article id 908,
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                            Ground-based skidding can have detrimental effects on soil properties  trough soil profile disturbance and compaction that can persist for  decades. We investigated the recovery of physical properties of  disturbed brown soils on four abandoned downhill skid trails in a  deciduous mountain forest in northern Iran. The most recent skidding  operations had taken place 1–5 yrs, 6–10 yrs, 11–15 yrs, and 16–20 yrs  ago, providing a 20-year chronosequence with four 5-year recovery  periods. For each recovery period, mean values for soil bulk density  (BD), total porosity (TP), macroporosity (MP), soil moisture content  (SM), and rut depth (RD) were assessed for three levels of traffic  intensity (Primary (PS), Secondary (SS) and Tertiary (TS) skid trails)  and two levels of slope gradients (Gentle (G) and Steep (S)) and  compared to those in undisturbed (control) areas. Over the 20-year  recovery period, PS trails on gentle slopes exhibited mean values that  were 35–42% (BD), 3–7% (SM), and 13–19 cm (RD) greater and 18–24% (TP)  and 19–28% (MP) lower compared to undisturbed areas; on steep PS trails,  values were 40–46% (BD), 2–13% (SM), and 13–21 cm (RD) greater and  23–27% (TP) and 28–35% (MP) lower, respectively. While RD and SM  recovered, 20 years was not long enough for the other physical soil  properties, particularly on steep slopes. To minimize soil disturbance,  skidding should be confined to areas with gentle slopes and alternative  harvesting methods such as cable yarding should be used where slope  gradients exceed 20%.
                        
                
                                            - 
                            Ezzati,
                            Department of Forestry and Forest Engineering, Tarbiat Modares University, P.O. Box 64414-356, Iran
                                                        E-mail:
                                                            se@nn.ir
                                                                                
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                            Najafi,
                            Department of Forestry and Forest Engineering, Tarbiat Modares University, P. Box 64414-356, Iran
                                                        E-mail:
                                                            a.najafi@modares.ac.ir
                                                                                          
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                            Rab,
                            Soil Physics Future Farming Systems Research Division, Department of Primary Industries, Victoria, Australia
                                                        E-mail:
                                                            mr@nn.ir
                                                                                
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                            Zenner,
                            Department of Ecosystem Science and Management, Pennsylvania State University, University Park, PA, USA
                                                        E-mail:
                                                            eric.zenner@psu.edu