Early growth and survival of 49 tropical tree species across sites differing in soil fertility and rainfall in Panama

Reforestation in the tropics takes place across a wide variety of edaphic and climatic conditions. Reforestation trials have demonstrated that edaphic conditions may have a strong effect on species growth and survival. However it is unclear how the relative importance of soil conditions influences species survival and growth under varying amounts of rainfall and lengths of dry season.Two-year growth and mortality of 49 tree species were evaluated in four sites across Panama, representing a soil fertility–rainfall matrix. Despite strong contrasts in environmental conditions, 65% of individual species did not show consistent differences in growth between high- and low-fertility sites or between wet and dry sites. However, early growth and survival were more strongly affected by soil fertility than by rainfall patterns for the second-largest group; 30% of the species grew significantly better in both high-fertility sites than in both low-fertility sites, compared to 6% in both wet sites vs. both dry sites. In the two high-fertility sites, growth of 47% and 69% of the species was better than their across-site means. On the other hand, 55% and 73% of the species grew significantly slower than their across-site averages in the two low-fertility sites.Survival did not appear to be associated to either soil fertility or rainfall. In each site, only a few species had a significantly higher or lower within-site survival than across-site survival.Diversifying the choice of tree species increases the options for reforestation strategies that match species characteristics to local site conditions and to the objectives and management possibilities of landholders. Testing the performance of potential species under different site conditions in screening trials is paramount, both to inform selection from among the vast diversity of tree species in the tropics that show good growth and survival under different local site conditions and to filter out unsuitable species and avoid early failure of the reforestation effort.

Research highlights▶ Survival of 35–57% of the species was below 85%. ▶ Survival did not appear to be associated to soil fertility or rainfall. ▶ Growth of most species did not differ consistently between high and low-fertility sites. ▶ The second-largest group grew consistently better in the 2 high-fertility sites. ▶ Only very few species grew consistently better in the 2 wetter sites.