Abstract
Successful tree regeneration is a key process in ensuring forest sustainability and one of the most crucial investments made in silviculture. This study compared the effects of three reforestation methods (planting, direct seeding, and natural regeneration) and three mechanical site preparation methods (double mould-board forest plough (FP); active plough (AP); and forest mill (FM)) on biometric parameters, survival, and density of Scots pine (Pinus sylvestris L.) seedlings in the first 4 years of growth in a clear-cut area in south-eastern Poland. Planted seedlings were higher, thicker in root collar, and had higher survival rates after the fourth growing season than trees from natural regeneration and direct seeding. Site preparation methods did not affect the density of planted seedlings. After natural regeneration and direct seeding, seedling density was lower and less homogeneous (plots with no seedlings) in FM soil preparation in comparison to other methods. The survival of pines in all reforestation methods was not affected significantly by site preparation methods. Our results indicate that the best mechanical site preparation method for planting is FM, as this is the one that least disturbs the soil environment. For direct seeding the best results were achieved after AP preparation. Natural regeneration of Scots pine was most effective after FP use, and in relatively wet years also after AP use.
Highlights
Scots pine (Pinus sylvestris L.) is the most widely distributed conifer species in the northern hemisphere and is the most important forest forming species throughout East-Central Europe [1]
In the first 3 study years, seedlings growing in forest mill (FM) plots were significantly those in forest plough (FP) plots, but in the first year this is true for direct seeding only
Reforestation by planting of pine seedlings results in faster growth and higher survival rate compared with natural regeneration and direct seeding
Summary
Scots pine (Pinus sylvestris L.) is the most widely distributed conifer species in the northern hemisphere and is the most important forest forming species throughout East-Central Europe [1]. Scots pine forest stands can be regenerated in three ways: planting, direct seeding, and natural regeneration. Natural regeneration of forest stands, by self-sown seedlings, has been practiced more frequently. In 2014, natural regeneration of all tree species accounted for 16.3 per cent of the total reforested area. A further increase of the percentage contribution of natural regeneration in Poland is possible primarily thanks to introduction of natural regeneration of Scots pine, which is the major tree species in the country, constituting 58.1 per cent of its total forest area [3]. Natural regeneration of pine is facilitated by natural conditions (prevalence of coniferous forest sites, frequently high pine seed yields) and promotion of this reforestation method, given that it is more ecologically and economically favourable than the others [4,5]
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