Decay and stain 10 years later in aspen suckers subjected to scarification at age 3

Abstract

A trembling aspen (Populustremuloides Michx.) sucker stand was scarified at age 3 to benefit subsequently planted white spruce (Piceaglauca (Moench) Voss). Survivors were examined 4, 6, and 10 years after treatment. The effects of scarification on aspen stem growth, and on external and internal quality of both roots and stems, were assessed at those times. Damage inflicted on the parent root system significantly reduced stem growth after scarification. Ten years after scarification normal height growth had resumed, but diameter growth was still slightly slower than that of unscarified suckers. Scarification wounds on the root systems were common and frequently associated with root and root-collar decay. Both the root systems and stems of scarified suckers had significantly more internal decay and stain than those of unscarified suckers. Stem wounds apparently caused by scarification were present on approximately 75% of the survivors, and accounted for most of the extra defect in scarified stems. The extent of advanced stem decay was closely correlated with the severity of stem wounds. Several basidiomycete fungi known to cause advanced butt and stem decay in mature aspen in Ontario were isolated from decay within the root systems and stems of scarified suckers. In unscarified suckers these basidiomycetes were not isolated or were isolated much less frequently. The large numbers of surviving suckers, their nearly normal growth rates, and the relatively small size of the planted spruce 10 years after scarification indicate that the aspen will develop into well-stocked, harvestable stands. However, a high proportion of the aspen that survive scarification will likely be more susceptible than unscarified aspen to windthrow or breakage. The scarified trees will likely be of lower quality as well, because the incidence and extent of decay in the root systems and lower stems are comparatively high.