Specific Root Surface Area Research Articles

Effects of Precipitation and Soil Moisture on the Characteristics of the Seedling Bank under Quercus acutissima Forest Plantation in Mount Tai, China

Natural regeneration is crucial for the development of sustainable forestry practices in light of the current global climate changes. In this paper, we compared the size distributions of Quercus acutissima seedlings in the understory of Q. acutissima forest plantations in Mount Tai in 2010 and 2017, studied the physiological and morphological responses of seedlings to the microenvironment, and explored the maintenance mechanisms of the seedling bank. The results showed that the density of understory seedlings in 2017 was only 61.63% of that in 2010, especially in the 20–40 cm height class. Between 2011 and 2016, the precipitation and soil water content were the highest in 2011, followed by 2013. The 2–4-year seedlings (height < 40 cm) were not significantly different in seedling biomass, biomass allocation, and root morphology (root total surface area, root volume, and root average diameter), and were significantly different in total root length, specific root length, specific root surface area, and nonstructural carbohydrate content of root, stem, and leaves. However, 5–6-year seedlings (height > 40 cm) showed the largest biomass. Principal component analysis indicated that altering root morphology, nonstructural carbohydrate, and biomass allocation played significant roles in the drought adaptation of seedlings in the understory. In conclusion, drought stress together with seedling adaptation influenced the dynamics of seedling bank in the understory of Q. acutissima plantations.

Root exudation in a sloping Moso bamboo forest in relation to fine root biomass and traits.

Exudation by fine roots generally varies with their morphological traits, but the effect of belowground resource availability on the root exudation via root morphological traits and biomass remains unknown. We aimed to determine the effects of morphological and physiological traits on root exudation rates and to estimate stand-scale exudation (Estand) by measuring the mass, length, and surface area of fine roots in a Moso bamboo forest. We measured root exudation as well as morphological and physiological traits in upper and lower plots on a slope with different belowground resource availability. The mean (± S.D.) root exudation rates per mass in the upper and lower slope were 0.049 ± 0.047 and 0.040 ± 0.059 mg C g-1 h-1, respectively, which were in the range of exudation found in woody forest ecosystems. We observed significant relationships between root exudation per mass and root respiration, as well as specific root length and surface area. In contrast, exudation per length and area did not correlate with morphological traits. The morphological traits did not differ between slope positions, resulting in no significant difference in root exudation per mass. Fine root biomass, length, and surface area on a unit ground basis were much higher in the lower than those in the upper slope positions. Estand was higher when estimated by mass than by length and area because the morphological effect on exudation was ignored when scaled using mass. Estand was 1.4–2.0-fold higher in the lower than that in upper slope positions, suggesting that the scaling parameters of mass, length, and area determined the Estand estimate more than the exudation rate per mass, length, and area. Regardless of scaling, Estand was much higher in the Moso bamboo forest than in other forest ecosystems because of a large fine-root biomass.

Root System Traits and Mechanical Properties of Three Shrub Species: Implications for the Structural Stability of the Ecological Slope

The purpose of this paper is to find the shrub species more suitable to enhance the structural stability of the ecological slope in the study area. Through the investigation, we found three common shrubs, there are Amorpha fruticosa Linn. (AFL), Syringa oblata Lindl. (SOL) and Forsythio mandshurica Uyeki. (FMU). In this study, the root system traits and mechanical properties were characterized and described using reliable experimental approaches. The results shown the root withdrawal force was proportional to diameter (from 0.6-6 mm). The mean specific root length, individual length, surface area, and mean diameter of fine roots in different slopes were higher for AFL and SOL than for FMU, especially for high root orders. Although previous studies have focused on the relevant content, the reinforcement ability of different shrubs is rarely quantitatively compared under the same road conditions. Moreover, the morphology traits of the fine root were considered in this study. These results suggested that the root system traits and mechanical properties of AFL would enable more effective consolidated slopes structure than SOL and FMU, revealing that planting AFL might be a better way for enhancing ecological slope structure stability.

Fine root vertical-seasonal distribution of Robinia pseudoacacia in relation to abiotic factors in a chronosequence in coastal saline alkali land of the Yellow River Delta, China

Despite the recognized importance of the fine roots in influencing tree growth and stand productivity, knowledge of fine roots is still limited, especially in adverse sites like saline-alkali land. In this paper, we applied sequential soil coring to assess the influence of stand age, soil depth and growth month on fine roots in 3, 16, 30 and 40-year old Robinia pseudoacacia stand in coastal saline-alkali land of the Yellow River Delta, China. Besides, the correlations between fine roots characteristics fine root biomass (FRB), fine root length (FRL), fine root surface area (FRSA), specific root length (SRL) and specific root surface area (SRA)) and abiotic factors (temperature, precipitation, soil water content (SWC), soil salt content (SSC) and soil nutrients) were discussed. In this paper, FRB, FRL, FRSA, SWC and soil nutrients increased, while SRL and SSC decreased with increasing stand age. Vertically, fine roots were concentrated in a 0-20 cm soil layer. SRL, SWC and SSC increased, while soil nutrients decreased with increasing soil depth. Temporally, FRB, FRL, FRSA, soil hydrolytic nitrogen and available potassium (AK) shared similar patterns and reached maximum in May or September. In July, SWC, SRL and SRA reached maximum while SSC reached the minimum. Soil total nitrogen (TN) and organic matter (OM) were highest in May or November. Correlation analysis showed that FRB, FRL and FRSA were negatively correlated with SWC and SSC, positively correlated with HN and AK. SRL was positively correlated with temperature, precipitation, SWC and SSC, while negatively correlated with TN. Among abiotic factors, temperature, precipitation and HN played key roles in the study area. This study improves our understanding of the fine roots and belowground ecology of R. pseudoacacia stands in coastal saline-alkali land of the Yellow River Delta.

Differential Variation in Non-structural Carbohydrates in Root Branch Orders of Fraxinus mandshurica Rupr. Seedlings Across Different Drought Intensities and Soil Substrates.

Non-structural carbohydrates (NSCs) facilitate plant adaptation to drought stress, characterize tree growth and survival ability, and buffer against external disturbances. Previous studies have focused on the distribution and dynamics of NSCs among different plant organs under drought conditions. However, discussion about the NSC levels of fine roots in different root branch orders is limited, especially the relationship between fine root trait variation and NSC content. The objective of the study was to shed light on the synergistic variation in fine root traits and NSC content in different root branch orders under different drought and soil substrate conditions. The 2-year-old Fraxinus mandshurica Rupr. potted seedlings were planted in three different soil substrates (humus, loam, and sandy–loam soil) and subjected to four drought intensities (CK, mild drought, moderate drought, and severe drought) for 2 months. With increasing drought intensity, the biomass of fine roots decreased significantly. Under the same drought intensity, seedlings in sandy–loam soil had higher root biomass, and the coefficient of variation of 5th-order roots (37.4, 44.5, and 53% in humus, loam, and sandy–loam soil, respectively) was higher than that of lower-order roots. All branch order roots of seedlings in humus soil had the largest specific root length (SRL) and specific root surface area (SRA), in addition to the lowest diameter. With increasing drought intensity, the SRL and average diameter (AD) of all root branch orders increased and decreased, respectively. The fine roots in humus soil had a higher soluble sugar (SS) content and lower starch (ST) content compared to the loam and sandy–loam soil. Additionally, the SS and ST contents of fine roots showed decreasing and increasing tendencies with increasing drought intensities, respectively. SS and ST explained the highest degree of the total variation in fine root traits, which were 32 and 32.1%, respectively. With increasing root order, the explanation of the variation in root traits by ST decreased (only 6.8% for 5th-order roots). The observed response in terms of morphological traits of different fine root branch orders of F. mandshurica seedlings to resource fluctuations ensures the maintenance of a low cost-benefit ratio in the root system development.

Drought induces shifts in soil fungal communities that can be linked to root traits across 24 plant species.

Root traits respond to drought in a species-specific manner, but little is known about how soil fungal communities and root traits respond to drought in concert. In a glasshouse experiment, we determined the response of soil pathogens, saprotrophs, and mutualistic and all fungi associated with the roots of 24 plant species subjected to drought. At harvest, soil fungal communities were characterized by sequencing. Data on root traits were extracted from a previously published work. Differences in fungal beta diversity between drought and control were plant species specific. For some species, saprotrophic fungi increased in relative abundance and richness with drought, whereas mutualistic fungi showed the opposite pattern. Community structure of pathogenic fungi was plant species specific but was slightly affected by drought. Pathogen composition was correlated with specific root surface area and root:shoot, saprotroph abundance with root tissue density, whereas mutualist composition was correlated with root:shoot. All these were the fungal attributes that best predicted shoot mass. Fungal response to drought depended highly on the fungal group and was related to root trait adjustments to water scarcity. This provides new insights into the role that root trait adjustments to drought may have in modulating plant-fungus interactions in grasslands ecosystems.

Functional root trait‐based classification of cover crops to improve soil physical properties

AbstractCover crop use is a well‐established soil conservation technique and has been proven effective for erosion control and soil remediation in many arable systems. Whereas the obvious protection mechanism of cover crops occurs through the canopy, plant roots perform multiple functions. It is important to consider the soil functions delivered by different root systems in order to increase the uptake of cover crops for sustainable soil and water management. A classification of cover crop root systems up to 0.6 m deep based on functional traits will allow us to better study their potential role in soil bio‐engineering, soil structural improvements for hydrological services and soil resource protection. This was a glasshouse experiment, using large 1‐m3 containers filled with loam soil, loose topsoil and compacted subsoil, in which seven cover crop species (oat, rye, buckwheat, vetch, radish, mustard, phacelia) were grown for 90 days. Root cores were taken at the end of the experiment, washed and imaged to determine root traits (total root length density, average root diameter, root specific length and root surface area) for both the topsoil and subsoil layers. Root identity was determined from a distinctive combination of single root traits and related to three soil functional variables, representing soil structural improvement, runoff mitigation and erosion control. The results showed that total root length and root surface area correlate well with aggregate stability and soil macroporosity. Buckwheat, mustard and rye had significantly greater aggregate stability, as well as 10, 8 and 7% greater microporosity, respectively, at the interface with the compacted layer when compared to the control bare soil. Furthermore, average root diameter negatively correlated with soil macroporosity, indicating that cover crops with a fine root system are more beneficial for creating pore‐space than those with thicker taproots. Selecting cover crop species with the right root traits is therefore crucial to improve soil health.Highlights Roots of cover crops are a largely unexplored frontier for bio‐engineering of agricultural soils. Combinations of root traits were identified that most improve soil characteristics. Cover crops with finer root systems were better at enhancing porosity. Root length and surface area were most important for enhancing soil structure.

Fine root biomass and morphology in a temperate forest are influenced more by the nitrogen treatment approach than the rate

Global nitrogen (N) deposition patterns have profoundly affected the production and morphological structure of fine roots, which in turn changed the distribution of carbon in forests. However, traditional experiments of N addition in forests have ignored the ecological processes in the canopy, such as nitrogen retention, and the effects of these on N deposition and fine root functional traits remain unclear. In this study, we quantified the effects of the canopy (CAN) and understory N addition (UAN) on the biomass and morphology of fine roots in a temperate deciduous forest. Based on the three-way ANOVA, we found that the N treatment approach (CAN vs. UAN; p < 0.05) and sampling time (July, October, and January; p < 0.001) significantly affected the fine root biomass, specific root length, specific root surface area, and root tissue density and diameter. Through the summation of fine root biomass, it was found that CAN treatment increased fine root biomass, while UAN treatment decreased fine root biomass, and canopy N addition at 50 kg ha-1yr−1 (CAN50) significantly increased fine root biomass compared with understory N addition at 50 kg ha-1yr−1 (UAN50) in July and October (p < 0.05). Redundancy analysis (RDA) showed that fine root biomass was most affected by NH4-N and NO3-N in July. There was no consistent response of fine root morphology to the N application method and N addition rate; it was mainly affected by season (p < 0.001). Different results were obtained using different N treatment approaches. The effects of UAN on forest fine root biomass were likely overestimated compared to the effects of CAN. Our experimental results will provide a scientific basis for a more accurate prediction of the impacts of future global N deposition on fine roots in forest ecosystems.

Belowground consequences of converting broadleaf to conifer forest: Comparing the fine root systems of European beech and Scots pine

Planted forests of Scots pine (P. sylvestris L.) and other Pinus species extend over >1.7 million hectares in the Pleistocene lowlands of northern Germany, replacing former broadleaf forests (primarily European beech, Fagus sylvatica L.). This transformation belongs to the world’s largest broadleaf-conifer forest conversions; yet, the belowground consequences of this species shift are poorly studied. Based on root coring, an ingrowth core study and root morphological analyses, we compared (i) the bio- and necromass, productivity and morphology of fine roots in pairs of beech and pine stands and (ii) analyzed the species’ fine root system response to variation in soil properties and climatic conditions across a climate continentality gradient. Fine root biomass was on average 6.5 times higher (237 vs. 37 g m−2) and fine root productivity 1.9 times greater (147 vs. 77 g m−2 yr−1, difference not significant) in beech than pine stands. Beech responded with considerable plasticity in fine root system size and fine root morphology to variation in soil acidity and soil fertility and to the contrasting growing conditions in organic layer and mineral soil, but was not responsive to the climatic gradient. In contrast, pine modified fine root biomass and root morphology in response to precipitation and temperature, but did not respond to soil chemistry and fertility. Pine had a somewhat higher mean fine root diameter and also higher specific fine root surface area than beech, while its fine root tip abundance and mean fine root lifespan were lower than in beech (4 vs. 13 months). We conclude that the conversion of broadleaf (beech) to coniferous (pine) forest is accompanied by marked root system changes, notably the reduction of standing fine root biomass and productivity and an apparently contrasting belowground responsiveness to climatic and edaphic changes, with possible consequences for the trees’ susceptibility to climate-warming and drought.

Root Traits and Mechanical Properties of Three Shrubland Species: Implications for Bioengineered Slope Stability

This study aimed to evaluate the ability of three shrubland species to consolidate slopes using root morphological traits and mechanical properties. The results showed that root tensile force increased and root tensile strength decreased with root diameter (from 0.3 to 5.5 mm) among all study species. Under the same level of root diameter, root tensile force and root tensile strength were highest for Amorpha fruticosa Linn. (AFL), followed by Swida alba Opiz (SAO) and lowest for Lespedeza bicolor Turcz (LBT). The mean branching ratio, root angle, stele to root diameter ratio, specific root length, individual length and surface area, and mean diameter of fine roots in different slopes were higher for AFL and SAO than for LBT, especially for high root orders (the third to fifth root orders). Furthermore, total hyphae length, total hyphae surface area, total hyphae volume, hyphae mean diameter, total glomalin-related soil proteins (GRSP), and easily extractable GRSP in different slopes also were highest for AFL, followed by SAO and lowest for LBT. However, root and mycelium traits had a positive effect on soil cohesion. These results suggested that root traits and mechanical properties of AFL and its impact on soil properties would enable more effective to consolidate slopes than SAO and LBT, revealing that planting AFL might be a better way for enhancing bioengineered slope stability in this study region.

Zinc-biofortified lettuce in aeroponic system

Zinc (Zn) deficiency can be mitigated by several procedures, including food biofortification. Agronomic biofortification is a process that aims to increase the concentration of mineral elements in plants through fertilization. Therefore, the objectives of this study were to evaluate the possibility of producing zinc-biofortified curly lettuce in an aeroponic system and to establish the appropriate zinc dose to be used. The experiment was conducted in a greenhouse under aeroponic system, with the Filó lettuce cultivar. The treatments consisted of four doses of Zn (25, 50, 75 and 100 μmol L−1 of Zn), plus the control (0 μmol L−1 of Zn). The source of Zn used was ZnSO4.7H2O. The experiment was set up in a completely randomized design with four repetitions. The nutrient solution was changed once a week and monitored daily by measuring the pH. Thirty-seven days after transplantation, the following variables were evaluated: fresh shoot mass, dry mass of leaves, stem and root system, Zn concentrations and accumulation in leaves, stem and root, shoot and root system ratio, total root length, specific root surface area and total root volume. No symptoms of Zn toxicity were seen the plants. The greatest accumulation of Zn occurred in the roots, followed by the leaves and stem. Lettuce shoot mass increased to 224.19 g with increasing Zn concentration in the solution to 47.2 μmol. Under the conditions of study, the curly lettuce cultivar can be considered biofortified with 50 μmol L−1 of Zn, without affecting the productive characteristics of the crop.

Plastic responses of fine root morphology and architecture traits to nitrogen addition in ectomycorrhizal and arbuscular mycorrhizal tree species in an evergreen broadleaved forest.

We measured the morphology traits (specific root length, specific root surface area, root tissue density, average root diameter) and architecture traits (root fork, root fork ratio, increase rate of root length, root tip density, root fork density) of fine roots in two mycorrhiza tree species, Castanopsis faberi (ectomycorrhizal) and Schima superba (arbuscular mycorrhizal), in an evergreen broadleaved forest in the middle subtropical zone. Root bags method was used in an in situ nitrogen deposition experiment. The aim of this study was to reveal the differences in the plastic responses of fine root morphology and architecture traits to nitrogen deposition between the different mycorrhizal trees. The plastic responses of specific root length, specific root surface area and root fork to nitrogen addition decreased from the first-order root to the fourth-order root, while root tissue density showed an opposite pattern. Such a result indicated a trade-off between nutrient acquisition and resource maintenance of different fine root orders. Different mycorrhizal tree species adopted diffe-rent adaptation strategies to the variations of soil nitrogen availability. C. faberi adopted an opportuni-stic strategy, which relied on fine root to improve nutrient absorption efficiency, enhanced the capacity of space expansion and in-situ nutrient absorption to focus on rapid nutrient absorption strategy. S. superba did not change fine root morphological traits through the trade-off between nutrient absorption efficiency and root construction cost, but relied more on the complementarity between mycorrhizal fungi and fine root architecture traits for nutrient acquisition. The differences in the cost of maintaining and constructing fine root C between different mycorrhizal trees led to fine root adopting the most suitable nutrient capture strategy.

Linking root traits and soil moisture redistribution under Achnatherum splendens using electrical resistivity tomography and dye experiments

The rooting traits of deep-rooted alpine grasses strongly control the redistribution of soil moisture (i.e., the changes in the soil volumetric water content, ΔSVWC), which is the most important water resource supporting vegetation growth in cold semiarid regions. However, due to the difficulty of developing appropriate methods to characterize the hidden structures of root-soil systems, the linkages between root traits and ΔSVWC remain challenging to detect. This study aims to identify how the roots of Achnatherum splendens (A. splendens) affect soil water infiltration and spatiotemporal variations in the rhizosphere under different root densities and rainfall patterns using electrical resistivity tomography (ERT) and dye experiments, as well as to determine the relationship between root traits and soil water redistribution. Manipulative rainfall experiments 5, 10, 20 and 40 mm simulated rainfall were applied to sample plots with no plants (control), single and double A. splendens plantings (BAS, SAS, DAS, respectively). The results of ERT and the dyeing profiles showed that the roots of A. splendens greatly affected infiltration processes and the soil water distribution. The soil water was vertically and laterally funneled along the roots. In SAS, which had a lower root length density (RLD), the soil water accumulated mainly in the shallow layer (0–20 cm), while in DAS, which had a higher total root mass density (RMD), the soil water mainly infiltrated rapidly into the deep soil (>20 cm), especially during the extreme (40 mm) rainfall event. The temporal increases in soil moisture below 20 cm under DAS were higher than that those under BAS and SAS after rainfall for 2 and 24 h. The RMD, specific root length (SRL), specific root surface area (SSA) and RLD were all negatively and significantly correlated with the ΔSVWC at 0–20 cm. At 20–40 cm, the RMD and RLD were positively and significantly correlated with ΔSVWC, whereas the SRL and SSA showed the opposite trend. These findings provide direct evidence of the linkages between A. splendens root traits and ΔSVWC using ERT and the dye tracing method, and this evidence is important for the development of soil-plant-atmosphere continuum (SPAC) models.

金塔绿洲不同林龄多枝柽柳根系分叉数与分支角度的关系

PDF HTML阅读 XML下载 导出引用 引用提醒 金塔绿洲不同林龄多枝柽柳根系分叉数与分支角度的关系 DOI: 10.5846/stxb201907261581 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（41861009，41461013） Relationship between root forks and branch angle of Tamarix ramosissima at different stand ages in oasis of Jinta County Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:根系构型影响根系空间分布和营养吸收效率，反映了植物适应环境胁迫的生存策略。采用标准化主轴估计（Standardized major axis estimation，SMA）的方法，分析了甘肃金塔北海子国家湿地公园3年生和6年生多枝柽柳（Tamarix ramosissima）根系分叉数与分支角度的异速生长关系。结果表明：随着林龄的增长，湿地群落盖度、高度逐渐增加，多枝柽柳种群的盖度、密度、高度和地上生物量以及根系深度、分叉数、比根长、比表面积、各级根系直径随之增加，根系分支角度和根冠比逐渐减小；多枝柽柳根系分叉数与分支角度回归方程的标准主轴斜率逐渐增大（P<0.05），随着林龄的增长，多枝柽柳根系分叉数的增加速度逐渐大于根系分支角度的生长速度，二者在林龄间呈现出差异化的异速生长关系。随着林龄的增长，多枝柽柳根系构型模式由"扩散型"转变为"紧缩型"，体现了种群应对生境胁迫和竞争的生态适应机制。 Abstract:The root architecture influences root spatial distribution and resorptiton efficiency of nutrients, which may reflect the plant growth strategies to adapt to the environmental stresses. This paper studied the relationship between root forks and branch angle of Tamarix ramosissim at three-year and six-year. The study site was located in Jinta Beihaizi Wetland Park of Gansu Province with the method of standardized major axis estimation (SMA). The height, density and above-ground biomass of the wetland communities were recorded from 5 m×5 m grids at two plots with six replicates. Seventy-two plants of Tamarix ramosissim were selected; the above-ground parts of those plants were cut while the roots were collected by excavating the whole root system, and both were taken back to the lab. In the laboratory, the roots were scanned with Win-RHIZO to measure the root forks and root length. The individual roots was dissected according to the branching order, starting from the distal end of the root system that was numbered as the first order and then increasing sequentially with each branch from the first order to the third order roots. The biomasses of different plots were put in an oven and dried (at 80℃ for 12 h), and then measured. Similarly, the soil moisture content was also measured by oven-drying (at 105 ℃for 24 h). The results showed that with the increasing stand ages, the density, cover, height of the plant community increased, while the root-shoot ratio, root branch angle decreased, the specific cover, density, height, above biomass, root depth, root forks, specific root length and specific root surface area increased, and diameter of different root orders increased. In addition, with the increasing stand ages, the standardized major axis slope of regression equation in the scaling relationships between root forks and branch angle increased (P<0.05). Additionally, the increase speed of the root forks was greater than the growth speed of the root branch angle, and the allometric relationship between root forks and branch angle of Tamarix ramosissima was distinguished at different stand ages. With the increasing stand ages, the root architecture model of Tamarix ramosissima form diffusion to gathering, reflected the mechanism of ecological adaptation under conditions of environmental stresses and competition of the population. 参考文献 相似文献 引证文献

Seedling regeneration techniques affect root systems and the response of Quercus robur seedlings to water shortages

Regenerating oak seedlings by different methods impacts taproot architecture, root-to-shoot allometry and, potentially, soil water use and plant growth under water limitations. In the present study, Quercus robur (L.) seedlings regenerated by four different methods – sowing (acorn-sown seedlings), sowing followed by shoot clipping (coppiced), sowing followed by root-pruning (root-pruned), and container planting with the root plug intact (containerized) – were subjected to four water-shortage regimes – full watering and 75, 50, and 25% of full watering. These treatments were used to test the hypotheses that root morphology, anatomy and biochemistry varied among regeneration methods, and, thus, differentially affected plant responses to water-shortages. For most traits, the response to water shortage of acorn-sown and containerized seedlings was similar, and opposite to that of coppiced and root-pruned seedlings. Water shortage did not change tree allocation to total root biomass among regeneration methods but altered the partitioning between absorptive and structural roots within the root system. Acorn-sown and containerized seedlings produced more pioneer roots, and coppiced and root–pruned seedlings more highly-branched fine roots with greater specific root length and specific root surface area under greater water shortage. Thus, acorn-sown and containerized oaks appeared to be primed for water foraging, and coppiced and root-pruned oaks for water absorption efficiency in response to water shortage. Water shortage caused a reduction in nonstructural carbohydrate concentrations in fine roots of acorn-sown and containerized seedlings and in the taproot of coppiced and root-pruned seedlings. Results generally indicated that seedling response to water limitation depended on the regeneration method, highlighting the importance of root–to–shoot allometry, taproot development, and carbon reserve mobilization for plant functioning under water shortage. Acorn-sown and containerized oaks seedlings might be more suitable for forest regeneration in sites characterized by severe water shortage periods. The reduction of taproot starch reserves under strong water shortage may render root-pruned oak trees more susceptible to topsoil water deficit than acorn-sown trees. This work contributes to understand drought acclimation and to identify the most adequate forestry regeneration practices to adapt forest ecosystems to ongoing climatic changes.

Wind intensity affects fine root morphological traits with consequences for plant-soil feedback effects.

Wind influences the development, architecture and morphology of plant roots and may modify subsequent interactions between plants and soil (plant–soil feedbacks—PSFs). However, information on wind effects on fine root morphology is scarce and the extent to which wind changes plant–soil interactions remains unclear. Therefore, we investigated the effects of two wind intensity levels by manipulating surrounding vegetation height in a grassland PSF field experiment. We grew four common plant species (two grasses and two non-leguminous forbs) with soil biota either previously conditioned by these or other species and tested the effect of wind on root:shoot ratio, fine root morphological traits as well as the outcome for PSFs. Wind intensity did not affect biomass allocation (i.e. root:shoot ratio) in any species. However, fine-root morphology of all species changed under high wind intensity. High wind intensity increased specific root length and surface area and decreased root tissue density, especially in the two grasses. Similarly, the direction of PSFs changed under high wind intensity in all four species, but differences in biomass production on the different soils between high and low wind intensity were marginal and most pronounced when comparing grasses with forbs. Because soils did not differ in plant-available nor total nutrient content, the results suggest that wind-induced changes in root morphology have the potential to influence plant–soil interactions. Linking wind-induced changes in fine-root morphology to effects on PSF improves our understanding of plant–soil interactions under changing environmental conditions.

Root trait responses to drought are more heterogeneous than leaf trait responses

Abstract Drought can strongly modify plant diversity and ecosystem processes. As droughts are expected to intensify in the future, it is important to better understand plant responses to this global driver. Root traits are an overlooked but powerful predictor of plant responses to drought because they are in direct contact with the soil environment and are responsible for taking up nutrients and water. Here, we determine which root traits are sensitive to drought and the magnitude of that response. We also tested whether root trait relationships with shoot biomass are affected by drought and to what extent all these responses depend on plant species identity. To do so, we conducted a glasshouse experiment with 24 plant species grown in pots (10 replicates per species), which included grasses, forbs and legumes. All replicates were well watered during the first month and then half of them were kept under drought (30% water holding capacity [WHC]), with the other half serving as control (70% WHC). After 2 months of treatment, leaf and root traits were measured. Leaf traits had a strong and more uniform response to drought compared to root traits. Root trait responses were variable and differed among plant species. Overall, grasses and several forbs had increased root diameter with drought while forbs had decreased specific root surface area (SRSA) and specific root length (SRL). Increase of root diameter and reduction of root elongation or sacrificing fine roots are different strategies that may promote nutrient and water acquisition, depending on plant species identity. Our results identify changes in root morphological traits as mechanisms to likely tolerate drought and highlight that, although such drought responses are species‐specific, they are phylogenetically clustered. A free Plain Language Summary can be found within the Supporting Information of this article.

Decoupled drought responses of fine-root versus leaf acquisitive traits among six Prunus hybrids

Abstract Aims Predicting drought consequences on forests and fruit crop plantings requires improved understanding of drought responses of both leaf and fine-root resource acquisitive traits (specific leaf area—SLA, specific root surface area—SRA and specific root length—SRL). We hypothesize their responses are coordinated towards integrated plant resource conservation under severe drought. Methods We tested the hypothesis with a greenhouse-based drought experiment on saplings of six Prunus hybrids with a priori known contrasting drought sensitivity. Saplings were subjected to either control (100% field capacity) or severe drought stress treatment (33% evapotranspiration of hybrid-specific control plants). Sample collections were carried out at 30 and at 60 days after the start of treatments, for both control and stressed saplings. Important Findings No hybrid showed concurrent significant decrease of SLA and SRA (or SRL) under severe drought. The fine-root traits of the six hybrids showed two major drought-response scenarios, in particular: (i) increased root tissue density (RTD) and decreased average root diameter without significant change of SRL and (ii) increased RTD and decreased SRL without significant change of average root diameter. Drought responses of leaf gas exchange, SRA, SRL and RTD were closely correlated along a gradient towards resource conservation from control to drought-stressed plants in all hybrids, which was orthogonal to another gradient characterized by a hybrid-dependent decrease of SLA. These findings highlight (i) the multi-dimensionality of root-trait drought responses, (ii) the decoupling between leaf economics and leaf hydraulics and (iii) the covariation of leaf and root hydraulics in terms of trait drought responses. The study contributes to identifying the origin of the multi-dimensionality of root-trait drought response at intraspecific scale, and highlights differential drought–response combinations of leaf and fine-root traits among hybrids to survive under severe soil drought stress.

Root Traits Determine Variation in Nonstructural Carbohydrates (NSCs) under Different Drought Intensities and Soil Substrates in Three Temperate Tree Species

Nonstructural carbohydrates (NSCs) are a key factor in the physiological regulation of plants and can reflect buffering capacity of plants under diverse environmental conditions. The effects of diverse environmental conditions on plant NSCs and tissue or organ scales have been thoroughly studied, but their effects on fine root (root diameter &lt; 2 mm) NSC concentrations are still not completely understood. Our aims were to explore the synergistic fluctuations in root traits and NSC concentrations under diverse environmental conditions. This study was conducted on two-year-old temperate seedling tree species (Juglans mandshurica Maxim., Fraxinus mandshurica Rupr., and Phellodendron amurense Rupr.) with different drought intensities and soil substrates. The specific root length (SRL) and specific root surface area (SRA) were significantly affected by drought intensities and soil substrates, while the root tissue density (RTD) and average diameter (AD) were not significantly affected by water intensities and soil substrates in all three species. The root C, N, and P concentration did not change according to drought stress but were significantly affected by the soil substrates in all three species. Similarly, the soluble sugar (SS) and starch (ST) concentrations were significantly affected by both the drought stress and the soil substrates in all three species. The AD explained 6.8% of the total variations in soluble sugar, while the SRL explains 32.1% of the total variation in starch. The root tip C, N, and P concentrations were not significantly correlated with NSCs under different treatments. The total variations in root tip morphology, chemistry, and NSC concentrations are greater among species than compared to different drought intensities and soil substrates. However, the root NSC concentrations were closely related to root morphological traits (SRL and AD) rather than chemical traits. On the basis of different soil resources, the species with thinner diameters have higher SS concentrations, while those of a thicker diameter have higher ST concentrations.

Growth and Tolerance of Eucalyptus Seedlings in Soil Contaminated by Copper

Abstract Copper damages plants when present in high concentrations in the soil. This study assessed the growth and tolerance of Eucalyptus grandis, E. saligna, E. dunnii, and Corymbia citriodora seedlings in soil contaminated by copper. The experimental design was completely randomized in a factorial scheme (4 × 6), with four eucalyptus species and six copper doses (0, 80, 160, 240, 320, 400 mg kg-1) with eight replications. The experiment was performed in a greenhouse for 120 days. The height, stem diameter, root dry mass and shoot dry mass, root specific surface area, Dickson quality index, and tolerance index were assessed. The results showed that the morphological parameters of the studied eucalyptus species were reduced by the copper doses added in the soil. However, the Corymbia citriodora and the Eucalyptus saligna species had a higher tolerance index to the metal.