Abstract
Forest management in Sweden can be characterized by even-aged silviculture heavily relying on three established harvest regimes: clearcutting, the seed-tree method, and the shelterwood system. Less intense, small-scale retention harvest systems such as single tree and group selection harvest are rarely used. In addition, natural regeneration dynamics without enrichment planting have barely been studied. Consequently, this study examined natural regeneration establishment in a multi-layered Pinus sylvestris-Picea abies forest stand in southwest Sweden after target diameter harvesting and soil scarification. The creation of forest canopy gaps had a positive effect on total seedling density five years after harvest, mainly due to a significantly higher number of Betula pendula individuals. Seedling density of more desirable tree species suitable for continuous cover forestry such as Fagus sylvatica, Quercus petraea and Picea abies also increased substantially in gaps when compared to pre-harvest conditions or the unharvested plots. In contrast, soil scarification did not increase the number of seedlings of desired tree species due to a significant decrease in Picea abies abundance. Soil moisture and gap size significantly improved Betula pendula seedling establishment while a larger number of Quercus petraea seedlings were observed in Vaccinium myrtillus patches. We conclude that canopy gaps are beneficial under the encountered stand conditions to initiate forest regeneration, and that soil scarification without the timely occurrence of a mast year of desired tree species is not effective in the type of forest studied.
Highlights
Managed forests in northern Europe are dominated by even-aged, single-species stands with trees forming a single canopy layer [1,2]
In order to promote more heterogeneous stand structures and to obtain more resilient, multifunctional forest ecosystems, management approaches are required that complement the prevailing systems of even-aged silviculture [3]
By using an experiment laid out in a multi-layered Scots pine-Norway spruce forest with varying small-scale stand structure, we aimed to analyze the effects of soil scarification and partial, low intensity tree removal on natural regeneration patterns
Summary
Managed forests in northern Europe are dominated by even-aged, single-species stands with trees forming a single canopy layer [1,2]. Some alternative management approaches such as single-tree selection in boreal Norway spruce stands and diameter limited cutting with enrichment planting in mature coniferous stands have been examined in northern and central. Forests 2017, 8, 35 multi-layered stands in Norway and Finland [12,13,14]. On poor sites in northern Sweden or Finland, patch cuttings can complement alternative approaches to continuous cover forestry in mature pine stands [15,16,17]. In northern Germany, Tremer [18] estimated the ingrowth of new trees in mature pine stands that have been managed by target diameter harvest for the last three decades.
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