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Highlights • Skidding machines reduced pore spaces and increased the bulk density of soil. • Chemical/mechanical treatments increased soil aeration and reduced the bulk density. • The root system of grey alder improved the soil aeration status of a damaged soil. • Active regeneration techniques accelerate the recovery of a compacted soil. Abstract Heavy harvesting leads to harmful soil compaction and negative effects of soil physical properties and rootability. We monitored the recovery of soil structure in a compacted forest soil, which had been treated with a combination of regeneration techniques (mulching, liming, planting of alder trees or a combination of those). Soil physical properties (relative apparent gas diffusion coefficient (D s /D 0), bulk density and the macropore volume) were measured in three successive campaigns, with two years between each, with fine root densities taken as a biological target variable. Distinct changes of soil physical properties were detected during the study period, mainly caused by the effects of the applied regeneration techniques. After four years, higher values of D s /D 0 and macropores indicated significant improvements of soil aeration in the topsoil. The deeper soil showed no distinct evidence of regeneration, regardless of the regeneration technique applied. However, rather a negative impact of mulching on soil physical properties was detected. The measured physical parameters, D s /D 0 , bulk density and macropore volume correlate highly with observed fine root densities. In the topsoil, root density increases with increasing soil gas permeability, while in the deeper horizons only few macropores are occupied by fine roots for gas exchange. [ABSTRACT FROM AUTHOR]

Abstract: The impact of structural deformations on soil properties controlling its function as habitat (“soil environment”) as well as the extent and rate of its regeneration are of particular interest for assessing the importance of soil compaction. The functional relationships between compacted soil structures, the resulting soil environments and soil microbial parameters were investigated in a 5-year (2004–2008) model experiment at field scale at Zurich-Reckenholz, Switzerland, using treatments differing in compaction events, soil tillage and irrigation. Soil structure was characterised by laboratory determination of macropore volume and air permeability on undisturbed soil cores. The soil environment was described by repeated field measurements of volumetric soil water content and O2 concentration in soil air. Soil microbial biomass (Cmic) and basal respiration were analysed using mixed soil samples and potential denitrification was determined in undisturbed soil cores. Samplings for both physical and biological analysis were repeated on several occasions. Soil structure analysis confirmed the expected impairment of topsoil properties by the compaction treatments. The results demonstrated clear quantitative and qualitative differences in the structural regeneration of the treatments, e.g. depending on subsequent soil management practices. Regeneration by natural processes clearly produced a different soil structure than alleviation of topsoil compaction by tillage. The effects of soil structure on the soil environment in the treatments strongly depended on the water regime. Compaction reduced air-filled porosity considerably and caused more frequent and pronounced conditions of low O2 concentration in soil air. The air regime in the compacted treatments clearly differed from that in the control treatment during the first 2 years after compaction. Topsoil compaction had a clear impact on subsoil environment and we recommend that this ‘functional subsoil compaction’ be considered in future decision-making on avoiding compaction risks. The clearly adverse effects on soil structure and soil environment resulted in different time courses of microbial parameters. However, repeated soil compaction combined with irrigation was the only treatment that strongly affected most soil microbial parameters. Potential denitrification was enhanced in compacted and irrigated treatments, where anoxic conditions in the field occurred more frequently. Under moist climatic conditions, as simulated in our irrigation experiment, microbial soil properties were not directly affected by the compacted soil structure itself, but by its gas exchange ability, which was strongly determined by the degree of air-filled pore space. [Copyright &y& Elsevier]

Describing the impact of farming on soil quality is challenging, because the model should consider changes in the physical, chemical, and biological status of soils. Physical damage to soils through heavy traffic was already analyzed in several life-cycle assessment studies. However, impacts on soil structure from grazing animals were largely ignored, and physically based model approaches to describe these impacts are very rare. In this study, we developed a new modeling approach that is closely related to the stress propagation method generally applied for analyzing compaction caused by off-road vehicles. We tested our new approach for plausibility using a comprehensive multi-year dataset containing detailed information on pasture management of several hundred Swiss dairy farms. Preliminary results showed that the new approach provides plausible outcomes for the two physical soil indicators "macropore volume" and "aggregate stability". [ABSTRACT FROM AUTHOR]