Wheel Tracks Research Articles

New Roughness Index of Passenger Car Rotational Vibration

Current road roughness indexes are limited to reflecting the unwanted rotational vibration of vehicles. This study focused on the relationship between the international roughness index (IRI) and rotational vibration around the longitudinal axis (pitch) and horizontal axis (roll) of the vehicle body. Sinusoidal wave input of different wavelengths and phase shifts between the left and right wheel tracks were used as excitation of a full-car model. Marked pitch and roll vehicle vibration were observed at shorter wavelengths (<1 m) and lower speeds (<50 km/h) of harmonic excitation. The IRI was limited to predicting the pitch and roll vibration of the full-car model at lower wavelengths, below 1 m. A simple alternative solution based on the IRI model was proposed as a robust, sensitive tool to detect unwanted rotational vibration of a vehicle. The proposal was based on the IRI approach using an alternative IRI model speed of 30 km/h, instead of the standard 80 km/h. The IRI for 30 km/h was several times more sensitive to pitch and roll vibration in the wavelength band up to 1.5 m than the IRI for 80 km/h. The new approach is recommended as an additional roughness index for monitoring roads with an allowable speed of up to 60 km/h.

AirSUM - Structure from Motion supported stock unearthing Method: Erosion modeling in Viennese vineyards

Soil mobilization is particularly high in viticulture. In Austria and especially in Vienna, soil protection measures are frequently implemented without the vintners knowing how high their erosion rates are and where in particular they can introduce additional measures. New, highly accurate and cost-efficient methods for erosion estimation are expected to improve this situation.A relatively fast and low-cost option is the stock unearthing method (SUM), which provides a rough estimation of erosion based on biomarkers, but neglects the inter-row area. The improved stock unearthing method (ISUM) approach uses additional measurement points in this area and therefore delivers more accurate erosion volumes. Additionally, the use of Structure from Motion (SfM) DEMs provides respectable results on small plots in vineyards. This study combines and evaluates the unmanned aerial vehicle (UAV) SfM approach with the SUM. This results in a millimeter scale resolution and can be applied to larger study areas. The combination of SUM and SfM forms the new airSUM approach that provides a more accurate representation of the recent relief, rendering interpolation techniques unnecessary, reproducing visible runoff patterns, and enhancing erosion volume estimations. The use of airSUM enabled the detection of 32.7 ± 17.5 m3 (avg. of ∼ 84.1 ± 45 t ha−1 yr−1) soil erosion on an area of 700 m2 in a period of 8 years. Erosion hotspots could be modeled mainly in the wheel tracks with depths of up to 20.5 cm parallel to the slope and correspond excellently with field observations. This is partly due to the compaction of the surface, but mainly due to the preferential runoff and erosion. The identification of the erosion hot spots, runoff breaches and consequent runoff concentration allows the precise allocation of mitigation funds to reduce overland flow and erosion.

Identification of wheel track in the wheat field

Agriculture machinery navigating along permanent traffic lanes in the farmland may avoid causing extensive soil compaction. However, the permanent traffic lanes are frequently covered up or eliminated by following tillage practices. It is necessary to identify the wheel tracks designed as permanent traffic lanes in order to ensure the agriculture machinery travels along the designated wheel tracks when cultivating the field. This study proposed an identification method of wheel tracks based on the morphological characteristics of wheel tracks and the environmental conditions around the wheel tracks in the wheat fields. The proposed method first utilized the maximum interclass variance to identify the contours of the main part of the wheel track and the shadow regions around the wheel track’s edges. The main part of the wheel tracks was then separated from interference pixels by moving the centerline of the main part of the wheel track, which was derived by skeleton algorithm and curve fitting, towards the right or left edge of the wheel track at a specific distance. In a morphological opening operation, specific linear and circular structural elements were used to segment the shadow regions along the edge of the wheel track. The remaining wheel track was finally recognized by computing the complement of the region identified. After achieving the segmentation of wheel tracks, many reference points near the outside of the wheel track edge in the original image were chosen as fiducial points for evaluating the differences between the actual value and the recognized wheel track edge. The evaluation was based on computing the root mean squared error (RMSE) and the mean absolute error (MAE) of coordinates of reference points and recognized wheel track edge. The results showed that the largest RMSE and MAE were 24.01 pixels (0.0045 m) and 17.32 pixels (0.0032 m), respectively. The low values of RMSE and MAE reveal that the accuracy of the algorithm developed in this study is high, and using this algorithm may segment the wheel track in the wheat field accurately.

Integrated control of braking-yaw-roll stability under steering-braking conditions

Sharp steering-braking at a high speed exposes sport utility vehicles with high gravity centers and narrow wheel tracks to the risks of tire locking, sideslip and rollover. To avoid these risks and ensure braking safety, yaw stability and roll stability upon steering-braking, a braking-yaw-roll stability integrated control strategy was proposed, which consists of a supervisor, an upper and a lower controller for the front and rear axle independent drive electric vehicle. In the supervisor, a nonlinear vehicle predictive model was constructed and four control modes were proposed according to the vehicle status and rollover indexes. The weight coefficients between braking force, yaw stability and roll stability are determined dynamically by the control mode and output to the upper controller. The upper controller used a nonlinear model predictive control to determine the longitudinal braking force distribution of the four wheels. And in the lower controller, the regenerative braking torque and friction braking torque of each wheel were distributed. Finally, simulation verifications were carried out on the high and low adhesion roads. The results show that the control strategy proposed in this study can effectively prevent the vehicle from rollover while ensuring braking safety and yaw stability.

An Examination of Soil Crusts on the Floor of Jezero Crater, Mars

AbstractMartian soils are critically important for understanding the history of Mars, past potentially habitable environments, returned samples, and future human exploration. This study examines soil crusts on the floor of Jezero crater encountered during initial phases of the Mars 2020 mission. Soil surface crusts have been observed on Mars at other locations, starting with the two Viking Lander missions. Rover observations show that soil crusts are also common across the floor of Jezero crater, revealed in 45 of 101 locations where rover wheels disturbed the soil surface, two out of seven helicopter flights that crossed the wheel tracks, and four of eight abrasion/drilling sites. Most soils measured by the SuperCam laser‐induced breakdown spectroscopy (LIBS) instrument show high hydrogen content at the surface, and fine‐grained soils also show a visible/near infrared (VISIR) 1.9 μm H2O absorption feature. The Planetary Instrument for X‐ray Lithochemistry (PIXL) and SuperCam observations suggest the presence of salts at the surface of rocks and soils. The correlation of S and Cl contents with H contents in SuperCam LIBS measurements suggests that the salts present are likely hydrated. On the “Naltsos” target, magnesium and sulfur are correlated in PIXL measurements, and Mg is tightly correlated with H at the SuperCam points, suggesting hydrated Mg‐sulfates. Mars Environmental Dynamics Analyzer (MEDA) observations indicate possible frost events and potential changes in the hydration of Mg‐sulfate salts. Jezero crater soil crusts may therefore form by salts that are hydrated by changes in relative humidity and frost events, cementing the soil surface together.

Determining Attribute—Response Relationships of Soils under Different Land Uses: A Case Study

Soil researchers are interested in a gaining better understanding of the soil system state by analyzing its properties and their dynamics in time as well as in relation to land use change. Tilled, abandoned, and forest soils were assessed regarding attribute–response relationships for the bulk density (BD), total porosity (TP), volumetric moisture (θv), and penetration resistance (PR) with the use of the interquartile ratio (IRI) integrated into a resilience formula and Shannon entropy indices. The IRI results differentiated soil properties according to agrotechnics (wheel track vs. between wheels) and the state of the system (tilled vs. abandoned vineyard). Entropy (En) indicated a high level of uncertainty for PR. The linear regression applied to the pairs of BD-TP, TP-θv, and PR-θv showed better results for the IRI weight (IRIweight) compared to the entropy weight (Enweight) for the soil between the wheels. The soil of the abandoned vineyard showed a faster tendency toward resilience that was more pronounced in the tilled wheel tracks than in the area between the wheels. The IRI can thus be an alternative to entropy in the evaluation of the response of some soil properties according to their use. When integrated into a resilience formula, the IRI can estimate the dynamics of soil properties for abandoned land compared to reference soil.

Vertical and horizontal stresses from a lightweight autonomous field robot during repeated wheeling

Some agricultural robots differ in design from traditional tractors which can affect load distribution among the wheels and the resulting soil stresses, especially when moving and carrying implements. Accurate measurements of soil stresses from these machines are needed to estimate their potential to reduce risk of compaction. The aim of this experiment was to study the vertical and horizontal stresses during repeated wheeling from a lightweight autonomous robot and to compare the measurements with calculations using the model Terranimo. We installed stress transducers at 10 cm depth in a loamy sand soil with water content close to field capacity. As an example of an agricultural field robot, we used a 55 kW 4WD robot (model ROBOTTI 150 D equipped with 320/65 R16 tyres) in two configurations: unloaded (33.6 kN) and loaded with a sprayer (37.2 kN). We conducted ten passes with the robot on the same wheel tracks over the transducers and measured the contact area, dynamic wheel load, mean ground pressure and maximum vertical and horizontal stresses during each wheel pass. We observed a significant increase in mean ground pressure with repeated wheeling. Measured values of maximum vertical stresses were 32% larger than the ones predicted by the model. On the same wheel and for different numbers of passes, we found differences between maximum and minimum dynamic wheel loads of up to 9.3 kN. Our results suggest that using static loads from this machine as inputs in models can result in inaccurate predictions of soil-tyre interface parameters due to the high variability and unknown redistribution of the load under dynamic conditions. The differences between static and dynamic loads also impede the correct on-field adjustment of tyre inflation pressures. These issues can result in an underestimation of the risk of soil compaction of this type of vehicle, especially in the topsoil. This work can help design new robots that aim to minimize soil compaction.

Computer Simulation and Visualization of Wheel Tracks on Solid Surfaces in Virtual Environment

The paper describes methods and approaches for implementation of traces from virtual prototypes of wheeled technical vehicles on solid objects in three-dimensional virtual scenes. Use of particle systems hierarchically linked to wheel models is the basis of solutions developed. Original type of particle system is proposed, in which generation of elements is regulated by special control signal. Creation, processing, storage and destruction of particles is performed by means of the CUDA architecture with use of computing cores of modern graphics processor and video memory resources. Creating geometric model of each particle and its rendering is carried out on programmable graphics pipeline with own vertex, geometry and fragment shaders. Visualization of virtual environment with simulation of wheel tracks is performed in real time. Software modules were created based on developed methods and approaches. Approbation of them was carried out in virtual environment system VirSim and showed adequacy and effectiveness of proposed solutions for simulation of wheel tracks in virtual environment systems and training complexes.

Stochastic Propagation of Fatigue Cracks in Welded Joints of Steel Bridge Decks under Simulated Traffic Loading.

The fatigue cracking of orthotropic steel bridge decks (OSDs) is a difficult problem that hinders the development of steel structures. The most important reasons for the occurrence of fatigue cracking are steadily growing traffic loads and unavoidable truck overloading. Stochastic traffic loading leads to the random propagation behavior of fatigue cracks, which increases the difficulty of the fatigue life evaluations of OSDs. This study developed a computational framework for the fatigue crack propagation of OSDs under stochastic traffic loads based on traffic data and finite element methods. Stochastic traffic load models were established based on site-specific, weigh-in-motion measurements to simulate fatigue stress spectra of welded joints. The influence of the transverse loading positions of the wheel tracks on the stress intensity factor of the crack tip was investigated. The random propagation paths of the crack under stochastic traffic loads were evaluated. Both ascending and descending load spectra were considered in the traffic loading pattern. The numerical results indicated that the maximum value of KI was 568.18 (MPa·mm1/2) under the most critical transversal condition of the wheel load. However, the maximum value decreased by 66.4% under the condition of transversal moving by 450 mm. In addition, the propagation angle of the crack tip increased from 0.24° to 0.34°-an increase ratio of 42%. Under the three stochastic load spectra and the simulated wheel loading distributions, the crack propagation range was almost limited to within 10 mm. The migration effect was the most obvious under the descending load spectrum. The research results of this study can provide theoretical and technical support for the fatigue and fatigue reliability evaluation of existing steel bridge decks.

Urban Road Surface Discrimination by Tire-Road Noise Analysis and Data Clustering

The surface condition of roadways has direct consequences on a wide range of processes related to the transportation technology, quality of road facilities, road safety, and traffic noise emissions. Methods developed for detection of road surface condition are crucial for maintenance and rehabilitation plans, also relevant for driving environment detection for autonomous transportation systems and e-mobility solutions. In this paper, the clustering of the tire-road noise emission features is proposed to detect the condition of the wheel tracks regions during naturalistic driving events. This acoustic-based methodology was applied in urban areas under nonstop real-life traffic conditions. Using the proposed method, it was possible to identify at least two groups of surface status on the inspected routes over the wheel-path interaction zone. The detection rate on urban zone reaches 75% for renewed lanes and 72% for distressed lanes.

Research on vehicle driving characteristics in narrow lanes based on different vehicle-following states

Drivers could be more careful when vehicles move in the non-standard narrow lane. This might cause the drivers to behave differently from other normal-size lanes. To investigate the characteristics of the traffic flow in narrow lanes, this paper collected the vehicle trajectory data on four-lane road segments with 2.8m width and 3.25m width respectively. Firstly, the spatial distribution of wheel tracks in the lane under low traffic volume is studied, and the results show that the wheel trails’ distribution is obviously affected by three factors: speed, lane width, and lane in cross-section position, which are significantly different from normal-size lanes. Secondly, statistical analysis shows that vehicle-following status in narrow lane environment can be divided into three types: staggered following, parallel following, and transitional following. Finally, a multivariate logistic regression model is constructed to predict the driver’s following strategy under different driving micro-environment parameters. The research results can support the fine management of lanes and help to improve the driving strategy of autonomous vehicles.

Nine Places Where You Can Still See Wheel Tracks from the Oregon Trail

Nine Places Where You Can Still See Wheel Tracks from the Oregon Trail

Transmission pathways of campylobacter spp. at broiler farms and their environment in Brandenburg, Germany.

Broiler meat is widely known as an important source of foodborne Campylobacter jejuni and Campylobacter coli infections in humans. In this study, we thoroughly investigated transmission pathways that may contribute to possible Campylobacter contamination inside and outside broiler houses. For this purpose we carried out a comprehensive longitudinal sampling approach, using a semi-quantitative cultivation method to identify and quantify transmissions and reservoirs of Campylobacter spp.. Three german broiler farms in Brandenburg and their surrounding areas were intensively sampled, from April 2018 until September 2020. Consecutive fattening cycles and intervening downtimes after cleaning and disinfection were systematically sampled in summer and winter. To display the potential phylogeny of barn and environmental isolates, whole genome sequencing (WGS) and bioinformatic analyses were performed. Results obtained in this study showed very high Campylobacter prevalence in 51/76 pooled feces (67.1%) and 49/76 boot swabs (64.5%). Average counts between 6.4 to 8.36 log10MPN/g were detected in pooled feces. In addition, levels of 4.7 and 4.1 log10MPN/g were detected in boot swabs and litter, respectively. Samples from the barn interior showed mean Campyloacter values in swabs from drinkers 2.6 log10MPN/g, walls 2.0 log10MPN/g, troughs 1.7 log10MPN/g, boards 1.6 log10MPN/g, ventilations 0.9 log10MPN/g and 0.7 log10MPN/g for air samples. However, Campylobacter was detected only in 7/456 (1.5%) of the environmental samples (water bodies, puddles or water-filled wheel tracks; average of 0.6 log10MPN/g). Furthermore, WGS showed recurring Campylobacter genotypes over several consecutive fattening periods, indicating that Campylobacter genotypes persist in the environment during downtime periods. However, after cleaning and disinfection of the barns, we were unable to identify potential sources in the broiler houses. Interestingly, alternating Campylobacter genotypes were observed after each fattening period, also indicating sources of contamination from the wider environment outside the farm. Therefore, the results of this study suggest that a potential risk of Campylobacter transmission may originate from present environmental sources (litter and water reservoirs). However, the sources of Campylobacter transmission may vary depending on the operation and farm environmental conditions.

Soil surface connectivity of tilled soil with wheel tracks and its development under simulated rainfall

• Linkage between soil surface microrelief and overland flow was examined. • Differently oriented wheel tracks served as water flow paths or as sediment sinks. • Increase of surface connectivity after a rain was shown by functional connectivity. • Structural connectivity showed reorganization of the surface runoff pathways. Although wheel tracks cover only a small portion of the surface of agricultural fields, their effect on surface runoff and sediment transport is substantial. Wheel tracks change the microrelief of the soil surface, and influence how the surface is further altered by rainfall and runoff. This study presents a plot-scale microrelief analysis of a tilled surface with wheel tracks under simulated rainfall. Digital elevation models of the microrelief with 1 cm spatial resolution were obtained using the Structure from Motion method. The random roughness, the structural connectivity, and functional connectivity were calculated for before-rainfall and after-rainfall soil surface conditions. The experiments were carried out on inclined, freshly-tilled plots (8 m long, 2 m wide). The wheel tracks were created by four passages of machinery in the slope direction (SWT) and in the contour-line direction (CWT). The experiments were compared to reference plots without wheel tracks (NWT). The wheel tracks increase water and sediment connectivity if they are oriented in slope-wise direction. Microrelief analysis shows that SWT drains water from the surrounding soil. The soil surface adjacent to SWT can also become more connected with the wheel track, due to changes in microrelief introduced by rainfall and runoff. The calculated higher connectivity in the SWT plot corresponded to the measured increased sediment loads. This suggests faster overland flow and therefore shorter flow pathways on the soil surface microrelief. CWT leads to a decrease in the water and sediment connectivity compared to the NWT and SWT plots. Although the surface runoff can overflow the CWT, the network of flow paths results in decreased flow velocity and a slower sediment transport rate. However, the CWT effect is not permanent, and declines as the wheel tracks become silted with the deposited sediment. It is shown that detailed microrelief data provide relevant information for a study of the changes in flow routing in a tilled agricultural field with the presence of a wheel track. SWT accelerates the runoff and especially the sediment transport. During a rainfall event, the hydraulic connection between the wheel track and the surrounding soil increases dramatically. CWT reduces the surface runoff and also the sediment transport. In the long term, rainfall events and surface runoff alter the microrelief connectivity, causing the soil surface to be more hydraulically connected, irrespective of the wheel track orientation. This study demonstrates the effect of wheel tracks on water and sediment transport. The results draw attention to the importance of appropriate soil protection measures, as a bare unprotected surface microrelief exposed to rainfall leads to increased sediment connectivity.

Rutting and strain characteristics of rubberized asphalt pavement based on accelerated pavement tester

This study aimed to investigate the rutting and strain characteristics of rubberized asphalt rejuvenated reclaimed asphalt pavement (RARR). Accelerated pavement tester (APT) was employed to apply wheel load and tire pressure on the instrumented test field. Seven embedded fiber grating sensors were placed at the bottom of the RARR surface layer to collect strain data. In total, 700,000 wheel passes were applied on RARR pavement in 25 loading cycles. Data on rutting deformation was collected after each loading cycle while strain data was collected throughout the test. Results revealed that RARR pavement presented rapid rutting depth and rutting area increase in the first 100,000 wheel passes. After 450,000 wheel passes, the rut area directly contacted with the wheel load presented an almost constant increasing rate with additional wheel passes, while the influence rut area remained unchanged. As regard to strain at the bottom of the RARR surface layer, it was found that the maximum strain after 100,000 wheel passes reached more than 70% of the maximum strain occurred during the final loading cycle. Large strain differences were found after 300,000 wheel passes and the worst case scenario occurred after 700,000 wheel passes. For strain right under the wheel tracks, results revealed that horizontal strain recovery ability was better than that of vertical strain. Moreover, it was found that wheel loadings actually enhance the strain recovery ability of RARR pavement. This was believed to be caused by the further densification of RARR while loading, which enhanced the elastic recovery ability of RARR asphalt mixture as a whole.

A small-amplitude hunting motion recognition method based on transfer learning

The hunting motion of the vehicle increases the wear of the wheel tracks and affects the lateral stability of the vehicle system and safety, so the hunting motion of the vehicle needs to be recognized. However, the existing recognition methods ignore the small-amplitude hunting motion that precedes the onset of the running motion. In addition, due to the scarcity of real hunting data of high-speed trains, there is a problem of underfitting when training with traditional deep learning methods. In this paper, first, the dynamics model of a high-speed train is established, and the normal, small-amplitude hunting and hunting motions of high-speed trains in the process are simulated. Second, this paper proposes a transfer learning-based method for high-speed train hunting motion recognition. The method uses easily collected normal data samples in the training process, does not use real data samples of small-amplitude hunting and hunting motions, and completes the high-speed train running motions recognition task by transferring from simulation data (source domain) to real data (target domain). Finally, the validation is carried out using the real data, which proves that the method-related approach has some engineering application value in the intelligent monitoring of high-speed trains.

Uneven crop residue distribution influences soil chemical composition and crop yield under long-term no-tillage

Conservation agriculture has three main components: crop residue retention; minimal soil disturbance; and diverse rotations. Whilst retaining crop residues on the soil surface is important to prevent erosion and conserve water, high residue amounts can also have negative effects. Residue spread behind harvesters is not always uniform, therefore, it is important to understand the impact of uneven residue spread on crop performance. These problems are likely to increase as more farmers windrow and burn residues for weed control, harvesters become larger and controlled traffic systems are implemented. The effect of residue distribution on soil properties and crop establishment and yield was studied under no-tillage and controlled traffic in cereal (wheat-wheat-barley) and diverse (wheat-legume-canola) rotations, over the final six years of a larger 12-year (2007–2018) rotation trial, in the Wheatbelt of Western Australia. Within each crop and rotation, residue management consisted of either spreading or windrow-burning and measurements were taken from three locations relative to the harvester wheel tracks: centre (between harvester wheel tracks), mid (2.25 m perpendicular) and outer (4.5 m perpendicular), representing the ~9 m working width of the machinery. In most years, the distribution of crop residue behind the harvester was uneven, with up to twice as much residue directly behind the harvester compared with mid and outer locations. Differences in residue amount had positive, negative or no effect on crop establishment and yield, depending on the crop and residue type and climatic conditions. Increasing residue amount had a positive effect on establishment and yield when conditions were dry around seeding and early crop growth stages, possibly associated with increased water availability with increased residue load. Conversely, there were negative effects when frost occurred at anthesis or under high rainfall conditions, the latter due to physical impairment, increased disease or lack of available nitrogen. Negative effects only occurred with cereal residue and could be minimised by growing more break crops, even under high residue loads. In the longer term, higher residue amounts resulted in increased soil nutrients behind the harvester, which increased yields in some years. Therefore, research to improve uniformity of residue spread behind harvesters is crucial. Otherwise, variation in crop performance will increase as harvesters get bigger and, in the long term, periodicities in soil chemistry under controlled traffic systems will occur.

Pioneer biocrust communities prevent soil erosion in temperate forests after disturbances

Abstract. Soil erosion continues to be one of the most serious environmental problems of our time and is exacerbated by progressive climate change. Until now, forests have been considered an ideal erosion control. However, even minor disturbances of the forest floor, for example, from heavy vehicles used for timber harvesting, can cause substantial sediment transport. An important countermeasure is the quick restoration of the uncovered soil surface by vegetation. To date, very little attention has been paid to the development of nonvascular plants, such as bryophytes, in disturbed areas of temperate forests and their impact on soil erosion. This study examined the natural succession of pioneer vegetation in skid trails on four soil substrates in a central European temperate forest and investigated their influence on soil erosion. For this purpose, rainfall simulations were conducted on small-scale runoff plots, and vegetation was continuously surveyed during the same period, primarily to map the development of bryophytes and the occurrence of biological soil crusts (biocrusts). Biocrusts appeared immediately after disturbance, consisting primarily of bryophyte protonemata and cyanobacteria as well as coccoid and filamentous algae that lost their biocrust characteristics as succession progressed. They were present from April to July 2019, with a particular expression in the skid trail that was on shale clay (Psilonotenton Formation) and silty clay loam substrate. In general, skid trails on clayey substrates showed considerably higher bryophyte cover and species richness. Although bryophytes were subsequently overtopped by vascular plants, they managed to coexist until their growth was restricted due to leaf litter fall. Brachythecium rutabulum and Oxyrrhynchium hians were the most important and persistent pioneer bryophyte species, while Dicranella schreberiana and Pohlia lutescens were volatile and quickly disappeared after spreading in the summer. Sediment discharge was 22 times higher on disturbed bare soil compared with undisturbed forest soil and showed the largest sediment removal in the wheel tracks. Counteracting this, soil erosion decreased with the recovery of surface vegetation and was particularly reduced with growing pioneer biocrusts in summer, but it again increased in winter, when vascular vegetation became dominant. This leads to the conclusion that the role of bryophyte-dominated biocrusts in forests has been underestimated so far, and they can contribute more to soil conservation at specific times of succession than vascular plants.

고려~조선시대의 도로 및 수레 연구

Roads and wheeled carts began to be used extensively in Korea during the Three Kingdoms Era. Their use continued, with periods of development and decline, throughout the Unified Silla, Goryeo, and Joseon periods. The bulk of archaeological research on Korean roads and cart use has been focused on the earlier Three Kingdoms and Unified Silla periods. Most of the research on the use of roads and wagons in the later Goryeo and Joseon dynasties has been conducted by studying historical records. However, these records may not be accurate representations of the actual road conditions during these periods. In this study, we will attempt to correlate the limited archaeological data with data from historical records to paint a more complete picture of road and cart use during the Goryeo-Joseon period. Since the rule of the Goryeo Dynasty, tax collection was centralized in the capital, which allowed for a significant expansion of the road system. As a result, in the early Goryeo Dynasty, 22 provinces were established with 525 stations built throughout the provinces to transfer goods and horses and provide lodging. Historical records and archaeological data confirm that there were regional differences in road systems during this period. Local roads were generally excavated before construction, which is an easier road building technique than the piling method. Historical records show that roads in the Goryeo Dynasty were divided into three categories: main roads, middle roads, and small roads. The archaeological record from the time shows that the typical main roads were at least 550 ㎝ wide, the middle roads were 350-550 ㎝ wide, and the small roads were 350 ㎝ wide or less. A number of wheel tracks were found at archaeological sites. These tracks usually show an average cart wheel width of 150 ㎝. The road system continued to develop into the late Goryeo Dynasty, but was largely destroyed during that dynasty’s collapse. Efforts were made to revitalize and reorganize the road system during the Joseon Dynasty. At this time, the roads were listed in the Gyeongguk Daejeon (National Code), divided into provincial roads and outbound roads. The provincial roads were further classified into main roads (56 cheoks wide), middle roads (16 cheoks), and small roads (11 cheoks). Setting the main roads at 56 cheoks can be interpreted to be an acknowledgement by Joseon itself that it was a princely state of China in pursuant to Juraegogonggi. However, archaeological evidence indicates that royal roads for the king’s passage were wider than the required width in Gyeongguk Daejeon. In other words, it legally followed the rules of China but did not follow them in reality. The outbound roads were divided into larger arterial roads and smaller branch roads. After analyzing the existing records and archaeological data, it is presumed that the Gyeongguk Daejeon arterial roads were supposed to be similar in width to the provincial main roads, and the branch roads were meant to be smaller than the middle roads. There is evidence that some roads were constructed with a thick infill to meet these standards, but in most cases, the roads were left as they had been. The average width of cart tracks from the Joseon period archaeological sites is approximately 100-110㎝, narrower than the tracks found in Three Kingdoms and Goryeo era sites. However, there is little evidence of marks in the case of wheeled carts, which is thought to be due to the increasing preference for palanquins over wheeled carts at that time. It is apparent that the attempts to improve and standardize the road system in the Joseon Dynasty were not widely successful.

Recovery of Soil Structure and Fine Root Distribution in Compacted Forest Soils

Soil compaction is a major concern in the context of ensuring sustainable forest and agricultural management practices. Productivity gains during the last decades were also achieved by increasing mechanization. This change was associated with growing machine weights and impacts on trafficked soils. Up to now, knowledge about the resilience of compaction phenomena is still poor. At 11 forest sites on compaction-sensitive silt and loam substrates in the federal state of Baden-Wuerttemberg (Germany), fine root distribution, macroporosity, and apparent gas diffusion coefficients were used to characterize the status of recovery from former soil compaction by machine impact. The time span of recovery at the investigated sites ranged from 6 to 37 years. The investigated soil physical parameters indicate the beginning of soil structure recovery in the wheel tracks, comprising the first 10 cm of soil depth at most sites that were trafficked 10 years or more before the investigation. Synchronously with this restructuring, fine root propagation has started to recover in the topsoils. However, a high persistence of damage was observed below that depth. A synoptic interpretation of the data led to the conclusion that time spans up to almost four decades are not sufficient for the restoration of soil functionality in formerly compacted soils characterized by silt loam texture and low activity of soil biota. In view of the long-lasting persistence of the negative compaction effects, soil protection strategies combined with monitoring of their strict compliance must be implemented into forest practice. In case of an insufficient natural recovery potential, active measures to accelerate the regaining of soil functionality in compacted soils at irregular wheel tracks should be considered in order to shorten the time spans of disturbed soil conditions.