Above- and below-ground vegetation recovery in recently clearcut and burned sites dominated by Gaultheria shallon in coastal British Columbia

Abstract

Above- and below-ground vegetation recovery was assessed 2, 4 and 8 years after logging and burning on an age sequence of sites dominated by salal ( Gaultheria shallon Pursh) on northern Vancouver Island, British Columbia. The total above-ground vegetation biomass quadrupled from 1372 kg ha −1 on the 2-year-old sites to 5574 kg ha −1 on the 8-year-old sites. These are low values for post-logging above-ground biomass when compared with many other forest ecosystems. Salal was the dominant species on these sites, representing 77%, 87% and 73% of the total above-ground biomass on the 2-, 4- and 8-year-old sites, respectively. Leaf area index increased from 0.67 to 2.31 between the 2- and 4-year-old sites, but was only 2.53 on the 8-year-old sites. The total below-ground biomass increased six times from 1908 kg ha −1 on the 2-year-old sites to 11 415 kg ha −1 on the 8-year-old sites. The proportion of fine-roots to total roots declined with increasing site age as new rhizomes were produced. The upper 15 cm of the forest floor was found to contain 56% and 74% of the live fine-roots and 64% and 49% of the new rhizomes of the Gaultheria-Vaccinium and Epilobium-Cornus species groups, respectively. The ratio of below-ground to above-ground biomass varied from 1.4 on the 2-year-old sites to 2.5 on the 8-year-old sites. The post-disturbance dominance of salal on these sites after logging and burning appears to be due to its ability to reoccupy the site rapidly and completely both above-ground and below-ground from rhizomes present before disturbance, and to resist invasion by other species by pre-empting resources (nutrients in this case). A conceptual model of the leaf and fine-root biomass of salal over a period of 60 years is presented.