The effect of site preparation on seed tree regeneration of drained Scots pine stands in Finland

Abstract

We studied the success of natural regeneration eight years after seed tree cutting on four drained peatland Scots pine stands in central and northern Finland (Parkano, Sievi, Vaala, Simo) when retaining ca. 50 Scots pine stems ha^-1 followed by site preparation. The total number and the number of crop seedlings and their mean height were investigated by species and methods of site preparation (control, scalping, mounding). The results showed that the total seedling numbers were very high (9,100 – 51,000 ha^-1) in all sites and treatments. The share of downy birch seedlings was 64 –76 %. The total number of crop seedlings varied from 1,450 to 2,000 ha^-1 (2,000 maximum density accepted), with number of Scots pine seedlings varying from 600 in Parkano to 1,950 ha^-1 in Sievi. Site preparation increased the number of pine crop seedlings on two of the four sites: at Parkano by 900 – 1,100 seedlings ha^-1 and at Vaala by 600 – 800 seedlings ha^-1. On average, the number of pine crop seedlings was slightly higher and that for all birch seedlings clearly higher when site preparation was applied. About 22 – 81% of crop seedlings were grown in a prepared surface in scalped plots and 75-91% on mounded plots. The mean height of the crop seedlings was not significantly affected by the site preparation treatment. With respect to the minimum requirements set for the regeneration result required by forest legislation, seed tree cutting appeared to provide sufficient regeneration in eight years in terms of the total seedling density and the number of crop seedlings when downy birches were included. The beneficial effect of soil preparation was seen in the increased share of Scots pine crop seedlings.