Regeneration after stump harvesting in southern Finland

Abstract

In southern Finland, large-scale stump harvesting from regeneration areas began in the early 2000s. At that time, stump harvesting and additional soil scarification for planting was performed simultaneously. The aim of this study was to investigate the regeneration result, particularly the outcome of the natural regeneration of birch after stump harvesting, compared to the result achieved on a conventionally soil prepared area without stump lifting.The study material consisted of 37 stump-harvested areas 4–9years old, and 10 conventionally soil prepared regeneration areas of a corresponding age. In the case of Norway spruce planting, the result did not differ between stump-harvested and conventionally soil prepared areas, but the share of pure coniferous stands after pre-commercial thinning was estimated to be 30% after stump harvesting and 50% in conventional regeneration areas.In stump-harvested areas, the share of disturbed soil surface seemed remarkably higher and the time for seedling emergence longer than in conventionally soil prepared areas without stump lifting. The number of Scots pine seedlings was somewhat higher after stump harvesting than after conventional soil preparation, but there was great variation between regeneration areas. As for Norway spruce, there were fewer natural seedlings on stump-harvested areas. The number of birch seedlings was somewhat higher after stump lifting, but there was huge variation between regeneration areas. Most birch-rich regeneration areas were discovered after the stump harvest; the maximum mean density was over 60,000 birch seedlings ha−1. Birch regeneration was most abundant on fine textured, moist mineral soils or peat layered spots. The mean temperature in May and June during the first summer, and rainfall in May and June during the second summer after the stump harvest, correlated positively with the abundance of birch seedlings.