| Abstrakt: |
The effects of the passage of forwarders on soil and damage to spruce root systems along an experimental trail were studied. The site was characterized by medium-textured soil of the pseudogley type under favorable moisture conditions. Due to the passages, the soil was compacted down to a depth of 20 cm, soil porosity was decreased by 5% (volume) and soil aeration was decreased by more than 5%. Substantially higher values of mechanical soil resistance occurred (estimated by penetrometric measurements) in a soil pit situated in a rut after passages. Pressure measured by sensors placed at a depth of 10 cm below the soil surface reached values ranging from 0.09 to 0.11 MPa in plots uncovered with slash and 0.03–0.07 MPa in plots covered with slash after two to four passages, and 0.06–0.07 after six to ten passages. Soil surface deformations occurred in the upper soil layers through tire impression. This resulted in the origin of ruts, whose depth and width was dependent on the type of tires, their load, surface conditions, type and texture of soil, soil moisture and number of passages. Pressure in the soil layers imposed by the tire of a given type, inflation and load changed in relation to depth, ground cover, soil properties and reinforcing components on the soil surface. Sap flow in coarse roots actually treated by a moving heavy load clearly and immediately responded with a sharp increase followed by a similar decrease (peak flow) after several minutes. On average, the flow rate decreased by about 8% after the first treatment compared to the untreated state, and remained the same after passing the peak during the second pass when the maximum load was applied. However, this decrease amounted to about 40%, when compared to the “relative zero flow” after root severing. This indicates serious local damage to the conducting system. Even when loading directly damaged rather small fractions of the total root systems, it opened tree tissues to subsequent fungal infection, whose impact could be very serious in future years. Flow in stem sections oriented in the opposite direction to the trail and the flow in stem sections and root buttresses oriented toward the trail (but where roots were not actually growing below the trail or grew deeper in the soil), neither responded to the treatment or responded insignificantly. Sap flow responded only in surface roots below trails, occurring down to a depth of about 10 cm below the original soil (litter) surface. This occurred only when a significant part of the roots (with the total projected area of treated root branches more then 500 cm2) were under the tires. This indicates the protective ability of soils and also, a possible method of artificial root protection. [ABSTRACT FROM AUTHOR] |
Full text from SpringerLink