Distribution Of Root System Research Articles

Spatial distribution of root systems of Pinus sylvestris var. mongolica trees with different ages in a semi-arid sandy region of Northeast China

Mongolian pine (Pinus sylvestris var. mongolica), the most important tree species for sand fixation in semi-arid sandy lands, experiences dieback in plantations after approximately 35–40 years since planting. Water limitation was considered as an important cause for the dieback. The spatial distribution of root systems plays a key role in determining water resources used by trees. However, it is still unknown for the spatial distribution of Mongolian pine trees with different ages, which constrains our understanding of the mechanism underlying the dieback and management of Mongolian pine plantations. Horizontal and vertical distributions of coarse roots [root diameter (RD) ≥ 5 mm] of Mongolian pine trees with 10, 20, 30, 40, 50 years old were estimated by ground-penetrating radar. Meanwhile, the distributions of fine roots (RD ≤ 2 mm) were simultaneously measured using soil coring method. Results showed that the horizontal distance of coarse roots from trees increased with tree ages up to 30–40 years, i.e., 3.0–4.0 m for 10- and 20-year-old trees, ca. 6.1 m for 30- and 40-year-old trees; but merely 4.85 m for 50-year-old trees. The fine root densities kept relatively even within 4.0 m from the trees for 10- and 20- year-old trees (ca. 0.02 mg cm−3), whereas, they decreased sharply with increasing of distances from the trees for 30-, 40- and 50-year-old trees (0.015–0.025 mg cm−3 at 1.0 m from trees to ca. 0.00 mg cm−3 at 5.0 or 6.0 m from trees). In the vertical direction, the rooting depth, at which 95% of roots located, was 83.5, 99.9, 123.6, 105.2 and 125.9 cm for the coarse roots of 10-, 20-, 30-, 40- and 50-year-old trees, respectively, whereas it was 140.6, 152.2, 135.5, 144.2 and 127.0 cm for fine roots, respectively. These findings indicated that the spatial distribution of roots of Mongolian pine trees shrank for the 50-year old trees, possibly due to being close to mature stage in plantation sites. Based on spatial distribution of roots, we suggested that the stand densities should be determined according to the area occupied by tree root systems in order to avoid the dieback or mortality due to water competition, i.e., 403–515, 321–402, 217–290, 139–179 trees ha−1 for 10-, 20-, 30- and 40-year-old trees, respectively (none for 50-year-old plantations as they were close to mature stage). Our findings provide new insights into stand density optimization of plantations from tree belowground competition for water in semi-arid and arid sandy regions.

Nitrogen fertilization affects maize grain yield through regulating nitrogen uptake, radiation and water use efficiency, photosynthesis and root distribution.

High external nitrogen (N) inputs can maximize maize yield but can cause a subsequent reduction in N use efficiency (NUE). Thus, it is necessary to identify the minimum effective N fertilizer input that does not affect maize grain yield (GY) and to investigate the photosynthetic and root system consequences of this optimal dose. We conducted a 4-year field experiment from 2014 to 2017 with four N application rates: 300 (N300), 225 (N225), 150 (N150), and 0 Kg ha−1 (N0) in the Northwest of China. GY was assessed by measuring the photosynthetic capacity and root system (root volume, surface area, length density and distribution). Grain yield decreased by −3%, 7.7%, and 21.9% when the N application rates decreased by 25%, 50%, and 100% from 300 Kg ha−1. We found that yield reduction driven by N reduction was primarily due to decreased radiation use efficiency (RUE) and WUE instead of intercepted photosynthetically active radiation and evapotranspiration. In the N225 treatment, GY, WUE, and RUE were not significantly reduced, or in some cases, were greater than those of the N300 treatment. This pattern was also observed with relevant photosynthetic and root attributes (i.e., high net photosynthetic rate, stomatal conductance, and root weight, as well as deep root distribution). Our results suggest that application of N at 225 Kg ha−1 can increased yield by improving the RUE, WUE, and NUE in semi-arid regions.

Research on the growth and development of some varieties of Lavandula Angustifolia (Mill.) in the South-East of Romania

The purpose of this paper was to analyze the canopy volume of lavender shrubs as a morphologic trait influenced by variety and also to evaluate the development of the root system on a Chromic Luvisol with an argic B horizon. The crop was established in 2017 at Belciugatele Didactic Station/Moara Domnească Farm (44°30′ North, 26°15′ East) using the following lavender varieties: Sevstopolis, Vera, Hidcote, and Buena Vista. During 2017-2019, plants’ height and diameters were measured at harvest, and these observations were used to determine lavender shrubs’ canopy volume, by applying the derived ellipsoid volume formula. Varieties (A) obtained different values in terms of canopy volumes, and these values also varied under the influence of the different doses and combinations of mineral and organic fertilizers (B). The highest canopy volume was registered by Vera, with values ranging from 0.0557 m3 (1st year, Control) and 0.0944 m3 (3rd year, organic fertilization with manure at 30 t/ha). The evaluation of the root system distribution and development was performed after carrying out a soil profile between two plants, along the row, for each researched variety. Measurements were conducted using a frame of 50/50 cm, and data sampling was performed for every 10 cm layer, by counting and measuring the roots. Based on these observations the root section area (RSA) was determined. The values of this indicator ranged between 283.06 mm2 (Buena Vista) and 378.29 mm2 (Vera).

Lensless imaging of plant samples using the cross-polarized light.

Lensless imaging has recently become an alternative and cost-effective choice for many macro and micro applications, like wave-front sensing, fluorescence imaging, holographic microscopy, and so on. However, the polarized imaging, especially the cross-polarized light, has rarely been explored and integrated in lensless imaging methods. In this paper, we introduce the cross-polarized illumination into the lensless system for high-contrast and background-free imaging of plant samples. We capture a snapshot measurement and apply the blind deconvolution for reconstruction, obtaining the depolarized imaging of plant samples. Experiments exhibit the specific and sparse structures of the root system and vessel distribution of samples. We also build a corresponding lens-based system for performance comparison. This proposed lensless system is believed to have the potential in studies on the root development and water transport mechanism of plants in the future.

Distribution of root system of hop plants in hop gardens with regular rows cultivation

Spatial distribution of the root system of hop (Humulus lupulus L.) in the soil profile is a less explored issue. However, it is known that it can play an important role in the development of new tillage technologies, fertilisation and irrigation, including the use of precision farming principles. In the period from 2015 to 2018, the distribution of the hop root system was evaluated on twelve hop plants of five Czech hop cultivars. The age of the plants ranged from 3 to 15 years. The evaluation took place in the Saaz region at regularly cultivated hop gardens. As part of the evaluation, the root systems of hop plants were removed from the soil profile and subsequently spatially reconstructed. With the help of infrared image analysis, the root intensity in the soil profile and the morphology of the root systems were determined. The root depth of the plants ranged from 1 m to 2.25 m. The lateral width of the hop root system ranged from 0.6 m to 1.5 m. As a result of the rows cultivation, the lateral development of the roots in the upper soil layers was limited. The results were confirmed using the infrared image analysis method to specify the distribution of the root system and the root density of hop plants in the soil profile.

Spatial-temporal distribution of winter wheat (Triticum aestivum L.) roots and water use efficiency under ridge–furrow dual mulching

In dryland agricultural production areas, knowledge on the growth and variation of winter wheat root systems under different mulching methods is important for guiding winter wheat production. We conducted a two-year field trial to explore the effects of different mulching practices on the spatial-temporal distribution of root growth, soil water storage, and grain yield. Four cultivation practices were tested: (i) traditional flat planting (CK), (ii) flat planting with half-film mulching (M1), (iii) ridge–furrow planting with film mulching over ridges only (M2), and (iv) ridge–furrow planting with film mulching over ridges and wheat straw mulching in furrows (M3). The results showed that the root diameter (RD), root length density (RLD), and root surface area density (RSD) of wheat under the four treatments were mainly concentrated in the 0–40 cm soil layer. The mean RLD in the 0–40 cm soil layer accounted for 62.2 %, 61.0 %, 59.3 %, and 55.8 % of the total root length density under M3, M2, M1, and CK, respectively, at maturity in both years. The M3 cultivation method produced the maximum values for RD, RLD, and RSD among all cultivation practices and the highest water storage efficiency after the three precipitation events. The M3 treatment had 11.1 %, 15.4 %, and 38.4 % higher mean grain yields than M2, M1, and CK, respectively, over the two-year study. Soil water storage had positive correlations with RD, RLD, and RSD. The RD, RLD, and RSD in the 0–40 cm soil layer had strong positive correlations with yield components, yield, aboveground biomass, and water use efficiency (WUE). Based on this study, ridge–furrow planting with film mulching over ridges and wheat straw mulching in furrows is an effective, sustainable cultivation method for wheat production in rainfed regions, which can increase the spatial-temporal distribution of root systems and soil water content across the root zones to increase crop production and WUE.

Tracking wireworm burrowing behaviour in soil over time using 3D X-ray computed tomography.

Wireworms (larvae of the click beetle, Elateridae) are a significant agricultural pest, causing crop damage and reducing yields globally. Owing to the complex nature and opacity of the soil environment, research to investigate wireworm behaviour in situ has been scarce. X-ray computed tomography (CT) has previously been demonstrated as a powerful tool to independently visualise the 3D root system architecture, macroinvertebrate movement and distribution of burrow systems in soil, but not simultaneously within the same sample. In this study, we apply X-ray CT to visualise and quantify wireworms, their burrow systems and the root architecture of two contrasting crop species (Hordeum vulgare and Zea mays) in a soil pot experiment scanned at different time intervals. The majority of wireworm burrows were produced within the first 20 h post inoculation, suggesting that burrow systems are established quickly and persist at a similar volume. There was a significant difference in the volume of burrow systems produced by wireworms between the two crop species suggesting differences in wireworm behaviour elicited by crop species. There was no significant correlation between burrow volume and either root volume or surface area, indicating this behavioural difference is caused by factor(s) other than the mass of root systems. X-ray CT shows potential as a non-destructive technique to quantify the interaction of wireworms in the natural soil environment with crop roots, and aid the development of effective pest management strategies to minimise their negative impact on crop production. © 2020 Society of Chemical Industry.

On the potential impact of root system size and density on salt distribution in the root zone

Soil salinization in agricultural environments is a major soil degradation process, particularly in dry regions. Soil salinization puts at risk the natural ecosystem and the agricultural crops, which are usually sensitive to elevated salinities. In this work, a conceptual model is proposed and tested experimentally, to examine the impact of root system dimension and distribution on solute transport and accumulation in the root zone. For this purpose, tomatoes were grown in growing chambers, under conditions of salty water irrigation. Root density, salt concentration and soil water content distributions were measured and correlations between the three parameters were found for different root system sizes. Results show that confined root systems were highly salinized with a strong correlation between root location and salt distribution in the soil. Broad root systems, on the other hand, showed a reduction in soil bulk salinity at the root zone and that about 50 % of the root system is under conditions of low salinity. The physical reasons for this observation are proposed herein and it is suggested that in the future, development of crops with large root systems could be considered as another tool to cope with soil salinization.

Root system distribution in bearing sapota trees under tarai conditions of Uttarakhand

Root system distribution in bearing sapota trees under <i>tarai</i> conditions of Uttarakhand

Influences of edaphoclimatic conditions on deep rooting and soil water availability in Brazilian Eucalyptus plantations

Brazilian roundwood industry is one of the most important and productive in the world, with Eucalyptus plantations alone representing 73% of the total planted forests. Deep rooting in these plantations represents a more common phenomena than generally expected. However, there is still a lack of information on environmental factors that drive root growth in deep soil layers, with particular emphasis on edaphoclimatic conditions, and related consequence in terms of soil water behavior. As a part of a larger project, this research aimed to investigate soil water and fine root system distribution in deep tropical soils under a commercial Eucalyptus plantation chronosequence. Along a 2800-km gradient (from south- to north-east Brazil), 14 experimental areas were planted with a “plastic” clone (E. urophylla) and investigated in terms of climatic conditions, soil and water features, and plant/stand development for an entire 6-years rotation period. Fine roots distribution were investigated in one site (in Brazil) till to 20 m deep at 3, 9, 24, 48, and 65 months after planting. Results showed a fast displacement of the root front down to 75, 325, 825, 1250, and 1575 cm at month 3, 9, 24, 48, and 65 after planting, respectively. Fine root densities (g cm−3) and proportional water capture exponentially decreased with soil depth. Deep fine roots showed a relativelly higher efficiency in acquiring water than the shallower, denser roots. The relationship between stand height vs root front depth followed an exponential trend, suggesting that these stands developed relatively faster in height rather than in depth during the first 48 months, with the opposite characterizing plantation afterwards. Regardless of stand age, E. urophylla trees rapidly explored a considerable volume of soil at a relatively limited carbon cost. Multivariate statistics showed that edaphoclimatic conditions play a major role in Eucalyptus plant/stand development. This study outlined the major role played by soil development. From poorly developed sandy Entisols, to medium developed Inceptisols, and to most developed fine textured Oxisols, both plant growth and stand productivity greatly improved accordingly. This study suggests that soil type, together with other environmental factors, are likely to influence both the development and behavior of Eucalyptus plantations for an extent greater than commonly anticipated.

The root-layer regulation based on the depth of phosphate fertilizer application of summer maize improves soil nitrogen absorption and utilization

Favorable root phenotypes can promote crops to obtain soil nutrients efficiently. The root-layer regulation technology based on the depth of phosphate fertilizer application can optimize the spatial and temporal distribution of summer maize root system and promote its spatial matching with soil water and nutrients to supply, providing a theoretical and technical support for realizing fertilizer saving and efficiency improvement by tapping potential of maize root system. In the present study, there were five treatments including CK (no P applied), P5 (phosphorus placement depth of 5 cm), P10 (phosphorus placement depth of 10 cm), P15 (phosphorus placement depth of 15 cm), and P20 (phosphorus placement depth of 20 cm). The effect of phosphorus application depth on root distribution, plant growth and yield formation, as well as nitrogen uptake, accumulation and transport in summer maize was analyzed. The suitable application depths of phosphate fertilizer promoted the growth of summer maize roots and increased root dry weight, root length density, root surface area and root volume significantly totally showing a trend of P15 > P10 > P20 > P5 > CK. With the increase of phosphate fertilizer application depth, the deep corn roots increased significantly. The proportion of root dry weight in P15 and P20 treatments was 12.3% and 12.1% in the 20–40 cm soil layer, and 6.7% and 6.9% in the 40–60 cm soil layer, respectively. The increase of root distribution depth promoted the absorption of nitrogen in the soil, and the nitrogen content in each soil layer, especially below 20 cm, was reduced significantly by the deep application of phosphate fertilizer. The optimization of root distribution promoted the accumulation and transportation of nitrogen in plants. Compared with P5 treatment, the averaged nitrogen fertilizer absorption efficiency, accumulation amount, accumulation rate, partial factor productivity and the grain yield in two years of P15 treatment increased by 14.5 kg kg–1, 19.2%, 48.9%, 6.4 kg kg–1, and 16.4% respectively, showing that under the conditions of the present study, concentrated application of phosphate fertilizer in −15 cm treatment can significantly promote the growth of deep soil roots, expand the space of nutrient utilization for root system, increase the absorption of nitrogen in deep soil, promote the accumulation and transportation of plant nitrogen, improve the productivity and ultimately yield in summer maize.

The Spatial Distribution of Root System in M9 Rootstock Is Affected by Apple Cultivar and Tree Age

The aim of study was to evaluate how different apple cultivars affect root morphology and spatial distribution of rootstock. The experiment was conducted with three different cultivars; ‘Golden delicious’, ‘Gala’ and ‘Starking’ grafted on M9 dwarfing rootstock. Nine and fourteen years old, French vertical axe trained trees were included in the experiment. The trench profile method was chosen to study the morphology of root system and the counted root intersects were divided into three classes; fine roots (&lt;2mm), medium-sized roots (2-5 mm), and coarse roots (&gt;5 mm). To analyze the spatial distribution of root system, the respective cumulative number of fine roots at three successive distances from the base of tree trunk and the cumulative number of fine roots in three successive distances from soil surface were expressed as percentage versus the total fine roots. Significant effects of scion on the total number of fine roots, and as well, on their side and in depth distribution were found. The pattern of root distribution is changing over years, tending to shift the bulk of absorptive roots further from the tank and deeper into the soil. This tendency was more visible to high yielding and late maturity cultivars.

Quantifying effects of root systems of planted and natural vegetation on rill detachment and erodibility of a loessial soil

The objectives of this study were to evaluate different root parameters for estimating rill detachment, and to compare and quantify the effectiveness of planted and natural vegetation on soil physical characteristics and in reducing rill detachment and erodibility. Laboratory-concentrated-flow flume tests were performed under a flow discharge of 3 L min−1 and a slope of 15° with intact soil samples. A silt loam soil (Calcic Cambisol, in Loess Plateau in China) was sampled in 2015 from laboratory with planted ryegrass (Lolium perenne L.) and in 2014 from natural vegetation fields under 12 to 36-a restoration. The results indicated that root length density was the best parameter for estimating the effects of roots on rill detachment and erodibility for both planted ryegrass and natural vegetation, with exponential reduction equations. The exponents were more negative for natural vegetation (−0.411) than for planted species (−0.217) because of the existence of more complex root networks under more diverse natural vegetation. Rill erodibility of soil samples with roots decreased exponentially from the baseline erodibility of the root-free soil as RLD increased. Root systems of the restored natural vegetation ameliorated soil characteristics (bulk density, aggregate stability and organic matter content) more profoundly than those of the laboratory tests due to stronger bonding and binding effects, resulting in a lower absolute soil detachment rate for a given root density. There existed a vertical decay distribution pattern of root densities with soil depth for natural vegetation and planted ryegrass, and this distribution of root systems reached a steady state after 12 years natural vegetation restoration. More vegetation types under more different hydraulic conditions should be evaluated in future studies to provide better scientific bases for modelling their impacts on rill detachment and erodibility.

GDS Triaxial Test on the Reinforcement Effects of Bermudagrass Root-soil Complex

GDS triaxial test system was conducted to investigate the stress-strain relationship, strength characteristic and failure mechanism of Bermuda grass root-soil complex, and the effect of different root system distribution on strength of root-soil complex was also studied. The results indicate: ①the root system can improve the shear strength of soil and limit the deformation of that complex effectively. ②The contribution of the root system to the strength promotion of the root-soil complex is mainly reflected in the increase of cohesion. ③The strength increase of the root soil complex is related to the arrangement of roots in the soil. The effects are listed in the sequence as mixed placement> intersectant placement> vertical placement >horizontal placement >inclined placement. The research results provide theoretical support for the formation mechanism of the shear strength of the root-soil complex, which is meaningful to guide the selection of slope protection plants.

Effects of micro-sprinkling with different irrigation amount on grain yield and water use efficiency of winter wheat in the North China Plain

It’s very important to guarantee the wheat production and improve water productivity in the North China Plain (NCP). In order to reduce irrigation and ensure the crop production in the NCP, a two-year field experiment of winter wheat was conducted in 2016–2018 using micro-sprinkling irrigation including different irrigation amount treatments (60 mm, MI60; 90 mm, MI90; 120 mm, MI120; and 150 mm, MI150), and the local traditional water-saving and productive flooding irrigation method (TI120) was as a control. The grain yield (GY), dry matter accumulation (DM), root system distribution and water utilization were investigated. The results showed that, the GY of MI60 decreased by 5.1–13.4% compared with TI120; GY of MI90 was comparable with TI120, while that of MI120 and MI150 increased significantly. The higher GY in micro-sprinkling treatments was mainly due to the significant increase of 1,000-grain weight (TGW), which was the result of the significant delay of the senescence in flag leaves during grain filling and then the increase in the post-anthesis DM. In addition, the roots mainly distributed in the 0−60 cm soil profile, and micro-sprinkling ensured the soil water supply in this areas at the critical growth stages; what’s more, micro-sprinkling with reducing irrigation treatments significantly promoted the growth of root system to the deep soil layer, which improved the absorption and utilization of moisture stored in soil. Compared with TI120, the same irrigation amount treatment under micro-sprinkling (MI120) significantly increased water use efficiency (WUE) due to higher GY and lower seasonal evapotranspiration (ET); the 125% irrigation amount treatment (MI150) increased WUE due to higher GY and comparable ET; the 75% irrigation amount treatment (MI90) obtained the similar WUE to TI120; the 50% irrigation amount treatment (MI60) got similar or lower WUE to TI120. Overall, suitable reduction of irrigation amount under micro-sprinkling (MI90) can ensure the grain yield of winter wheat and efficient utilization of irrigation water in the NCP.

Subsoiling and Planting Method on the Initial Growth of ‘Pera’ Sweet Orange (Citrus sinensis (L.) Osbeck)

The objective of this work was to evaluate the vegetative vigor and root architecture of &amp;lsquo;Pera CNPMF D-6&amp;rsquo; sweet orange grafted on Rangpur lime at early stage of development, submitted to different planting methods (planting of nursery trees produced in a protected environment-PNT and planting of seeds at the definitive place-PS) and soil preparation with and without subsoiling. The experiment was carried out at the Lagoa do Coco Farm, Rio Real, Bahia, Brazil. Biometric evaluations were performed to estimate the variables: canopy volume (CV), vegetative vigor index (VVI) and canopy cover rates in the planting row (CCR-R) and interrow (CCR-I). Root samples were also collected up to a depth of 1.45 m at five points in the planting row. The roots were digitized and processed to obtain total root length (TRL), root length density (RLD), average root diameter (RD) and root length for the diameter classes. Plants produced in protected environment exhibit greater shoot vegetative and root development compared to those produced by sowing at the definitive place, at least for the young orchard and under rainfed conditions. Subsoiling did not affect root system distribution and PNT favored the increase in TRL along the soil profile compared to PS, for all diameter classes evaluated, contributing to the increase in vegetative vigor observed in the plants. Regardless of the management practices adopted, roots were concentrated in the first 0.35 m of the vertical soil profile, due to physical impediment caused by the presence of cohesive horizons.

Minirhizotron as an In-Situ Tool for Assessing Sugarcane Root System Growth and Distribution

Crops root information is necessary in modern agriculture to provide information that promotes water and nutrient use efficiency. The minirhizotron is a non-destructive root method and it allows monitoring root growth along time and seasons. In this context, the aim of this paper is to provide an overview about minirhizotron method use for root growth and distribution assessment in sugarcane crop in irrigated and rainfed areas. We presented information in order to improve minirhizotron methodology and its use by providing highlights concerning critical aspects. Among critical points, the tube installation, tube protection, scanning-schedule and data analysis are addressed. Our information could help future users to acquire high-quality data with proper efficiency

Growth, Biomass Production and Root Development of Chinese fir in Relation to Initial Planting Density

Chinese fir (Cunninghamia lanceolata (Lamb) Hook) is a commercially valuable timber species that is widely planted in southern China and accounts for 6.1% of the global plantation forests. However, appropriate planting density that ensures high plantation productivity is largely unexplored in this species. The aim of the study was to examine tree growth, biomass production, and its allocation among different organs in relation to initial planting density, and to examine whether planting density has an impact on root development. Mortality, diameter at breast height and tree-height of all trees were determined and measured in wider (2.36 × 2.36 m), intermediate (1.83 × 1.83 m) and narrow (1.44 × 1.44 m) spacing with stand density of 1450 trees ha−1, 2460 trees ha−1 and 3950 trees ha−1, respectively. In each stand, three plots of 20 × 20 m at a distance of 500 m were delineated as the sampling unit. Biomass was determined by destructive sampling of trees in each stand and developing allometric equations. Root morphological traits and their spatial distribution were also determined by carefully excavating the root systems. The results showed an increase in diameter of trees with decreasing stand density while tree height was independent of stand density. Biomass production of individual trees was significantly (p &lt; 0.05) less in high-density stand (32.35 ± 2.98 kg tree−1) compared to low-density stand (44.72 ± 4.96 kg tree−1) and intermediate-density stand (61.35 ± 4.78 kg tree−1) while stand biomass production differed significantly in the order of intermediate (67.63 ± 5.14 t ha−1) &gt; high (57.08 ± 3.13 t ha−1) &gt; low (27.39 ± 3.42 t ha−1) stand density. Both average root length and root volume were significantly (p &lt; 0.05) lower in the high-density stand than stands with low and intermediate density. Analysis of spatial distribution of root systems revealed no overlap between roots of neighboring trees in the competition zone in low-density stand, a subtle overlap in the intermediate density stand and larger overlap in the high-density stand. It can be concluded that better growth and biomass production in intermediate density stand could be explained by better root structural development coupled with minimal competition with understory vegetation and between trees; thus intermediate stand density can be optimal for sustaining long-term productivity and may reduce the management cost in the early phase of the plantation.

Characteristics of the Soil and Vegetation along the Yulin–Jingbian Desert Expressway in China

Transportation infrastructure dramatically affects ecological processes. However, the environmental assessment process does not often consider how transportation impacts biodiversity, especially in ecologically fragile areas. The aim of this study was to assess the impacts of the Yulin–Jingbian expressway on vegetative diversity and to discuss the reason for the differences in soil-moisture distribution and vegetation diversity along the expressway. Samples were collected from 60 quadrats, along 6 transects. The α diversity indices and soil-moisture content calculated for each layer were used to represent habitat heterogeneity within a quadrat. A total of 49 species representing 39 genera and 16 families were recorded. Perennial herbs (42.9%) and annual herbs (36.7%) were the dominant life form. Species richness, diversity, and evenness indices of the vegetation varied with the distance between sampling points along the expressway. The vegetation with high diversity and evenness were near the expressway and areas with low diversity were farther from the expressway. The soil-moisture content in the 0–20 cm soil layer was a driving factor for the α diversity indices, and soil-moisture content below 20 cm played an inhibitory role on the α diversity indices. The greatest impact of the expressway on vegetation diversity was its effect on surface runoff and the distribution of plant root systems in the top layer of soil.

Soil and Root Attributes in Pastures Managed under Different Stocking Rates and Nitrogen Fertilization Levels

Core Ideas Grassland is a widespread agroecosystem in the globe; however, not enough attention has been given to link grazing management to soil health. Grazing management practices greatly impact soil quality. Moderate stocking rate are more adequate to keep grassland stability. Pasture management affects soil physical–chemical properties and root depth distribution. Adjusting grazing pressure and N fertilization are key management tools affecting these responses. This study evaluated the effect of N fertilization and stocking rate (SR) on soil physical and chemical attributes and root depth distribution in grazed elephantgrass (Pennisetum purpureum Schum. cv. 381) pastures (2009 and 2010). Treatments consisted of three SR (2.0, 3.9, and 5.8 AU ha−1; 1 AU = animal unit = 450 kg body weight) and three N doses (0, 150, and 300 kg N ha−1 yr−1) on elephantgrass pastures. Response variables included soil bulk density (BD), particle density (PD), total porosity (TP), aggregate stability (AS), water infiltration rate (WIR), light fraction of soil organic matter (LF‐SOM), soil fertility, root length density (RLD), and root biomass. Increased SR resulted in greater BD. Soil bulk density ranged from 1.42 to 1.58 g cm−3 for SR ranging from 2.0 to 5.8 AU ha−1, respectively. The C concentration of the LF‐SOM decreased with increasing SR, ranging from 383 to 174 mg C kg−1 soil. Soil fertility, RLD, and the stock of C and N in the root system varied among soil layers. At the end of 2 yr, SR and N fertilization did not affect TP, WIR, and AS nor influenced soil fertility and root system distribution. Overgrazing led to soil compaction and reduced LF‐SOM, indicating a trend of pasture degradation. Moderate SR resulted in greater LF‐SOM, indicating a positive trend for C accumulation in the long term.