Tree regeneration in active and passive cloud forest restoration: Functional groups and timber species

Tree regeneration of late-successional, animal-dispersed and/or timber species in restored forests is key to the recovery of ecological functions and interactions, as well as ecosystem services. We assessed whether active restoration is more effective than passive restoration at increasing the recovery of these groups in the tree seedling community. We analysed tree seedlings (>0.3 m to 1.5 m in height) over four years under three conditions in a tropical montane cloud forest landscape in Mexico: mature cloud forest (MF) as the reference system, active restoration (AR; mixed plantation with native species) and passive restoration (PR; natural succession). The AR and PR were 24 years old and were originally established in abandoned grazing land located at similar distances to the MF (709 +/- 67 m and 906 +/- 66 m, respectively). We recorded similar to 488 seedlings/year belonging to 51 tree species. Seedling density was higher in AR than in PR, but no differences were found in recruitment or survival rates between these restoration conditions. The density of late-successional, barochorous-synzoochorous and timber species was much higher in MF than in the restoration conditions. Seedling density of timber species was similar in AR and PR. Our results support higher recovery of the richness and density of late-successional and barochorous-synzoochorous functional groups in the tree seedling community in AR than in that of PR. However, the overall low seedling density and recruitment found in both restoration conditions highlight the need for additional intervention, even after 24 years, in order to overcome barriers to tree regeneration. Direct seeding and enrichment plantings of late-successional, barochorous-synzoochorous and high-value timber species could contribute towards more ecologically and economically valuable forests.