Land-based mitigation measures are needed to achieve climate targets. One option is mitigation of currently high greenhouse gas (GHG) emissions of nutrient-rich drained peatland forest soils. Continuous cover forestry (CCF) has been proposed as a measure to manage this GHG emission source; however, its emission reduction potential and impact on timber production at regional and national scale have not been analysed.

To quantify the potential emission reduction, we simulated four management scenarios for Finnish forests: (i) clearcutting of nutrient-rich drained peatlands replaced by selection harvesting (CCF) and (ii) the current prevailing forest management regime (BAU), and both at two harvest levels, namely (i) the mean annual harvesting (2016–2018) and (ii) the maximum sustainable yield. The simulations were conducted with a forest simulator (MELA) coupled with hydrological model (SpaFHy), soil C model (Yasso07) and empirical GHG exchange models.

Simulations showed that the management scenario (CCF) that avoided clear-cutting on nutrient-rich drained peatlands produced approximately 1 Tg CO₂ eq. higher carbon sinks annually compared to the BAU at equal harvest level for Finland. This emission reduction can be attributed to the maintenance of higher biomass sink and to the mitigation of soil emissions from nutrient-rich drained peatland sites.

How to cite: Lehtonen, A., Eyvindson, K., Härkönen, K., Leppä, K., Salmivaara, A., Peltoniemi, M., Salminen, O., Sarkkola, S., Launiainen, S., Ojanen, P., Räty, M., and Mäkipää, R.: Could continuous cover forestry on drained peatlands increase the carbon sink of Finnish forests? , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6553, https://doi.org/10.5194/egusphere-egu24-6553, 2024.

Different climate scenarios predict a clear rise in temperatures and a modest increase in precipitation to high latitudes. In forested peatlands, the consequent lowering of the water table and increasing peat temperature will enhance organic matter decomposition leading to higher nutrient release and CO2 emissions from the peat. These biogechemical changes will fundamentally alter the management schemes of peatland forests. Hydrological and biogeochemical processes in forested peatlands are complicated, interlinked and characterized by different feedback mechanisms. In addition, all these are dependent on weather conditions, peat characteristics, drainage dimensions, and stand structure.  High-resolution geospatial data combined with process-based ecosystem models provides a solution in searching for new forest management schemes that balance between different ecosystem services. We have developed this kind of ecosystem model, peatland simulator SUSI, and applied it to study how manipulation of drain network, ash fertilization and forest management affect tree growth, greenhouse gas balance and nutrient export to water courses under different temperature and rainfall scenarios. We found that without a change in the water management, the stand growth, the soil C emissions and nitrogen export to water courses will increase substantially. However, less intensive drainage together with ash fertilization helped to mitigate the harmful effects of changing climate whilst keeping the stand growth in adequate level. 

How to cite: Laurén, A. and Palviainen, M.: Decreasing carbon emissions in boreal peatland forests using fertilization and less intensive drainage in current and changing climate, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3103, https://doi.org/10.5194/egusphere-egu24-3103, 2024.

Projections of soil carbon (C) models are known to underestimate soil C stocks in boreal soils with higher nutrient status which is likely because they do not account for effects of soil nutrient status on the kinetics of microbial respiration and their sensitivities to environmental conditions. Here we evaluated the effects of long-term N addition (once per decade since 1960 until 2020) on soil heterotrophic respiration (Rh) and its dependence on soil temperature and moisture in an originally N limited boreal Scots pine (Pinus sylvestris) forest.

We measured Rh, soil temperature and soil moisture biweekly during the vegetative seasons of 2021-2023 in both fertilized and control forests. We fitted Rh rates to soil temperature and moisture separately for the control and N fertilization treatment using parametric non-linear regression models and non-parametric machine learning (boosted regression tree) models.

The functional dependencies of Rh were similar between fertilized and control forests for soil temperature but differed for soil moisture. In the N fertilized forest soil, Rh increased rapidly from dry conditions towards a soil moisture optimum followed by a clear reduction in wet conditions. In contrast, in the N limited forest soil, Rh mainly increased with soil moisture.

The models based solely on temperature (assuming identical and non-limiting effect of moisture) predicted higher annual Rh than the models accounting for soil moisture effects. Thus, to avoid overestimation of soil CO₂ emissions and underestimation of soil C stocks accumulation in fertile boreal soils, it is crucial to link the soil moisture dependencies in soil C models to nutrient status. The different Rh response to moisture between N limited and N fertilized soils could be related to different levels of enzyme activities and contrasting microbial traits found by other studies.

How to cite: Ťupek, B., Lehtonen, A., Manzoni, S., Baldrian, P., Adamczyk, B., and Mäkipää, R.: Increased sensitivity of microbial respiration to soil water content in a fertilized boreal forest, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17138, https://doi.org/10.5194/egusphere-egu24-17138, 2024.

Site factors determine the occurrence and growth of forest stands. The climate is one of the most important. In Hungary, several forest stands located near to the Xeric limit, where climate change is more sensitive. Therefore carbon-rich forests and their soils are being prioritized to achieve carbon neutrality as soon as possible. Our research aims to assess and compare the organic carbon stored in oak and beech forest ecosystems of different climate classes.

In the last period, we sampled 2 Beech, 11 Sessile oak and 13 Turkey oak forest stands to determine the amount of soil organic carbon stored in the soil.

The soils were collected by soil boring to 0-110 cm. Besides the soil sampling, the existing forest stand composition assessed on each stand near to sampling points.

Based on the analyses carried out in the 26 selected forest stands, the soils of the sites can be classified as Cambisols and Luvisols (WRB 2023). The soil pH showed slightly acidic to neutral (mean H2O = 6.7), and the texture can be determined as loam. The relative organic matter content (SOM) was 0.67% on average between 0-110 cm. It corresponds to ~8.2 t of carbon per hectare.

With the accelerated rate of climate change (drought), there is an increasing urgency to assess the status of ideal organic matter-rich soils and to develop adaptation strategies to increase the carbon stock.

This article was made in the frame of the project TKP2021-NKTA-43 which has been implemented with the support provided by the Ministry of Innovation and Technology of Hungary (successor: Ministry of Culture and Innovation of Hungary) from the National Research, Development and Innovation Fund, financed under the TKP2021-NKTA funding scheme. This publication was supported by the project GINOP-2.3.3-15-2016-00039.

How to cite: Végh, P., Balázs, P., Bidló, A., and Horváth, A.: Investigation of SOM sequestration and storage in the Southern Transdanubian region of Hungary, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-998, https://doi.org/10.5194/egusphere-egu24-998, 2024.

Soils play a key role in regulating atmospheric concentrations of greenhouse gases notably by their action on organic carbon dynamics (storage vs. release). Forests occupy 31% of the continental surface and store around 40% of the continental organic carbon, half of it in soils. Ongoing climate change could alter the balance of this stock, and the effect of temperature on soil carbon fluxes remains an important question. In this study, we use the Q₁₀ parameter (i.e. increase in CO₂ emission for a 10°C rise in temperature) to estimate the temperature sensitivity of soil organic matter in four forest tree species (beech, spruce, douglas fir and silver fir). In addition, soil organic carbon stocks were estimated and compared with Q₁₀ values and forestry data (volume, basal area, density and dead wood).

The mont Beuvray site (Morvan Regional Park, France), a mid-mountain area of around 1,000 ha with a quite homogeneous geology and pedology, was selected. On this site, Beech forests correspond to historical land use, while softwood forests have been gradually introduced over the past 70 years. Thus, 48 soil samples (0-20 cm) were collected (12 per tree species) and the main physicochemical characteristics were determined (bulk density, stone content, pH, organic carbon and total nitrogen contents, water-extractable organic carbon). The Q₁₀ was calculated for a temperature range of 5 to 25°C in the laboratory using a Respicond X (Nordgren Innovations AB, Sweden).

Results show that soil organic carbon and water-extractable organic carbon contents are higher in silver fir and beech stand soils than in Douglas fir stand soils. For soil organic carbon stocks, the average values are slightly higher for beech and silver fir than for Douglas fir and spruce, but there is no statistical difference between the four tree species.  Q₁₀ values range from 2.3 to 3.0, with a statistical higher value for beech (2.8 ± 0.1) than for the other softwood species (2.6 ± 0.1). This last result suggests that, for similar initial soil conditions, CO₂ emissions from soil in beech stands would increase more strongly with temperature than in other species.

In conclusion, several decades after the introduction of softwood species, we did not measure in the top soil (0-20 cm) significant difference in carbon stocks. However, CO₂ emissions and Q₁₀ values are different and related to forest species. Hence, beech stand soils, corresponding to the historical land cover, could see their CO2 flux increase as they are the most sensitive to temperature. Conversely, silver fir stands, with their lower sensitivity to temperature, could be of interest in mitigating emissions. These results need to be confirmed by field data on soil respiration and compared with above-ground forest biomass and stand health.

How to cite: Bonnefoy-Claudet, C., Thevenot, M., Lévêque, J., Cognard, E., Santoni, A.-L., Cacot, J., and Mathieu, O.: Could tree species be a key factor on soil carbon balance in temperate forest?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16030, https://doi.org/10.5194/egusphere-egu24-16030, 2024.

Norway spruce monocultures in the boreal region are vulnerable to the effects of climate change and unfavourable in terms of soil fertility. Introducing broadleaved tree species to these forests may increase not only the resilience of the forest ecosystem to climate change but also enhance soil productivity and carbon (C) stock. We studied how grey alder, having symbiosis with N₂-fixing Frankia, and birch affect soil nitrogen (N) and carbon pools as an admixture in Norway spruce stands in Southern Finland.

Study sites were three 40–60-year-old Norway spruce (Picea abies (L.) Karst.) -dominated stands with both grey alder (Alnus incana) and birch (both Betula pendula and Betula pubescens) as an admixture and a 20-year-old spruce stand with an admixture of grey alder. The forest type was a relatively fertile Oxalis acetosella – Vaccinium myrtillus type (OMT) on the two older (60 yr) sites and a slightly less fertile Vaccinium myrtillus type (MT) on the two younger sites (20–40 yr), applying the Finnish forest type classification. We took the soil samples at a 50–100 cm distance from 3–8 stems of the different tree species for the determinations of soil C and N stocks from all sites and for additional characterisation of organic matter only from the 60-year OMT sites. Soil diffusive N fluxes were measured using in situ microdialysis sampling and the subsequent laboratory analyses of plant-available N compounds.

On average, forest floor N stock was larger under the canopy of alder versus birch or spruce. C-to-N ratios of forest floor and topmost 10 cm mineral soil layer were lower under alder versus spruce. Soil C stock was affected by tree species only at the 40-year MT site, where alder had a higher forest floor C stock than birch or spruce. Differences in diffusive N fluxes between tree species were non-significant, and we observed inconsistent trends at different sites. C mineralisation rate tended to be lower under alder versus spruce on the two 60-year OMT sites, and the amount of microbial biomass N was lower under alder versus birch. Microbial biomass C-to-N ratio and forest floor thickness were lower under birch than spruce on one of the 60-year OMT sites.

The results point towards complex interactions and dynamics between tree species in mixed forests. Although we observed tree-species-induced spatial variation in soil properties, the distribution of above- and belowground litter and root activities in mixed stands reduces the differences between tree species. We found tree species to affect N stocks and C-to-N ratios most strongly, alder altering soil properties of spruce stands more than birch.

How to cite: Soronen, P., Jämtgård, S., Myllymäki, M., and Smolander, A.: Grey alder and birch as an admixture in Norway spruce stands: Effects on soil nitrogen and carbon pools, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9810, https://doi.org/10.5194/egusphere-egu24-9810, 2024.

Structural properties of undisturbed soils are critical for water retention and the reduction of peak flows after heavy rainfall events. Forest soils commonly show high infiltration rates that can be attributed to a high organic content and the formation of larger pores through biological activity. Though soil disturbances, especially soil compaction, due to timber logging can be considered a rare event, the impacts may be long lasting. The productive, often fine textured soils of the Alpine Flysch belt are particularly susceptible to compaction, posing a challenge for timber harvesting.

In a controlled experiment in the Flysch zone (Vienna Woods, Austria), we assessed the effects of different timber harvesting technologies – specifically harvester-forwarder (with or without bogie tracks) and chain saw-cable yarder – on soil functions. For the quantification of the surface runoff, we applied rainfall simulation experiments on seven plots of 50 m² each. All rainfall simulation experiments were conducted for one hour with a targeted intensity of 100 mm/h before and after harvesting. Within each irrigation plot, we sampled undisturbed soil cores at up to five depth levels (5, 15, 25, 40, 65 cm) for further analyses in the laboratory. We measured saturated hydraulic conductivity (KSAT device; METER Group, Munich, Germany), as well as soil water retention in the wet and medium soil moisture range using the HYPROP device (METER Group, Munich, Germany). In the dry soil moisture range (pF>4.2) we measured water retention with the dew point method using the WP4C device (METER Group, Pullman, USA). Additionally, soil texture and soil organic carbon were determined from the same soil samples.

Preliminary results suggest a strong impact of the harvester-forwarder system (w/wo bogie tracks) on all hydrologically effective soil properties, while the cable yarder system seems to have lower, yet still noticeable impacts. For the log₁₀ of the saturated hydraulic conductivity (log₁₀KS) the harvester-forwarder treatments cause significantly lower values, with reductions of up to >99% compared to values prior to harvesting. The decline of log₁₀KS in cable yarding systems is only marginally significant (up to -49%). First order analyses of runoff coefficients show a strong effect of the harvester-forwarder system with observed values of up to 0.66. Undisturbed sites had no surface runoff and cable yarding only generated minimal surface runoff. 

How to cite: Behringer, M., Scheidl, C., Markart, G., Meißl, G., Froemel, M., Gasser, L., Grünberg, J., Haas, C., Hofbauer, A., Kitzler, B., Kühmaier, M., Nemestothy, N., Rewald, B., Wieshaider, A., and Katzensteiner, K.: On the impact of timber harvesting on soil water retention and surface runoff, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6522, https://doi.org/10.5194/egusphere-egu24-6522, 2024.

Temperate forests are a substantial sink for the greenhouse gases (GHG) methane (CH₄), carbon dioxide (CO₂) and soil emissions of nitrous oxide (N₂O) are low. However, most of these forests are managed with ground-based harvesting systems causing severe soil disturbance. Soil displacement and compaction has a long-term effect on the soil microbial community structure and alters soil respiration, CH₄ uptake, and nitrogen turnover. This significantly reduces the soil ecosystem services on extraction tracks and landings. Soil disturbance is particularly severe and persistent in compaction-prone silty and loamy soils, emphasizing the urgent need for specific techniques for these sites.

In an empirical Before-After Control-Impact study we compare the effects of harvester-forwarder use with/without tracks (HF/HFt) and cable-yarding with motor-manual-felling (CMM), on the soil chemistry, microbial community, and the soil-GHG balance. Our study is carried out within the project HoBo: Securing the Sustainability of Forest Soil Functions via Optimized Harvesting Technologies (https://dafne.at/projekte/hobo). The study sites are located in the Flysch zone and in the Molasse basin (North Alpine foreland basin). Soil GHG flux rates of CO₂, CH₄, and N₂O are measured with trace gas analyzers (Li-Cor 7810 and 7820), either manually at the recently thinned stands, or continuously with automatic chambers at plots that were thinned in 2016.  For deeper understanding of the effects on soil chemistry and the changes in the microbial community, we determine nitrogen availability, microbial biomass carbon and nitrogen as well as the phospholipid fatty acids (PLFA).

Preliminary results show a significant impact of all applied mechanized timber harvesting systems (HF/HFt/CMM) reducing CH₄ uptake rates and increasing N₂O emissions of both skid trails and cable yarding corridors, compared to the control plots outside the extraction tracks (thinned stand). Our findings underline that sustainable forest management practices should not only reduce soil compaction. It should also consider additional factors, particularly soil displacement induced by logging activities.

How to cite: Hofbauer, A., Behringer, M., Froemel, M., Gasser, L., Grünberg, J., Haas, C., Katzensteiner, K., Kühmaier, M., Markart, G., Meissl, G., Nemestothy, N., Rewald, B., Scheidl, C., Schlögl, M., Wieshaider, A., and Kitzler, B.: Effects of timber harvesting techniques on soil biodiversity and greenhouse gas fluxes of temperate forest soils susceptible to compaction, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10630, https://doi.org/10.5194/egusphere-egu24-10630, 2024.

Soil compaction in forests, often a result of logging activities, poses a significant threat to soil functioning and ecosystem services. Root systems and their symbiotic relationships with mycorrhizae are particularly affected. Given the vital role that sustainably managed forest ecosystems play for climate change resilience and mitigation, understanding the effects of soil compaction on belowground functioning is critical. To address knowledge gaps on the interactions between soil compaction, root growth, and mycorrhizal associations under real-world conditions, it is essential to conduct comparative studies on different harvesting methods. Detailed analyses are required to better understand the spatiotemporal effects of logging on soil as a rooting space. 

To investigate the complex relationships, we implemented different harvesting methods (harvester-forwarder with or without bogie tracks, cable-yarding with motor-manual-felling) and a control treatment between skidding trails in a beech-dominated forest in Lower Austria during the winter of 2022/23. In addition, we sampled ~20-year-old skidding trails (harvester-forwarder) to assess soil recovery.

Using a replicated transect approach across the skidding trails, we studied spatially explicit effects on standing fine root biomass to a depth of ~45 cm in a before-after control-impact design. To allow for upscaling, each transect included areas directly impacted by logging (i.e. skidding trails, cable-yarding corridors) and areas potentially indirectly affected (i.e. between the ruts, bulge area etc.). We conducted comprehensive assessments of fine root biomass depth distribution, and key traits such as anatomy, morphology and fine root nutrient content, as well as mycorrhization rates. 

The data indicate a significant negative influence of both recent and historical timber harvesting on standing root biomass, revealing altered patterns of root distribution with notable differences between and within transects. Our results suggest that different harvesting methods result in very different levels of soil compaction, leading to contrasting effects on fine root traits such as a reduction of absorptive surface area relative to biomass in compacted soil. 

The persistence of negative effects on the old skidding trails highlights the long-lasting impact on root systems and their mycorrhizal symbionts, and thus key ecosystem functions. This emphasizes the importance of conserving forest soils and the need to identify and implement management strategies to minimize soil compaction and promote recovery. These efforts are vital for ensuring the sustainable provision of ecosystem services by the 'hidden half' of forests.

How to cite: Gasser, L., Behringer, M., Froemel, M., Godbold, D., Grünberg, J., Haas, C., Hofbauer, A., Katzensteiner, K., Kitzler, B., Kühmaier, M., Markart, G., Meissl, G., Nemestothy, N., Sandén, H., Scheidl, C., Wieshaider, A., and Rewald, B.: Effects of Logging-Induced Soil Compaction on the Abundance and Characteristics of Fine Roots and Mycorrhizal Associations in Forest Soils and their Recovery, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17507, https://doi.org/10.5194/egusphere-egu24-17507, 2024.

Soil compaction has adverse impacts on key soil functions and can result in restricted root distribution. However, deep roots provide access to water and nutrient reservoirs and might enhance carbon (C) storage in subsoils. Deep rooting is thus a central element for climate-adapted plant productivity and has potential for climate mitigation. Clarity is missing, to what extent different soil traffic intensities impact root depth distribution and root-derived C inputs at field scale.

The present study was conducted to assess the impact of differing soil traffic intensities (i) on soil physical parameters related to compaction, and (ii) to what extent this affects root length density and depth distribution, as well as (iii) above ground biomass and (iV) SOC-stocks. Negative effects of increasing traffic intensities on soil physical parameters are expected to result in reduced root depth distribution and therefore reduced biomass productivity and root-induced carbon allocation.

Soil and plant biomass were sampled along increasing soil traffic intensities at three field sites in central Germany characterized as Luvisols. Penetration resistance was measured in the field, and undisturbed soil rings of top and sub soils were analyzed for bulk density and air capacity. Undisturbed soil cores were taken up to one meter depth during peak root biomass. Root biomass, depth distribution and root length density were evaluated with the core-break method using an automated root spectroscopy imaging system. Based on the results, root-derived C inputs were estimated and C/N-measurement of soil core samples was conducted.

Preliminary findings indicate higher penetration resistance and bulk density, coupled with reduced air capacity in top and subsoils on the headland, where greater traffic intensity takes place. The complete data set will be presented and discussed at the conference.

The conclusions of this study will provide a better understanding of the interactions between soil compaction, root growth and carbon storage. These findings are relevant to assess how soil management affects soil compaction and thus may hinder climate-adapted agriculture.

How to cite: Wiedermann, E., Reinelt, L., Rolfes, L., and Don, A.: Restricted root growth caused by traffic induced soil compaction – a field study in wheat and maize, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9353, https://doi.org/10.5194/egusphere-egu24-9353, 2024.

Analysis of the effects of soil penetrometer resistance (PR) on root elongation and relative classic prediction models mostly ignore the role of macropores, which are important for root to penetrate compacted soils. In this study, undisturbed soil samples were collected from an 11-years tillage experiment (no-tillage and conventional tillage) in Northeast China, and their bulk density (BD), PR, air-filled porosity (AFV), and pore-size distribution were determined. Root elongation of maize seedlings was determined on each soil cores following equilibration at -20 kPa. Our results showed root elongation is significant negatively correlated with BD, PR, and the volume of Pores _{< 6 µm}, while positively correlated with the AFV and macropores (Pores _{> 60 µm}) (P < 0.001). Root elongation rate exhibited a 50% reduction when PR was over 1.3 MPa or AFV was below 10%. A new model has been developed to estimate the rate of root elongation that taken into account the interaction between PR and macropores. The new model had a better performance than previous ones and the root mean square error (RMSE) was 0.13.

How to cite: Qin, S., Liu, L., Whalley, W. R., Zhou, H., Ren, T., and Gao, W.: Revisiting the relationships between maize root elongation and penetrometer resistance, air-filled porosity and macro- porosity on a clay loam Mollisol, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9895, https://doi.org/10.5194/egusphere-egu24-9895, 2024.

Compaction is one of the main types of soil degradation worldwide. The macropores left by ex-plant roots were expected to provide channels to root to penetrate hard soil layers. However, there are few studies to quantitate the relationship between the elongation of maize roots and the root pores, due to complex morphological characteristics of the real root pore systems. In this study, we tried to build an artificial pore with sheath to simulate the effects of root pores on maize root growth in the compacted soil by X-ray CT. Our results indicated that the method for simulating root pores worked well. The sheath width of artificial root-pore was about 2.69 mm. Moreover, sheath of pores had higher organic carbon content and abundance of actinobacteria compared with bulk soil. Compared with artificial macropores, the presence of artificial root-pores diminished the border effects of the pot wall and increased the growth angle of node1 roots and the maximum growth depth of maize roots. However, there were no significant differences in terms of roots spatial distribution (in soil matrix, macropore sheath, macropore), and the ways (crossing or colonizing) of utilization by maize roots to macropores between the treatments with artificial macropores and artificial root-pores. This study provides a new insight into the interactions between root pore, root-pore sheath and maize roots.

How to cite: Gao, W., Liu, L., and Qin, S.: Effects of artificial root-pores on maize roots growth in compacted soil using X-ray computed tomography, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10487, https://doi.org/10.5194/egusphere-egu24-10487, 2024.

Monitoring soil structure is of paramount importance due to its key role in the critical zone as the foundation of terrestrial life. Variations in the arrangement of soil components significantly influence its hydro-mechanical properties, and therefore its impact on the surrounding ecosystem. Soil compaction, resulting from inappropriate agricultural practices, not only affects soil ecological functions by reducing soil porosity and water infiltration, but also decreases the yields spoiling the socio-economic aspect.

In this study, we compared the ability of electrical and electromagnetic geophysical methods, i.e. Electrical Resistivity Tomography and Frequency-domain Electromagnetic Method, to monitor the effects of compaction on agricultural soil. The objective is to highlight the electro-magnetic response caused by plastic deformation of the soil generated by both a super-heavy vehicle and the usual interrows surface compaction generated by tractor traffic for common practices. The survey was conducted both on a small scale, covering an area of 1.5 hectares, and in detail on individual targeted transects. This allowed to capture the 2-D and 3-D spatial heterogeneity that is often difficult to obtain with punctual and invasive traditional methods.

This work aims to contribute to the methodological optimization of agro-geophysical acquisitions and data processing, so as to obtain accurate soil models through non-invasive approach. Results, validated with traditional soil characterization techniques (i.e. penetration resistance, bulk density and volumetric water content on collected samples), show pros & cons of both techniques and how differences in their spatial resolution heavily influence the ability to characterize compacted areas with good confidence.

How to cite: Carrera, A., Peruzzo, L., Cassiani, G., and Morari, F.: Soil compaction signatures on electromagnetic and DC-current geophysics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8055, https://doi.org/10.5194/egusphere-egu24-8055, 2024.

Organic amendment of soils with composts or slurries affects compaction resistance and resilience, but the longevity of these impacts has not been explored, and few data are available from controlled field studies.  Here we carried out a rapid soil compaction resilience test, where coarsely sieved soil to simulate a freshly prepared seedbed are exposed to controlled compaction and cycles of wetting and drying in the laboratory. Agricultural soils with long history of compost and slurry amendments were sampled from the Lower Pilmore field of the James Hutton Institute, Dundee, UK.  Replicated plots received three levels of compost (35, 100 and 200 Mg ha^-1), three levels of slurry (10, 20 and 40 Mg ha^-1) and control (no amendment) from 2005 to 2009. Subsequently, normal rates of 35t ha^-1 and 10 t ha^-1 were applied until 2014. Loose soils sampled in 2023 were sieved to 4mm and then compressed cyclically under uniaxial stresses of (i) 50kPa to simulate a roller, (ii) 200kPa to simulate a tractor, and (iii) again at 200kPa. Between each of these stress cycles the soils were saturated (wetting) for 24 hours and drained (drying) to field capacity (5kPa) for 12 hours on a sandbox. Changes in void ratio during the loading and unloading phases were obtained directly from sample displacement, while the void ratio after wetting and drying was calculated from soil mass-volume relationship. Void ratio increased with increase in organic carbon in both compost and slurry soils. Soil wetting-drying following the first and second 200kPa compression cycles caused significant recovery of void ratio for both compost and slurry. Final void ratio (measured after the wet-dry cycle that followed the second 200kPa compression) was 0.40 m³ m^-3 in the control, versus 0.45 m³ m^-3 in 35 Mg ha^-1 compost and 0.49 m³ m^-3 in both 100 and 200 Mg ha^-1 compost. For slurry soils, final void ratio was 0.40, 0.41 and 0.45 m³ m^-3 for 10, 20 and 40 Mg ha^-1, respectively. Organic carbon accounted for a significant percentage (R² = 0.48; p = 0.00) of variability in the final void ratio for compost soils whilst there was no significant relationship between void ratio and organic C in slurry soils. Compression and recompression indices increased more with increase in compost than with increase in slurry, but overall, they displayed no significant (p≤0.05) relationships with organic carbon. Soils treated with compost are therefore, better able to absorb compressive stresses than their slurry counterparts and could significantly recover their form and capacity to perform their ecological functions following stress withdrawal. Moreover, legacy applications of compost than slurry can affect compaction resilience for several years.

How to cite: Utin, U., Smith, J., Geris, J., and Hallett, P.: The legacy of compost and slurry amendments to soil on physical resilience to compaction, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17045, https://doi.org/10.5194/egusphere-egu24-17045, 2024.

Soil structure influences important soil functions like hydraulic conductivity and air permeability, which in turn influence plant growth. The physical structure of soils is thus, besides chemical and biological parameters, one major component of soil fertility. Unfortunately, this physical fertility is often impaired by agricultural practices.

To study the structural status and the relationships between structural and functional parameters, 45 representative arable sites in Schleswig-Holstein, Germany, were sampled at three depths in top- and subsoil. Soil structure was described quantitatively using X-ray computed tomography of soil cores (continuity and size distribution of macropores). Measured soil functions included saturated hydraulic conductivity, air permeability, air capacity, and pore size distribution (via water retention curves).

The results not only help elucidate relations between structural and functional soil parameters. They also give a detailed and comprehensive insight into the structural state and their relation to soil physical functions of typical arable sites across Schleswig-Holstein that has not existed before.

How to cite: Roosch, S., Ormeno, J., Uteau, D., Fleige, H., Mordhorst, A., Rostek, J., Wiermann, C., Müller, G., and Peth, S.: Correlating tomography structure parameters with physical soil functions in representative sites in Schleswig-Holstein, Germany, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12523, https://doi.org/10.5194/egusphere-egu24-12523, 2024.

Aim: Anthropogenic compaction is typically assumed to be major threat to soil health in agriculture. Compaction of the subsoil is considered irreversible and therefore more severe than topsoil compaction. To-date, quantitative estimates about the extent and severity of soil compaction are hardly available. This study aims to quantify anthropogenic subsoil compaction in German croplands by reanalyzing data from the German Agricultural Soil Inventory (BZE-LW). Grassland sites, which are assumed to exhibit negligible traffic-induced compaction below 30 cm depth, serve as a reference for the prediction of bulk density in cropland sites before anthropogenic compaction.

Methods: A data-driven reciprocal modelling approach is employed to estimate human-induced increases in bulk density at 1477 cropland sites scattered in a regular 8 x 8 km grid across Germany. The model is trained on data from ~400 grassland sites using information about soil texture, organic C content, soil pH, climate, and geological parent material. The model is then applied to the cropland sites to predict the bulk density of the upper subsoil in 30-50 cm depth prior to anthropogenic compaction. The disparity between modelled and observed bulk density represents the trafficking induced changes in soil compactness. To explain the drivers of this change, another data-driven model, incorporating soil and climate information as well as cropland management data, is trained and interpreted.

Results: Traffic-induced compaction has significantly increased the median bulk density of subsoils under cropland by 0.055 g cm⁻³, corresponding to a 4% increase. The modelled effects ranges from -0.07 g cm-3 to 0.180 g cm⁻³ (10th and 90th quantile), with the largest increases in subsoil compaction observed in eastern Germany. For the 20% most severely affected sites in Germany, the median increase in bulk density was 0.180 g cm⁻³ (0.142 g cm⁻³ – 0.267 g cm⁻³, 10th and 90th quantile), which corresponds to a 12% increase in subsoil bulk density. The anthropogenic increase in soil bulk density was most pronounced in loamy soils with relatively low soil organic carbon content.

Conclusion: This study represents a significant advancement in our ability to quantitatively assess the extent and severity of anthropogenic subsoil compaction at a national scale. The data-driven reciprocal modelling approach employed is promising for broad application in relation to soil health monitoring initiatives across Europe. 

How to cite: Harbo, L. S. and Schneider, F.: Estimating anthropogenic subsoil compaction in Germany using data-driven reciprocal modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5503, https://doi.org/10.5194/egusphere-egu24-5503, 2024.