Abstract: Dynamic compactors with parameters that adjust automatically to the condition of the subgrade form the basis for intelligent compaction. Dynamic soil compactors create nonlinear vibrations, and the typical characteristics of these vibrations are taken as the basis for the feedback control system for intelligent compaction. With the model of the machine and the soil as the starting point, the periodic loss of contact between the drum and the subgrade is postulated to be the main nonlinear effect. This nonlinearity leads to near periodic and subharmonic vibration phenomena, and it can bring about unstable drum dynamics. The machine behavior can be investigated with the help of the chaos theory. Feedback control systems for rollers are based on the results from the theory of nonlinear oscillations, and they allow optimal compaction performance thanks to continuous adjustment to the compaction status. Starting with large amplitudes and low frequencies, the automatic control system ensures a good depth effect....

Abstract: The effects of organic matter removal, soil compaction, and vegetation control on soil microbial biomass carbon, nitrogen, C-to-N ratio, and functional diversity were examined in a 6-year loblolly pine plantation on a Coastal Plain site in eastern North Carolina, USA. This experimental plantation was established as part of the US Forest Service's Long Term Soil Productivity Study. Sampling was undertaken on eight treatments within each of three blocks. Treatments sampled included main 2×2 factorial treatments of organic matter removal (stem-only or complete tree plus forest floor) and compaction (none or severe) with split-plot treatment of vegetation control (none or total vegetation control). Two blocks were located on a somewhat poorly drained, fine-loamy, siliceous, thermic aeric Paleaquult (Lynchburg soil) and one on a moderately well drained, fine-loamy, siliceous, thermic aquic Paleudult (Goldsboro soil). Soil microbial C and N were positively related with soil C and N, respectively. Microbial C and N on the Lynchburg soil were higher than those on the Goldsboro soil. Organic matter removal decreased microbial N. Compaction reduced microbial C-to-N ratio. Vegetation control decreased microbial C and C-to-N ratio. The number of C compounds utilized by bacteria was not affected by soil type or treatment. However, soil types and treatments changed bacterial selections for a few C compounds on BIOLOG plates. Soil microbial properties varied more due to the natural soil differences (soil type) as compared with treatment-induced differences.

Abstract: This study examines the short-term impact of forest soil compaction and organic matter removal on soil mesofauna, in general, and oribatid mite species, in particular. Both soil compaction and organic matter removal re- duced the density of soil mesofauna. Stem-only harvesting reduced total mesofauna densities by 20% relative to uncut forest values. A combination of whole-tree harvest and forest floor removal with heavy soil compaction significantly reduced total soil mesofauna densities by 93% relative to the uncut forest control. Removal of the forest floor repre- sents a substantial loss of habitat for most soil mesofauna. The forest floor apparently buffered the mineral soil by lim- iting both the impact of soil compaction and fluctuations in soil temperature and moisture. The relative abundance of Prostigmata and Mesostigmata increased with treatment severity, whereas that of Oribatida decreased. Species richness of the oribatid mite fauna was reduced as the severity of treatments increased. The number of rare oribatid species (those representing <1% of the total oribatid mite sample) decreased by 40% or more relative to the uncut forest con- trol. Evenness also decreased as treatment severity increased. Oppiella nova and Suctobelbella sp. near acutidens were the dominant oribatid species in both the forest floor and mineral soil, regardless of treatment. Soil compaction and or- ganic matter removal significantly impacted the density and diversity of soil mesofauna and oribatid mite fauna in the short term at these study sites.

Abstract: In determining stress limits to prevent soil compaction, it is important to know the mechanical properties of soils. One important parameter is the precompression stress, which is often used as a criterion for soil susceptibility to compaction. A series of uniaxial compression tests on Swedish arable soils was conducted by Eriksson [Markpackning och rotmiljo (soil compaction and root environment), Report 126, Division of Agricultural Hydrotechnics, Department of Soil Sciences, Swed. Univ. Agric. Sci., Uppsala, Sweden, 1982 (in Swedish, with English summary)]. The objective of the present study was to derive precompression stress values from these data. Eighteen soils, generally classified as Eutric Cambisols and with clay contents ranging from 62 to 863 g kg−1 were used. Soil cores (25 mm high, 72 mm in diameter) were sampled at 10 cm intervals to a depth of 1 m and equilibrated at 0.5 or 60 kPa water tension. The cores were then compressed in an oedometer by sequential stresses of 25, 50, 100, 200, 400 and 800 kPa. Precompression stress was determined according to Casagrande [The determination of the pre-consolidation load and its practical significance, in: Proceedings of the International Conference on Soil Mech. and Found. Eng. (ICSMFE), vol. 3, Cambridge, MA, 22–26 June 1936, pp. 60–64] and by regression methods. Precompression stress was higher for subsoils than for topsoils and higher at higher soil water tension, but was difficult to relate to soil physical properties. Values determined according to Casagrande were generally between 100 and 200 kPa. Values determined by regression methods had a smaller range compared to the Casagrande method. The values of precompression stress indicate a low risk for subsoil compaction on Swedish soils, which is not in line with practical experience in compaction experiments. The concept of precompression stress as a clear transition from small, elastic deformation to larger, plastic deformation could not be supported by the stress–strain relationships obtained in this study. There is an urgent need to design laboratory tests that reflect soil behaviour in the field.

Abstract: The effects of grazing intensity on selected soil characteristics in the feather-grass steppes of the autonomous region of Ningxia (northern China) were investigated by a comparison of non-grazed areas (grazing intensity 0), slightly grazed areas (grazing intensity I), moderately grazed areas (II), intensively grazed areas (III) and over-grazed areas (IV). Even in areas used only minimally for grazing activities (I), a serious increase (doubling) in soil hardness was apparent in the upper soil layer. A continual decrease in organic matter in the surface soil can be correlated directly to soil compaction. The content of organic matter in soil of degree IV amounts to only a third of the organic matter found in non-grazed areas. This decrease can be attributed partly to the poor living conditions for soil organisms in compacted soils, but also to a significant reduction in litter. This is because intensive grazing causes reduced vegetation cover leading to litter being blown away by wind or washed away by heavy rainfall. Thus in level III hardly any plant litter remained to be incorporated into the soil as humus. Likewise root density also suffered its largest decrease in areas with a grazing intensity level III. With regard to the content of nitrogen and phosphorous (total and available) hardly any difference between soils of grazing intensity 0 and I was observed, whereas a noticeable decrease was apparent between levels I and II. Available Potassium was similar for all grazing levels. The pH-value of the soil solution is not significantly affected by grazing. We did not observe differences in the soils of the two main types of steppe vegetation (Stipa grandis and Stipa bungeana steppe) in response to grazing. Only the amount of litter in the S. grandis-steppe in non-grazed or slightly grazed areas is noticeably higher than in the S. bungeana steppe.

Abstract: This paper quantifies soil compaction and natural recovery of soil physical properties during a 3-year trial on a dairy farm in Southland, New Zealand. The study investigated the magnitude of soil compaction over spring, and natural recovery of soil physical properties over summer and autumn. Changes in soil physical condition were measured while pastures were intermittently grazed by lactating dairy cows, and also over winter when cows were removed from pasture. Soil bulk density at 0–5 cm increased (P 30 μm) at 0–5 cm decreased (P < 0.001) from 13.5 to 7.5%, with similar trends in spring 2002. Many of the soil physical properties showed significant recovery over summer and autumn. Bulk density decreased (P < 0.001) by 0.09 Mg/m3, from December 2001 to May 2002. Soil macroporosity also recovered markedly during summer and autumn. Macroporosity increased (P < 0.001) from 12.5% in December 2001 to 18% in May 2002. Significant changes in soil compaction and recovery were also measured at 5–10 cm depth. For many soil physical properties, recovery over winter was much less than over summer and autumn. Implications of the compaction and recovery cycle are discussed in terms of measurement protocols appropriate to routine monitoring of soil physical condition.

Abstract: The objective of this study was to evaluate the effects of prolonged recreational disturbance on vegetation structure. Therefore, plant species variation along trails was determined in some common vegetation types of Flanders (Belgium). The study sites included two forest types, one grassland and one heathland. Inventory was conducted in transects perpendicular to trail centre. Field data on frequency, percent cover and multiple habitat variables were collected in the path, transition and undisturbed zones of the respective transects. In order to determine plant response groups in relation to recreational disturbances, distribution of plant species across paths was linked with their respective life form and plant strategy. Generally, species diversity increased towards the trail centre. The intensity of soil compaction was highly correlated with species cover and composition. Since soil compaction is interrelated with other aspects of the biotic and abiotic environment, it is clear that trampling exerts multiple stress on vegetation.

Abstract: Soil compaction induced by the use of agricultural machinery changes the mechanical and structural properties of soils. Assessment of its effects may be made by acoustic techniques. In this study, a triaxial cell modified to measure the acoustic velocity was used to simulate the compaction process. Unconsolidated-undrained triaxial tests were performed on two air-dry remolded soils and one undisturbed field soil taken from sites in Sharkey, Neshoba, and Marshall Counties, Mississippi. Both the deformation and the acoustic behaviors of the soils were studied during a compaction process. It was found that the acoustic velocity and the deviator stress behaved similarly. Both the acoustic velocity and the deviator stress increased linearly at the early stage of compaction and they changed nonlinearly with intermediate compaction. At the extreme case where the soil was compacted to failure, the acoustic velocity and the deviator stress changed only slightly with further compaction. During the unload-reload cycle, the acoustic velocity and the deviator stress varied steeply and presented hysteretic and load-history-dependent properties. Significant influence of water content on both acoustic and deformation behaviors was found. The similarity between the acoustic behavior and the deformation characteristics make the acoustic velocity a promising parameter for monitoring the ongoing compaction process in situ and for long-term soil survey.

Abstract: The effects of soil compaction and mechanical damage to stools at harvesting on the growth and biomass production of short rotation coppice (SRC) of willow (Salix viminalis L.) were monitored on clay loam (CL) and sandy loam (SL) soils. Moderate compaction, more typical of current harvesting situations did not reduce biomass yields significantly. Even heavy compaction only reduced stem biomass production by about 12% overall; effects were statistically significant only in the first year of the experiment on sandy loam. Heavy compaction increased soil strength and bulk density down to 0.4 m depth and reduced soil available water and root growth locally. Soil loosening treatments designed to alleviate the effects of heavy compaction did not markedly improve the growth of willow on compacted plots. Hence the focus fell on harvesting. Extensive mechanical damage to stools caused a 9% and 21% reduction in stem dry mass on the clay loam and sandy loam soils as a result of fewer stems being produced. The particularly severe effect on the sandy loam soil probably resulted from a combination of dry conditions in the year of treatment, root damage and soil compaction under stools and might have been aggravated by the young age of the plants (1 year) at the time of treatment.

Abstract: The National Forest Management Act of 1976 mandates that a site's productive capacity must be protected on federally managed lands. Monitoring the effects of management on a site's productive capacity is not easy, and in 1989 a national program of Long-Term Soil Productivity (LTSP) research was established to assist National Forests toward this end. The LTSP program focuses on disturbances associated with timber harvest, but fi ndings apply to any activities altering vegeta- tion or soil. LTSP centers on core experiments that manipulate site organic matter, soil porosity, and the complexity of the plant community. Results from a dozen decade-old LTSP installations in the Sierra Nevada and the Southern Coastal Plain do not indicate that site productivity has been impaired despite substantive soil compaction and massive removals of surface organic matter. The strongest effect of treatment on planted tree growth on sites governed by temperate and subtropical climates was the control of competing vegetation. With only one-fi fth of the LTSP in- stallations reporting, fi ndings should not be generalized to other sites and climates.

Abstract: Rural tree decline (RTD) in Australia is a complex biological issue involving dieback of native trees following the removal of native vegetation, the introduction of improved pasture species, soil fertilisation and the grazing of livestock. The extent and severity of RTD has reached historically high levels in the past two to three decades. As this period has coincided with an unprecedented increase in atmospheric carbon dioxide concentration, it may be speculated that climate change, a result of the Greenhouse Effect, has played a signifi cant role in RTD. Ecological similarities between two geographically and climatically distinct Australian case studies (the Midlands of Tasmania and the New England Tablelands of New South Wales), both characterised by severe RTD, suggest that the underlying causes of this phenomenon have a common basis. The biological and ecological effects of rural land use are manifold. These include exposure of remnant trees to increased wind and soil drying; decreased water availability due to competition with improved pasture and decreased infi ltration due to soil compaction by cloven-hooved livestock; increased salinity; loss of ectomycorrhizal fungal diversity; changed nutrient balance due to direct addition of fertiliser and/or nitrogen fi xation by clover-based pastures; changed pest/predator and biodiversity balance; and lack of seedling recruitment due to browsing by livestock and/or native animals. Superimposed on these factors are below-average rainfall and above-average temperatures over the past three decades, phenomena that are associated with climate change. Climate change has been linked to eucalypt decline in landscapes with little or no rural land use, and to tree decline across Europe. The contributions of climate change and rural land use to RTD are considered in this review and recommendations for management are discussed.

Abstract: Forest management operations have the potential to reduce soil productivity through organic matter and nutrient removal and soil compaction. We measured pine volume, bulk density, and soil and foliar nitrogen and phosphorus at age 5 on the 13 southern Long-Term Soil Productivity study sites. The treatments were organic matter removal (bole only (BO), whole tree (WT), whole tree and forest floor (WTFF)), and soil compaction (none, moderate, severe). The WT and WTFF treatments reduced pine volume by 18 percent overall compared to the BO plots, with the greatest reductions occurring on the sites with the lowest inherent site quality. Soil compaction had little effect on pine volume, but bulk density of the com- pacted plots at age 5 was still elevated, by an average of 5 percent, over the noncompacted plots.

Abstract: Soil compaction from human trampling, biking, and off-road motor vehicle traffic was quantitatively investigated in a blackbrush ( Coleogyne ramosissima ) shrubland in Kyle Canyon of the Spring Mountains in southern Nevada. A significant difference was detected in soil compaction, bulk density, and percent pore space at a particular frequency of visits in each of 4 disturbance types. On average a single vehicle pass was equivalent to 10 human footprints. Ten and 100 footprints were equivalent to 1 motorcycle pass and 10 vehicle passes, respectively. Soil compaction is a product of increased bulk density and decreased pore space. The degree of soil compaction is a function of disturbance type and visit frequency when examining these 2 factors independently. However, interactive effects of disturbance type and visit frequency on soil bulk density, compaction, and percent pore space were not significantly different. The greatest effects occurred during the first few passes, with changes per pass decreasing as the number of passes increased in all 4 trails. Results of this study suggest that the effects of hiking and biking slowly increase over time relative to the effects of motor vehicle traffic in the Coleogyne shrubland of Kyle Canyon in southern Nevada.

Abstract: This Phase I report describes a preliminary evaluation of a new compaction monitoring system developed by Caterpillar, Inc. (CAT), for use as a quality control and quality assurance (QC/QA) tool during earthwork construction operations. The CAT compaction monitoring system consists of an instrumented roller with sensors to monitor machine power output in response to changes in soil-machine interaction and is fitted with a global positioning system (GPS) to monitor roller location in real time. Three pilot tests were conducted using CAT's compaction monitoring technology. Two of the sites were located in Peoria, Illinois, at the Caterpillar facilities. The third project was an actual earthwork grading project in West Des Moines, Iowa. Typical construction operations for all tests included the following steps: (1) aerate/till existing soil; (2) moisture condition soil with water truck (if too dry); (3) remix; (4) blade to level surface; and (5) compact soil using the CAT CP-533E roller instrumented with the compaction monitoring sensors and display screen. Test strips varied in loose lift thickness, water content, and length. The results of the study show that it is possible to evaluate soil compaction with relatively good accuracy using machine energy as an indicator, with the advantage of 100% coverage with results in real time. Additional field trials are necessary, however, to expand the range of correlations to other soil types, different roller configurations, roller speeds, lift thicknesses, and water contents. Further, with increased use of this technology, new QC/QA guidelines will need to be developed with a framework in statistical analysis. Results from Phase I revealed that the CAT compaction monitoring method has a high level of promise for use as a QC/QA tool but that additional testing is necessary in order to prove its validity under a wide range of field conditions. The Phase II work plan involves establishing a Technical Advisory Committee, developing a better understanding of the algorithms used, performing further testing in a controlled environment, testing on project sites in the Midwest, and developing QC/QA procedures.

Abstract: The widespread use of heavy machinery during harvesting and site preparation in timber plantations in British Columbia (BC) has led to concerns that compaction causes a reduction in long-term soil ...

Abstract: The effects of soil compaction on earthworm ( Aporrectodea caliginosa nocturna) activity were studied using pot experiments. Two compaction pressures were used when packing the pots; loose soil was packed by applying a pressure of 96 kPa, and compact soil was packed using a compaction pressure of 386 kPa. “Split pots” which contained both loose and compact soil were also used. In split pots peripheral burrows (those next to the pot wall), were generally longer in the loose half of the pot than they were in the compact half. This implies that earthworms preferred the loose soil. An important finding was that peripheral burrows in the split pots were longer than those made in pots packed uniformly with either loose or compact soil. Our data suggest that the increase in activity in split pots is a response to spatial variation in soil compaction. In the split pots the earthworms tended to avoid the compact half, and we discuss how the avoidance response in the split pots may have increased the proportion of burrows in these pots that were peripheral.

Abstract: It is well established that increasing soil bulk density (SBD) above some threshold value reduces plant root growth and thus may reduce water and nutrient acquisition. However, formation and elongation of maize seminal roots and first order lateral (FOL) roots in various soil layers under the influence of SBD has not been documented. Two studies were conducted on a loamy sand soil at SBD ranging from 1.25 g cm -3 to 1.66 g cm -3 . Rhizotrons with a soil layer 7 mm thick were used and pre-germinated plants were grown for 15 days. Over the range of SBD tested, the shoot growth was not influenced whereas total root length was reduced by 30 % with increasing SBD. Absolute growth rate of seminal roots was highest in the top soil layer and decreased with increasing distance from the surface. Increasing SBD amplified this effect by 20 % and 50 % for the top soil layer and lower soil layers, respectively. At the end of the experiment, total seminal roots attributed to approximately 15 % of the total plant root length. Increasing SBD reduced seminal root growth in the lowest soil layer only, whereas FOL root length decreased with SBD in all but the uppermost soil layer. For FOL, there was a positive interaction of SBD with distance from the soil surface. Both, increasing SBD and soil depth reduced root length by a reduction of number of FOL roots formed while the length of individual FOL roots was not influenced. Hence, increasing SBD may reduce spatial access to nutrients and water by (i) reducing seminal root development in deeper soil layers, aggravated by (ii) the reduction of the number of FOL roots that originate from these seminal roots.

Abstract: The emergence of annual species depends on the number of seeds present and the biotic and abiotic conditions directly surrounding those seeds (the microsite). A field experiment was conducted to study the relative importance of seed presence vs. microsite conditions in determining the emergence of four annual species. Green foxtail, wild mustard, wild oat, and canola were seeded at 200, 400, and 1,200 seeds m−2 in separate plots in a coarse, loamy, mixed Typic Haplocryoll and a fine, mixed Typic Haplocryoll soil. Five microsite modification treatments (control, irrigation, soil compaction, soil compaction plus irrigation, and no crop) were applied to all weed seed density treatments for each weed species. All plots were seeded to spring wheat. Irrigation or soil compaction increased percent emergence of wild oat. Green foxtail emergence tended to increase with soil compaction in 2001 but not in 2002. Wild mustard and canola emergence were largely unaffected by microsite modification treatments. W...

Abstract: An experiment was conducted to determine the optimum moisture content to subsoil based on tillage forces and soil disruption. Two different shanks, a straight shank and a “minimum-tillage” shank, were tested in a Coastal Plain soil in the soil bins of the National Soil Dynamics Laboratory in Auburn, Alabama. A three-dimensional dynamometer measured tillage forces, and a laser profilometer measured soil disruption. Tillage forces and soil disruption measured in the driest soil condition were greatest. The “minimum-tillage” shank required more energy and disrupted less surface soil than the straight shank. An index, the trench specific resistance (TSR), was developed to aid in determining the minimum amount of draft force necessary for maximally disrupting a deeper soil profile. Reduced values of TSR were found for the straight shank compared to the “minimum-tillage” shank, as minimum draft produced maximum soil disturbance. Reduced values of TSR were also found for subsoiling operations conducted at all soil conditions other than the driest. Based on this research, subsoiling should not be conducted at the extreme driest soil condition due to increased draft forces and increased aboveground soil disruption.

Abstract: Eastern subterranean termites, Reticulitermes flavipes (Kollar), workers were introduced into arenas containing low, moderate, and high compaction builder’s sand (1.05 g/cm3, 1.18 g/cm3, or 1.35 g/cm3 bulk densities, respectively), and they immediately began tunneling. Termites built the tunnel network significantly fastest in soil of low compaction compared with moderately or highly compacted soil. In soil of low compaction, 221.67 ± 4.73 cm of total tunnel distance was constructed in 1 d compared with only 96 cm of tunneling in highly compacted soil. At 14 d, total tunnel distance averaged 216.83 ± 4.56 cm in soil of low compaction compared with 169.70 ± 4.10 and 181.18 ± 6.13 cm in moderately and highly compacted soil, respectively. Decreases in total tunnel distance between 1 and 14 d were caused by backfilling of seldom-used tunnels. Termites did the majority of tunneling during the first day of introduction into arenas. In soil of low and moderate compaction, termites essentially constructed the entire tunnel network within the first day, only modifying it by backfilling or maintaining tunnels. In highly compacted soil, 53% of the final tunnel network was constructed during the first day, 87% was constructed by the third day, and 97% was constructed by the seventh day. Soil compaction did not affect the number of primary tunnels or the number and diameter of secondary tunnels. The angle between the secondary tunnel and primary tunnel also was not significantly affected by soil compaction. However, the number of secondary tunnels in soil of low compaction (5.89 ± 0.51) was significantly greater than in moderately (2.74 ± 0.36) and highly (3.58 ± 0.59) compacted soils.

Abstract: The objective of this work was to evaluate the modifications on morphological and physical properties of a Fragiudult caused by continuous sugarcane cultivation in the Low Coastal Tablelands region of Alagoas State, Brazil. Three sites were selected, one from native forest and two cultivated with sugarcane for periods of two and thirty years. The sugarcane cultivation promoted morphological changes on the soil surface with the development of an Ap horizon, and changed the soil structure of the two upper horizons. The morphological changes, however, were not expressive due to the small clay content of the horizons. The cropping practices adopted decreased macroporosity and, consequently, increased the soil water availability. Land use increased microporosity and decreased significantly the hydraulic conductivity of the surface horizons. Significant changes in bulk density, total porosity, macroporosity, wilting point, and in the size and distribution of aggregates were not observed. The development of compaction on the Ap and AB horizons as a result of sugarcane cultivation, and the presence of a dense layer (cohesion) in the Bt horizon of all soil profiles were observed.

Abstract: —More frequent use of heavy equipment in intensive forest practices can lead to soil compaction and reduced productivity. The growth of 8-year-old planted shortleaf pine (Pinus echinata Mill.) and seasonal soil moisture stress and soil temperature were measured on cherty silt loam soil from which surface organic materials (whole tree plus leaf litter) had been removed before applying compaction treatments. Three levels of compaction and two levels of understory control were compared. Trees were significantly taller and had more height and diameter at breast height (d.b.h.) growth in compacted treatments than in the no compacted treatment and when the understory was absent than when present. Mean seasonal soil moisture stress was much higher for compacted treatments than for the no compaction treatment during the measurement period, except for September. But differences were significant only for May (severe compaction>no compaction) and September (severe compaction