Higher Root Density Research Articles

Three-dimensional image analysis specifies the root distribution for drought avoidance in the early growth stage of rice.

Root system architecture (RSA) plays a key role in plant adaptation to drought because deep rooting enables better water uptake than shallow rooting under terminal drought. Understanding RSA during early plant development is essential for improving crop yields, as early drought can affect subsequent shoot growth. Herein, we demonstrate that root distribution in the topsoil significantly impacts shoot growth during the early stages of rice (Oryza sativa) development under drought, as assessed through three-dimensional (3D) image analysis. We used 109 F12 recombinant inbred lines (RILs) obtained from a cross between shallow-rooting lowland rice and deep-rooting upland rice, representing a population with diverse RSA. We applied a moderate drought during the early development of rice grown in a plant pot (25cm height) by stopping irrigation 14 days after sowing (DAS). Time-series RSA at 14, 21, and 28 DAS was visualized by X-ray computed tomography, and subsequently compared between drought and well-watered conditions. Following this analysis, we further investigated drought-avoidant RSA by testing 20 randomly selected RILs under drought conditions. We inferred the root location that most influences shoot growth using a hierarchical Bayes approach: the root segment depth, which positively impacted shoot growth, ranged between 1.7-3.4cm under drought conditions and between 0.0-1.7cm under well-watered conditions. Drought-avoidant RILs had a higher root density in the lower layers of the topsoil compared to the others. Fine classification of soil layers using 3D image analysis revealed that increasing root density in the lower layers of the topsoil, rather than in the subsoil, is advantageous for drought avoidance during the early growth stage of rice.

Yard phytoarchitecture for onsite sanitation of household wastewater containing copper

Copper can be found in various equipment, building materials, and consumer products. When buildings are used, copper can enter wastewater in different ways. It is challenging for occupants to remove copper physically or chemically since they can potentially reduce copper levels through yard phytoarchitecture. This study aims to formulate houseplants' suitability to become decorative plants for the yard phytoarchitecture, simultaneously as onsite sanitation. This study identified the copper deconcentration pathway in wastewater by studying published works-based research. Literature was collected and selected based on recency, accessibility, and the relationship among copper, wastewater, and plants. The study findings show that processing copper by plant has the greatest opportunity to be implemented on a building scale. The yard phytoarchitecture system involves arranging plants in the yard, which serves both as a decorative feature and a way to treat the building's wastewater. It can be used on dry yards or ponds and only requires a small amount of land. The plants used should have low leaf density and high root density. It plays a dual role consisting of onsite sanitation infrastructure and yard aesthetics, which mutually strengthen the environmental health locally and positively effect on a larger scale.

Advancing circular economy for the growth, root development and elemental characteristics of bamboo (Bambusa vulgaris) on galamsey-degraded soil

Landscape restoration of degraded mining sites, crucial for agroecology and carbon farming in Ghana, remains poorly understood and underutilized. Bamboo has historically played a role in restoring such sites, but there is a need to integrate circular economy principles fully into harnessing its ecosystem services potential. In this study, we evaluated the impact of biochar and poultry manure amendments on galamsey-degraded mining sites to operationalize circular economy principles in ecosystem restoration, using Bambusa vulgaris as the test crop.Conducted in the Asikasu mining area of the Amansie Central District of Ashanti, a randomized complete block design (RCBD) experiment was used comprising five treatments: 1) 10 tonnes/ha biochar, 2) 10 tonnes/ha poultry manure, 3) Combined biochar and poultry manure at 10 tonnes/ha each, 4) Galamsey-degraded soil control, and 5) Forest topsoil control. Each treatment and control type was replicated three times. The experiment spanned from February 2020 to March 2021.The combined application of biochar and poultry manure resulted in the highest root density and average root diameter, demonstrating the potential for restoring galamsey-degraded sites to support bamboo-based agroecology. The elemental profiles of the bamboo varied in response to different treatments, indicating differing availabilities of micro- and macro-nutrients in the soil solution following soil amendments.This study underscores the viability of circular economy principles in ecosystem restoration, offering a pathway to sustainable land use and agroecological practices in Ghana's mining-impacted landscapes.

The Optimization of Medium Conditions and Auxins in the Induction of Adventitious Roots of Pokeweed (Phytolacca americana L.) and Their Phytochemical Constituents.

Pokeweed, Phytolacca americana L., is considered a widely spreading invasive plant, while saponin contents accumulated in the roots have pharmaceutical uses, such as rheumatism treatments and anti-inflammation. Adventitious root cultures are an important source of diverse secondary metabolites, which have significant applications in various fields. This study focused on the optimization of parameters for root induction using different medium states and treatments with auxins on a pokeweed leaf. Semisolid and liquid MS (Murashige and Skoog, 1962) media were supplemented with indole-3-butyric acid (IBA) and 1-naphthylacetic acid (NAA) at 0.5, 1, 2, and 4 mg/L. Root growth parameters, e.g., induction percentage, root numbers, length, and weight, were measured to determine the adventitious root induction efficiency. Total phenolic content, total flavonoid content, total saponin content, and antioxidant activity were recorded. Results showed that adventitious roots induced in semisolid MS medium supplemented with 0.5 mg/L NAA exhibited a high density of lateral roots. Appropriate medium state and auxin for adventitious root induction in pokeweed were determined as semisolid medium supplemented with 2 mg/L NAA. Considering phytochemicals, adventitious roots induced in liquid medium containing 0.5-1 mg/L NAA had the highest yield extract percentage. Additionally, adventitious roots cultivated in a liquid medium enriched with 1 mg/L NAA exhibited the highest phenolic and saponin contents. A principal component analysis (PCA) biplot and hierarchical cluster analysis (HCA) heatmap demonstrated different response patterns between semisolid and liquid media applied with NAA. The results of the semisolid media were grouped together due to high expression levels of the root induction parameters, while elevated phytochemical values were observed in the liquid media treatments. The results suggested two different media that provide the highest adventitious root induction efficiency and the greatest phytochemical contents: semisolid medium with 2 mg/L NAA and liquid medium with 1 mg/L NAA, respectively. These culture media can be applied to optimize adventitious root culture of pokeweed and in vitro phytochemical production.

Putting down roots: Afforestation and bank cohesion of Icelandic Rivers

AbstractRiparian vegetation is widely recognized as a critical component of functioning fluvial systems. Human pressures on woody vegetation including riparian areas have had lasting effects, especially at high latitude. In Iceland, prior to human settlement, native downy birch woodlands covered approximately 15%–40% of the land area compared to 1%–2% today. Afforestation efforts include planting seedlings, protecting native forest remnants, and acquiring land areas as national forests. The planted and protected nature of vegetation along rivers within forests provides a unique opportunity to evaluate the various taxa within riparian zones and the channel stabilizing characteristics of the vegetation used in afforestation. We investigated bank properties, sediment textures, and root characteristics within riparian zones along four rivers in forests in Iceland. Bank sediment textures are dominantly sandy loam overlying coarser textures. Undercut banks are common because of erosion of the less cohesive subsurface layer. Quantitative root data indicate that the woody taxa have greater root densities, rooting depths, and more complex root structures than forbs or graminoids. The native downy birch has the highest root densities, with <1 mm roots most abundant. Modeling of added bank cohesion indicates that willow provides up to six times and birch up to four times more added cohesion to the coarse sediment textures comprising stream banks compared to no vegetation. We conclude that planting and protecting the native birch and willow helps to reduce bank erosion, especially where long‐term grazing exclusion can be maintained.

Cover crops affect soybean yield components, but not grain quality

AbstractCover cropping is mainly used to prevent soil erosion, but the effects of individual cover crops on the subsequent soybean [Glycine max (L.) Merr.] are hardly known. Therefore, two annual field trials with 15 cover crop species and bare fallow as control were conducted in semi‐arid East Austria in 2016 and 2017. Cover crops were sown in July in 3‐ × 10‐m plots in a randomized block design with three replicates and were incorporated in mid‐April before soybean were seeded. Cover crop biomass differed between plant species and year (2016, 626 ± 390; 2017, 84 ± 86.1 g m−2). Aboveground cover crop biomass did not affect soybean establishment, but single cover crop species such as ryegrass (Lolium multiflorum Lam. var. westerwoldicum Wittm.), kidney vetch (Anthyllis vulneraria L.), and corn cockle (Agrostemma githago L.) impeded soybean seeding due to high root densities and prevented germination or fostered outbreak of two‐spotted spider mites (Tetranychus urticae Koch). These three cover crops reduced soybean grain yield by 12–84%. Grain yield was a function of grain density m−2 in a three‐way interaction with year and cover crop treatment, but not by plant or pod density. Protein, oil, and sucrose content of soybean were unaffected by cover crop treatments. Overall, with the exception of ryegrass, kidney vetch, and corn cockle, cover crops can be grown ahead of soybean without any yield loss and can be used for their versatile ecosystem services.

Effects of restoration of degraded lands on soils physicochemical properties and adaptability of planted woody species in southwestern Niger

AbstractThis study examines the effects of restoration of degraded lands on soils physicochemical properties and adaptability of planted woody species over a period of 4–6 years. It is based on: (1) Physicochemical analyses of soils (granulometry, calcimetry, and organic matter); (2) measures carried out for the dimensioning of anti‐erosion structures; (3) dendrometric measurements on planted woody species on a density from 96 to 625 plants/ha, and the excavations of their root systems. The soils are characterized by low levels of organic matter (<1%), and no calcium carbonate. Soil tillage through deep sub‐soiling resulted in an improvement in soils quality marked by average proportions of clay (28.3%), silt (27.3%) on the anti‐erosion structures, whereas the control sites are dominated by sand particles (64%) on average. The degradation mechanism of anti‐erosion structures is mainly controlled by natural factors including topography, rainfall, and sand content of the soils with strong positive correlations (; ; respectively). Restoration activities have led to the reconstitution of vegetation cover on degraded soils. Eucalyptus camaldulensis groups showed better adaptation as evidenced by their high structural shape parametres including Lorey's mean height (5.16–8.03 m), and mean crown diameter (1.66–3.3 m) with a tracer‐type root system and high root density (74–88 roots) observed at 30 cm from the main stem. This study provides substantial information on the contribution of erosion control measures and their interactions with soil and vegetation resources. It constitutes a scientific tool that is well‐adapted to the Sahelian (Niger, Mali, Burkina Faso, Chad, Mauritania and Senegal) context indispensable for the implementation of sustainable development strategies. The results thus obtained can be used as a reference for the choice of woody species to be planted according to the toposequence and the nature of the anti‐erosion structures made, with a good control of their durability while taking into account the productivity of the soils.

Contribution of fine roots mechanical property of Poaceae grasses to soil erosion resistance on the Loess Plateau

Plant roots play a key role in soil erosion process, but less studies are focused on analyze the soil erosion resistance in terms of grassland roots mechanical properties. The objective of this study was to examine the root diameter, root density, root tensile strength and soil shear strength for five typical and widely distributed Poaceae grasses in semi-arid regions, thus determine the contribution of roots of artificial grassland to soil erosion resistance. Results showed that the roots of five grasslands were densely distributed in the surface soils (0–10 cm). Bromus inermis had the strongest roots that characterized by the highest average tensile strength (40.2 MPa) The shear strength significantly increased as the vertical stress increased from 50 kPa to 300 kPa, but the degree varied with grassland types. Shear strength was also linearly correlated with root density when vertical pressure reached 300 kPa (p < 0.01, R2 = 0.47), indicating that high root density might help resist extreme external stress. Moreover, Bromus inermis showed a high soil cohesion of 122.7 kPa (next to the highest value of 128.71 kPa in Panicum virgatum). Overall, Bromus inermis showed the highest soil erosion resistance among these five grasslands, could be a good candidate in Poaceae artificial grasslands to improve soil shear strength for topsoil conservation. These findings have potential implications for understanding the contribution of Poaceae grasses’ roots on the topsoil reinforcement, and provide a theoretical basis for artificial grassland establishment on soil erosion resistance on the Loess Plateau.

Effects of stand condition and root density on fine-root dynamics across root functional groups in a subtropical montane forest

Fine roots play key roles in belowground C cycling in terrestrial ecosystems. Based on their distinct functions, fine roots are either absorptive fine roots (AFRs) or transport fine roots (TFRs). However, the function-based fine root dynamics of trees and their responses to forest stand properties remain unclear. Here, we studied the dynamics of AFRs and TFRs and their responses to stand conditions and root density in a subtropical montane mixed forest based on a 2-a root window experiment. Mean (± SE) annual production, mortality, and turnover rate of AFRs were 7.87 ± 0.17 m m−2 a−1, 8.13 ± 0.20 m m−2 a−1and 2.96 ± 0.24 a−1, respectively, compared with 7.09 ± 0.17 m m−2 a−1, 4.59 ± 0.17 m m−2 a−1, and 2.01 ± 0.22 a−1, respectively, for TFRs. The production and mortality of fine roots were significantly higher in high root-density sites than in low-root density sites, whereas the turnover of fine roots was faster in the low root-density sites. Furthermore, root density had a larger positive effect than other environmental factors on TFR production but had no obvious impact on AFR production. Tree species diversity had an apparent positive effect on AFR production and was the crucial driver of AFR production, probably due to a complementary effect, but had no evident impact on TFR. Both tree density and tree species diversity were positively correlated with the mortality of AFRs and negatively related to the turnover of TFRs, suggesting that higher root density caused stronger competition for rooting space and that plants tend to reduce maintenance costs by decreasing TFR turnover. These findings illustrated the importance of root functional groups in understanding root dynamics and their responses to changes in environmental conditions.

C and N stocks in silvopastoral systems with high and low tree diversity: Evidence from a twenty-two year old field study

This paper aimed to quantify the C and N stocks and the natural abundancy of 13C (δ13C) in organic matter fractions of soil, as well as soil labile C, in a long-term experiment (1997–2019) on silvopastoral systems (SSP) with low and high tree diversity in the Mata Atlântica biome. Disturbed and undisturbed soil samples were collected in transects that were perpendicular to the tree rows every five meters (0, 5, 10, and 15 m of distance), at depths of: 0.0–0.10, 0.10–0.30. 0.30–0.60, 0.60–1.0 m. Litterfall, root density, total organic C and N content, δ13C values for particulate organic matter (POM) fractions as well as mineral-associated organic matter (MAOM) and soil labile C, whilst stocks were calculated afterwards. Litterfall production was higher in the high diversity SSP for all distances, except for 5 m from the tree row. In contrast to litterfall, higher root density was observed for the longest tree distances (15 m) in the low diversity system. The high tree diversity SSP increased TOC stocks in the top soil layer (0.0–0.10 m, distances of 0 and 10 m) only and C-MAOM stocks in the surface (0.0–0.10 m, 10 m distance) and subsurface (0.10–0.30 m, 0 m distance). In contrast, total N stocks or stocks associated with MAOM and POM were higher in the high tree diversity system. The increases were of 37, 36 and 63%, respectively, for total N, N-MAOM, and N-POM up to 1 m depth. The smallest δ13C values found close to the tree row (0 and 5 m distances), especially in the high diversity system, indicate the influence organic residue from leguminous tree species, whilst the C4 grass held the highest contribution at the 15 m distance, also in the high diversity system. In general, the high diversity tree silvopastoral system has shown potential at storing most C in the 0.0–0.10 m soil layers only and N up to 1 m depth. Results showed very little shift in total C stocks, but the increased N stocks with the inclusion the legumes trees, which is reflected in a lower C:N ratio of the SOM. The silvopastoral system containing signal grass both legumes trees can be looked at as a viable strategy towards sustaining existing soil C stocks, whilst increasing N stocks and SOM quality.

Adaptation strategy of karst forests: Evidence from the community-weighted mean of plant functional traits.

Conservative survival strategy of plants growing in harsh karst habitats is observed from the view of plant functional traits, such as morphological traits and ecological stoichiometry. However, whether the plant communities in karst forests with high species turnover adopt a conservative strategy remains undetermined. This study comprehensively investigated the characteristics of functional traits of dominant plant species in four forests (i.e. Platycarya strobilacea, Quercus fabri, Quercus variabilis, and Pinus massoniana forests) in a trough‐valley karst watershed in Northern Guizhou Province, Southwestern China to explore the adaptation strategy of karst forests at the community level. At the organ and the species levels, traits differed among species, and the leaf and the bark morphological traits and root C:N:P ecological stoichiometry presented large interspecific variations. At the community level, the P. massoniana forest presented the lowest specific root length and dry matter content and tissue density of roots, branch, twig, and bark; the Q. fabri and the Q. variabilis forests displayed low specific leaf area and high dry matter content and tissue density of roots, branch, and twig; and the Platycarya strobilacea forest exhibited high specific leaf area. The P. massoniana forest was subjected to N and P colimitation, and the three other broad‐leaved forests were limited by P supply. The community‐weighted means rather than the arithmetic means of traits were preferential to represent the trait characteristics at the community level. From the view of plant functional traits at the community level, karst forests develop multiple functional traits like low specific leaf area, high dry matter content and tissue density of leaf, roots, branch, and twig, and decrease N and P investments in leaf for a conservative survival strategy to adapt to harsh habitats.

Root Distribution of Four Tree Species Planted in Living Hedges according to Two Types of Soil and Three Agroforestry Technologies in the Sudano-Sahelian Zone of Cameroon

In the agroforestry systems of sub-Saharan Africa, the vertical and horizontal distribution of tree root biomass according to the soil profile is still poorly documented. The objective of this study is to verify the root distribution of four species of trees established in living hedges, namely, Commiphora kerstingii, Erythrina sigmoidea, Ficus thonningii and Jatropha curcas according to two types of soil (light soil and heavy soil) and three agroforestry technologies (fallows, wooded parks and plantations). The hedges were mostly monospecific in order to facilitate the identification of the roots. The experimental set-up is an entirely random factorial design with two factors. The evaluation of the distribution of tree roots was carried out using the profile method. To determine the different textural classes, a particle size analysis was undertaken in the laboratory. The results obtained show that the number of roots decreases rapidly after 30 cm of depth. The highest root densities are observed in the first 30 cm. Soil type has a slight effect (p &lt;0.05) on rooting density in the last 30 cm of depth for all root classes, higher densities were obtained in light soil compared to heavy soil. Commiphora kerstingii stands out significantly by obtaining a higher number of roots than the other species for all classes. Among the technologies, the plantations showed the lowest root density at 0-5 cm and the highest at 55-60 cm. The root density was higher in the fallows. The results show that the root system is mainly concentrated near the stump.

Nitrogen and residue management effects on performance of happy seeder sown wheat

A field experiment was conducted during rabi 2016-17 and 2017-18 to evaluate the influence of different residue and nitrogen management practices on soil physico-chemical properties, root density, weed growth and grain yield of happy seeder sown wheat. Experiment was conducted in randomized block design consisting of eleven residue and nitrogen management treatments in four replications. The results inferred that weed biomass was significantly less in chopped straw treatments (C) as compared to unchopped treatments (NC). Treatments receiving 150 kg N/ha had higher root density than 125 kg N/ha treatments at all soil depths during both years. Soil physical and chemical properties were not significantly affected but there was improvement in these properties after two years of residue retention. Grain yield (5.42 and 5.36 t/ha) was maximum in treatment where 150 kg N (30 kg at chopping of straw and 120 kg as per recommendation) was applied along with 5 t/ha FYM (C+N30+120+FYM5), which was significantly better than NC + N125, C + N125, C + FYM5 + N125 and C + N20+105 treatments but statistically at par with rest of the treatments.

Root Characteristics and Water Erosion-Reducing Ability of Alpine Silver Grass and Yushan Cane for Alpine Grassland Soil Conservation

In Taiwan, intensive forest fires frequently cause serious forest degradation, soil erosion and impacts on alpine vegetation. Post-fire succession often induces the substitution of forest by alpine grassland. Alpine silver grass (Miscanthus transmorrisonensis Hay.) and Yushan cane (Yushania niitakayamensis (Hay.) Keng f.) are two main endemic species emerging on post-fire alpine grassland. These species play a major role in the recovery of alpine vegetation and soil conservation of alpine grassland. However, their root traits, root mechanical properties and water erosion-reducing ability have still not been well studied. In the present study, root characteristics were examined using a complete excavation method. Root mechanical characteristics were estimated by utilizing the uprooting test and root tensile test, and hydraulic flume experiments were performed to investigate the water erosion-reducing ability using 8-month-old plants. The results show that the root architecture system of Alpine silver grass belongs to fibrous root system, while the Yushan cane has sympodial-tufted rhizomes with a fibrous root system. Root characteristics reveal that relative to Alpine silver grass, Yushan cane has remarkably larger root collar diameter, higher root biomass, larger root volume, higher root density, and a higher root tissue density. Furthermore, uprooting resistance of Yushan cane is notably higher than that of Alpine silver grass. However, the root tensile strength of Alpine silver grass is significantly higher than that of Yushan cane. Additionally, hydraulic flume experiments reveal that Yushan cane has significantly lower soil detachment rates than that of Alpine silver grass. Collectively, these findings clearly show that Yushan cane has superior root characteristics and water erosion-reducing ability than Alpine silver grass and is thus more suitable for the conservation of alpine grassland.

Trade-Off between Root Efficiency and Root Size Is Associated with Yield Performance of Soybean under Different Water and Phosphorus Levels

(1) Background: Root traits play important roles in acclimating to water and phosphorus (P) shortages. However, the relative importance of root size and efficiency under these conditions is unknown. (2) Methods: This study investigated the role of root size and efficiency in acclimating to water- and P-limited environments. Three soybean genotypes with contrasting root sizes were grown in tall cylindrical pots to compare grain yield, root density, and water- and nutrient-uptake efficiencies under two water (well-watered and water-stressed) and three P levels (0 (P0), 60 (P60), and 120 (P120) mg P kg−1 dry soil). (3) Results: Water or P deficit, and combined water and P deficit significantly decreased grain yield, which was associated with greater P uptake per unit root dry weight (DW) under water stress. The genotype Zhonghuang 30 (ZH) with the greatest water, nitrogen, and P uptakes per unit root DW had the highest grain yield at P60 and P120 under water stress and P0 under well-watered conditions, but ZH had the lowest grain yield at P60 and P120 under well-watered conditions, due to its small root size. (4) Conclusions: High root efficiency—which was correlated with high root density—improved grain yield under P- and water-limited conditions, but restricted yield potential when P and water were not limited.

Simulation of palm oil root water uptake by using 2D numerical soil-water flow model.

The lack of water resource in these past decades encourages the implementation of the precision agriculture system towards the sustainability in palm oil plantation. Therefore, it requires a specific information about the palm oil performance regarding the water balance system that affect the water consumption through the plant root water uptake. However, the prediction of root water uptake distribution is still a challenge. Another method to investigate the soil water dynamics under the plant root system is through the numerical simulations that are widely use to assess the soil water flow of the plant. In alignment with the idea of promoting the sustainable palm oil plantation, the investigation of root water uptake and water content under oil palm tree is highly demanding. As an introduction, through this study, it is find of interest to simulate the root water uptake and water content pattern of oil palm tree using the 2D simulation soil-water flow. The study was performed by applying the 2D simulation soil-water flow model to 17th year old oil palm tree located in Siak, Riau with the loam soil type. The climate data was used as primary data to predict the rate of evapotranspiration. The soil properties and root dimension and distribution of oil palm was taken by the literature study. The simulation over 30 days illustrated the root water uptake distribution, water content change, pressure head and flow velocity. The most intensive root water uptake occurred in the upper root zone of oil palm tree as an impact of the higher root density. The significant root water uptake in the upper root zone lead to the decreasing of water content and increasing of pressure head in the soil. Consequently, there was a change of water flow direction from the wet area in the downward and sideward do dry root zone as the water supply to the oil palm tree.

How grazing management can maximize erosion resistance of salt marshes

Abstract Combining natural saltmarsh habitats with conventional barriers can provide a sustainable and cost‐effective alternative for fully engineered flood protection, provided that a minimal salt marsh width can be guaranteed for a long period. Hence, it is essential to understand both the key factors and management options driving the lateral erodibility/stability of salt marshes. We aimed to determine how salt marsh management (i.e. grazing by large vs. small grazers vs. artificial mowing), marsh elevation and marsh age affect soil stability (i.e. soil collapse) and intrinsic lateral erodibility of salt marshes (i.e. particle‐by‐particle detachment). Soil cores were collected in high and low marshes (above and below 0.5 m MHWL, respectively) of different ages. At these locations, we compared cores from grazed areas to cores inside grazer exclosures, with and without artificial mowing. All cores were exposed to waves in flumes to test their stability and lateral erodibility. All soil cores were characterized by a stable fine‐grained layer deposited on top of readily erodible sand. The thickness of the fine‐grained layer was a key parameter in reducing salt marsh instability (cliff collapse). This layer thickness increased with marsh age and at lower elevations, but decreased with cattle grazing due to compaction. The erosion resistance of the fine‐grained layer increased with (a) large grazers that compacted the soil by trampling, (b) mowing that excluded soil‐bioturbating species, and (c) grazing by small grazers that promoted vegetation types with higher root density. Synthesis and applications. Overall, marshes with thinner cohesive and/or fine‐grained top layers are more sensitive to lateral erosion than marshes with deep cohesive soils, independently of the management. Grazing and artificial mowing can reduce the erodibility of fine‐grained soils, making salt marshes more resilient to lateral erosion. However, compaction by large grazers simultaneously leads to thinner fine‐grained layers and lower elevation, potentially leading to more inundation under sea‐level rise. Hence, to effectively manage salt marshes to enhance their contribution to coastal protection, we recommend (a) moderate/rotational livestock grazing, avoiding high intensity grazing in sediment‐poor systems sensitive to sea‐level rise and (b) investigating measures to preserve small grazers.

Intraspecific plant interaction affects arbuscular mycorrhizal fungal species richness

It is well established that mycorrhizal symbiosis can affect plant-plant interactions. On the other hand, how intraspecific plant interactions influence communities of arbuscular mycorrhizal fungi (AMF) is still very poorly understood. We applied 454 pyrosequencing to determine the responses of AMF communities to intraspecific shoot and root interactions using Medicago sativa L. as host plant. We found that intraspecific plant interaction caused significant variation in the structure of the AMF community assessed from roots but not from soil. Intraspecific root system interaction resulted in significantly elevated AMF species richness, greater total mycorrhizal and arbuscular colonization, and a larger root:shoot ratio compared to plants experiencing intraspecific shoot interaction or no interaction. Intraspecific shoot interaction resulted in significantly depressed AMF species richness. Our results support two hypotheses. The first is that increased AMF species richness in plants experiencing intraspecific root interaction originates from competitive release provided by high root density. The second is that shoot interaction leads to reduced allocation to root systems, increasing the stringency with which host plants selectively reward the most cooperative fungi. Because intraspecific interactions among host plants can influence the structure of their AMF community, interactions among species in complex plant communities may influence AMF community structure in addition to a plant diversity effect.

Relationship Between Distribution of the Radicular System, Soil Moisture and Yield of Sugarcane Genotypes

The objective of the study was to associate soil moisture, aerial biometric characteristics, and root distribution patterns in the yield of sugarcane genotypes in the fourth ratoon and the relationships between these characteristics. We used five sugarcane genotypes (CTC9002, RB044311, RB044313, RB044336, and RB867515) and five soil depths (0–20, 20–40, 40–60, 60–80 and 80–100 cm deep). The evaluations were carried out in December 2019. We evaluated the root systems, the soil water content at the five depths, the aerial biometric characteristics, and the productive yield. In the roots, the genotypes RB044311, RB044313, RB044336, and RB867515 showed a higher yield. On average, genotypes showed 50% of dry weight and total root length at a depth of 0–20 cm, 73% between 0 and 40 cm, and 86% between 0 and 60 cm. The RB044336 genotype showed maximum height and number of buds. The RB867515 genotype had the largest average stem diameter and CTC9002, the largest number of tillers. The genotypes CTC9002 and RB867515 presented the highest soluble solids' content, apparent sucrose in the juice, and total reducing sugars. These genotypes showed a 26% and 57% higher root density in soil layers at depths of 60–80 cm, respectively, 79% and 86% in the 80–100 cm layer, about the layer with the highest concentration of 0–20 cm roots. These layers remained with the highest soil moisture levels during the period of establishment and intensive cultivation growth. Thus, there was a relationship between root distribution dynamics and soil moisture in different areas.

Controls on Interactions Between Surface Water, Groundwater, and Riverine Vegetation Along Intermittent Rivers and Ephemeral Streams in Arid Regions

AbstractIntermittent rivers and ephemeral streams (IRES) make up the majority of waterways in arid and semi‐arid regions. While the physical underpinnings of surface water‐groundwater (SW‐GW) flow systems are well understood, how ephemerality, hydraulic properties and vegetation interact along IRES is not clear, posing severe challenges to their sustainable management. This study sought to identify the controls for SW‐GW‐vegetation interactions along IRES. To this end, numerical experiments on a quasi‐hypothetical IRES cross‐section with an integrated surface‐subsurface hydrological model were undertaken. The influence of different degrees of ephemerality on infiltration and riverine transpiration was tested by varying the duration of no‐flow periods. The influence of hydraulic conductivity (K), moisture retention capacity, root density, and local rainfall was also explored. Experiments showed that infiltration is controlled by ephemerality and K, with infiltration decreasing rapidly with increasing ephemerality and decreasing K. Transpiration is influenced by a complex interplay between ephemerality, hydraulic properties, and vegetation. While transpiration is strongly controlled by the degree of ephemerality, the capacity of the subsurface to maintain variably saturated conditions can strongly attenuate the effects of ephemerality. A large moisture retention capacity of the subsurface can partly compensate for the reduced infiltration under increasing ephemerality. Transpiration can be as large under ephemeral as under perennial conditions, especially where water table fluctuations exhibit large amplitudes within the zone of high root density. Overall, the results provide important insights into the complex dynamics of IRES and highlight how changes in flow dynamics can have significant impacts beyond instream processes.