Biomass accumulation and population dynamics of a flooded forest in the Magdalena Basin (Colombia)

Few studies in Colombia have quantified population dynamics on private conservation lands, making it difficult to know whether passive restoration (secondary succession) is a good option to increase forest biomass. We analyzed three permanent plots (0.3 ha) in the Reserva El Paujil (Middle Magdalena Valley, Colombia), in secondary forests, after 8-9 y. We tested whether population changes and aboveground biomass accumulation should be higher in secondary flooded forests than in terra firme forests. We found that mortality rates (7.98/y ± 4.50 DE) were higher than recruitment rates (5.89/y ± 5.29 SD), generating a mean negative change (-2.09/y ± 4.36 SD). However, the growth of surviving individuals was high (0.028 ± 0.019 SD), causing a positive rate of biomass accumulation (3.33 ton/y/ha ± 5.15 SD). This rate was much higher than in terra firme forests in the area (0.10 ton/y/ha ± 1.90 SD), which was associated with soil fertility. The most dominant species with high biomass accumulation was Anacardium excelsum. In contrast, the highest increase in mortality was observed for pioneer species (i.e., Cecropia membranacea and C. peltata), Bauhinia picta, and Guadua angustifolia (which also showed the highest recruitment). Overall, establishing a biological reserve has allowed the growth of large trees, generating carbon stocks equivalent to those from active ecological restoration processes.