Cost-efficiency analysis of seedling introduction vs. direct seeding of Oreomunnea mexicana for secondary forest enrichment

Among recovery strategies for secondary and degraded tropical forests, the introduction of tree species is one of the most commonly used. This is achieved particularly through the planting of nursery-grown seedlings (i.e. seedling introduction). Another less common technique, but one that could prove efficient, is sowing seeds (i.e. direct seeding) in the forest floor. However, very few comparisons have been made in the literature in terms of the ecological and economic costs and benefits between these two techniques. This study presents a cost-efficiency analysis of the introduction of seedlings and seeds of Oreomunnea mexicana (a threatened species in Mexico) in a secondary Tropical Montane Cloud Forest in central Veracruz, evaluating (1) the performance of the seedlings derived from each of the two practices, (2) the relationship of their performance with the environmental variables at the microsite level, and (3) the ecological and economic cost-efficiency of each practice. At the end of the experiment, survival was higher in the nursery-grown than in the direct-seeded seedlings (97% vs. 22%, respectively); however, the relative growth rate in height was lower for the planted than the emerged seedlings (0.02 ± 0.002 vs. 0.03 ± 0.002 cm cm−1 month−1). Relative growth rate in diameter was similar in seedlings introduced by either technique. No predation of seeds or seedlings was registered. The cost-efficiency analysis revealed that, considering the costs of production and plantation, introducing seedlings was almost two times more expensive compared to direct seeding. Results suggest that recovery of this species is feasible with combined practices depending upon the life stage of the plant and the conditions of the microsite. Improvements to these techniques, such as protection of the seed plumules, could confer even greater ecological and economic advantages for the introduction of O. mexicana in tropical secondary forests.