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JOURNAL OF FOREST SCIENCE, 57, 2011 (7): 321–339 Saturated hydraulic conductance of forest soils affected by track harvesters K. Rejšek1, P. Holčíková1, V. Kuráž2, A. Kučera1, P. Dundek1, P. Formánek1, V. Vranová1 1 Department of Geology and Pedology, Faculty of Forestry and Wood Technology, Mendel University in Brno, Brno, Czech Republic 2 Department of Irrigation, Drainage and Landscape Engineering, Faculty of Civil Engineering, Czech Technical University in Prague, Prague, Czech Republic Abstract: The exact data from the field of soil mechanics from specific forest stands exposed to forestry mechanization operation were obtained. Field surveys were performed on four study plots within the Křtiny Training Forest Enterprise, Masaryk Forest, followed by laboratory analyses of the collected soil samples aimed at evaluation of the impacts of Zetor 7245 Horal System, PONSSE ERGO 16 harvester and Gremo 950 forwarder on the compaction of upper soil horizons as well as on the dynamics of soil saturated hydraulic conductivity. A specific objective of the performed investigation was to assess the influence of the used hauling/skidding technology on measurable parameters of soil mechanics with the emphasis on a possibility to apply the Guelph permeameter for direct study of soil saturated hydraulic conductivity. In the measurement points affected by machinery operation, the impact of the changed soil structure on the values of saturated conductivity is very well noticeable – on study plots No. 3 and 4, the values decreased by one order of magnitude from 0.7 × 10 –5 m·s –1 to 0.09 × 10 –5 m·s –1: specifically, (i) on study plot No. 3 and from 6.9 × 10 –5 m·s –1 to 0.7 × 10 –5 m·s –1, and (ii) on study plot No. 4; on study plot No. 2 even by two orders, i.e. from 1.6 × 10 –5 m·s –1 up to 0.03 × 10 –5 m·s –1. After the operation of a universal wheeled tractor at the Babice nad Svitavou locality, the situation partially improved by one order to 0.3 × 10 –5 m·s –1, similarly like at the Rudice locality to 1.5 × 10 –5 m·s –1. Significant changes were found in both surface and subsurface horizons. Field-saturated hydraulic conductivity indicates also a reduction of the pore volume after machinery traffic; however, tendencies towards restoration of the original state were detectable as soon as after six months. Keywords: forest soil; saturated hydraulic conductivity; hauling technology; Guelph permeameter The total area of forest stands in the Czech Republic is 2,653,033 ha, which represents 33.64% of the area of the Czech Republic. In 2008, 16.2 million m3 of raw timber were harvested from the total stock of 676.4 million m3 of raw timber with the average standing volume of 260.4 m3 of raw timber per 1 ha of stand area, including clearcuts (Report on the State of Forest and Forestry in the Czech Republic in 2008, 2009). The significance of the presented numbers is important from the aspect of the influence on the state and dynamics of forest soil development as harvested timber is hauled or skidded from the stands by methods with very different impacts on soil. Information from the Report on the State of Forests and Forestry in the Czech Republic by 2009 shows that almost one third of the annual cut is processed by the shortwood logging method (the rest by the tree-length logging method) and that all raw timber was transported for further handling or processing from the regenerating Supported by the Ministry of Agriculture of the Czech Republic, Project No. QH71159. J. FOR. SCI., 57, 2011 (8): 321–339 321 forest stands by a universal wheeled tractor with a winch (UWT/UKT), special forest prime mover (SFPM/SLKT), forwarder or by a cableway installation. However, cableway installations are presently employed in the transport of less than 350,000 m3 of timber per year in the Czech Republic due to low effectiveness of their use and complexity of the whole technological procedure, which leads to practically full-area employment of UKT and SLKT with such potentially serious impacts on forest soils that research on the relation between forestry hauling technologies and soil mechanics is inevitable. A specific goal of the investigation presented in this paper was to assess the impacts of the applied hauling/skidding technology on measurable parameters of soil mechanics with special focus on the possible application of a Guelph permeameter for direct study of soil saturated hydraulic conductivity dynamics. The field surveys were combined with standard soil-physical laboratory methods (Rejšek et al. 2010), with the objective to detect any changes in physical, hydrophysical and soil-mechanical properties of forest soil in reaction to logging and hauling machinery operations. The soil conditions at the individual localities were described by the basic physical, physicochemical and chemical properties of the individual horizons, obtained from open soil profiles (Dundek et al. 2010). Within the field survey, saturated hydraulic conductivity was measured with a Guelph permeameter: the aim of the author team was to use the obtained data to assess changes in the conditions for pedogenetic processes in the upper soil horizons. Simultaneously, repeated measurements with a dynamic permeameter and sampling of the examined forest soil profiles with uniform metal cylinders were carried out. Saturated hydraulic conductivity of forest soils affected by the operations of a universal wheeled tractor Zetor 7245 Horal System, PONSSE ERGO 16 harvester and Gremo 950 forwarder on selected study plots within the Křtiny Training Forest Enterprise, Masaryk Forest, was investigated by laboratory analyses aimed at the basic physical and hydrophysical methods as well as by a field survey with the application of a Guelph permeameter (Reynolds, Elrick 1985). From the aspect of forestry, saturated flow is not of key importance, contrary to the state of steady flow depending on water sorbents. Therefore, we differentiate between the stationary flow with flow speed and moisture content that are constant in time, and non-stationary flow with changing speed and soil moisture content (Homolák et al. 2010). The flow can be further classified according to the saturation of pores with 322 water as saturated flow, filling up all the pores, and non-saturated flow, where some of the pores are filled up with air and so the soil can further saturate with water, or reversely drain (Rehák et al. 2006). Morphology and structure affected by compaction have a fundamental significance for hydraulic conductivity as well as water, air and heat regimes. The authors of this paper have focused on stationary saturated flow since it can indicate the changes of soil physical properties due to machinery traffic and at the same time its measurement is easy to perform within forestry research (Lhotský 2000). Saturated hydraulic conductivity is nowadays measured either in a laboratory (cylindrical samples of soil) or by field measurements. However, analyses performed on sampled soil are less accurate as the sampling and transport may change some important properties. The dynamics of saturated hydraulic conductivity of soil is expressed by the coefficient Kfs and evaluated on the basis of field experiments. This characteristic is measured either by a single-well test or by so-called auger-hole method, in relation to the instantaneous depth of the groundwater level: if the groundwater level is close to the surface, a hole is bored to a specified depth under the water level; after measuring the hole’s depth and the water level, water is pumped out and the rise rate of the groundwater in the hole is determined with a float and a stopwatch. If it is not possible to reach the water level in this way, Kfs is determined by a pump-in test with a Guelph permeameter. In this case, the rate of water discharge from the apparatus into the hole is read at regular time intervals until stationary flow is reached, i.e. the rate of flow through the hole is constant (Kutílek et al. 1996). An advantage of this method is that only few variables are necessary for Kfs calculation, consumption of water is low and the equipment needed to perform the measurement is simple. MATERIAL Parameters of operating machines Zetor 7245 Horal System. Universal wheeled tractor with four-wheel drive (4×4) and standard tyres Mitas 11.2-24“, profile TD-19, on the front axle, and tyres 16.9-30“, profile TD-13, on the rear axle. The pressure recommended by the manufacturer is 240 kPa for the front tyres and 200 kPa for the rear tyres. 60% of the weight of the tractor act upon the rear axle. The total weight of the tractor with the forestry body (front platform loader, shield with a winch and safety frame) is about 5 t. PONSSE ERGO 16 harvester. A three-axle harvesting machine designed with maximum attention to the low impact of operations on forest stands. J. FOR. SCI., 57, 2011 (8): 321–339 It is equipped with a tilting cabin with antivibration equipment, a modern hydraulic system of all wheel drive and an electronic control unit (front tyre dimensions 700/50-22.5“, rear tyre dimensions 700/55-34“. The tyres were not fitted with any supplementary devices such as tracked wheels or non-skid chains. The total weight of the machine (depending on the equipment used) is about 16 t. Gremo 950 forwarder, A four-axle universal forwarder Gremo 950 is designed for the low-impact extraction of timber after harvester logging. The rear part of the machine has a capacity to carry up to 4.1 m3 of timber, load capacity 9.5–10 t. Timber is loaded with a hydraulic crane placed traditionally in front of the loading space. The electronically controlled hydrodynamic drive of all wheels ensures the smooth operation of the machine without wheel spinning. Service weight of the machine is almost 12 t. The forwarder was equipped with Nokian tyres of 700 × 22.5“ at all axes. All wheels of the forwarder were fitted with non-skid chains. Measurement equipment used in field surveys Guelph permeameter (constant head permeameter). The device works on the principle of Mariotte bottle (Kutílek et al. 2000), i.e. it maintains the constant head of water at the outlet by means of a negative-pressure air cushion that forms above the liquid level. The permeameter consists of a water reservoir and an outlet with perforated bottom and walls. A hole of 2 to 5 cm in diameter and depth up to 1 m is bored into soil and the outlet part is inserted; the authors used a hole of 3 cm in diameter and of 15 cm in depth. By raising the air tube, the level of water in the hole was set and gradual outflow of water from the reservoir began. The rate of the water level decrease in the reservoir was measured until stationary flow Q (m3·s–1) was reached. The following equation by Kutílek et al. (2000) was used for the evaluation: cQ Kfs = (2πH + cπr) where: c – non-dimensional factor depending on texture and H/r ratio (c ± 1.59), Q – stationary value of water flow from the permeameter, r – radius of the bored hole, H – level of water in the hole. Study plots The survey was carried out on four study plots within the Křtiny Training Forest Enterprise, J. FOR. SCI., 57, 2011 (8): 321–339 Masaryk Forest, a special-purpose facility of Mendel University in Brno. All study plots are situated in a special-purpose forest with high forest silvicultural system and shelterwood (small area felling) or with clear-cutting system of management. Generally we can say that the study plot in Babice nad Svitavou represented the group of forest types 3A, i.e. lime-oak beech forest, and according to the framework management guidelines it represented the management set of stands 306 Special-purpose beech management of drying and drier acerous and basic sites at medium altitudes. In Rudice, the study plots belonged to the group of forest types 4K, i.e. acidic beech stands, the management set of stands 421 Special-purpose spruce management of acidic sites at medium altitudes. Field surveys Soil pits were described at all four localities, sampling of physical cylinders and subsequent analyses were performed only at localities No. 2–4. In order to obtain the overall characteristic of soil conditions, the following properties were determined: physical (grain size, density, bulk density and wet bulk density, maximum capillary water capacity, porosity, volume and weight moisture, aeration, minimum air capacity, relative capillary moisture, relative saturation of pores and dry matter content), physicochemical (active soil reaction, reserve/potentially exchangeable soil reaction, base saturation, cation exchange capacity, content of exchangeable base cations) and chemical (content of oxidizable carbon, total nitrogen content and C:N ratio). To assess the impact of forestry mechanization traffic, physical properties and saturated hydraulic capacity were measured repeatedly. In order to obtain detailed characteristics of soil properties, a soil pit 110–120 cm in depth was excavated on each plot in a place reflecting natural conditions in the specific stand. Its position was chosen on the basis of terrain reconnaissance and evaluation of potential influences affecting the specific plot. The terminology from the Taxonomic Soil Classification System of the Czech Republic (Němeček et al. 2001) and the Munsell system of colour notation of soil horizons were applied for description of soil profiles. Undisturbed samples, i.e. samples with unchanged macrostructural features, from the described horizons were taken with uniform metal cylinders of 100 cm3 in volume. In addition, the soil profiles of the study plots were sampled and analysed in laboratory using standardized proce323 dures (Rejšek 1999). At the same time, field measurements of saturated hydraulic capacity Kfs with Guelph permeameter were performed. The collection of physical cylinders from the first three diagnosed soil horizons and the permeameter measurements were repeated shortly after a harvesting operation and again 6 months later, i.e. in October 2007, April 2008 and October 2008. Due to different physiological depth of soil, the physical samples were collected from the first three diagnosed horizons, beginning with the organomineral horizon, where the most significant impact of machinery traffic is expected. The plots were divided by harvesting into areas with ongoing operations and areas where the stand was left without intervention. The measurements were divided into control measurements monitoring the seasonal dynamics of the studied characteristics and measurements in the places of machinery traffic. Therefore, two measurements were performed on each study plot: one in a place exposed to multiple traffic of machinery and the other in a control place, intact by any machinery operation or its influence. Values of water flow rate v into the soil profile were read each minute, until stationary flow Table 1. Properties of particular soil horizons, study plot No. 2, Babice nad Svitavou, universal whelled tractor Zetor 7245 No. of forest stand: 314B10; District in Masaryk Forest Křtiny: Bílovice; Hauling machine: UWT; Pedogenetic substrate: decalcified loess; Soil group: Luvisol; Soil subunit: Haplic; Code: haLV Horizon Ah Soil physics Designation of a property El Designation of a property Bt 2–0.25 2.36 2.20 3.20 0.25–0.1 2.98 2.18 1.20 0.1–0.05 10.34 0.05–0.01 50.08 0.01–0.002 18.32 19.12 12.20 > 0.002 15.92 18.36 43.40 Maximum capillary capacity ΘMKK 25.97 Moisture content by mass w sandy loam waterholding 14.94 43.2 sandy loam 12.24 27.76 Designation of a property clay 30.74 strongly waterholding 36.74 strongly waterholding 27.25 moderately wet 17.07 moderately wet 21.05 moderately wet Wet bulk density ρw 0.94 – 1.53 – 1.87 – Bulk density ρd 0.74 – 1.30 – 1.54 – Density ρs 2.24 – 2.59 – 2.79 – Porosity P 67.15 high 49.72 moderate 44.67 low Moisture content by volume Θ 20.07 – 22.24 – 32.44 – Soil aeration A 47.08 – 27.48 – 12.23 – Minimal air capacity AMKK 41.18 very highly aerated 18.98 moderately aerated 7.93 low aerated Relative soil moisture RV 77.28 – 72.35 – 88.3 – Relative saturation RNP 29.89 – 44.73 – 72.63 – pH/H2O 4.23 moderately acid 4.49 moderately acid 6.49 neutral pH/KCl 3.71 strongly acid 3.51 strongly acid 5.34 moderately acid Cation exchange capacity T 38.1 very low 67.5 very low 101.7 low Content of exchangeable basic cations S 10.1 very low 50.9 low 98.3 moderate Base saturation V 26.6 unsaturated Soil physicochemistry 75.5 moderately saturated 96.7 highly saturated Soil chemistry Cox Nt C:N 324 8.50 very high content of 1.75 humic compounds 0.469 very high 0.104 18.1 – 16.8 1.05 high content of humic compounds moderate 0.096 – 10.9 low content of humic compounds moderate – J. FOR. SCI., 57, 2011 (8): 321–339 Q was reached, which was then used to calculate the saturated hydraulic capacity Kfs of the specific soil. Results from study plot No. 2 are linked to a skidding trail with the total of 5 passes of the universal wheeled tractor Zetor 7245 Horal that transported 12 m3 of timber in semi-suspension. It is necessary to take into account that the stand 314B10 had been previously prepared for regeneration with a release cutting measure, and so the harvesting and skidding operations did not involve high volumes of timber, but rather required frequent traffic of the tractor. The control measurements were performed 15 m from the testing trail in a young stand unaffected by the described tractor operations. The exact characterisation of the soil units on the plot is given in Table 1. On study plot No. 3, harvester thinning was carried out in order to open up the stand, which is classified as a source of reproductive material for spruce and larch in the phenotype category B. Within the operation, 560 m3 of timber were harvested, both roundwood assortments and pulpwood. A three-axle PONSSE ERGO 16 harvester was used for the opening up operation and the following haulage was performed by a four-axle Gremo 950 forwarder. The exact characterisation of the soil units on the plot is given in Table 2. On study plot No. 4, motor-manual thinning was carried out. The following extraction and skidding works were performed by a universal wheeled tractor Zetor 7245 Horal with forestry body. 16.4 m3 of raw timber were harvested in total. The exact characterization of the soil units on the plot is given in Table 3. Laboratory analyses Analyses were performed in the laboratories of the Department of Geology and Pedology at the Faculty of Forestry and Wood Technology, Mendel University in Brno, separately for the uniform metal cylinders and for the soil samples as such. After assessing the content of water and dry matter in the samples with the original moisture content, the samples were dried out for other standardised procedures (Rejšek 1999). The proportion of the individual particle size fractions in a sample was assessed by a pipetting method, when 20 g of a sample are mixed with 20 ml of dispersing medium and 20 ml of distilled water, the mixture is left to stand for one day and then boiled for one hour. The dispersed solution is transferred into a sedimentation cylinder and distilled water is added up to 1,000 ml. The suspension is stirred up for 1 min, after which the sedimentation J. FOR. SCI., 57, 2011 (8): 321–339 time measurement begins. The samples of the suspension are pipetted with a 25 ml volume pipette at the depth of 25 cm at the time of 10 s, at the depth of 10 cm at 12.5 s and at the depth of 7 cm at 15 s in compliance with the appropriate time data, i.e. with both time after the end of stirring and time before the end of sedimentation. Particles of diameter < 0.05 mm are found at the depth of 25 cm at the time of 112 s from the beginning of measurement, particles < 0.01 mm are at the depth of 10 cm at 18 min 51 s and particles < 0.001 mm may be pipetted at the depth of 7 cm after 22 h 6 min 12 s from the beginning of measurement. The analysis of uniform metal cylinders began by weighing in the original state, in the water-saturated state after 24 h, in the state after saturation with the frequency of 90 min and again after being re-dried at 105°C (Zbíral et. al. 2004). Density was determined pycnometrically. The remaining basic chemical and physical-chemical properties were assesseh by methods according to Rejšek (1999), including calculations of the basic physical characteristics. RESULTS The basic physical and hydro-physical properties of the individual soil horizons of the soils from the study plots are presented in both tables and figures: for study plot No. 2 (Table 4 and Fig. 1), for study plot No. 3 (Table 5 and Fig. 2), and for study plot No. 4 (Table 6 and Fig. 3). In general, the authors have proved that the soils on study plots No. 3 and 4 collectively show sandy silt loam and clay loam in surface horizons to silty clay and clay in horizons Bt (very heavy grain size composition). Porosity and aeration decrease with depth at locality No. 3 up to the category “nonarerated” in E/B horizon. In surface horizons a strong acidity (low pH/H2O), the maximum capacity of the sorption complex is very low and extremely unsaturated to saturated (towards the Bt horizon) for all horizons. As regards the chemical properties, the soils found on study plots No. 3 and 4 are humic with medium nitrogen content and, compared to the study plots at thy Babice nad Svitavou locality, with higher C:N ratio, corresponding to the quality of the organic matter entering the soil, i.e. corresponding to the fact that common spruce (Picea excelsa [L.] Karst.) is the main commercial species there. Regarding the dynamics of change of the field saturated hydraulic conductivity Kfs, the original measurementt detected changes caused by the machinery traffic (the section Discussion 325 326 J. FOR. SCI., 57, 2011 (8): 321–339 13.45 46.16 18.36 16.84 25.68 0.1–0.05 0.05–0.01 0.01–0.002 > 0.002 Maximum capillary capacity ΘMKK 26.55 Minimal air capacity AMKK 0.187 Nt 18.3 3.43 Soil chemistry Cox C:N 36.30 13.5 Content of exchangeable basic Cations S Base saturation V 37.3 3.21 3.87 28.30 Cation exchange capacity T pH/KCl pH/H2O Soil physicochemistry Relative saturation RNP 57.55 37.45 Relative soil moisture RV 14.78 Soil aeration A 52.23 2.42 1.16 1.30 Moisture content by volume Θ Porosity P Density ρs Bulk density ρd Wet bulk density ρw 12.78 2.14 0.25–0.1 Moisture content by mass w 3.05 Ah 2–0.25 Soil physics Horizon – very high content of humic compounds moderate low saturated very low very low very strongly acid strongly acid – – highly aerated – – moderate – – – dry waterholding sandy loam Designation of a property 17.5 0.053 0.93 56.80 17.30 30.40 3.49 4.14 32.28 56.75 21.90 34.40 16.40 50.80 2.59 1.27 1.44 12.87 28.90 16.80 18.64 46.56 12.61 2.030 3.36 El – low content of humic compounds low moderately saturated very low very low strongly acid moderatedly adic – – highly aerated – – moderate – – – fairly moist waterholding sandy loam Designation of a property 8.9 0.062 0.55 78.90 21.80 27.60 4.09 5.20 76.68 86.37 4.36 9.06 29.79 38.85 2.65 1.62 1.92 18.37 34.49 37.04 15.44 35.36 8.83 1.25 22.24 EB – high content of humic compounds moderate very highly saturated very low very low strongly acid slighly acid – – very low aerated – – low – – – moderately wet strongly waterholding sandy clay Designation of a property 12.0 0.069 0.83 93.20 29.30 31.50 5.95 7.32 80.80 82.04 0.64 8.14 34.25 42.39 2.83 1.63 1.97 21.01 41.75 51.12 13.92 22.40 10.21 0.88 1.47 Bt – low content of humic compounds moderate highly saturated low very low slighly acid slightly alkaline – – very low aerated – – low – – – fairly moist strongly waterholding clay Designation of a property No. of forest stand: 146D7; District in Masaryk Forest Křtiny: Habrůvka; Hauling machine: Harvestor; Pedogenetic substrate: decalcified loess; Soil group: Luvisol; Soil subunit: Haplic; Code: haLV Table 2. Properties of particular soil horizons, study plot No. 3, Rudice, the harvestor PONSSE ERGO 16 and the forwarder Gremo 950 J. FOR. SCI., 57, 2011 (8): 321–339 327 17.18 29.92 19.24 20.96 26.70 0.1–0.05 0.05–0.01 0.01–0.002 pod 0.002 Maximum capillary capacity ΘMKK 28.75 Minimal air capacity AMKK C:N Nt Soil chemistry Cox highly unsaturated 16.9 – very high content of humic compounds 0.26 high 4.4 9.60 very low Base saturation V Content of exchangeable basic cations S 2.60 very strongly acid strongly acid – – very low 3.33 3.92 31.38 highly aerated – – high – – – moderately wet waterholding loam Designation of a property 27.4 Cation exchange capacity T pH/KCl pH/H2O Soil physicochemistry Relative saturation RNP 65.17 38.05 Soil aeration A Relative soil moisture RV 17.40 55.45 2.39 1.07 1.24 Moisture content by volume Θ Porosity P Density ρs Bulk density ρd Wet bulk density ρw 16.33 5.18 0.25–0.1 Moisture content by mass w 7.52 Ah 2–0.25 Soil physics Horizont unsaturated very low very low strongly acid moderatedly adic – – highly aerated – – moderate – – – fairly moist waterholding loam Designation of a property 22.2 – high content of humic compounds 0.099 moderate 2.2 20.00 3.90 19.60 3.60 4.26 37.84 64.34 20.22 30.52 18.58 49.10 2.44 1.24 1.43 14.93 28.88 20.68 18.56 28.92 13.51 8.24 10.09 Eh low saturated very low very low strongly acid moderatedly adic – – moderately aerated – – low – – – fairly moist waterholding loam Designation of a property 17.0 – high content of humic compounds 0.099 moderate 1.68 34.50 6.40 18.50 3.81 4.22 51.85 79.13 14.36 20.06 21.61 41.67 2.56 1.49 1.71 14.49 27.31 18.44 16.96 25.96 14.21 9.38 15.05 El clay loam Designation of a property 40.84 12.76 7.80 24.87 6.23 7.50 Bt clay Designation of a property 8.6 0.093 0.80 44.01 6.60 14.90 3.98 4.75 68.66 87.65 9.18 13.28 29.10 42.38 2.73 1.57 1.87 18.49 – low content of humic compounds moderate low saturated very low very low strongly acid moderatedly adic – – low aerated – – low – – – fairly moist 12.7 0.093 1.18 66.50 10.10 15.20 4.21 5.13 61.37 82.03 11.24 17.24 27.39 44.63 2.89 1.60 1.87 17.12 – high content of humic compounds moderate moderately saturated very low very low strongly acid slighly acid – – highly aerated – – low – – – fairly moist 33.20 strongly waterholding 33.39 strongly waterholding 39.00 13.68 18.20 13.06 6.80 9.26 EB No. of forest stand: 146A7; District in Masaryk Forest Křtiny: Habrůvka; Hauling machine: UWT; Pedogenetic substrate: polygenetical loams mixed with flintstones; Soil group: Luvisol; Soil subunit: Dystic; Code: dyLV Table 3. Properties of particular soil horizons, study plot No. 4, Rudice, universal whelled tractor Zetor 7245 2.58 2.51 April 08 October 08 2.79 October 07 Bt 2.54 2.59 April 08 October 08 2.79 October 07 Bt 2.58 2.56 April 08 October 08 2.59 October 07 El 2.56 2.65 April 08 October 08 2.59 October 07 El 2.55 2.55 April 08 October 08 2.24 October 07 Ah 2.56 October 08 2.55 Ah April 08 Density (g·cm–3) 2.24 Soil horizon October 07 Month of the field investigation 1.92 1.84 1.87 1.84 1.88 1.87 1.82 1.71 1.53 1.83 1.81 1.53 1.58 1.54 0.94 1.96 1.62 0.94 Wet bulk density (g·cm–3) 1.58 1.49 1.54 1.46 1.56 1.54 1.47 1.35 1.30 1.48 1.49 1.30 1.22 1.18 0.74 1.59 1.27 0.74 Bulk density (g·cm–3) 36.78 39.24 36.74 40.06 35.11 36.74 38.72 40.93 30.74 38.88 38.13 30.74 41.86 40.91 25.97 37.37 42.54 25.97 Maximum capillary capacity (%) 38.64 40.87 44.67 42.48 39.92 44.67 42.81 47.31 49.72 42.10 43.56 49.72 52.16 53.59 67.15 37.85 50.41 67.15 Porosity (%) 21.65 35.29 32.44 26.04 32.04 32.44 23.5 35.91 22.24 23.48 31.49 22.24 29.79 35.70 20.07 22.74 35.45 20.07 Moisture content by volume (%) 34.23 23.75 21.05 38.01 20.58 21.05 34.64 26.58 17.07 34.86 21.09 17.07 36.36 30.15 27.25 36.23 28.02 27.25 Moisture content by mass (%) 4.41 5.58 12.23 4.470 7.88 12.23 8.17 11.40 27.48 7.24 12.07 27.48 15.80 17.89 47.08 1.62 14.96 47.08 Soil aeration (%) 1.86 1.63 7.93 2.42 4.81 7.93 4.09 6.38 18.98 3.22 5.43 18.98 10.30 12.68 41.18 0.48 7.87 41.18 Minimal air capacity (%) 93.07 89.93 88.30 94.88 91.26 88.30 89.46 87.74 72.35 89.66 82.59 72.35 86.86 87.26 77.28 96.95 83.33 77.28 Relative soil moisture (%) Table 4. The changes in soil physical parameters after the travel of the universal wheeled tractor, study plot No. 2, Babice nad Svitav ou, the topsoil (7–60 cm) Study plot (effect of a travel) Control plot Study plot (effect of a travel) Control plot Study plot (effect of a travel) Control plot 328 J. FOR. SCI., 57, 2011 (8): 321–339 88.58 86.35 72.63 89.48 80.26 72.63 80.92 75.9 44.73 82.81 72.28 44.73 69.71 66.62 29.89 95.71 70.33 29.89 Relative saturation (%) deals also wite potential influences of the actual weather course). For the individual study plots, the influence of the changed soil structure is very well manifested in the values of saturated conductivity as well as in the compaction of upper soil horizons. Study plot No. 1, Babice nad Svitavou, lies in the top part of a ridge, where an exceptionally high skeleton content is typical within the soil profile. Due to this fact, it was not possible to use the Guelph permeameter – the skeleton would distort the respective measurement to such an extent that the obtained results would be absolutely misleading. (%) 120 100 For this reason, the authors inevitably regarded the high skeleton content as a factor making the survey on this study plot impossible. However, the authors are aware of the fact that from the forestry aspect, skeleton is quite beneficial, as the stones that are in mutual contact show much higher bearing capacity and also reinforce the soil profile: in sharp-edged skeleton, the stones are strongly engaged and work as the so-called railway superstructure; therefore, forestry mechanization does not cause any high compaction of upper soil horizons there. The locality is on a terrain elevation passing to a slope of Ah horizon Maximum capillary capacity Moisture content by mass Relative saturation Porosity Minimal air capacity 80 60 40 20 0 October 07 (%) 90 80 70 60 50 40 30 20 10 0 100 October 08 October 07 El horizon Study plot (effect of a travel) October 07 (%) April 08 April 08 October 08 October 07 Study plot (effect of a travel) Bt horizon April 08 October 08 Control plot April 08 October 08 Control plot 90 80 70 60 50 40 30 20 10 0 October 07 April 08 October 08 Study plot (effect of a travel) J. FOR. SCI., 57, 2011 (8): 321–339 October 07 April 08 Control plot October 08 Fig. 1. The results of the laboratory analyses, the metal cylinders, study plot No. 2, Babice nad Svitavou, UWT 329 2.60 2.65 April 08 October 08 2.65 October 07 EB 2.62 October 08 2.65 April 08 EB 2.65 October 07 2.63 2.60 April 08 October 08 2.59 October 07 El 2.58 2.62 April 08 October 08 2.59 October 07 El 2.56 2.45 April 08 October 08 2.42 October 07 A 2.56 October 08 2.50 April 08 Density (g·cm–3) 2.42 A Soil horizon October 07 Month of the field investigation 1.88 1.92 1.92 2.03 1.91 1.92 1.42 1.93 1.44 1.75 1.72 1.44 1.45 1.66 1.30 1.77 1.51 1.30 Wet bulk density (g·cm–3) 1.63 1.65 1.62 1.70 1.62 1.62 1.30 1.62 1.27 1.50 1.43 1.27 1.30 1.24 1.16 1.54 1.13 1.16 Bulk density (g·cm–3) 36.18 30.64 34.49 33.12 31.57 34.49 33.14 34.11 28.90 36.28 33.55 28.90 33.32 44.00 25.68 38.00 41.98 25.68 Maximum capillary capacity (%) 37.30 37.55 38.85 35.03 38.59 38.85 50.66 37.80 50.80 41.79 45.27 50.80 49.42 49.39 52.23 39.93 54.87 52.23 Porosity (%) 15.43 27.20 29.79 19.51 28.12 29.79 9.40 31.59 16.40 16.9 28.77 16.40 11.54 42.18 14.78 15.11 38.49 14.78 Moisture content by volume (%) 25.19 16.46 18.37 33.18 17.31 18.37 12.20 19.55 12.87 25.36 20.08 12.87 14.96 34.00 12.78 23.21 34.11 12.78 Moisture content by mass (%) 12.11 10.35 9.06 1.85 10.47 9.06 38.46 6.21 34.40 16.43 16.50 34.40 34.46 7.21 37.45 16.72 16.38 37.45 Soil aeration (%) 1.12 6.91 4.36 1.91 7.02 4.36 17.52 3.69 21.90 5.51 11.72 21.9 16.10 5.39 26.55 1.93 12.89 26.55 Minimal air capacity (%) 69.62 88.77 86.37 100.18 89.07 86.37 36.81 92.61 56.75 69.90 85.75 56.75 44.90 95.86 57.55 61.08 91.69 57.55 Relative soil moisture (%) 67.54 72.44 76.68 94.72 72.87 76.68 24.08 83.58 32.28 60.68 63.56 32.28 30.27 85.41 28.30 58.12 70.15 28.30 Relative saturation (%) Table 5. The changes in soil physical parameters after the travel of the harvestor PONSSE ERGO 16 and the forwarder Gremo 950, study plot No. 3, Rudice, the topsoil (4–55 cm) Study plot (effect of a travel) Control plot Study plot (effect of a travel) Control plot Study plot (effect of a travel) Control plot 330 J. FOR. SCI., 57, 2011 (8): 321–339