Seedling responses to changes in canopy and soil properties during stand development following clear-cutting

The role of natural regeneration in silvicultural systems is attracting increasing interest, but much is unknown about how stand development after clear-cutting affects seedling regeneration. We looked at the impact of tree canopy and ground layer vegetation (i.e., 'stand type') as well as soil properties (i.e., 'soil origin' or stand from which soil originated) on survival and growth of Pinus sylvestris and Picea abies seedlings at three forest developmental stages, i.e., 4, 16 and 34 years after clear-cutting. To do this we transplanted soil cores between stands of different stages to separate the effects of soil properties versus canopy closure on seedling performance. We found that seedling survival of both species was highest when planted in the oldest stands independent of soil origin. P. sylvestris seedling growth responded to stand type but not soil origin, and biomass was highest at the youngest stand likely because of greater light availability. Meanwhile, although P. abies seedling root biomass responded to stand type, this species was mostly responsive to soil origin, with shoot and total biomass being greatest when seedlings were grown in soil originating from the oldest stands. These findings have implications for our understanding of tree regeneration of species that differ in their responsiveness to light and soil characteristics. The results can further inform forest managers about how to optimize survival and growth of seedlings by means of canopy regulation as well as provide information to assist the regeneration and development of multi-storied forest stands.