Saturated hydraulic conductance of forest soils affected by track harvesters

The exact data from the field of soil mechanics from specific forest stands exposed to forestry mechanization operation were obtained. Field surveys were performed on four study plots within the Křtiny Training Forest Enterprise, Masaryk Forest, followed by laboratory analyses of the collected soil samples aimed at evaluation of the impacts of Zetor 7245 Horal System, PONSSE ERGO 16 harvester and Gremo 950 forwarder on the compaction of upper soil horizons as well as on the dynamics of soil saturated hydraulic conductivity. A specific objective of the performed investigation was to assess the influence of the used hauling/skidding technology on measurable parameters of soil mechanics with the emphasis on a possibility to apply the Guelph permeameter for direct study of soil saturated hydraulic conductivity. In the measurement points affected by machinery operation, the impact of the changed soil structure on the values of saturated conductivity is very well noticeable – on study plots No. 3 and 4, the values decreased by one order of magnitude from 0.7 × 10^–5 m·s–1 to 0.09 × 10–5 m·s^–1: specifically, (i) on study plot No. 3 and from 6.9 × 10–5 m·s–1 to 0.7 × 10–5 m·s–1, and (ii) on study plot No. 4; on study plot No. 2 even by two orders, i.e. from 1.6 × 10–5 m·s–1 up to 0.03 × 10–5 m·s–1. After the operation of a universal wheeled tractor at the Babice nad Svitavou locality, the situation partially improved by one order to 0.3 × 10–5 m·s–1, similarly like at the Rudice locality to 1.5 × 10–5 m·s–1. Significant changes were found in both surface and subsurface horizons. Field-saturated hydraulic conductivity indicates also a reduction of the pore volume after machinery traffic; however, tendencies towards restoration of the original state were detectable as soon as after six months.