Effect of site condition, seasonality and species selection on tropical dry forest restoration

Background/Question/Methods

Restoring tropical forests in dry habitats is a worldwide priority, since tropical dry forests are the most threatened of all major tropical forest types. In Veracruz, Mexico, TDF has been reduced to fragments and successional sites representing 7% of the original cover. The aim of this study was to determine the effect of site condition and seasonality on the seedling performance of selected tree species. We studied the effect of existent vegetation and soil conditions on native tree species performance during two dry and two rainy seasons. Six tree species were tested (Cedrela odorata, Ceiba aescutifolia, Guazuma ulmifolia, Ipomoea wolcottiana, Luhea candida and Tabebuia rosea) in four fallows. Sites differed in tree density (36 to 190 ind/0.04 ha), tree richness (8 to 18 species/0.04 ha), and soil characteristics. A total of 960 seedlings, 40 individuals of each species, were transplanted per site. Survival and growth (height and diameter) were monitored every 4 months during two years.

Results/Conclusions

Seedling survival was higher in sites with existent vegetation with more woody individuals and species richness, and RGR was significantly higher for all species and sites during the rainy season. Survival decreased from 80% after the first dry season to 42% after the second dry season. Overall, Ceiba showed the highest survival (80 %), and Guazuma had a high survival (65%) and the highest RGR (height = 0.21,diameter = 0.1 cm/cm/month). Cedrela showed the lowest survival but high RGR (height = 0.24, diameter = 0.14 cm/cm/month). Important implications for the ecological restoration of deforested areas in TDF regions are related to take advantage of existent vegetation even if it is scarce.  Restoration assays established on degraded sites, with poor richness and scarce woody plant density performed worst during the dry season. In conclusion, the site condition is as important as tree species selection in a success restoration, existent woody vegetation in an abandoned site nurses planted seedlings and thus contributes to the achievement of TDF restoration.