Abstract
The large-scale introduction of lodgepole pine (Pinus contorta ssp. latifolia, LP) into Swedish forests was initiated around 1970, and currently 520,000 hectares of the forest land are dominated by the species. Even though the tree has mostly serotine cones, adapted to open after forest fires, it has proved able to self-regenerate in Sweden. This study is the first to present, scientifically, the extent of self-regeneration covering the whole current range of LP-forests in Sweden. LP-saplings were recorded for three years, 2015–2017, in 8194 subplots distributed over 214 randomly selected LP-stands from latitude 59.6–66.9°N and altitude 88–710 m asl. Of all subplots, 3% contained LP-saplings, and regeneration was found in 53% of all stands. The probability of finding LP-saplings was significantly dependent on the plots’ distance from the edge of the LP-stand, and 78% of all saplings were found within and up to 15 m beyond the stand edge. Most, 63%, of the plots with LP were found on disturbed ground such as wheel tracks, roadsides and where there had been site preparation. The results show that LP can naturally spread under a range of conditions in the studied region. The regeneration is, however, concentrated in particular stands and should be possible to control with monitoring programmes and measures to eradicate self-dispersed trees in unwanted areas.
Highlights
Tree species have been spread with human assistance over nation boarders since ancient times, often in small and scattered groups to gardens or parks, but sometimes in order to introduce new trees on a larger scale (Peterken 2001)
The hypotheses tested were: (1) the presence of naturally regenerated seedlings is dependent of the distance to the stand edge; (2) natural regeneration increases with stand age; (3) natural regeneration is more common on wet soil
The results show, not surprisingly, that LP has the potential to naturally regenerate in the prevailing conditions in northern Sweden
Summary
Tree species have been spread with human assistance over nation boarders since ancient times, often in small and scattered groups to gardens or parks, but sometimes in order to introduce new trees on a larger scale (Peterken 2001). The motives for the introductions have varied from curiosity to seeking new ornamentals, timber traits, improved growth or adaptation to sites where native species fail or are less productive. Latifolia, here denoted LP) is the most prominent human-assisted introduction. The species was introduced on a trial basis in the 1920s and this was followed by extended provenance trials in the 1960s (Elfving et al 2001). Based on the promising results, large-scale planting schemes were established in the central and northern parts of Sweden, with a peak in the 1970s and 1980s (Engelmark et al 2001).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
