Tree growth on rehabilitated skid roads in southeast British Columbia

Implementation of The Forest Practices Code of British Columbia Act (FPC) i n 1995 made skid road rehabilitation mandatory on many sites effective imme diately and on all sites by December, 1999. This requirement implies that s kid road rehabilitation will restore slope hydrology and site productivity. These assumptions require verification. Tree growth on excavated and blade d trail (skid road) rehabilitation was examined at 10 sites in the East and West Kootenays of southeast British Columbia. Height and diameter growth o f lodgepole pine (Pinus contorta), Engelmann spruce (Picea engelmannii), an d Douglas-fir (Pseudotsuga menziesii) trees were monitored at retrospective and new research sites established between 1984 and 1994. The study examin ed several 'worst case' scenarios with regard to soil and climatic conditio ns, and rehabilitation techniques. Soil conditions included line and coarse textured material; a number of these sites have unfavourable subsoils such as calcareous, high pH parent materials. Site climates ranged from relativ ely dry and warm to cold and wet. Older rehabilitation techniques resulted in the subsoil mixed with the forest floor during excavation and recontouri ng, and the original running surface not decompacted prior to recontouring the slope. In contrast, newer techniques involve separate topsoil handling during excavation and rehabilitation, and decompacting of the skid road run ning surface. Growth on four disturbance types was compared: the undisturbed area adjacen t to the skid road and three recontoured road locations equivalent to the p revious inner track, midroad, and berm/sidecast. Data was analyzed using AN OVA and disturbance type contrasts in regional and biogeoclimatic groupings . The trees growing on the berm and undisturbed treatments commonly display ed better growth than the trees growing on the inner track and midroad trea tments. For example, in the analysis of all 10 blocks for three year height increment, trees growing on the berm were either the leading or second ran ked treatment in seven out of 10 blocks, with differences in growth relativ e to the undisturbed ranging from 89 to 161%. Height growth of trees growin g on the berm, and on the berm and undisturbed together, was also significa ntly better in the biogeoclimatic analysis. Diameter and volume growth foll owed the same trend as height for all analyses. Poorer growth on inner hack and midroad trees was similar to but not as pronounced as in previous stud ies on unrehabilitated skid roads, suggesting that characteristics of the o riginal skidroad are still affecting the growth of trees on recontoured slo pes. However, the results suggest that, for the site conditions studied, re habilitated skid roads will support trees of merchantable quality, particul arly with improved rehabilitation techniques. (C) 2000 Elsevier Science B.V . All rights reserved.