Afforestation of Black Spruce Lichen Woodlands by Natural Seeding

Abstract

Black spruce-lichen woodlands (LW) are naturally occurring unproductive low tree density stands within the eastern North American closed-crown boreal forest. Natural reforestation in LWs is impeded by the lichen mat and ericaceous shrubs that inhibit seedling establishment. Disk scarification is a mechanical site preparation method that creates furrows where lichens and shrubs are removed and mineral soil is exposed, which is the preferred seedbed for black spruce natural regeneration. The objective of this study was to quantify the impact of disk scarification on black spruce establishment in LWs by natural seeding. Disk scarification was performed amid scattered seed trees in six study sites located in the central area of boreal Quebec's spruce-moss bioclimatic domain. Newly established black spruce seedlings were significantly more abundant (ca. 81%; χ2 = 28.72, P < 0.001) in the furrows of scarified plots even though the proportion of disturbed soil was small (ca. 20%). Seedling establishment occurred for at least 3 years following scarification, with a peak in the first year. The distribution and density of seed trees (112‐363 stems ha−1) did not limit natural seedling establishment in this study. Five years after scarification, observed densities and stocking levels of newly established black spruce seedlings were sufficient to expect afforestation without planting in scarified LWs.