## 3 Results
### Changes in the Trafficked Soil  
Figure 4 shows the results on differences in the mean penetration resistance by taking as a reference the control data and measurements taken after the first, second, third, fourth, fifth, tenth and fifteenth passes (panels on the left) and the differences in the mean penetration resistance by taking successive measurements (panels on the right).  
Figure 4: _Cont._  
As shown, in the H testing area, positive changes were found mostly in the first 15 cm of soil irrespective of the number of passes at which the measurements were taken (Figure 4a). These, however, increased the penetration resistance only to a small extent, with up to 0.28 MPa in this soil layer. Changes in the mean penetration resistance also occurred at depths of 20 to 25, 35 to 40 and 50 to 55 cm, but these appeared mostly after 10 to 15 passes and were minor. There was found a consistent soil loosening in the layers at depths of 20 to 35 and 45 to 65 cm. In the S testing area, important changes occurred in the first 30 cm of soil, and mostly after the second pass, and a consistent loosening appeared at a depth between 40 and 65 cm (Figure 4c). Finally, in the F testing area (Figure 4e), the changes were rather inconsistent, but they show a high increment in the first 10 cm of soil.  
At the first pass with horses (Figure 4b), positive changes in the mean penetration resistance occurred in the first 15 cm of soil relative to the control data. The second pass did not contribute with positive changes but rather loosened the soil at a depth of 0 to 5 cm. The third pass increased the mean penetration resistance at depths of 20, 33 and 40 to 65 cm. The fourth pass did not bring positive changes, and the fifth pass produced higher changes at depths of 15 to 35 and 50 to 65 cm. Five more passes (P10) did not produce important changes relative to the first five passes in the mean penetration resistance, but the last five passes (P15) produced changes at depths of 10 to 15 and 20 to 25 cm relative to the first ten.  
At the first pass with the skidder, minor positive changes in the mean penetration resistance occurred in the first 5 to 10 cm of soil. The second pass contributed to high increments at depths of 10 to 30 and 50 to 65 cm. The third pass added minor changes relative to the second, the fourth pass increased the penetration resistance at 20 cm and the fifth pass loosened the soil. The following five passes (P10) increased the penetration resistance at depths of 30 to 65 cm and the next five passes (P15) increased the penetration resistance significantly in the first 30 to 35 cm of the soil. Compared to horse logging the changes between measurements seem to be higher in magnitude.  
Finally, the first pass with a forwarder produced the most important changes in the first 10 cm. In terms of magnitude, these were much higher as opposed to skidding and horse logging. The second pass did not produce high increments in the mean penetration resistance relative to the first one, but the third pass produced important changes at depths of 25 to 50 cm. The fourth pass did not bring important changes and the fifth pass increased the penetration resistance mostly between 30 and 65 cm. The next five passes (P10) seemed to loosen the soil relative to the first five, which also held true for the next five passes (P15).  
Figure 4: Differences (\(\Delta\)) in the mean penetration resistance between the control (C) and measurements taken after the first (P1), second (P2), third (P3), fourth (P4), fifth (P5), tenth (P10) and fifteenth (P15) passes (left panels, (**a**,**c**,**c**)), and differences (\(\Delta\)) in penetration resistance based on the measurements taken successively (right panels, (**b**,**d**,**f**)). Legend: H—horse logging, S—skidding, F—forwarding.