Tropical dry forests are complex and fragile ecosystems with high anthropogenic intervention and restricted reproductive cycles. They harbor unique richness, structural, physiological and phenological diversity. This research was carried out in the upper Magdalena valley, in four forest fragments with different successional stages. In each fragment, four permanent plots of 0.25 ha were established and the light habitat associated with species richness, relative abundance and rarity was evaluated, as well as the forest dynamics that included mortality, recruitment and diameter growth for a period of 5.25 years. In mature riparian forest, species richness was found to be higher than that reported in other studies for similar areas in the Cauca Valley and the Atlantic coast. Values of species richness, heterogeneity and rarity are higher than those found in drier areas of Tolima. Forest structure, diversity and dynamics were correlated with light habitat, showing differences in canopy architecture and its role in the capture and absorption of radiation. The utilization rate of photosynthetic effective radiation in the forest underlayer with high canopy density is low, which is related to the low species richness, while the underlayer under light is more abundant and heterogeneous.

1. Murphy P, Lugo A. Dry forests of Central America and the Caribbean. In: Mooney H, Bullock S (editors). Seasonally tropical forests. Cambridge: University of Cambridge Press; 1996. p. 9–34.

2. Lobo J, Quesada M, Stoner K, et al. Factors affecting phenological patterns of bombacaceous trees in seasonal forests in Costa Rica and Mexico. American Journal of Botany 2003; 90(7): 1054–1063.

3. Lüttge U. Physiological ecology of tropical plants. 2nd ed. Berlin: Springer-Verlag; 2008. p. 458.

4. Janzen D. Tropical dry forests: The most endangered major tropical ecosystem. In: Wilson EO (editor). Biodiversity. Washington D.C.: National Academy Press; 1986. p. 130–137.

5. Mooney H, Bullock S, Medina E. Introduction to tropical dry forest. In: Bullock S, Mooney H, Medina E (editors). Seasonally dry tropical forests. Cambridge: Cambridge University Press; 1996. p. 1–6.

6. Burnham K. Distributional results for special cases of the Jolly-Seber model. Communications in Statistics 1997; 26: 1395–1409.

7. Instituto Alexander von Humboldt Institute (IAVH). El bosque seco tropical (bs-t) en Colombia, programa de inventario de la biodiversidad (Spanish) [The tropical dry forest (bs-t) in Colombia, biodiversity inventory program]. Bogotá: Alexander von Humboldt Institute; 2002. p. 1–24.

8. Chazdon R, Denslow J. Floristic composition and species richness. In: Chazdon R, Whitmore T (editors). Foundations of tropical forest biology. Chicago: University of Chicago Press; 2002. p. 513–522.

9. Gentry A. Diversity and floristic composition of neotropical dry forest. In: Bullock S, Medina E, Mooney H (editors). Tropical deciduous forest ecosystems. Cambridge: Cambridge University Press; 1995. p. 116–194.

10. Kalascka M, Sanchez-Asofeifa G, Calvo-Alvarado J, et al. Species composition, similarity and diversity in three successional stages of a seasonally dry tropical forest. Forest Ecology and Management 2004; 200: 227–247.

11. Bazzaz F, Pickett S. Physiological ecology of tropical succession: A comparative review. Annual Review of Ecology, Evolution, and Systematics 1980; 11: 287–310.

12. Quesada M, Stoner K. Threats to the conservation of the tropical dry forest in Costa Rica. In: Frankie G, Mata A, Vinson S (editors). Biodiversity conservation in Costa Rica: Learning the lessons in a seasonal dry forest. Berkeley (CA, U.S.A.): University of California Press; 2004. p. 266–280.

13. Montagnini F, Jordan C. Tropical forest ecology: The basis for conservation and management. Berlin: Springer Verlag; 2005. p. 295.

14. Repizzo A, Devia C. Árboles y arbustos del valle seco del río Magdalena y la región Caribe colombiana: su ecología y usos (Spanish) [Trees and shrubs in the dry valley of the Magdalena River and the Caribbean region of Colombia: Ecology and uses]. Bogotá D.C.: Faculty of Environmental and Rural Studies, Pontificia Universidad Javeriana; 2008. p. 120.

15. Linares R, Fandiño M. Estado del bosque seco tropical e importancia relativa de su flora leñosa, islas de la Vieja Providencia y Santa Catalina, Colombia, Caribe suroccidental (Spanish) [State of the tropical dry forest and relative importance of its woody flora, islands of old Providence and Santa Catalina, Colombia, southwestern Caribbean]. Revista de la Academia Colombiana de Ciencias 2009; 33(126): 1–12.

16. Etter A. Ecosystem diversity in Colombia today. In: Nuestra diversidad biótica (Spanish) [Our biodiversity]. Bogotá: CEREC y Fundación Alejandro Ángel Escobar; 1993. p. 43–61.

17. University of Tolima. Informe técnico proyecto “Caracterización biofísica de la Eco-región Estratégica del desierto de la Tatacoa y su área de influencia” (Spanish) [Technical report of the project “biophysical characteristics of the ecological strategic area and its affected areas in the Tatacoa desert”]. Ibagué: Universidad del Tolima, Universidad Surcolombiana, Universidad de Cundinamarca; 2002. p. 250.

18. Sánchez-Azofeifa A, Kalacska M, Quesada M, et al. Need for integrated research for a sustainable future in tropical dry forests. Conservation Biology 2005; 19(2): 1–2.

19. Prance W. Tropical savannas and seasonally dry forests: An introduction. Journal of Biogeography 2006; 33: 385–386.

20. Fernández F, Melo O, Álvarez E, et al. Status of lnowledge, conservation and management of tropical dry forest in the Magdalena river Valley, Colombia. In: Sanchez-Asofeifa A, Power J, Fernandes G, et al. (editors). Tropical dry forest in the Americas. Florida: CRC Press; 2014. p. 35–68.

21. Melo O, Vargas R. Evaluación ecológica y silvicultural de ecosistemas boscosos (Spanish) [Ecological and silvicultural evaluation of forest ecosystems]. Ibagué: Universidad del Tolima; 2003. p. 235.

22. Phillips O, Vasquez R, Monteagudo A, et al. Large lianas as hyperdynamic elements of the tropical forest canopy. Ecology 2005; 86(5): 1250–1258.

23. Colwell R, Chao A, Gotelli N, et al. Models and estimators linking individual-based and sample-based rarefaction, extrapolation, and comparison of assemblages. Journal of Plant Ecology 2012; 5: 3–21.

24. Magurran A. Ecological diversity and its measurement. New York: Princeton University; 1988. p. 179.

25. Magurran A. Measuring biological diversity. Oxford: Blackwell Publishing; 2004. p. 256.

26. Magurran A, McHill B. Biological diversity: Frontiers in measurement and assessment. New York: Oxford University Press; 2011. p. 345.

27. Castro G, Nigard R, Gonzalez B, et al. Stand dynamics and basal area change in a tropical dry forest reserve in Nicaragua. Forest Ecology and Management 2005; 208: 63–75.

28. Carson W, Schnitzer S. Tropical forest community ecology. Hoboken: Wiley-Blacwell; 2008. p. 517.

29. Weiskittel A, Hann D, Kershaw J, et al. Forest growth and yield modeling. Hoboken: Wiley-Blacwell; 2011. p.415.

30. Pallardy S. Physiology of woody plants. 3rd ed. San Diego: Academic Press, Elsevier; 2008. p. 454.

31. Mendoza C. Estructura y riqueza florística del bosque seco tropical en la región Caribe y el valle del río Magdalena, Colombia (Spanish) [Structure and floristic richness of the tropical dry forest in the Caribbean region and the Magdalena River valley, Colombia]. Caldasia 1999; 21(1): 70–94.

32. Gentry A. Changes in plant community diversity and floristic composition on environmental and geographical gradients. Annals of the Missouri Botanical Garden 1988; 75: 1–34.

33. Cabrera E, Galindo G. Aproximación metodológica para la delimitación de ecosistemas de enclaves secos: caso piloto, cañones del río Dagua y del río Tuluá, Valle del Cauca-Colombia (Spanish) [Methodological approach for the delimitation of dry enclave ecosystems: A pilot case of the Dagua River and the Tulua River Gorge in the Cauca Valley, Colombia]. Bogotá, D.C.: Instituto de Investigación de Recursos Biológicos Alexander von Humboldt; 2006. p. 105.

34. Flynn B, Mirotchnick N, Jain M, et al. Functional and phylogenetic diversity as predictors of biodiversity-ecosystem-function relationships. Ecology 2011; 92(8): 1573–1581.

35. Burkhart H, Tomé M. Modeling forest trees and stand. Berlin: Springer-Verlag; 2012. p. 457.

36. Trinder C, Brooker R, Robinson D. Plant ecology’s guilty little secret: Understanding the dynamics of plant competition. Functional Ecology 2013; 27: 918–929.

37. Pretzch H. Canopy space filling and tree crown morphology in mixed-species stands compared with monocultures. Forest Ecology and Management 2014; 327: 251–264.

38. Sterck F, Schieving F, Lemmens A, et al. Performance of trees in forest canopies: Explorations with a bottom-up functional-structural plant growth model. New Phytologist 2005; 166(3): 827–843.

39. Craine J, Dybzinski R. Mechanisms of plant competition for nutrients, water and light. Functional Ecology 2013; 27: 833–840.