Soil chemistry under a chronosequence of primary forest, active pasture, teak (Tectona grandis) and mixed native plantations in Costa Rica

Former cattle ranchers in Costa Rica can opt to establish teak or mixed native plantations on abandoned pastures, yet the plantations' effect on soil fertility or their capacity to rehabilitate degraded sites may vary. In this study, soil samples from the O/A and B horizons were taken and analyzed from a chronosequence of primary forests, active pastures, and 10-year-old teak and mixed native plantations. Significantly higher base forming cation concentrations were found in the teak plantation compared to primary forest (Mg, K in the B horizon) and active pasture (Ca in the O/A horizon). SOC concentration was significantly higher in the active pasture than in the teak plantation. SOC content in the O/A horizon was highest in the primary forest, lower in the plantations, and lowest in the active pasture. Total SOC content was similar for all land uses. Bulk density was significantly lower in the primary forest than all other land uses. Teak plantations had more high fertility plots than other land uses, but this may be a result of management activities. The importance of understory recruitment in nutrient cycling with respect to forest fertility and forest rehabilitation is discussed.