Scarification, fertilization and herbicide treatment effects on planted conifers and soil fertility

Abstract

The influences of soil surface modification (blade scarification and plas tic mulching),fertilization and herbicide application on planted Jack pine (Pinus banksiana Lamb.) and black spruce (Picea mariana (Mill.) B.S.P.) trees were examined after seven years on one site within the Boreal forest region of Canada. Seedling survival, growth and quality; and foliar,forest floor and mineral soil nutrient status were assessed. Seedling survival doubled with scarification, but declined generally from 84 to 75% (mean for both species) during the last five years. Combined silvicultural treatments increased productivity as much as 20 times for Jack pine and 120 times for black spruce; however, negative impacts on seedling quality were noted especially by herbicide application, and scarification reduced the carbon and nutrient reserves in the forest floor. Foliar nutrient concentrations were little affected by the applied treatments. Soil temperatures increased in response to scarification during the frost-free growing period, but no seasonal differences in soil moisture were noted. Innovative future management approaches in such stands should include the use of softer approaches to vegetation management that reduce plant competition levels without significantly lowering forest floor carbon and nutrient reserves or reducing tree quality.