Accelerating tropical cloud forest recovery: Performance of nine late-successional tree species

Abstract

Tree planting is a common strategy for forest restoration. The use of mid- and late-successional species is less common, but could accelerate succession, enhance diversity and secure their presence. In this study, we determined the survival and growth of 559 saplings from nine native mid- and late-successional species after three years of growth under a range of habitat conditions to evaluate their potential utility in restoration plantings. Since mid- and late-successional tree species have shade-tolerant attributes and the light environment is a determinant factor for their growth and survival, we expected sapling performance to vary among species depending on the percentage of canopy cover and on factors associated with this variable. For this, we identified habitat conditions that influenced sapling performance in a degraded tropical cloud forest: the conditions ranged from closed-canopy secondary forest to open pastures dominated by exotic grasses. Overall, the studied species presented a high performance: sapling survival (40 to 90%) and relative growth rates in height (0.14 to 0.50 cm cm−1 year−1) and in diameter (0.04 to 0.50 mm mm−1 year−1) were within or above the ranges previously reported for cloud forest species. The final sizes and growth rates in height and diameter were mostly explained by the canopy and grass cover (71.5% of the variation). Integrated Response Index (IRI) values showed wide variation among species (from 6.44 to 41.41 with inclusion of height, and from 2.13 to 44.77 with inclusion of diameter). In general, there was a negative correlation between canopy cover and final sapling size and growth rates in height and diameter, but there were important variations among species. Based on their IRI values, species such as Ulmus mexicana and Oreomunnea mexicana are suggested for restoration plantings. Given their low performance, however, Fraxinu uhdei and Juglans pyriformis are recommended for use only in advanced forest successional stages or in conjunction with other restoration techniques to increase their survival. Our results show that these threatened mid- and late-successional native species can be successfully matched to microsite conditions and established in degraded areas as a strategy by which to secure their presence and accelerate forest recovery.