Browsing by Subject "rakenteelliset ominaisuudet"

Spruce stumps have been harvested in large scale for combustion in heat and power plants since the beginning of the 21th century. Normally the stump harvesting operations are done by excavators. On stump harvesting areas the risk to serious soil damage is greater because there are more driving tracks on the ground than in original logging operations. In stump harvesting areas machines cannot get benefit from frozen soil or coarse roots to increase bearing capacity. Compacted soil can reduce tree root penetration, increase nutrient leaching and affect soil water properties. The aim of this study was to clarify if the stump harvesting compacts the forest soil and if it possibly recovers in the long run. I also studied how much the soil surface will be disturbed after stump harvesting operations. In this study there were three stump harvesting sites which varied in the time passed since harvesting. Comparable reference sites were chosen from nearby areas where the stumps were not harvested. All sites were located in Southern and Central Finland. Every site had three 5 x 5 meter study plots in which soil strength was measured by a cone penetrometer. Soil core samples were also taken from every study plot. The soil surface disturbance proportions were estimated visually and using a soil sampling probe. Measurements were carried out under summer of 2014. The results indicate that the soil has been compacted by stump harvesting in the 4-year-old site but differences were statistically significant (p<0.05) only in 2 of 6 depth classes. In the middle aged (7 years) site the impacts were the opposite. In the oldest (13 years) site there were no differences between the treatments. The soil surface in stump harvesting sites has been disturbed most in the youngest site (50 %), and at the other sites the disturbed soil surface proportion was about 40 %. About 25 % of soil surface was disturbed in all reference sites. The soil disturbance results in this study were minor compared to other studies in the literature. In the upper depth classes soils were not too compacted for tree growth, root penetration and nutrient uptake. This indicates that the changes in soil structural properties caused by stump harvesting are not harmful for forest growth but more long-term studies are needed.