Soil physical disturbance resulting from stump harvesting

Abstract

This paper describes a detailed study of stump harvesting in Lamloch Forest in north Dumfries and Galloway from 2010 to 2014. The study explored both the nature and extent of soil disturbance resulting from stump harvesting using a variety of standard and innovative techniques. Stump harvesting disturbance was compared with that of other forestry practices. To complement the two-dimensional and subjective nature of visual assessment techniques, a radiometric approach was adopted, utilising residual Chernobyl 137Cs fallout to determine the degree of soil mixing. To support bulk density measurements, micromorphological analyses of soil thin sections were carried out to investigate the impact of compressive force on pore space. Low-cost tracer devices were deployed in the soil around stumps prior to extraction to permit the monitoring of soil lateral movement during stump extraction.  The study showed that stump harvesting followed by restock, when carried out under current guidelines, disturbed around five times the volume of soil compared to that disturbed by trench mounding. Stump harvesting also resulted in a net reduction in soil bulk density. Suggestions for modification of stump harvesting operations are made to reduce soil disturbance, including avoiding raking over the site following stump harvesting which is estimated to add a further 10% to the volume of soil disturbed.