Initiating the transition from open-canopy lichen woodland to productive forest by transplanting moss, results from a 10-year experiment

Abstract

Abstract Background and aims Low productivity open lichen (Cladonia spp.) woodlands have been rapidly expanding in the closed-crown feather moss (Pleurozium schreberi (Brid.) Mitt.) boreal forest in eastern Canada. While open-woodland areas are progressing, there is little information on the recoverability of open lichen woodlands back to closed-canopy forests. Methods An experimental set-up using moss transplantation was installed in a poor jack pine (Pinus banksiana Lamb.) stand with a lichen ground cover in 2011. Treatments included: 1) lichen cover removed (No Lichen), 2) lichen cover removed and transplantation of a feather moss cover (Moss Transplanted), 3) lichen control (No Treatment) and 4) a natural jack pine site with feather moss cover (Moss Control). We extracted tree stem increment cores and collected needles and soil samples for nutrient analyses. Results The transplanted-moss treatment can counteract the adverse effects of lichen on jack pine growth, and this treatment enhanced foliar nutrition and soil nutrients, especially ammonium (N-NH4+), nitrate (N-NO3-). With this treatment, the soil conditions (e.g., soil nutrients, soil moisture) and foliar nutrition were closer to that of the moss control. Surprisingly, lichen removal treatment not only does not improve growth but appears to result in poorer jack pine growth and harsher soil conditions. Conclusion Feather moss can establish, survive, and remain healthy in an environment previously occupied by lichen. The replacement of lichen by feather moss establishes soil conditions that appear conducive to better tree growth and that has the potential of restoring the productivity of boreal forests in open-canopy lichen woodlands.