Tree seedling dynamics in two abandoned tropical dry forests of differing successional status in Yucatán, Mexico: a field experiment with N and P fertilization

The effects of nitrogen (N) and phosphorus (P) fertilization on seedling survival, recruitment, species richness and diversity in two abandoned tropical dry forests (10-yr old, young forest, and c. 60-yr old, old forest) in Yucatán, Mexico, were studied over two years. The seedling dynamics in the control plots were found to be highly seasonal with highest recruitment and lowest death rates during the rainy season. A low percentage of seedlings were resprouts; this important mechanism for forest regeneration had a higher-than-expected survival when compared to seedlings regenerated from seeds. Nutrient addition had significant effects on seedling dynamics in both of the forest regeneration stages. In the young forest, N fertilization facilitated the increase of seedling density. In the old forest, the addition of P decreased seedling diversity, while it increased the recruitment of only a few species. In both forests, P fertilization increased the survival time of seedlings when interacting with light availability and bulk density on the topsoil layer. Results suggest that low nutrient availability combined with low light availability constrain forest succession in Yucatán, Mexico.