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Este trabalho teve como objetivo avaliar a resistência do solo à penetração (RSP) em seção transversal à trilha de tráfego dos tratores "Feller-buncher" e "Skidder" na colheita de madeira, utilizando-se as técnicas de geoestatística na determinação da dependência espacial e interpolação por krigagem. Ajustaram-se modelos de semivariogramas para determinação da dependência espacial antes do tráfego e depois do corte e do arraste. O coeficiente de variação da RSP na trilha diminuiu com o tráfego. Os resultados indicaram moderada dependência espacial da RSP antes e depois do corte, ajustando-se o modelo esférico. O modelo linear ajustou-se às semivariâncias após o arraste da madeira, indicando, nesse caso, a necessidade de se trabalhar com uma malha maior para representar a continuidade do atributo. A metodologia geoestatística mostrou ser boa ferramenta para estimar valores em pontos não amostrados e na construção dos mapas de isolinhas da RSP pelo método de interpolação por krigagem. This work was carried out to evaluate soil penetration resistance (SPR) in a transversal section of the traffic trail of the tractors Feller-buncher and Skidder during wood harvesting. Geostatistic techniques were used to determine spatial dependence and kriging interpolation. Semivariogram models were fit to determine spatial dependence before traffic and after cutting and skidding. The SPR variation coefficient in the trail reduced with traffic. The result showed a moderate SPR spatial dependence in the soil section before and after cutting,with the spherical model being adjusted. The linear model was adjusted to semivariance after wood skidding, indicating the need to use a larger grid to represent the continuity of the attribute. The geostatistic methodology was found to be a good tool to estimate the values in non-sampled points and in SPR contour map building

Exposure to whole-body vibration (WBV) has been associated with a wide variety of health disorders. While previous work has established that forest machine operators are exposed to high levels of translational WBV, there are no reports which have quantified field levels of rotational vibration; therefore, the purpose of this work was to quantify six degree of freedom (6-DOF) accelerations that forest machine operators are exposed to during routine machine operations as well as to assess potential health risks and determine the effect of various measurement locations (chassis, seat/operator interface (SOI)), driving conditions (driving loaded (DL), driving unloaded (DUL)) and axis ( X , Y , Z and roll, pitch, yaw). Simultaneous measures of 6-DOF acceleration from both the SOI and chassis were determined for seven skidders operating in Northern Ontario boreal forest conditions during the months of June and July 2006. Average running root mean squared (RMS) ISO 2631-1:1997 weighted accelerations were between 0.72 and 1.12 m/s 2 and 0.33 and 0.79 rad/s 2 at the SOI in the translational and rotational axes, respectively. The dominant frequency and the SOI and chassis was determined to be 1 Hz at both at the chassis and SOI while DL and DUL in the X - and Y -axes, and 2 Hz in Z -axis. The acceleration data indicate an uncomfortable/very uncomfortable ride for skidder operators. The acceleration skidder operators are exposed to exceed the upper exposure limit for a 4-h work day as outlined in ISO 2631-1:1997, and are thus likely to incur some health effects. ANOVA procedures revealed significant ( p ⩽0.05) differences between weighted RMS accelerations at the dominant frequency and running weighted RMS accelerations for driving condition (DUL>DL), measurement location (SOI >chassis) and axis ( Y > X > Z and roll>pitch>yaw). To our knowledge, this data represents the most comprehensive 6-DOF field data set collected and analyzed to date for any type of forestry vehicle. The results of this study indicate that skidder seats amplify the WBV accelerations occurring at the SOI when compared to corresponding values measured at the chassis. The acceleration values outlined in this study are similar to those published over the past 20 years suggesting that little has changed with respect to the ability of the seat to attenuate harmful vibration and/or the ability and/or willingness of the operator to adjust the seat in order to optimize seat effectiveness. Relevance to industry Quantification provided by this study is useful to forest machine and heavy equipment seat designers. Field profiles developed from this data are being used in 6-DOF robot laboratory studies to assess WBV attenuation capabilities of current and future seat designs and to develop new biodynamic measures of seat effectiveness.

This study was carried out in a steep and difficult terrain. Trees were logged downhill to the landing by a wheeled skidder Timberjack 450C. Selection cutting was performed on a 66-hectare tract with an average slope of 30%. The elemental time study method was applied to develop the skidding time predicting model. In this study 43 working cycles were included. The skidding cycle time was mainly affected by skidding distance, winching distance and interac - tion between skidding distance and slope. The gross and net production rate was 20.51 and 22.93 m 3 /h, respectively. The unit cost considering the gross and net production rate was 6.31 and 6.22 USD/m 3 , respectively.

Forest soils are sensitive to compaction by forest machinery. Forest operations such as harvesting and skidding have a high potential for soil compaction. This study was carried out in the Hyrcanian hardwood forests of Iran to measure the changes in bulk density (ρb) in the top 10 cm of soil following machine and animal skidding. The density change or compaction was induced by (i) a rubber-tired skidder in three skid trails: flat skid trail (STF), skid trail with transversal slope (STTS), and skid trail with longitudinal gradient (STLG) and (ii) a mule in two animal trails: flat animal trail (ATF) and animal trail with transversal slope (ATTS). Soil cores were collected pre- and post-skidding at random locations along the upslope and downslope tracks of each skid trail to determine bulk density and moisture content of the soil. Average soil bulk density in the tracks of machine skid trails was significantly greater than the soil density outside the tracks, but the increase in bulk density was not significant on the animal trails. An increase in soil density was considered significant if p < 0.05. A highly significant increase in soil bulk density (p < 0.01) occurred with machine skidding after the first 12 skidding cycles on the STF before stabilizing. In comparison, on STLG and STTS the increase of bulk density was greatest after the first six skidding cycles. Additional cycles did not cause a significant increase in soil density. While the number of skidding cycles to reach the steady compaction state varied between flat trails and those with a slope, the severity of compaction was the same between them. Concentrating machine operations will minimize the areal extent of compaction and the use of mules could further reduce the impact of the extraction of short logs.

Effects of Skidder on Soil Compaction, Forest Floor Removal and Rut Formation An extensive field trial was set up to examine the influence of traffic intensity (5, 10, and 15 skidding cycles) (i.e. pass back and forth on the skid trail) and skid trail slope (0-10, 10-20, and > 20)% on soil compaction, forest floor removal, and rut depth after logging. The results showed that dry bulk density and rut depth increased with the increase of traffic frequency and slope, but floor coverage decreased. Within each traffic treatment soil compaction raised with the increase of skid trail slope, so that significant differences in dry bulk density were observed between slopes lower than 20% and those greater than 20%. Bulk density has become quite close to the critical value after 15 cycles. We observed soil rutting on the treatments started with 10 cycles. Soil disturbance increased significantly on slopes with less than 20% inclination with a dry bulk density of 1.157 g cm -3 after 5 cycles compared to 0.923 g cm -3 on slopes lower than 10%. In addition the litter mass on the treatments with 10 cycles and slopes greater than 20% (386.586 kg ha -1 ) was significantly lower (p < 0.05) than treatments with 15 cycles and slopes lower than 10% (545.382 kg ha -1 ). Data suggest that disturbance increased earlier in the steep treatments than in less sloping conditions. The dramatic increase of soil disturbance on treatments with slopes greater than 20% may be associated with increasing load on the rear axle combined with slipping on steep slope trail.

Prohodnost šumskog vozila, određena je njegovom mogućnošću svladavanja terenskih nepravilnosti šumskoga bespuća, pri čemu dolazi do interakcije dva geometrijska sustava – geometrije vozila i geometrije površine terena. Sama se prohodnost vozila (kao sastavnica kretnosti) očituje kroz: 1) mogućnost kretanja vozila po nepravilnostima terena, 2) mogućnost upravljanja (kontrole) vozilom, ali i 3) udobnost vožnje.Dimenzijske su značajke šumskih vozila određene tijekom njihove konstrukcije (gabaritne mjere, kretni sustav i način upravljanja, masa vozila i položaj točke težišta) te utječu na razinu njihove prohodnosti. Neovisno o namjeni vozila, poznati su mnogi pokazatelji njihove prohodnosti koji im određuju područje operativne primjene, a među koje se ubrajaju i kutovi te polumjeri prohodnosti vozila. Literatura poznaje navedene pokazatelje, ali i samo približno točne izraze za njihovo izračunavanje uslijed različitosti konstrukcije i primjene vozila uopće.Rad se bavi, na primjeru skidera s vitlom, značenjem kutova i polumjera prohodnosti šumskih vozila, kao pokazateljima njihove prohodnosti pri kretanju po nepravilnostima šumskoga bespuća. Uvažavajući posebnosti konstrukcije skidera s vitlom te ustaljenost odnosa među dimenzijskim značajkama neovisno o njihovim proizvođačima, izvedeni su izrazi za: prednji, središnji i stražnji kut prohodnosti te uzdužni i poprečni polumjer prohodnosti skidera., Maneuverability of specialized forestry vehicles is defined by their ability to overcome terrain unevenness during which interaction between vehicle and terrain geometry occurs. Maneuverability, as a segment of vehicle mobility, is defined by: 1) obstacle crossing, 2) vehicle controllability and 3) ride comfort.Vehicle specifications are determined during design and construction (dimensions, steering and locomotion systems, mass and its distribution on axles etc.) and together affect the level of vehicle maneuverability. Independently of vehicle purpose, many maneuverability parameters (directly connected to operational use) including approach, departure and ramp (break-over) angles as well as clearance radii are known, but their calculation for varying types of vehicles (different construction, purposes etc.) is still vague.On the example of wheeled cable skidder, this paper deals with approach, ramp (break-over) and departure angles, longitudinal and transversal clearance radii as significant parameters for skidder mobility and maneuverability on uneven forest stands. Considering specific wheeled cable skidder design and construction together with constant relation of dimension characteristics regardless of different manufacturers, expressions for approach, ramp break-over and departure angles, longitudinal and transversal clearance radii are derived.

International audience; Abstract Key messageSkidding operations significantly influenced soil physical properties up to a 2-m distance from the wheel ruts in a forest ecosystem. The most significant changes in soil properties were identified within a 0.5 m to 1 m transitional zone. AimsThe main purpose of this investigation was to determine how far into a forest stand changes in soil physical properties were evident due to skidding operations. MethodsTreatment plots with three replications included combinations of four distance zones at 0.5 m intervals (0 to 2 m in distance) on both sides of skid trail edges to the forest, three slope gradient levels were applied (gentle 20 %) and two levels of traffic intensities 20 and 40 passes (with a rubber-tyred skidder, model HSM 904). A total of 576 soil samples were used in this study. ResultsResults showed that the physical properties of soil were significantly changed by each traffic intensity in the first distance zone, where the slope was >20 % compared to soil changes at a slope of 20 % after 20 and 40 skidding cycles. DiscussionDry bulk density values reached its maximum levels in the first 0.5 m from the skid trail on slopes >20 % after 40 skidding cycles.

Skidder mobility during timber extraction is defined by: 1) basic dimensional features of the vehicle, 2) ability to overcome obstacles during movement, 3) traction performance and 4) environmental soundness. Traction performance depends on the ground conditions (soil bearing capacity) and the total effect of all forces on the vehicle. In downhill skidding, the skidder is under great influence of parallel component of forces, adhesion weight and longitudinal terrain slope, which combined result in negative traction force, torque and thrust force. When the horizontal component of rope force is equal to zero i.e. the moment when the weight of the load and resistance to traction are in equilibrium, the slope angle α is a function of load mass distribution factor and skidding resistance factor. This is a »turning point« that can be defined as a critical slope because the load starts to push the vehicle downhill, which results in negative horizontal component of rope force. Depending on skidder Ecotrac 120V dimensional features, centre of gravity, load mass distribution factor, skidding resistance factor of previous research, five different loads were analyzed (1 to 5 tonnes) in order to define the critical slope angle for each of them. Critical slope for downhill skidding of 1 tonne timber is on longitudinal slope of –26%, for 2 tonne timber on –30%, 3 tonne timber on –34%, 4 timber on – 38% and for 5 tonne timber on –43% of terrain longitudinal slope. Even though skidding bigger load increases vehicle mobility to even greater slope angles, the most important in downhill skidding, is to avoid blocking of the wheels, which will lead to a complete vehicle slippage and the driver must be constantly aware of that fact. The general recommendation should be that skidding small loads (1 to 3 tonnes) downhill is suitable for smaller longitudinal terrain slopes (up to maximum –34%), while the heavier the load, the further down the slope the skidder can go. The load of 5 tonnes »anchors« the skidder better and therefore it can go on terrain slopes up to –43%, during which less traction force is used (torque is used for braking) and skidder pulls the load by its own weight. It can be concluded that extending the operating range of skidder onto steeper slopes with heavier loads has the potential to decrease harvesting costs and increase productivity.

Traffic of heavy machinery at harvest and log extraction causes structural degradation of the soil, but studies on the effects of forest harvesting on soils with high organic matter content and exchangeable Al are scarce. The objective of this study was to evaluate the effect of mechanized forest harvesting operations on a Dystric Cambisol (Humic) with high organic matter (more 50 g kg1) content and exchangeable Al (more 6,0 cmolc kg-1), reforested with Pinus taeda L. The evaluated harvesting system were the whole-tree, in which the feller-buncher cuts and lays the trees down in bundles; the skidder drags the tree bundles up near a road; and the harvester delimbs and cuts the trees into short logs, stacking them on the roadside to be loaded onto trucks. The areas were evaluated for soil conditions at pre-harvest, prior to harvest, and at post-harvest, consisting of areas of low disturbance, high disturbance, forest residues and log yards. The effects of compaction after forest harvesting are observed by the decrease in total porosity (especially biopores and macropores), soil saturated hydraulic conductivity, and stability of aggregates. After forest harvesting, soil compaction was observed in all evaluated situations, but with different depths depending on operation type and the intensity of traffic carried in each area.

Prohodnost šumskog vozila, određena je njegovom mogućnošću svladavanja terenskih nepravilnosti šumskoga bespuća, pri čemu dolazi do interakcije dva geometrijska sustava – geometrije vozila i geometrije površine terena. Sama se prohodnost vozila (kao sastavnica kretnosti) očituje kroz: 1) mogućnost kretanja vozila po nepravilnostima terena, 2) mogućnost upravljanja (kontrole) vozilom, ali i 3) udobnost vožnje. Dimenzijske su značajke šumskih vozila određene tijekom njihove konstrukcije (gabaritne mjere, kretni sustav i način upravljanja, masa vozila i položaj točke težišta) te utječu na razinu njihove prohodnosti. Neovisno o namjeni vozila, poznati su mnogi pokazatelji njihove prohodnosti koji im određuju područje operativne primjene, a među koje se ubrajaju i kutovi te polumjeri prohodnosti vozila. Literatura poznaje navedene pokazatelje, ali i samo približno točne izraze za njihovo izračunavanje uslijed različitosti konstrukcije i primjene vozila uopće. Rad se bavi, na primjeru skidera s vitlom, značenjem kutova i polumjera prohodnosti šumskih vozila, kao pokazateljima njihove prohodnosti pri kretanju po nepravilnostima šumskoga bespuća. Uvažavajući posebnosti konstrukcije skidera s vitlom te ustaljenost odnosa među dimenzijskim značajkama neovisno o njihovim proizvođačima, izvedeni su izrazi za: prednji, središnji i stražnji kut prohodnosti te uzdužni i poprečni polumjer prohodnosti skidera.

Primary transportation is an upper time, expensive and hard labour. The most skidding are with using of rubber wheel of Timber jack 450C in Iran country that has devoted 60% of utilization expenses. In order to, investigate of slope and loading volume effects on time of loaded traveling had used time study for Timberjack 450C. In one of strip roads in parcel eleven of district two of Langa management plan forest (Kelardasht region in North of Iran) determined 5 and 3 different slopes classes and volumes classes, respectively. Then, time study was performed in slope classes with different loading volume in downward skidding. The first, collection of data have noted in special form and then have converted to uniform unit of m sec(-1). Descriptive statistics for each data set were calculated using the SPSS software. With presupposition that loading volume and slope are effective on the obtained time, these parameters have analyzed. ANOVA and Tukey test were used for loading volume factor. For investigation slope factor had used of Mann Whitney non-parametric test in order to comparison of loaded traveling speed in different slopes. Results of present research had showed that influence of loading volume on the loaded traveling time is insignificant, but loaded traveling speed in different slope classes is significant (in slopes >30%) as, speed of skidder machine is decreased with increase of slope variable.

We investigated the effects of different levels of ground-based skidding traffic intensity on soil disturbance, characterized by resistance to penetration (RP) within the top 15 cm of soil, as well as soil recovery, regeneration, and early growth of quaking aspen (Populus tremuloides Michx.) suckers 3 years after a clearcut with reserves summer harvest. Equipment traffic was confined to a network of skid trails, and a GPS was used to determine the number of skidder passes at each of 30 sampling points that were preestablished along an anticipated disturbance gradient ranging from landings to skid trails to areas off skid trails. Thirty-one percent of the harvest area was affected by skid traffic, and up to 603 passes were recorded for a plot. RP increased nonlinearly with the number of passes and reached highest levels at the soil surface. Three years after harvest, soils showed partial recovery in the upper 10-cm layer, with full recovery of the surface layer (0–5 cm depth) when affected by 4 or fewer passes. The deepest layer (10–15 cm), however, showed little recovery since harvest. Sucker density, height, and basal diameter of all suckers and height, basal diameter, and dbh of the tallest suckers were significantly reduced with increasing traffic intensity but were not related to increases in RP. Predicted reduction of sucker density was approximately one-third after 10 passes; reductions of height, basal diameter, and dbh were between 1.5 and 2.5% at 10 passes and 3.5 and 6.5% at 25 passes. Because skidding traffic affected only a limited portion of the stand, the productivity of the future aspen stand was not severely impaired, at least in the very short term.

A harvesting system consisting of chainsaw felling and cable skidder extraction was studied to determine soil bulk density changes in a central Appalachian hardwood forest site. Soil bulk density was measured using a nuclear gauge preharvest and postharvest systematically across the harvest site, on transects across skid trails, and for a subset of skid trail transects closest to log landing after each of the first ten loaded machine passes. Bulk density was also measured in skid trails after their construction but prior to skidding. Bulk density did not change significantly across the harvest site, because the extraction equipment stayed on the preplanned skid trails. Bulk density increased on the skid trails as a result of construction by crawler bulldozer and during skidding. Bulk density in the skid trail increased by 30% because of construction by a crawler bulldozer. Fifty-five percent of the increase in bulk density attributable to skidding occurred after one loaded pass, and 80% of the bulk density increase was experienced after two loaded passes. Bulk density increased by only 5% between passes five and ten.

Optimization of forest road network is an important part of logging planning. Matthews (1942) was the first to introduce a method for optimization of road spacing based on minimization of roading and skidding cost. The goal of this paper is to find the best road network for a district harvested by skidder. The skidding model developed by stepwise regression model was used to predict the cost of skidding per cubic meter for the 39 nodes, which were planned in the district map. The harvesting volume and roading cost per each node were computed. The data were entered into NETWORK 2000 and shortest path algorithm; simulated annealing and great deluge algorithms were run to find the best solution to optimize logging cost of the district. The results showed which roads can be eliminated from the existing forest road network.

Disturbances to forest catchments have profound effects on the environment of headwater streams and have an impact on suspended sediment (SS) management. Forest harvesting is a dominant factor in increasing SS yields. Road construction, skidder activity and ploughing associated with harvesting cause serious soil disturbance that results in SS increases. However, few studies have shown whether harvesting itself increases SS yields. This study examined how harvesting influenced SS yields in a steep forested area. During harvesting, soil surface disturbance was prevented as much as possible by using skyline logging treatments and piling branches and leaves at selected locations in the watershed. Using these methods, the representative SS rating curve did not change significantly after harvesting. The results also show that the characteristics of SS transport were related to the SS source area, and reveal that the riparian zone/stream bank was a dominant SS source area at the study site. Annual SS yields did not increase despite increasing annual water yields after harvesting. The limited water capacity of the soil at the study site likely led to only slight differences in pre- and post-harvest water discharge from heavy rainfall events. Most SS was transported during heavy rainfall events, and increases in SS yields were not detected after harvesting. We concluded that it is possible to prevent post-harvest SS increases by performing careful, low-impact harvesting procedures.

RESUMO A mecanização das atividades de colheita florestal tornou-se imperiosa para a sua sustentabilidade, buscando ganhos de produtividade e redução de custos operacionais. Como a produtividade e o custo operacional das máquinas florestais podem ser influenciados pela volumetria das florestas (m3/ha), o conhecimento dessa correlação vem a ser importante ferramenta de trabalho no planejamento da colheita. Este estudo foi desenvolvido em áreas de colheita de eucalipto no Estado de Minas Gerais, e seu principal objetivo foi analisar técnica e economicamente as atividades de colheita florestal mecanizada, bem como sua correlação com a volumetria das florestas. Para isso, foram aplicadas técnicas estatísticas de regressão linear e análise de correlação entre a variável volumetria das florestas e produtividade e custos operacionais das máquinas de colheita. Os resultados indicaram haver forte correlação entre a volumetria das florestas e a produtividade das máquinas, bem assim com os custos operacionais, demonstrando maiores produtividades das máquinas e menores custos de colheita com o incremento da volumetria das florestas. O feller buncher apresentou maior correlação, seguido das máquinas de extração (skidder e clambunck skidder) e da garra traçadora, sendo esta, provavelmente, mais sensível a outros fatores operacionais. A volumetria das florestas deve ser levada em consideração quando da indicação e dimensionamento das máquinas no momento da colheita, bem como no planejamento das atividades, de forma a aumentar a produtividade das atividades e contribuir para a redução dos custos operacionais. ABSTRACT The mechanization of forest harvesting activities has become imperative to their sustainability, seeking productivity gains and operating costs reduction. As the operating costs and the productivity of forest machines can be influenced by the volumetry of forests (m3/ha), knowledge of this correlation can be an important tool in the harvest planning. This study was conducted in eucalyptus harvest areas in the state of Minas Gerais. The main objective was to technically and economically evaluate the mechanized harvesting activities as well their correlation with volumetry of forests. For this, were applied linear regression statistics techniques and correlation analysis between the volumetry of forests and the productivity and operating costs of harvesting machines. The results showed a strong correlation between the volumetry of forests andproductivity of machines as well as operating costs, demonstrating increase of productivity of the machines and reduction of harvesting costs with increasing volumetry of forests. The feller buncher presents higher correlation, followed by the extraction machineries (skidder and clambunck skidder) and grapple saw, this one probably more susceptible to other operationalfactors. The volumetry of forests should be considered when indicating and sizing of the machines for harvest, as well as in planning activities in order to increase the productivity of activities and contribute to reduction of operating costs.

Aim of study: The aim of this research was to analyze the workload of the operators while logging at the motor-manual level in coniferous stands undergoing two tending treatments (early and late thinning). The technologies under the investigation employed a power chainsaw, tractor equipped with a cable winch as well as delimbing and cross-cutting Hypro 450W processor.Area of study, materials and methods: The research areas were located in lowlands and in a mountain range of the Western Carpathians. In the analysis it was assumed that the heart rate at work, expressed in beats per minute, would be an indicator of the workload affecting the human organism. Based on the heart rate, three indicators were calculated: relative heart rate at work (%HRR), 50% level of heart rate reserve, ratio of working heart rate to resting heart rate.Main results: The lowest average workload (typical for light work, %HRR40%) was for the chainsaw operator in early thinning, working with a processor. Cumulative distribution function of the workload at the work station of the skidder operator was characterized by bimodality – an occurrence of two extreme, high and low, workload values.Research highlights: The workload in early thinning was higher by about 7% than in late thinning at the work station of both, the processor operator as well as the chainsaw operator working with a processor.Keywords: logging; tractor processor; heart rate; workload; cardiovascular strain.

Harvesting trials were performed during the winter and spring of 2003–2004 in central Oregon to compare the costs, production rates, and soil compaction impacts of two systems for harvesting western juniper (Juniperus occidentalis). The two systems compared were a conventional system consisting of manual felling, delimbing, and bucking using a chainsaw and skidding logs with a rubber-tired grapple skidder and a mechanical system that used a feller-buncher, a rubber-tired grapple skidder to skid whole trees, and a stroke-boom delimber. Stump to deck harvesting costs ranged from $32.15 to $49.48/ton for the conventional system and from $60.07 to $63.11/ton for the mechanical system. A limited trial was conducted with the mechanical system that merchandized fence posts as well as sawlogs. When fence posts were produced also, stump to deck costs were reduced to $31.56/ton. Soil compaction was measured pre- and postharvest using a soil penetrometer. Paired t-tests showed a statistically significant difference between harvested sites and nonharvested sites at depths of 2 and 4 in. (P = 0.032 and 0.001, respectively) but no difference between harvest systems. West. J. Appl. For. 21(4):185–194.

Ground-based timber harvesting operations in forested wetlands have the potential to cause soil disturbances. Soil disturbances on upland sites have been linked to reduced site productivity, but the effects of such disturbances on the long-term site productivity of bottomland hardwoods is not well documented. In 1986, a long-term research project was established to compare the effects of helicopter and skidder timber harvesting on the regeneration, growth, and development of naturally regenerated water tupelo ( Nyssa aquatica )–baldcypress ( Taxodium distichum ) stands. At stand age 16-years, both treatments have well-stocked, vigorously growing stands composed of coppice-regenerated water tupelo, Carolina ash ( Fraxinus caroliniana ), baldcypress, and seed-origin black willow ( Salix nigra ). Although both treatments are well stocked, the skidder treatment favored the establishment and growth of water tupelo, while the helicopter treatment had greater densities and growth rates for Carolina ash. Apparently, the initial effects of the skidder traffic puddled the soils and resulted in more reduced soil conditions, which favored the very flood tolerant water tupelo rather than the less flood tolerant species. Stand growth parameters suggest that both treatments will produce stands that will be similar to the previous stand in terms of species and volumes. Recovery in this area was speeded by annual inputs of nutrient rich sediment, the shrink-swell nature of the soil, and rapid growth of the coppice regeneration.

O presente estudo teve como objetivo avaliar técnica e economicamente atividades de extração de madeira em vários declives, utilizando-se um trator florestal arrastador ("clambunk skidder") com rodado de pneus recoberto por esteiras. A avaliação técnica consistiu em determinar os índices de produtividade, e a avaliação econômica baseou-se na determinação dos custos operacionais da máquina. O delineamento experimental foi inteiramente casualizado, no esquema fatorial 3 x 2 x 5 (três níveis de declive, duas classes de produtividade florestal e cinco níveis de distâncias de extração com três repetições). Os resultados demonstraram que os estratos situados em menores declives e distâncias de extração apresentaram maior produtividade em relação àqueles de maiores declives e distâncias de extração. A produtividade do trator florestal arrastador avaliado variou entre 18,34 m³.h-1 e 72,08 m³.h-1, com custo operacional médio de US$90,93 por hora efetiva de trabalho.

We present a comparison of woody browse availability and white-tailed deer (Odocoileus virginianus) use among clearcut interiors, skidder trail edges, and mature forest and an evaluation of the relative importance of aboitic factors in predicting browsing pressure within regenerating clearcuts in the central Appalachians of West Virginia. We sampled 810 1-m2 plots in or adjacent to nine regenerating clearcuts (8–19 ha) during the summer of 2001. Availability and use of woody browse did not differ between clearcut interior and skidder trail plots for any species observed. Plots in the adjacent mature forest had less woody browse availability and higher utilization. Overall use of available woody browse in clearcuts was >15%. Combining all woody species, elevation (wI = 0.618) and distance to mature forest (wI = 0.379) were more important than landform index, plot surface shape, aspect, and slope in predicting deer browsing pressure in regenerating clearcuts. We believe that without management activities aimed at reducing deer browsing, in many parts of this region the ability of forest managers to regenerate stands will be jeopardized and the forested ecosystem will be compromised.

RESUMO n Este trabalho foi realizado com tratores florestais utilizados em um sistema mecanizado de colheita de madeira em povoamento de eucalipto, tendo como objetivo avaliar quantiqualitativamente as dimensies de acesso, assento, comandos, campo visual, condiAies tOrmicas e vibraAao no posto dos operadores. O acesso ao posto do operador no trator iFeller-buncheri apresentou um grau de dificuldade, sendo classificado, na avaliaAao qualitativa, como mOdio e, no iSkidderi, como bom. A abertura das portas de acesso apresenta ‚ngulo menor que 90", dificultando, assim, a entrada e saIda do operador. O posto do operador do trator iFeller- buncheri foi classificado como mOdio na avaliaAao qualitativa, em virtude de o espaAo livre da plataforma de apoio ser de 30% da AErea total e, no iSkidderi, de 55% da AErea total, sendo classificado como bom. O campo visual frontal do iFeller-buncheri, mesmo tendo uma AErea do pAEra-brisa maior, O limitado pela presenAa do cabeAote, tanto em operaAies diurnas quanto noturnas, sendo, portanto, inferior ao do iSkidderi. ABSTRACT n This work was carried out in forest tractors used in a mechanized system for wood harvesting in a stand of eucalyptus, to evaluate quanti-qualitatively the dimensions of access, seat, commands, field view, thermal conditions and vibration in the operatorsi station. The access to the operatoris station in the Feller-Buncher tractor presented a degree of difficulty classified in the qualitative evaluation as average and the Skidder as good. The opening of the access doors presents an angle smaller than 90", thus rendering the entrance and exit of the operator more difficult. The operators station of the Feller-Buncher tractor was classified as medium in the qualitative evaluation, due to the free space of the support platform being 30% of the total area, and in the Skidder 55%, therefore being classified as good. The front field view in Feller- Buncher, even having a wider windscreen area, is limited by the presence of the headstock in by day as well as by night operations, therefore being smaller than the Skidderis.

Forest managers are concerned about the potential damage to residual trees and site from cyclic harvest re-entries into the same forest stand. This study summarizes logging and felling damage resulting from the harvesting of silvicultural treatments on a large landscape experiment in southern Missouri that is designed to compare impacts of even-aged, uneven-aged and no management on a wide array of ecosystem components. Although damage levels to bole and crown of leave trees was low for all treatments, the individual tree selection (uneven-aged) treatment did show: (1) higher levels of surface area skidder impact; (2) higher percentage of leave trees with one or more bole wounds; (3) higher number of bole wounds; (4) higher percentage of wounded trees in the dominant and co-dominant crown classes; and (5) the highest percentage of leave trees impacted by logging activity. Preharvest planning that involves the layout and discussion with the skidder operator(s) will reduce the area impacted by skidding to less than 12%. Also, the probability of a bole wound to a residual tree can be reduced to less than 5% if skid trails are kept 30 ft or more from the leave tree. North. J. Appl. For. 21(4):187–193.

Ground-based forestry practices can negatively affect soil productivity by altering the physical, chemical, and biological properties of soil. The effect of soil disturbance on soil properties and tree growth was evaluated following single-pass hydraulic excavator and multiple-pass combined excavator and flexible track grapple skidder forwarding in four silvicultural systems treatments: Clearcut (CC), Green Tree Retention (GT), Patch Cut (PC), and Uniform Shelterwood (SW). The effectiveness of an excavator soil-rehabilitation technique (tilling) in decompacting skidtrails (i.e., reducing soil bulk density) and nutrient availability was also evaluated. Western hemlock (Tsuga heterophylla (Raf.) Sarg.) and amabilis fir (Abies amabilis Dougl. Ex. Forbes) seedlings were planted on undisturbed plots, within tracks and between tracks of skidtrails, and in rehabilitated trails within the four harvesting treatments in the spring of 1994. Seedling growth was measured after five growing seasons, and nutrient concentrations of current-year foliage were determined at the end of the fourth growing season. Seedling survival and growth was generally reduced by soil disturbances associated with skid-trails. Effects of disturbance on physical properties of soil (e.g., compaction, puddling) and disruption of drainage were the most likely causes. Nutrient deficiencies do not appear to be a factor. Nonetheless, nitrogen concentrations were lower in current-year foliage taken from rehabilitation treatments than from either undisturbed or skidtrail treatments. Effectiveness of soil rehabilitation varied. In well-drained deeper soils, tilling reduced soil bulk density to levels below those of undisturbed soils and, in the short-term (five years), improved tree growth. In wetter conditions, rehabilitation treatment decreased survival and growth of both species. Thus specific rehabilitation (tilling) prescriptions should not be universally applied across a landscape. Key words: Abies amabilis, Tsuga heterophylla, foliar analysis, soil bulk density, soil compaction, soil rehabilitation

Little is known about nest tree use of the endangered Virginia northern flying squirrel (Glaucomys sabrinus fuscus). Because nesting sites could be a limiting factor, it is important to understand the denning ecology to further manage and protect this subspecies. We compared characteristics of nest trees used by Virginia northern flying squirrels with randomly selected trees during summer and fall of 2000 and 2001. We tracked 13 Virginia northern flying squirrels to 59 nest trees. The squirrels used an average of 3.6 nest trees/month, switching trees frequently. Sixty-nine percent of the nests were in cavities and 31% were leaf nests. Yellow birch (Betula alleghaniensis) and Fraser magnolia (Magnolia fraseri) were selected for nest trees more than expected based on availability. A large portion of nest trees were in larger and taller trees than trees in the surrounding area. There also was a significant number of trees located next to or near skidder and hiking trails. Although a large number of nest trees were similar across sites, there was variation in the characteristics of nest trees used, suggesting that Virginia northern flying squirrels may not be as specialized in nest tree selection as indicated by previous studies.

Sustainable natural forest management initiatives in the lowland tropical forests of Bolivia require that cost-effective measures be identified to help maintain timber stand quality and reduce damage to advance regeneration during logging operations. This study considered the potential costs and benefits of including two ‘best’ management practices—the pre-harvest flagging of future crop trees (FCTs) and improved planning of skid trails—in adjacent 45 ha plots, in conjunction with conventional planned diameter-limit logging in a lowland tropical forest in the Department of Santa Cruz, Bolivia. The study also included a general assessment of FCT damage and timber waste associated with standard felling operations. The additional costs of flagging FCTs ≥30 cm DBH were estimated to be US$ 0.38/ha. FCT flagging significantly reduced damage by 20% in felling gaps and by 10% along skid trails that received 2–10 skidder passes. A mean directional error of ±35° per tree felled was observed for felling operations, indicating that damage to FCTs during felling could be reduced through implementation of directional felling techniques. Improved felling techniques could increase mean timber utilization by as much as 0.16 m3 or US$ 3.20 per tree felled through reduced wood waste associated with stump pull, a common problem observed during felling operations. Pre-harvest skid trail planning increased costs an estimated US$ 1.46/ha, but reduced mean skidder “search times” (min/m3 harvested) by 23% and unnecessary skid trails by 96%. Compared to normal harvesting operations, overall operational efficiency increased by approximately US$ 3.00/ha. Pre-harvest skid trail planning significantly reduced FCT damage along skid trails that received 2–10 skidder passes. The results of this study indicate that pre-harvest skid trail planning and improved timber felling techniques yield short-term financial gains relative to conventional management as well as potential long-term gains through FCT conservation and, therefore, warrant implementation. Forest certification groups should consider FCT flagging for inclusion in timber certification criteria for the region given its low cost and proven utility for maintaining timber stand quality.

The objective of this study was to analyze soil surface disturbances resulting from logging tractors, of different types (skidder and forwarder), used for clear-cutting in natural Aleppo pine forests and their consequences on plant species and functional group diversity. Results indicate that shallow disturbances (litter left in place or removed) were more frequent than deep disturbances (topsoil removed, subsoil exposed, rut exposed) regardless of the logging tractor used. The forests with previously cultivated terraces were the least disturbed. Moreover, with the aid of a functional group analysis we distinguished four plant species response groups to soil surface disturbance types. The mosaic created by these groups after clear-cutting and log removal probably contributes to a rapid auto-regeneration of a mixed plant community similar to that existing just prior to the clear-cutting.

We examine in this paper the concurrent appearance of the first two woods machines--the skidder and forwarder. By replacing the horse they initiated the industrial revolution in tree harvesting. We describe their invention and technological development. We then assess their diffusion in the woods, revealing the greater success of the skidder. We demonstrate that this cannot be accounted for solely in terms of their respective technologies. Instead, we argue that the interaction of technology with the social organization of their respective harvesting systems must be analyzed. By doing so, we find that the skidder altered that social organization whereas the forwarder did not. This paper, contributing to the understanding of an important area of economic activity which has been seriously understudied, illustrates concretely that comprehending technology requires locating it in the social organization of work.

Forests in southern Italy are mainly located in mountainous areas, where ground-based extraction is still the most common harvesting technique. In particular, 60% of southern Italy’s forests are on slopes with an angle of inclination between 20–60%. The low level of mechanization in forest operations is due to the difficult site conditions, as well as the small-scale characteristics of both the forest owners and the harvesting contractors. The most common work method uses chainsaws to fell the trees, and animals or farm tractors equipped with winches for bunching and extraction. This study assesses the productivity and cost effectiveness of extraction with a purpose-built John Deere 548H skidder, including a comparison of winch and grapple configurations. The results show that the productivity of skidding depends on distance as well as the condition of the skid trail. The number of trees per cycle and volume of each load also had a clear effect. While large purpose-built skidders represent a significant investment, this study demonstrates that the productivity is very high compared to traditional extraction methods and the resulting extraction costs are very competitive. As such, this study indicates that, over time, southern Italian harvesting operations should invest in purpose-built harvesting systems.

Planning is an intellectually demanding process that requires a conscious determination of actions and decisions based on related purpose, knowledge and right decisions. During planning timber harvesting it is very important to choose the best possible technology for timber extraction. The use of multi-criteria-decision-making models is a very good way of dealing with various forestry issues especially in terms of choosing the best applicable technology for timber extraction. Modern forest management in the Republic of Croatia in terms of timber harvesting mostly relies on ground based wheeled systems. The goal of this research is to show how the current way of planning timber harvesting (timber extraction) and accordingly the construction of secondary forest road network affects future planning and introduction of »new« technologies for timber extraction i.e. forest cableway. Analysis of suitable forest stands for different timber extraction technologies s was carried out in the management unit Garjevica-Cazma with an area of 4380.20 ha. The paper presents multi-criteria-decision-making model for defining terrain suitable for ground based wheeled systems (skidder with a winch and forwarder) and forest cableway on the base of raster maps (grid of 20×20 m i.e. 0.04 ha). The criteria used to select different technologies for timber extraction were: terrain slope, distance from the forest road, distance from the skid road and harvesting density. Analysis using GIS tools in ArcGIS and Idrisi applications goes in two directions, first the analysis of suitability of using selected technologies for timber extraction using four criteria, and comparison with results of the analysis where the criterion »distance from the skid road« has been excluded.

The importance of environmental and economical aspects in sustainable forest management (SFM), demands a continuing need for the application of efficient methods in this field. In this paper, we applied analytic network process (ANP) with benefits, opportunities, costs, and risks (BOCR) to evaluate four existing wood extraction methods (rubber-tired skidder, tracked skidder, cable logging and animal skidding) and select the best one based on SFM strategies in the Caspian (Hyrcanian) Forest, in northern Iran. The required data were obtained either from the previous studies or through pairwise comparisons conducted by a panel of forest engineering experts. Based on the BOCR subnetworks and their corresponding criteria, four alternatives were synthesized. ANP analysis indicated that the benefits and risks were more important in terms of decision-making, compared to the opportunities and costs. Finally, the alternative of 'rubber-tired skidder' was selected as the most suitable method for meeting SFM strategies. The decision framework proposed in this study offers a means for the reorganizing and planning of timber harvesting operations as an integral step toward SFM. By making minor adjustments for local conditions, this decision framework can be adapted for many other regions and countries.

Skidder’s ability to extract timber is defined by: 1) basic dimensional features of the vehicle, 2) the ability to overcome obstacles during movement, 3) traction performance and 4) environmental soundness. Traction performance depends on the ground conditions (soil bearing capacity) and the total effect of all forces on the vehicle. In downhill skidding, skidder is under great influence of parallel component of forces, adhesion weight and slope, which combined result in negative traction force, torque and thrust force. When the horizontal component of rope force is equal to zero i.e. the moment when the weight of the load and resistance to traction are in equilibrium, the slope angle α, is a function of load mass distribution factor and skidding factor. This is a »turning point« that can be defined as a critical slope because the load starts to push the vehicle downhill which results in negative horizontal component of rope force. Depending on skidder Ecotrac 120V point of gravity, load mass distribution factor, skidding factor and previous research, five different loads were analyzed (1 to 5 tones) in order to define the critical slope angle for each of them. Critical slope for downhill skidding of 1 tone timber is on longitudinal slope of –26%, for 2 tone timber on –30%, 3 tone timber on –34%, 4 tone timber on –38% and for 5 tone timber on –43% of terrain longitudinal slope. Even though skidding is possible on even greater slope angles, the most important in downhill skidding, is to avoid blocking of the wheels, which will lead to a complete vehicle slippage and driver must be constantly aware of that fact. When load pushes the vehicle down the slope, due to the constant thrust of the timber at the back end of a skidder, one can conclude that such performance in a due time will result in fatigue of the material and early damage to the vehicle as well as the negative influence on psycho-physical state of the driver.

The impact of skidder disturbance on recruitment of commercial tree regeneration within logging gaps was studied using paired scarified and unscarified plots as well as whole-gap surveys of scarified and unscarified areas in a Bolivian tropical humid forest. More than a year following gap creation, variability in the density of regeneration among logging gaps was high, but commercial tree regeneration density tended to be greater in scarified areas than in unscarified areas within gaps for most species. Height growth was also significantly greater for trees in scarified compared to unscarified areas, despite a near doubling of soil compaction in scarified areas. The principal species benefiting from soil disturbance by skidders was Schizolobium amazonicum, which had nearly 10× higher density and 2× greater height growth in scarified compared to unscarified areas. Although initially devoid of vegetation and litter cover, scarified areas had vegetation and litter cover levels similar to unscarified areas after 7 months. Vegetation cover on scarified areas tended to be dominated by early successional tree species while unscarified areas were dominated by forbs and grasses.

Forest harvesting is likely to have greater impacts on site productivity than any other activity during the rotation. We determined eflects of commercial, winter-logging of four aspen-dominated stands on "pi. p t3c b ;; EqQ. site disturbance and development of regeneration on clay soils in western Upper Michigan. A large skidder - m i-e caused deep rutting on 20% of a site in a thinning that removed 7.8 m2 ha-' (34ftz ac-') of basal area, and on @t CE g4 38% of a clearcut site. After the first growing season, 45% of the clearcut had no aspen regeneration, and 82 % 2 2. U had less than the recommended minimum of 15,000 (15 k) suckers ha-' (6 k ac-I). Options that can be utilized z 2 to minimize logging impacts include: (1) excluding riparian areas andpoorly drained inclusions from cutting units; (2) dry season harvesting; (3) plowing snow from (or packing the snow or^) skid trails and landings, permitting them to freeze; (4) felling with delayed skidding until trails and landings have frozen; and (5) application of best management practices (BMP) recommendations such as progressive (back-to-front) harvesting. Each of these should have minimal efSects on logging costs and may be economically advanta- geous. As an interim guide, a minimum of 7.5 cm (3.0 in.) of soil frost is recommended for small equipment & 0 r,"","" "I? and 15 cm (6.0 in.) for large equipment. BMP guides could be egective in communicating management objectives to foresters, sale administrators, contractors, and operators, increasing their awareness of (and sensitivity toward) soil disturbance and thus, contribute to sustaining future productivity. North. J. Appl. For. 19(3):115-121.

The performance of alternative equipment for the whole-tree harvesting of eucalypt stands was evaluated, using data from five different commercial operations. The study covered three machines for felling and bunching, two for extraction (skidding), and two for combined delimbing, debarking and chipping. Productivity and operating cost models were evaluated for each of the machines, in order to estimate the net harvesting costs under varying forest stand and site conditions. It was found that under easy terrain conditions (flat terrain, dry ground), trees should be felled by threewheeled feller-bunchers and extracted by front-end loaders, as this combination had the lowest harvesting costs. Due to mobility limitations, this equipment may have to be replaced by tracked feller-bunchers and conventional skidders in steep terrain and/or soft ground. It was estimated that the cost of using the wheeled feller-buncher and the front-end loader system ranged between 16–22$ per oven-dry-ton (odt), depending...

The effects of forest management practices on the spatial activity patterns of bats are poorly understood. We determined the effect of group selection timber harvests on the spatial activity patterns of bats below the forest canopy at the Savannah River Site, Aiken, SC, using the Anabat system. We monitored the effect of group selection timber harvests on feeding and foraging activity of bats at three spatial scales: among habitats within a landscape, among harvested and unharvested areas in the stand where patches were harvested, and within an individual gap. Habitats examined included Carolina bays, unharvested bottomland hardwoods, bottomland hardwoods in which a group selection harvest occurred, and upland stands containing a hardwood/pine mix. Within the harvested stand, we compared the level of foraging and feeding activity among large patch cuts (gaps), small gaps, skidder trails, and forested areas. Within the large gaps, we compared activity among the center of the gap, the edge of the gap, and the forest surrounding the gap. Levels of bat activity differed among stands. More activity occurred in the bottomland stand in which patches had been harvested and around Carolina bays than in unharvested stands of bottomland hardwoods and upland hardwoods and pines. Levels of bat activity also differed among harvested and unharvested areas within the stand and among different positions within gaps and the surrounding forest. Activity was concentrated in forest gaps and along skidder trails. Within gaps, activity was concentrated along the edge between the gap and forest. Spatial activity patterns also depended on the species of bat. These results suggest that the inclusion of gaps in bottomland hardwoods increases the total level of foraging and feeding activity of bats below the canopy. They also suggest differences in the size and shape of the harvest affect the total amount of bat activity recorded in the gap and that these effects may be species specific.

Little is known about the impacts of selective logging on herbaceous plants of tropical forests. If logging impacts on nontimber species are low and little time is required for recovery, logged forests could be compatible with conservation of some elements of the understory flora. As many nontimber species may have commercial value, knowledge about the impacts of different logging intensities is necessary to determine levels of timber extraction compatible with multiple use of forests. In this study, we examined the effects of logging intensity, time after logging, and skidder tracks, on the composition and diversity of the ground-level herb community of a terra-firme forest in central Amazonia. Logging was carried out at varying intensities in eight 4-ha experimental plots in 1987, three plots in 1993, and five plots were controls. Herb community composition, analyzed with hybrid multidimensional scaling (HMDS), was not significantly affected by logging intensity, but was significantly related to the are...

We (i) quantified effects of skidder yarding on soil properties and seedling growth in a portion of western Oregon, (ii) determined if tilling skid trails improved tree growth, and (iii) compared results with those from an earlier investigation in coastal Washington. Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings were hand planted at eight recent clearcuts in skid ruts in either nontilled or tilled trails, in adjacent soil berms, and in adjacent logged-only portions. Four and 5 years after skidding, rut depths averaged 15 cm below the original soil surface; mean fine-soil bulk density (0–30 cm depth) below ruts of nontilled trails exceeded that on logged-only portions by 14%. Height growth on nontilled trails averaged 24% less than on logged-only portions in year 4 after planting and decreased to 6% less in year 7. For years 8–10, mean height growth was similar for all treatments. Reduced height growth lasted for about 7 years compared with 2 years for coastal Washington. Ten years after planting, trees in skid-trail ruts averaged 10% shorter with 29% less volume than those on logged-only portions. Tillage improved height and volume growth to equal that on logged-only portions. Generalizations about negative effects of skid trails on tree growth have limited geographic scope.

Aim of the study: The objective of this study was to evaluate skidding from stump area to roadside with a tracked skidder (Caterpillar 3DG XL) using two different types of cable (steel or synthetic).Area of study: NW of Spain.Material and methods: A time study was performed to calculate productivity for the two types of cable and two regression models were fitted to predict the productive and cycle time of the tracked skidder.Research highlights: An increase of 12.53% in productivity (m3/SMH) and improvements in working conditions using synthetic rope were found.Keywords: Chestnut; synthetic rope; time study; tracked skidder.

Made available in DSpace on 2015-02-02T12:39:24Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-06-01Bitstream added on 2015-02-02T13:08:42Z : No. of bitstreams: 1 S0104-77602014000200004.pdf: 461297 bytes, checksum: 3bbaec8cc179c1d7042093d627819192 (MD5) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) A compactação devido ao tráfego de maquinários ocasiona danos ao solo que podem interferir no adequado desenvolvimento do sistema radicular das plantas, apresentando como principal dano a diminuição da produtividade das culturas. O objetivo deste trabalho foi avaliar a compactação do Cambissolo Háplico ocasionada pelo tráfego do Skidder na extração de Pinus elliottii var. elliottii em ramal secundário de extração de madeira, nos rastros dos pneus e dos fustes, variando-se a frequência de tráfego do trator. Os rastros dos pneus e dos fustes foram na mesma linha de tráfego da passada anterior, cada qual localizado em seu respectivo rastro. A área de estudo localizou-se no município de Capão Bonito-SP, em cultivo de Pinus elliottii var. elliottii, e os dados de compactação foram obtidos da área sem tráfego (testemunha) e dos tratamentos com 1, 2, 3, 4 e 5 passadas do Skidder, em duas camadas, de 0,00-0,05 m e de 0,10-0,15 m de profundidade. Os resultados demonstraram que houve compactação adicional sob tráfego de cada passada do Skidder, sendo maior na camada de 0,00-0,05 m de profundidade. Adicionalmente, a compactação do solo foi mais acentuada sob menores teores de água no solo, sendo contrário ao esperado. The compaction due to machinery traffic causes damage to the soil that can interfere with the development of the root system of plants, resulting in decreased crop yields. The objective of this study was to evaluate the Inceptisol compaction caused by Skidder traffic in extraction of Pinus elliottii var. elliottii in secondary extension logging in tire tracks and stems, varying the frequency of tractor traffic. The tire tracks and stems were in the same line of traffic passage earlier, each located in their respective tracks. The study area was located in the municipality of Capão Bonito-SP, in cultivation of Pinus elliottii var. elliottii and samples were obtained from an area without traffic (control) and applications with 1, 2, 3, 4 and 5 Skidder passes in two layers, 0.00 to 0.05 and 0.10 - 0.15 m depth. The results showed that there was additional compaction by each passage of the Skidder, being higher in the layer of 0.00 to 0.05 m depth. Soil compaction was more pronounced under lower water content in the soil, being contrary to the expected. Universidade Estadual Paulista Universidade Estadual do Mato Grosso do Sul Universidade Estadual Paulista

We time-studied a Caterpillar 950F front-end loader and a Caterpillar 528 grapple skidder used to extract bunched whole trees to a landing in a short rotation Eucalyptus plantation. The loader was 40–60% more productive than the grapple skidder, depending on extraction distance. Alternatively, the single loader could both extract trees and handle the landing duties, such as moving residues from the flail-chipper, whereas the skidder required a second machine (skidder or small loader) to handle landing activities. Front-end loaders appear to be very promising as extraction devices for short rotation plantations where tree characteristics, terrain and soil conditions allow them to be used.

We compared the impacts of helicopter and rubber-tired skidder extraction of timber after harvesting on the structure and function of a blackwater forested wetland. This study was initiated in 1991, in a cypress-tupelo forest adjacent to the South Fork Edisto River in South Carolina, USA. Our objective, eight growing seasons after harvest, was to focus on the properties that showed effects of the harvest after three years: soil chemistry, organic matter decomposition, groundwater chemistry, and plant community composition. Concentrations of total nitrogen, phosphorous, and magnesium were lower in some of the harvest treatments than in the unharvested control. Cellulose decomposition at 5 and 10 cm below the soil surface was significantly greater in the harvested treatments than the unharvested, though there were no differences in soil temperature. There were no differences among treatments in the concentrations of NO3−, NH4+, and PO4 in groundwater sampled from depths of 0.2 and 1 m. Sedimentation was significantly greater in the harvested treatments than the unharvested treatment, and had apparently filled the ruts caused by the skidder. Ordination of the canopy vegetation plots using their importance values showed no separation of vegetation communities by treatment. In contrast, ordination of the midstory and understory vegetation plots cover showed a separation of communities between the harvested and unharvested treatments. There was no apparent environmental advantage to using helicopters rather than skidders to extract timber from this forest.

Compaction by harvesting equipment has a potential to decrease the quality of root environment through alteration of soil pore space. Effects of skidder traffic on soil water retention and pore-size distribution were studied on medium-textured Inseptic and Oxyaquic Haplocryalfs , and Typic Dystrocryepts at 14 sites in Alberta foothill and boreal forests. Treatments included 3, 7, and 12 cycles by skidders equipped mostly with wide tires. Soil cores were collected at four random points Of each treatment at an average depth of 5 and 10 cm, Soil water content of each core was measured at six potentials. Tempe cells were used to measure water retention at potentials from -2 to -30 kPa; a conventional pressure plate was used in the range of -100 to -1500 kPa. The four-parameter water retention function developed by van Genuchten (1980) was fitted to the data, The pore space of trafficked soil was not significantly affected when soil was drier than field capacity, At higher soil water contents, the first few skidding cycles caused a decrease in theta (s) and alpha parameters, which reflected flattening of water retention curves in the high potential range and a simultaneous shift of the steepest part of the slope to a lower potential. The result of compaction was a decrease in air-filled porosity below 0.10 m(3) m(-3)), which restricted aeration without changing field capacity or available water holding capacity. Most modifications of soil pore space by wide-tired skidders can be avoided if the soils are drier than field capacity. Language: en

Sustaining forest productivity requires maintaining soil productivity and prompt establishment of adequate regeneration following harvest. We determined effects of commercial, winter-logging of aspen-dominated stands on soil disturbance and development of regeneration on three sites with clay soils. We established transects across each site, recorded pre-harvest stand information, post-harvest site disturbance, and first-year aspen sucker density and height. Use of large logging equipment produced heavy disturbance on 38% of a well-drained site; 45% of the area had no aspen suckers and 82% had less than the recommended minimum of 15 000 (15 k) suckers per ha (6 k ac−1). Mean height of dominant suckers was 45 cm (18 in). Hand felling and a small skidder caused heavy disturbance on 12% of a moderately well-drained site. Sucker density averaged 34 k ha−1 (14 k ac−1) and height was 97 cm (38 in). Cut-to-length (CTL) equipment produced heavy disturbance on 11% of a somewhat poorly-drained site, mean sucker density of 24 k ha−1 (9.6 k ac−1), and height of 101 cm (40 in). These severely disturbed areas essentially are removed from the aspen-producing land base. Retaining the northern hardwood and conifer growing stock would result in less site disturbance and help maintain natural hydrologic and nutrient cycling processes. Key words: aspen management, site disturbance, sustainable management, logging damage, soil rutting, root damage, evapotranspiration, soil aeration, clearcutting with residuals

Tree regeneration was compared among closed-canopy sites and 4–11-year old natural and felling gaps in a selectively logged semideciduous tropical forest in southeastern Mexico. Closed-canopy sites and gaps were selected stratified randomly. In addition, all large natural and felling gaps encountered were sampled. All stems ≤5 cm dbh were sampled in sets of 10 m 2 plots in closed-canopy sites and gaps. The origins of the 10 tallest stems in each gap were also determined. Rubber-tired skidder disturbance in felling gaps resulted in a fourfold increase in the relative abundances of a set of shade-intolerant species. The logging process also promoted root sprouting, primarily among shade-intolerant species, but also in several shade-tolerant species. Advance growth accounted for a higher proportion of tall stems in natural than felling gaps and most of these stems were of shade-tolerant species. The proportion of tall stems that originated from seeds or small seedlings at the time of gap formation was higher in felling than natural gaps and increased with canopy openness only in felling gaps. These stems were primarily from shade-intolerant species. A lack of response to canopy openness in natural gaps was likely a result of relatively low levels of understory and substrate disturbance coupled with the absence of large natural gaps with high canopy openness. The maintenance of shade-intolerant and tolerant timber species in this forest would appear to require, at minimum, the creation of large gaps with understory and substrate disturbance within a matrix of forest logged by single-tree selection methods in which understory damage was minimized.

Because increasing demands are being placed on industry to harvest timber by aesthetically, economically, and ecologically acceptable means, we investigated the effects of a ground-based group selection harvest on logging productivity. Results show that size of opening had little or no effect on skidding productivity. However, significant skidder operator differences existed. Some skidder operators consistently, in shorter periods of time, loaded their machine with larger payloads resulting in larger turn volumes. Group selection unit size, skidder operator, and utilization level had no statistically significant impact on delay times. Results also suggest that additional time spent training skidder operators to hook larger payloads faster could pay dividends in increased daily production and improvements in logging profitability. North. J. Appl. For. 17(2):51-56.

SYNOPSIS The study of seven articulated wheeled cable skidders at five different locations revealed that the optimism skidder pay load is not skidded. The average results of three similar Timberjack 380C skidders that formed part of tile study are discussed. The optimum payload of a skidder, whether a cable skidder or a grapple skidder, is the most important element determining its optimal use or productivity for a given stand of trees and therefore the cost of the extracted timber per cubic metre. Several methods of determining the optimum payload are discussed.

A 216 kW biomass harvester, modified from a John Deere silage harvester, was field tested in Texas and New Mexico to examine the productivity and cost of harvesting shrubs and small trees for energy purposes. The harvester was tested on mesquite ( Prosopis glandulosa var. glandulosa ) in Texas and salt cedar ( Tamarisk pentandra ) and pinyon ( Pinus edulis )/juniper ( Juniperus monosperma ) stands in New Mexico. While the harvester severed and chipped a few individual 20-cm basal diameter trees, the harvester was much more efficient harvesting dense stands of small trees that were less than 10-cm in basal diameter. During the course of these trials, major modifications were made to increase the efficiency of the cutterhead and the materials handling system. After these modifications, when harvesting mesquite stands less than 10-cm in basal diameter, the machine harvested at the rate of 0.95 ha h −1 with a fresh weight harvest production of 7050 kg h −1 . Using $70 h −1 operating cost data for similar commercial equipment, we estimated an energy cost of $1.00 kJ −1 which compares favorably to energy sources such as low sulfur Wyoming coal, natural gas and fuel oil. The swath harvester described here did not bale the chips. However, baling trials with 3 commercial balers found that 2 commercial balers could pick up dense windrows of the chips and make a satisfactory 300 kg square bale and a 595 kg round bale. The large square bale with a density of 319 kg m −3 , provides an opportunity for full load potential of flat bed truck trailers to be realized. As the harvester is built on an agricultural frame, it is not sufficiently robust to operate in a forestry environment. A commercial version will need to be built on a high clearance, heavy duty frame with 4 wheel drive similar to a forestry skidder. Brown Bear Corporation, the company that manufactures the cutterhead, is anxious to build this harvester for a purchase price of about $280000. We estimate that an annual demand for about 12000 Mg of biomass at $9 per green Mg will be necessary to justify the purchase of the first harvester. The market potential for non-energy related biomass i.e., potting soil base, landscape mulch, wood chips for bioremediation, mesquite barbecue products, appears sufficiently great in some locations to justify purchase of the first commercial version of a harvester.