important to choose the correct species which grows adequately to deliver these potential benefits. In the region this study is conducted, Northern Ireland, there has been little research to investigate not only what optimum cover crop species are but also what species could respond to additional nutrients in the slurry. This study comprises two experiments, in consecutive years, including a combination of three factors: cover crop species (five species; a mixture and a control representing fallow); pig slurry. Consequently, it was found that with good growing conditions, in the trial year of 2018/19, species such as forage rape and tillage radish could significantly (p < 0.05) increase the amount of N contained in their biomass and the soil (to 15 cm) by 70 and 63%, respectively, in response to slurry. Alternatively, when slurry was applied to fallow land (conventional practice), low amounts (14 and 0% in the two trial years, respectively) of the N from the slurry were detected in weed biomass or retained in the soil. This demonstrates a large loss of N from the system. Thus, the integration of responsive cover crops with slurry is a better practice to abate N loss than conventional practice, if slurry applications can not be delayed.

Understanding changes in root traits of high-yielding genotypes that consistently perform during different drought periods is crucial for improving wheat production and yield stability. A 2-year field trial and a pot experiment were conducted to determine the response of root growth and grain yield to early and terminal droughts in old and modern cultivars (FC3: 1960s and CH1: 2010s) under rainfed and irrigated conditions in the field. Rainfed wheat faced terminal drought in 2015–2016 and early drought in 2016–2017. Plants in the pot experiment were exposed to terminal drought, early drought, and well-watered. Both field and pot experiments showed higher grain yield in modern cultivar CH1 compared to FC3. Early and terminal droughts reduced grain yield in both cultivars, with a greater reduction in FC3. CH1 exhibited higher yield stability under drought conditions and experienced less reduction in early drought. Compared to FC3, CH1 produced more root biomass in the early growth stage. At anthesis, CH1 had significantly lower root biomass and root length density in the topsoil layer (00.2 m) and higher in the subsoil layer (0.21.0 m) than FC3, respectively. At maturity, the retention rate of subsoil root biomass in CH1 was higher, especially under early drought (80.2 % in field and 93.9 % in pot experiments). Both cultivars consumed similar seasonal water use, but CH1 reduced pre-anthesis water use and consumed more water after anthesis. This study indicates that modern cultivar had vigorous root growth at early stage. A higher proportion of root biomass preserved in deep soil after anthesis enhanced post-anthesis water use and photosynthetic rate, improved post-anthesis dry matter accumulation, and thus resulted in higher thousand kernel weight. These factors ensure higher yield and yield stability under both early and terminal drought stress.

Soil structure is important for plant growth and ecosystem functioning, and provides habitat for a wide range of soil biota. So far, very few studies directly compared the effects of three main farming practices (conventional, organic and conservation agriculture) on soil structure and soil physical properties. Here, we collected undisturbed soil cores from the FArming System and Tillage long-term field experiment (FAST) near Zurich (Switzerland). This trial compares the effects of conventional tillage, conventional no-tillage, organic tillage and non-inversion reduced tillage under organic farming since 2009. We assessed 28 soil chemical and physical properties and related them to root and microbial biomass as well as to the diversity of bacteria and fungi. Tillage decreased bulk density (−14 %) and penetration resistance (−40 %) compared to no/reduce-tillage, potentially promoting a facilitative environment for plant root growth. Water holding capacity varied among systems, being the lowest in conventional tillage and highest (+10 %) in organic reduced tillage. We observed that microbial biomass and rhizosphere microbial diversity was positively associated with water holding capacity and the occurrence of mesopores. The presence of mesopores could provide additional niche space for microbes possibly explaining its positive effect on microbial diversity. Soil microbial biomass and rhizosphere microbial diversity were higher in plots subjected to soil conservation practices, indicating that tillage has a detrimental effect on soil microbes. Our work demonstrates that organic, conventional and conservation agriculture create contrasting soil physical environments. This work highlights the trade-off between creating a facilitative environment for root growth by tillage and maintaining complex and diverse soil microhabitats for microbes under conservation agriculture.

The potential of Leersia hexandra grass in phytoremediation and natural attenuation of three groups of bacteria in soil contaminated with crude oil was evaluated for 180 days. The quantities of new shoots, root and aerial biomass were evaluated; changes in antioxidant concentrations in leaf and root caused by abiotic stress; population densities of Azotobacter, Azospirillum and Pseudomonas; and microbial respiration. The experimental data showed oil-induced increases of 315% and 196% in new shoots and root phytomass, respectively, and a 44% decrease in leaf + stem phytomass. The enzymatic defence in the grass leaf was manifested by higher concentrations of hydrogen peroxide, phenylalanine ammonium lyase and total flavonoids; the increases fluctuated from 35% to 52%. The response in the root was positive in catalase (16%), and in ammonium phenylalanine lyase, it increased 275% due to the effect of crude oil. The group of indigenous Azotobacter bacteria were tolerant to crude oil exposure, both in the phytoremediation process and in natural attenuation; the population densities varied from 212 to 438 × 103 colony-forming units (CFUs); they are greater than 49% to 106% compared to densities in control soil. Azospirillum spp. and Pseudomonas spp. recorded population abiotic stress. The grass activates enzymatic and plant defence, complementing microbial respiration in response to adaptation to crude oil.

Estimation of carbon (C) stocks revealed a very high carbon sequestration potential of mangroves, which play a major role in the global C cycle. The C stored in the biomass of live trees can be estimated from above- and below-ground measurements, i.e., tree diameter and height, leaf litter, root biomass, necromass, and soil. The allocation of biomass and C in the scrub mangrove forest is influenced by various factors, including low structural development. The objective of this study was to estimate the carbon stock (in relation to biomass) and storage in the soil of the San Ignacio and El Dátil lagoons in an arid region of the north Pacific. Above-ground biomass (AGB) was estimated based on mangrove structure and leaf litter; below-ground biomass (BGB) was measured by extracting root cores (45 cm depth) and soil (1.2 m depth). Biomass values were converted to carbon with allometric equations. We found an inverse relationship between BGB content (roots) and above-ground structural development, with a mean total biomass (AGB + BGB) of 101.7 MgC ha−1. Below-ground carbon content (roots, necromass, and soil) was 2.8 times higher than above-ground carbon content (trees and litter). Control sites (devoid of vegetation) adjacent to the mangrove have recorded low carbon stocks of 7.3 MgC ha−1, which supports the recommendations for conserving and restoring degraded areas. The present study contributes valuable information on carbon related to mangrove biomass and stored in the soil of arid mangrove areas of northwestern Mexico.

Soil CO2 and CH4 concentrations are crucial determinants of crop physiology and the soil environment. However, the intricate relationships among soil respiration, soil nutrients, enzyme activities, and winter wheat growth in the presence of shallow groundwater remain enigmatic. This study aimed to investigate the dynamics of soil CO2 and CH4 concentrations and their correlations with soil nutrient content, enzymatic activities, and wheat root biomass to better understand the influence of shallow groundwater on soil environmental conditions. Lysimeter experiments were conducted at five groundwater depths (20, 40, 50, 60, and 80 cm) and three fertilizer application rates (low, 75%; normal, 100%; high, 125%). Soil CO2 (soil layer > 10 cm) and CH4 concentrations significantly decreased with increasing groundwater depth. The maximum values of root parameters and shoot biomass were mainly concentrated at 50–60 cm at the high fertilization level (except root length density, which was higher at the normal fertilization level), and were 0.36–77.4% higher than other treatments. Soil CO2 concentration showed positive correlations with organic matter and total N content, enzyme activities, and root biomass. Soil CH4 concentration had significant correlations with soil organic matter, total N, and available K. Compared to the fertilization level, groundwater depth emerged as a crucial factor as it affected soil physicochemical properties, soil enzymatic activities, root respiration, and winter wheat growth in shallow groundwater. [ABSTRACT FROM AUTHOR]

This article is an editorial that highlights the ecological links between aboveground and underground ecosystems. It emphasizes the importance of studying the interactions between these systems in the context of global environmental changes. The editorial presents a compilation of six articles that cover various topics, including the effects of radiation on soil microbial communities, the relationship between leaf dry mass and leaf age, the impact of non-native species on native ecosystems, the phenotypic plasticity of trees in response to climate change, the nesting behaviors of birds in urban greenspaces, and the influence of plant diversity on root biomass. The article concludes by emphasizing the complexity and interconnectedness of aboveground and underground ecosystems and the need for multidisciplinary research and conservation strategies to address environmental challenges. [Extracted from the article]

The potential of Leersia hexandra grass in phytoremediation and natural attenuation of three groups of bacteria in soil contaminated with crude oil was evaluated for 180 days. The quantities of new shoots, root and aerial biomass were evaluated; changes in antioxidant concentrations in leaf and root caused by abiotic stress; population densities of Azoto-bacter, Azospirillum and Pseudomonas; and microbial respiration. The experimental data showed oil-induced increases of 315% and 196% in new shoots and root phytomass, respectively, and a 44% decrease in leaf + stem phytomass. The enzymatic defence in the grass leaf was manifested by higher concentrations of hydrogen peroxide, phenylalanine ammonium lyase and total flavonoids; the increases fluctuated from 35% to 52%. The response in the root was positive in catalase (16%), and in ammonium phenylalanine lyase, it increased 275% due to the effect of crude oil. The group of indigenous Azotobacter bacteria were tolerant to crude oil exposure, both in the phytoremediation process and in natural attenuation; the population densities varied from 212 to 438 x 10³ colony-forming units (CFUs); they are greater than 49% to 106% compared to densities in control soil. Azospirillum spp. and Pseudomonas spp. recorded population abiotic stress. The grass activates enzymatic and plant defence, complementing microbial respiration in response to adaptation to crude oil. [ABSTRACT FROM AUTHOR]

The aims of this study are To clarify soil organic carbon content of each plant community and to provide a theoretical basis for grassland conservation. [Methods]Six plant communities(Stipa breviflora, Koeleria cristata, Leymus chinensis, Stipa krylovii, Convolvulus ammannii, Allium mongolicum) in the enclosed area of Xilamuren Desert Grassland were studied for soil mechanical composition, soil organic carbon content and root characteristics of different plant communities.[Results](1) The soil mechanical composition of soil depth of 0-30 cm in six plant communities was mainly composed of silt and extremely fine sand, with the average values of 26.50%～54.62% and 16.90%～34.08%, respectively.(2) The root biomass of six plant communities gradually decreased with soil depth, and the total root biomass was between 229.21 and 731.71 g/m~2. Judging from characteristics of root distribution, the root distribution of Stipa breviflora was ‘E’ type distribution, and the root distributions other plant communities were ‘V’ type distribution.(3) Soil organic carbon content of six plant communities gradually decreased with soil depth. The average organic carbon content in 0-30 cm ranged from 6.07 to 11.75 g/kg.(4) There was a significant positive correlation between root biomass, soil organic carbon and clay, and a significant positive correlation with silt, indicating that the more soil particles and clay content, the richer the root biomass and soil organic carbon of different plant communities. [Conclusion] Enclosure could effectively promote the increase of soil organic carbon, but organic carbon varied in response to different vegetation communities. The accuracy of grassland organic carbon storage should be determined according to the characteristics of grassland vegetation communities. [ABSTRACT FROM AUTHOR]

Estimation of carbon (C) stocks revealed a very high carbon sequestration potential of mangroves, which play a major role in the global C cycle. The C stored in the biomass of live trees can be estimated from above- and below-ground measurements, i.e., tree diameter and height, leaf litter, root biomass, necromass, and soil. The allocation of biomass and C in the scrub mangrove forest is influenced by various factors, including low structural development. The objective of this study was to estimate the carbon stock (in relation to biomass) and storage in the soil of the San Ignacio and El Dátil lagoons in an arid region of the north Pacific. Above-ground biomass (AGB) was estimated based on mangrove structure and leaf litter; below-ground biomass (BGB) was measured by extracting root cores (45 cm depth) and soil (1.2 m depth). Biomass values were converted to carbon with allometric equations. We found an inverse relationship between BGB content (roots) and above-ground structural development, with a mean total biomass (AGB + BGB) of 101.7 MgC ha-1. Below-ground carbon content (roots, necromass, and soil) was 2.8 times higher than above-ground carbon content (trees and litter). Control sites (devoid of vegetation) adjacent to the mangrove have recorded low carbon stocks of 7.3 MgC ha-1, which supports the recommendations for conserving and restoring degraded areas. The present study contributes valuable information on carbon related to mangrove biomass and stored in the soil of arid mangrove areas of northwestern Mexico. [ABSTRACT FROM AUTHOR]

Summary: The distribution of roots throughout the soil drives depth‐dependent plant–soil interactions and ecosystem processes, particularly in arctic tundra where plant biomass, is predominantly belowground. Vegetation is usually classified from aboveground, but it is unclear whether such classifications are suitable to estimate belowground attributes and their consequences, such as rooting depth distribution and its influence on carbon cycling.We performed a meta‐analysis of 55 published arctic rooting depth profiles, testing for differences both between distributions based on aboveground vegetation types (Graminoid, Wetland, Erect‐shrub, and Prostrate‐shrub tundra) and between 'Root Profile Types' for which we defined three representative and contrasting clusters. We further analyzed potential impacts of these different rooting depth distributions on rhizosphere priming‐induced carbon losses from tundra soils.Rooting depth distribution hardly differed between aboveground vegetation types but varied between Root Profile Types. Accordingly, modelled priming‐induced carbon emissions were similar between aboveground vegetation types when they were applied to the entire tundra, but ranged from 7.2 to 17.6 Pg C cumulative emissions until 2100 between individual Root Profile Types.Variations in rooting depth distribution are important for the circumpolar tundra carbon‐climate feedback but can currently not be inferred adequately from aboveground vegetation type classifications. See also the Commentary on this article by Weber & Iversen, 240: 457–460. [ABSTRACT FROM AUTHOR]

Understanding the phenotypic variability in root system architecture and root-shoot relationships across different growth stages of wheat is of utmost importance for the improvement of genotypes with enhanced nutrient uptake and resource-use efficiency. This study focused on identifying variations and relationships in the root and shoot characteristics of seven modern cultivars and twelve ancient wheat accessions of different species, including T. monococcum, T. turanicum, T. polonicum, T. mirabile, T. durum, and T. aestivum, during the early vegetative growth and stem elongation stages. The results demonstrated significant phenotypic variation among the genotypes for shoot traits, root biomass, rooting depth, R/S ratio, and seminal and nodal root numbers. When considering both growth stages, the dry land-adapted cultivar 'Taner' and ancient wheat species, such as T. turanicum (2) and T. monococcum (1) accessions, exhibited deeper roots, which can enhance access to water in drought-prone areas. Furthermore, it was observed that modern wheat cultivars and T. turanicum accessions exhibited increased root biomass, suggesting a higher allocation of resources towards root growth, which could potentially enhance nutrient uptake. Conversely, T. monococcum accessions and T. mirabile revealed lower root biomass compared to other ancient species and modern cultivars. Additionally, the unrooted cluster analysis based on root biomass, rooting depth, and root to shoot ratio at both growth stages indicated a distinct separation of T. monococcum accessions and T. mirabile from other genotypes. Overall, these findings underscore the importance of phenotypic diversity in root traits for crop improvement and adaptation to varying environments. Identifying genotypes with desirable root characteristics can enhance nutrient and water uptake efficiencies, leading to increased crop productivity and sustainability. [ABSTRACT FROM AUTHOR]

African montane forests harbor some of the greatest biodiversity worldwide, with high levels of species endemism. However, the loss of these forests through fragmentation, deforestation and climate change has been rapidly increasing in recent years. Montane forests in Africa are more susceptible to changes in climate than their lowland counterparts, yet their ecological value is still underrepresented. These montane forests have recently been highlighted as a major aboveground carbon (C) stock. The estimated 149.4 Mg C ha−1 from aboveground live trees surpasses estimates from the Intergovernmental Panel on Climate Change for these endangered forests, and exceeds reported values for neotropical montane and lowland forests by up to 70%. Despite the tremendous implications of these findings, coordinated and available research on the C storage potential of the other share of African montane forest biomass, that is in tree roots, is largely missing. Broadly estimated from the allometry of aboveground C stocks and from root:shoot ratios in lowland forests, more than 60 Mg C ha−1 can be stored in African montane forest roots, about 40% more than previously determined. While this broad estimation points at the potential importance of root C stocks in African montane forests, it also unveils a far-reaching knowledge gap. Here, we advocate for a more quantitative representation of the root C stock from dominant forest tree species of African tropical montane forests and ultimately for a better grasp on tree C stocks from this endangered ecosystem.

Simple Summary: Today, Panax ginseng C. A. Meyer, which has high economic value, is cultivated for the purpose of using the shoot as well as the root, which is better known as the medicinal properties. However, when ginseng is grown outdoors, the quantity and quality of the crop are negatively affected by the climatic environment. In this study, we compared and analyzed the physiological and growth responses of P. ginseng under different LED spectra in a plant factory to achieve continuous and increased productivity. Red and yellow light effectively increased shoot biomass, whereas white light effectively increased root biomass. Furthermore, the intercellular CO2 partial pressure was identified as the most significant physiological variable contributing to root production. Research on light spectra in controlled environments can provide insights into increasing P. ginseng production and contribute to the understanding of the physiological and growth responses of shade-tolerant plants such as P. ginseng. To identify effective light spectra for increasing the productivity of Panax ginseng, we conducted experiments in a controlled environment using a hydroponic cultivation system in a plant factory. We investigated the effect of single LEDs (red, blue, and yellow) and mixed LEDs (red + blue and red + blue + white). The relationships between four light spectra (red, blue, yellow, and white) and physiological responses (net photosynthetic rate, stomata conductance, transpiration rate, and intercellular CO2 partial pressure), as well as growth responses (shoot and root biomass), were analyzed using multivariate statistical analysis. Among the four physiological response variables, shoot biomass was not increased by any pathway, and root biomass was increased only by the intercellular CO2 partial pressure. Red and yellow light increased shoot biomass, whereas white light promoted an increase in the net photosynthetic rate and enhanced root biomass. In contrast, blue light was less effective than the other light spectra in increasing both shoot and root biomass. Therefore, red and yellow light are the most effective light spectra for increasing shoot biomass and white light is effective for increasing root biomass in a plant factory that uses artificial LED lighting. Furthermore, the intercellular CO2 partial pressure is an important physiological variable for increasing the root biomass of P. ginseng. [ABSTRACT FROM AUTHOR]

Aim: This study aimed to infer the allocation of belowground net primary productivity (BNPP) to sequential soil depths down to 2 m across the globe at a 1 km resolution and assess underlying environmental drivers. Location: Global. Time Period: Contemporary (1932–2017). Major Taxa Studied: Terrestrial plants. Methods: Global datasets including field net primary production (NPP, i.e., the difference between plant assimilated and respired carbon) from 725 soil profiles, root biomass and its depth distribution from 559 soil profiles were compiled and used to infer the depth distribution of BNPP across the globe and digitally map depth‐resolved BNPP globally at 1 km resolution. Drivers of the depth distribution of BNPP were evaluated using machine learning‐based models. Results: Global average BNPP allocated to the 0–20 cm soil layer is estimated to be 1.1 Mg C ha−1 yr−1, accounting for ~60% of total BNPP. Across the globe, the depth distribution of BNPP varies largely, and more BNPP is allocated to deeper layers in hotter and drier regions. Edaphic, climatic and topographic properties (in order of importance) explain >80% of such variability; and the direction and magnitude of the influence of individual properties are soil depth‐ and biome‐dependent. Main Conclusions: The findings suggest that mean annual temperature and precipitation are the two most important factors regulating BNPP across the globe. Soil properties such as soil actual evaporation and total nitrogen also play a vital role in regulating the depth distribution of BNPP. The maps of BNPP provide global benchmarks of depth‐resolved BNPP for the prediction of whole‐profile soil carbon dynamics across biomes. [ABSTRACT FROM AUTHOR]

Site class is a quantitative indicator used to evaluate site quality. It reflects site conditions, mainly climate, the suitability of soil for tree species and soil fertility. Despite the economic and ecological importance of tree competition and site class in sustainable forest management, there has been little research on its impact on the stump and coarse root biomass allocation within plantations. The stump and coarse roots were divided into five components ((stump disc (SD), stump knot (SK), coarse roots (>10 cm in diameter) (CR1), medium coarse roots (5–10 cm) (CR2) and fine coarse roots (2–5 cm) (CR3)), and the biomass of each component was obtained via the weighing method. It was found that the biomass of SD, CR1, CR2 and CR3 was mainly affected by competition (p ≤ 0.01). In the three site classes, the biomass of CR3 increased significantly with the increase in the competition index (CI) (p < 0.01); the biomass of CR1 decreased gradually. In site V, the biomass of SK, sapwood and heartwood increased significantly with the increase in CI. The results show that competition affects the allocation of stump and coarse root biomass mainly by changing the coarse root biomass. The development of stump knots is greatly influenced by site class. This study provides a reference for solving the competition mechanism underlying larch wood forest development, which will in turn promote more effective utilization of larch wood forests. This study also provides a scientific basis for accurately estimating the belowground biomass and carbon storage of artificial plantation forests. [ABSTRACT FROM AUTHOR]

We screened four strains (Burkholderia sp. St-A, and Pseudomonas spp. St-B, St-C, and St-D) from 21 bacterial isolates isolated tomato cultivation fields based on their plant growth-promoting traits. Then, tomato (‘Micro-Tom’) seedlings inoculated with each of the four selected strains were grown under non-salinity and salinity (NaCl) treatment conditions. Under non-salinity conditions, St-C and St-D strains increased the total biomass of roots, stems, and leaves and fruit yield. Under NaCl treatment conditions, St-B, St-C, and St-D strains increased total biomass and fruit yield. In roots, Na content was not suppressed, but K, P, and water content were increased by bacterial inoculations. Correlation analysis showed a significant and positive relationship between fruit yield and root under both non-salinity and salinity conditions. This indicates that the maintenance of homeostasis and water relations in roots may contribute to the improvement of plant growth, including root and fruit yield, under salinity conditions.

Stumps and coarse roots form an important C pool and nutrient pool in a Larix olgensis (Larix olgensis Henry) plantation ecosystem, and their decomposition processes would affect nutrient cycling dynamics of the overall Larix olgensis plantation. We studied the decomposition and release of nutrients from stumps and coarse roots that were cleared 0, 6, 16, 26 and 33 years ago in Northeast China. The stumps and coarse roots were divided into stump discs (SD), stump knots (SK), coarse roots (>10 cm in diameter) (CR1), medium-coarse roots (5–10 cm in diameter) (CR2) and fine-coarse roots (2–5 cm in diameter) (CR3). During the entire 33-year study period, SK, CR1, CR2 and CR3 lost 87.37%, 96.24%, 75.76% and 91.98% of their initial mass, respectively. The average annual decomposition rate (k) was 0.068 for SD, 0.052 for SK, 0.092 for CR1, 0.068 for CR2 and 0.066 for CR3. After 33 years of decomposition, CR3 lost 5% of its initial C, CR2 lost 2%, and SK accumulated 1%, indicating slow C release. The N residues in SK, CR1, CR2 and CR3 were 186%, 109%, 158% and 170%, respectively. Coarse roots released P significantly faster than SD and SK, with 13% of the initial P released in CR1. SD and SK release cellulose, hemicellulose and lignin faster than coarse roots. The results show that Larix olgensis stumps and coarse roots could contribute to soil fertility recovery and serve as a long-term nutrient reservoir for forest vegetation. [ABSTRACT FROM AUTHOR]

Species mixtures have been widely reported to increase aboveground productivity; however, how tree species mixtures affect root systems in natural forests remains unclear. We hypothesize that mixtures have a greater fine root length compared to single species‐dominated stands to support their greater productivity.Here, we collected monthly root images from the minirhizotrons installed in 18 stands either dominated by Populus tremuloides, Pinus banksiana, and their mixtures for three years (2015–2017) in post‐fire boreal forests of two stand ages (8 and 34 years old) to test our hypotheses.We found that the fine root length was higher in mixtures than in single species‐dominated stands, and the magnitude of mixture effects was greater in the 34‐ than in the 8‐year‐old stands in the third year. The mixture effects on fine root length revealed a positive relationship with forest net primary productivity. Root length production, which is the growth of new roots within a year, was not affected by tree species mixtures except for the 8‐year‐old stand in 2015. Tree species mixtures did not affect root length turnover. Root length and root biomass were not significantly correlated at stand level.Synthesis. Our results show that tree species mixtures positively affect fine root length, with that positive effect increasing with stand development in the studied natural forests. Our results suggest that the greater root length in species mixtures supported the greater forest productivity in species mixtures as the greater root length benefits plant uptake of nutrients and water. Therefore, conserving tree species diversity has implications for improving forest productivity and carbon sequestration in forest ecosystems. [ABSTRACT FROM AUTHOR]

Deforestation accounts for the majority of greenhouse gas emissions in developing countries. In Brazil, deforestation represents ~ 70% of the nation's greenhouse gas emissions. Among the main deforested vegetation, Cerrado (Brazilian savanna) occupies a prominent position as it is the second biggest biome in Brazil. Despite its importance, there are still few estimates of above and belowground biomass of Cerrado vegetation encompassing its structural and spatial complexity. Also, Cerrado holds a specific biodiversity that is normally undervalued and which is being lost in the fires of agricultural fronts. In this context, this study aimed to verify the relationship of the existing flora biodiversity in a cerrado stricto sensu with its aboveground biomass and carbon stocks. The possibility of a relationship between fine root mass and soil organic carbon content was also verified. The study area presented a total of 67 species and 798 trees (average: 1596 trees ha−1). The mean total aboveground biomass and carbon stocks were 77.08 Mg ha−1 and 38.54 Mg ha−1 respectively. Soil organic carbon stock (0–30 cm) was 8.51 Mg ha−1 whereas fine roots were 1.637 Mg ha−1. Total aboveground biomass presented a highly significant asymptotic relationship with biodiversity demonstrating its importance in reaching high biomass accumulation. A significant relationship between soil organic carbon content and fine root biomass was found making easier belowground biomass estimates. [ABSTRACT FROM AUTHOR]

Roots play an important role in the carbon cycle of ecosystems.The Earth System Models （ESMs） of the Coupled Model Intercomparison Project （CMIP） have been widely used to simulate and predict root biomass.In this paper， the spatial distribution， dynamic change， and comparison with observed values of root biomass of 14 ESMs simulated historical experiments were analyzed.The results showed that： （1） The global distribution of multi-year average from 1850 to 2005 of root biomass indicated that 7 ESMs had maximum or minimum values， while the rest ESMs showed that root biomass was higher in the middle and high latitudes of the equator and the northern hemisphere.The root biomass distribution at different latitudes showed that 40°S is also one of the high value areas； （2） The simulation results from 1995 to 2005 are compared with the site observation data （1990 -2010） in different climatic zones by using SS index， the result showed deviations are relatively large but the simulation effect of temperate zone is slightly better than frigid zone and tropical zone.On the global scale， BCC-CSM2-MR is the best simulated ESM； （3） In the Qinghai-Xizang Plateau， ESMs can reasonably simulate the seasonal variation over the years 1850 to 2005 of root biomass， but the relationship between interannual variation of the simulated root biomass and the meteorological factors （temperature， precipitation） by different ESMs is different.In order to conduct more precise and in-depth research and analysis， in addition to improving the model， it is also necessary to improve the collection of observational data.

Ecological restoration of today's urban soils is a global challenge. Soil quality improvement through groundcover is one of the practical ways in urban ecological restoration practice, and the selection of suitable groundcover types is the key to successful soil ecological restoration. Spontaneous groundcover and lawn, as the two typical urban groundcovers, are mostly used for urban soil restoration. However, few studies have quantified and compared their effects on improving soil quality in urban environments, making it difficult to make scientific choices in practice. Furthermore, the improving mechanism of groundcovers on soil quality is still not quite clear. First, root biomass is commonly considered to be a direct factor affecting soil quality, however, most of the current studies focus on the relationship between a single soil quality index and root mass, and few studies systematically explore the relationship between soil quality index and root mass. Second, species richness and functional group are two main differences in species composition between autochthonous groundcover and lawn, one of which must be the driving factor for the difference in soil improvement effect. At present, there are inconsistent results on whether the driving factors of groundcover for soil quality improvement are species richness or functional groups. In order to explore the above problems, this study sets up a comparative experiment in the urban environment. this study. Twelve typical groundcovers (including six urban groundcovers and six lawns) covering five functional groups (grass (G), forbs (F) and grass (L), G + F and G + F + L) were selected for experiments. Soil quality indicators including nitrogen (N), phosphorus (P), potassium (K), boron (B), iron (Fe), soil organic carbon (SOC), catalase (CAT), root biomass and species richness were tested, and the soil quality index (SQI) reflecting soil quality was calculated. The results showed that the soil quality index (SQI) of autochthonous groundcover was 35 % higher than that of lawn, and the contents of N, P, K and SOC in autochthonous groundcover were significantly higher than those in lawn. N, P, SOC, CAT showed a response to the root mass of groundcovers. Among all the indicators, only CAT was significantly correlated with groundcover species richness, while N, P, K, and SOC were significantly dependent on their functional diversity, and showed significant differences in different functional combinations. This study shows that the improvement effect of urban autochthonous groundcover on soil quality is significantly better than that of lawn. Functional groups may be the driving factors for the change of groundcover soil quality. Different functional groups may affect the root system of groundcover through compensation effect, thus affecting soil quality, which ultimately leads to the difference in the improvement effect of spontaneous groundcover and lawn on soil quality. This study provides a theoretical basis for the application of groundcover and lawn in urban soil ecological restoration in the future. In the practice of ecological restoration, if the goal is to improve soil quality, groundcover will be a more sensible choice than lawn. At the same time, attention should be paid to the diversity of functional groups to maximize the benefits of soil ecological restoration.

Root growth and development of maize (Zea mays L.) is an important process in determining grain yield. The effects of combined fulvic acid (FA, potassium humate as FA source) and super absorbent polymer (SAP) uses on maize root growth and yield were studied. A 2×3 factorial field experiment was applied by combining two SAP doses (0, 45 kg ha-1) and three FA rates (0, 1, and 2 g L-1) over 2 yr. Super absorbent polymer was applied to upper 20 cm soil layer at sowing, and FA solutions (1 or 2 g L-1, corresponding to FA1 and FA2) were sprayed onto the canopy three times during growing season. Root parameters, including root biomass, root length density (RLD), root surface-area density (RSD), and root diameter, were determined in the top 40 cm soil layer. Relative to control plants, both chemicals significantly increased root biomass, but these effects were not significantly different from their combined use. Compared to individual FA or SAP treatment, combined applications increased RLD and RSD in 0-20 cm depth. The combined SAP and FA2 improved RLD at 0-10 cm by 32% compared to FA2 treatment alone and by 82% compared to non-chemicals control plots over 2 yr. Averaged root diameters also significantly increased in the 40 cm soil layer in FA and SAP treatments alone compared to control, but they were not significantly different with the combined treatment. Similar patterns were found for maize yield each year. The combined application of SAP (45 kg ha-1) and FA2 (2 g L-1) greatly increased root length density and biomass than their individual application, and it could be suitable for high production of maize grown under low rainfall conditions. [ABSTRACT FROM AUTHOR]

Background and Aims Polyploids are often hypothesized to have increased phenotypic plasticity compared with their diploid progenitors, but recent work suggests that the relationship between whole-genome duplication (WGD) and plasticity is not so straightforward. Impacts of WGD on plasticity are moderated by other evolutionary processes in nature, which has impeded generalizations regarding the effects of WGD alone. We assessed shifts in phenotypic plasticity and mean trait values accompanying WGD, as well as the adaptive consequences of these shifts. Methods To isolate WGD effects, we compared two diploid lineages of Arabidopsis thaliana wiht corresponding autotetraploids grown across different salt and nutrient conditions in a growth chamber. Key Results For the few cases in which diploids and polyploids differed in plasticity, polyploids were more plastic, consistent with hypotheses that WGD increases plasticity. Under stress, increased plasticity was often adaptive (associated with higher total seed mass), but in other cases plasticity was unrelated to fitness. Mean trait values and plasticity were equally likely to be affected by WGD, but the adaptive consequences of these shifts were often context dependent or lineage specific. For example, polyploids had extended life spans, a shift that was adaptive in one polyploid lineage under amenable conditions but was maladaptive in the other lineage under stress. Conclusions Our work shows that increased phenotypic plasticity can result from WGD alone, independent of other evolutionary processes. We find that the effects of WGD can differ depending on the genotype of the progenitor and the environmental context. Though our experiment was limited to two genotypes of a single species, these findings support the idea that WGD can indeed increase plasticity. [ABSTRACT FROM AUTHOR]

Abstract Background The incorporation of root traits into elite germplasm is typically a slow process. Thus, innovative approaches are required to accelerate research and pre-breeding programs targeting root traits to improve yield stability in different environments and soil types. Marker-assisted selection (MAS) can help to speed up the process by selecting key genes or quantitative trait loci (QTL) associated with root traits. However, this approach is limited due to the complex genetic control of root traits and the limited number of well-characterised large effect QTL. Coupling MAS with phenotyping could increase the reliability of selection. Here we present a useful framework to rapidly modify root traits in elite germplasm. In this wheat exemplar, a single plant selection (SPS) approach combined three main elements: phenotypic selection (in this case for seminal root angle); MAS using KASP markers (targeting a root biomass QTL); and speed breeding to accelerate each cycle. Results To develop a SPS approach that integrates non-destructive screening for seminal root angle and root biomass, two initial experiments were conducted. Firstly, we demonstrated that transplanting wheat seedlings from clear pots (for seminal root angle assessment) into sand pots (for root biomass assessment) did not impact the ability to differentiate genotypes with high and low root biomass. Secondly, we demonstrated that visual scores for root biomass were correlated with root dry weight (r = 0.72), indicating that single plants could be evaluated for root biomass in a non-destructive manner. To highlight the potential of the approach, we applied SPS in a backcrossing program which integrated MAS and speed breeding for the purpose of rapidly modifying the root system of elite bread wheat line Borlaug100. Bi-directional selection for root angle in segregating generations successfully shifted the mean root angle by 30° in the subsequent generation (P ≤ 0.05). Within 18 months, BC2F4:F5 introgression lines were developed that displayed a full range of root configurations, while retaining similar above-ground traits to the recurrent parent. Notably, the seminal root angle displayed by introgression lines varied more than 30° compared to the recurrent parent, resulting in lines with both narrow and wide root angles, and high and low root biomass phenotypes. Conclusion The SPS approach enables researchers and plant breeders to rapidly manipulate root traits of future crop varieties, which could help improve productivity in the face of increasing environmental fluctuations. The newly developed elite wheat lines with modified root traits provide valuable materials to study the value of different root systems to support yield in different environments and soil types.

The physical and mechanical behavior of alpine meadow in Tibetan Plateau is now attracting widespread attention. In this paper, a series of experiments were conducted to study the influence of roots on hydrothermal behavior of alpine meadow located at Nangqian district, in the east of Tibetan Plateau, China. Root biomass, physical properties and hydrothermal properties were measured at a soil depth of 0–25 cm. The results showed that the root biomass within the depth of 0–15 cm accounts for 86% of the total root biomass. With the increase of soil depth, the root biomass shows a decreasing trend. The hydraulic conductivities and thermal conductivities of alpine meadow soil increase with the decrease of root biomass. There are lower hydraulic conductivity and thermal conductivity of swallow soil (0–5 cm) than that of deep layer soil. For the bottom soil layer, swallow alpine meadow acts as a “cap” and plays a function of ecological barrier of reducing water infiltration and heat transfer. Under the background of global warming, this insight is helpful to understand the relationship between soil hydrothermal properties and natural disasters in Tibetan Plateau.

IntroductionSoil organic carbon (SOC) accumulation changed with forest succession and hence impacted the SOC storage. However, the variation and underlying mechanisms about SOC during tropical forest succession are not fully understood.MethodsSoil samples at four depths (0–10 cm, 10–20 cm, 20–40 cm and 40–60 cm), litter, and roots of 0–10 cm and 10–20 cm were collected from three forest succession stages (plantation forest, secondary forest, and old– growth forest) in the Jianfengling (JFL) National Nature Reserve in Hainan Island, China. The SOC, soil enzyme activities, physiochemical properties, the biomass of litter and roots were analyzed.ResultsResults showed that forest succession significantly increased SOC at 0–10 cm and 10–20 cm depth (from 23.00 g/kg to 33.70 g/kg and from 14.46 g/kg to 22.55 g/kg, respectively) but not at a deeper depth (20–60 cm). SOC content of the three forest succession stages decreased with increasing soil depth and bulk density (BD). With forest succession from plantation to secondary and old–growth forest, the soil pH at 0–10 cm and 10–20 cm depth decreased from 5.08 to 4.10 and from 5.52 to 4.64, respectively. Structural equation model (SEM) results showed that the SOC at depths of 0–20 cm increased with total root biomass but decreased with increasing soil pH value. The direct positive effect of soil TP on SOC was greater than the indirect negative effect of decomposition of SOC by soil acid phosphatase (AP).DiscussionTo sum up, the study highlighted there was soil P– limited in tropical forests of JFL, and the increase in TP and total root biomass inputs were main factors favoring SOC sequestration during the tropical forest succession. In addition, soil acidification is of great importance for SOC accumulation in tropical forests for forest succession in the future. Therefore, forest succession improved SOC accumulation, TP and roots contributed to soil C sequestration.

Arbuscular mycorrhizal fungi play an important role in mediating plant-soil interactions across succession stages. However, AMF community dynamics which about the change of community composition and member activity remain unclear. To complete the gap knowledge about microbial community dynamics during restoration succession, soil AMF community composition was studied within a tropical forest ecosystem in the Ganshiling nature reserve using high throughput sequencing methods. The results revealed that soil AMF communities characteristics about speices diversity, species composition and microbial correlation network showed significant differences between shrubland (SC) and secondary forest ecosystems, but the same differences were not found between 40-year recovery secondary forest (SF40) and 60-year recovery secondary forest (SF60). Plant community dynamics were the key factor for regulating soil AMF communities among succession stages. An important biotic factor explaining variance in AMF community composition was root biomass. The correlation network analysis showed that although the nodes were similar among succession stages, the complexity of networks was significant higher in SF40 than in SC and SF60, suggesting that AMF communities were more active in SF40, which verified the hypothesis of intermediate disturbance hypothesis. This study provides new insights into AMF community dynamics and their driving factors across succession stages, as well as expanding knowledge of the ecological value of AMF for tropical forest restoration processes.

Background: The expanding Acacia decurrens woodlots in Northwestern Ethiopia is recognized for carbon storage via root biomass and soil organic carbon (SOC) enhancement but its planting densities have varied considerably. This study evaluated the effect of planting density on the root biomass, SOC stock, and vertical distributions in the stands. Methods: Five planting densities (0.5 m x 0.5 m, 0.75 m x 0.75 m, 1 m x 1 m, 1.25 m x 1.25 m, and 1.5 m x 1.5 m) were replicated four times with randomized complete block design. Soil core (6.67 cm diameter) and pit (900 cm 2 area) methods were used to collect fine and coarse root samples within 0–50 cm soil depth (having five soil layers in 10 cm intervals), respectively. Fine root biomass samples were classified as live and dead (necromass) and further as tree and herbaceous root. All root biomass samples were washed, oven-dried, weighed, and standardized into gram per meter square (g m -2) for root biomass comparisons for each planting density and soil depth, then summed up for 0–50 cm depth as a total root biomass. The vertical distributions of fine and coarse root biomass at each depth were expressed as a percentage (in decimal) of the total root biomass (0–50 cm). Conclusions: Planting density had significant effects on root biomass, SOC stock, and root distributions (P < 0.05) but inconsistent for the percentage of SOC stock at all soil layers except at 40-50 cm. Planting A. decurrens with high density is recommended to increase root biomass, SOC, and percentage of roots in deep soil layers. Further study is suggested for the effects of stand age on root biomass dynamics and SOC stock with large scale.

Root traits are often used to predict the ecological adaptations of plants. Water and nutrient availability together with fragment size are likely to affect the adaptative capacity of Stipa breviflora and help plants spread and explore new sites, while the effects of water, nutrients and fragment size on S. breviflora's root traits have rarely been studied in combination. Here, a standard Taguchi L8(27) array design was conducted with four single factors, water (W), nitrogen (N), phosphorus (P) and fragment size (C), and three interactions (N × P, N × W and P × W). Each of the four factors had two levels (1 = low level and 2 = high level). This study found that water was the most important contributor influencing S. breviflora root growth, followed by N and P, respectively. W2 and P2 additions both promoted root growth, whereas N2 addition significantly inhibited root growth. Though C2 had higher values of total root length, surface area, volume, number of tips and biomass than C1, its root growth rate was lower than C1, and its small size fragment had a higher capacity of root growth under low N addition. These findings suggest that clonal fragmentation may enhance the adaptation of S. breviflora in low nitrogen habitats, and that nitrogen is one of the limiting factors influencing their growth and distribution. [ABSTRACT FROM AUTHOR]

We screened four strains (Burkholderia sp. St-A, and Pseudomonas spp. St-B, St-C, and St-D) from 21 bacterial isolates isolated tomato cultivation fields based on their plant growth-promoting traits. Then, tomato ('Micro-Tom') seedlings inoculated with each of the four selected strains were grown under non-salinity and salinity (NaCl) treatment conditions. Under non-salinity conditions, St-C and St-D strains increased the total biomass of roots, stems, and leaves and fruit yield. Under NaCl treatment conditions, St-B, St-C, and St-D strains increased total biomass and fruit yield. In roots, Na content was not suppressed, but K, P, and water content were increased by bacterial inoculations. Correlation analysis showed a significant and positive relationship between fruit yield and root under both non-salinity and salinity conditions. This indicates that the maintenance of homeostasis and water relations in roots may contribute to the improvement of plant growth, including root and fruit yield, under salinity conditions. [ABSTRACT FROM AUTHOR]

Warming and precipitation reduction have been concurrent throughout this century in most temperate regions (e.g., Northeast China) and have increased drought risk to the growth, migration, or mortality of tree seedlings. Coexisting tree species with different functional traits in temperate forests may have inconsistent responses to both warming and decreased precipitation, which could result in a species distribution shift and change in community dynamics. Unfortunately, little is known about the growth and physiological responses of coexisting species to the changes in these two meteorological elements. We selected two coexisting species in a temperate secondary forest of Northeast China: Quercus mongolica Fischer ex Ledebour (drought-tolerant species) and Fraxinus mandschurica Rupr. (drought-intolerant species), and performed an experiment under strictly controlled conditions simulating the predicted warming (+2°C, +4°C) and precipitation reduction (-30%) compared with current conditions and analyzed the growth and physiology of seedlings. The results showed that compared with the control, warming (including +2°C and +4°C) increased the specific area weight and total biomass of F. mandschurica seedlings. These were caused by the increases in foliar N content, the activity of the PSII reaction center, and chlorophyll content. A 2°C increase in temperature and reduced precipitation enhanced root biomass of Q. mongolica, resulting from root length increase. To absorb water in drier soil, seedlings of both species had more negative water potential under the interaction between +4°C and precipitation reduction. Our results demonstrate that drought-tolerant species such as Q. mongolica will adapt to the future drier conditions with the co-occurrence of warming and precipitation reduction, while drought-intolerant species wi l l accommodate warmer environments. [ABSTRACT FROM AUTHOR]

Shallow slope failures due to erosion are common occurrences along roadways. The use of deep-rooted vegetative covers is a potential solution to stabilize newly constructed slopes or repair shallow landslides. This study compared species that may provide slope stabilization for sites in the Piedmont region of the southeastern USA. Six species were tested on experimental plots under natural rainfall conditions, and vegetation health and establishment were monitored. Two methods were used to measure surface erosion, measurement of total suspended solids in collected runoff and erosion pins. While measurement uncertainty was high for both methods, differences were evident between species in the spatial distribution of surface erosion that was related to the quality of vegetation establishment. For three species that established well, soil cores were collected to measure root biomass at depths up to 40 cm. Vetiver grass (Vetiveria zizaniodies) had substantially higher mean root biomass (3.75 kg/m3) than juniper shrubs (Juniperus chinensis; 0.45 kg/m3) and fescue grass (Lolium arundinaceum; 1.28 kg/m3), with the most pronounced difference in the deepest soil layers. Seeding with turf grass such as fescue is a common practice for erosion control in the region but replacing this with vetiver on steep slopes may help prevent shallow landslides due to the additional root reinforcement. Additional work is needed to measure the magnitude of the strength gain. [ABSTRACT FROM AUTHOR]