Seedling survival and growth of tree species: Site condition and seasonality in tropical dry forest restoration

Abstract

Restoring seasonally dry tropical forest is a worldwide priority, since it is the most threatened of all major tropical forest types. In Veracruz, Mexico, the dry forest has been reduced to fragments and fallows representing 7% of the original cover. Our objective was to determine the effect of site condition and seasonality on seedling survival and relative growth rate in height and diameter of selected native tree species. We studied plant performance during two dry and two rainy seasons and the effect of existent woody vegetation > 1 m height. A total of 960 seedlings were transplanted: 40 individuals of six species (Cedrela odorata, Ceiba aesculifolia, Guazuma ulmifolia, Ipomoea wolcottiana, Luehea candida, Tabebuia rosea) in four fallows. Seedling survival and relative growth rate were monitored every four months during two years. Survival was higher in sites with more woody species richness, whereas relative growth rate in height was positively correlated with existent vegetation height. Relative growth rate was higher for all species and sites during the rainy season. In the site with less existent woody vegetation, seedling performance was poor and only Guazuma survived. Overall, Ceiba showed the highest survival rate (82-90%) and the lowest relative growth rate. Guazuma had a high survival (20-94%) and the highest relative growth rate; Cedrela showed the lowest survival (3-7%) and high relative growth rate. Our results suggest that site condition, seasonality, and tree species selection act together on seedling performance during early establishment. A vital implication in terms of ecological restoration is the importance of taking advantage of existent vegetation even if it is scarce.