SIMULATION OF CHANGES IN SOIL ORGANIC CARBON IN TROPICAL TREE SPECIES USING THE ROTHC 26.3 MODEL

This study was conducted in the municipality of La Huerta, Jalisco, Mexico, in 15-year-old plantations of four tropical tree species: rosa morada (Tabebuia rosea (Bertol) DC), teca (Tectona grandis L.), melina (Gmelina arborea Roxb.) and parota (Enterolobium cyclocarpum (Jacq.) Griseb.). The objective was to estimate changes in soil organic carbon (SOC) after land use change (LUC) from agriculture to forest plantation: with (i) and without (ii) herbs and shrub control. Carbon contributed to the soil by plant residues (PR) from trees and the SOC in soil depths of 0-15 and 15-30cm were measured after LUC. SOC changes were simulated with the RothC 26.3 model of carbon dynamics. Plantations without herbs and shrub control, compared with those with control, had a greater PR contribution (9.3 to 6.3Mg C ha(-1)/year and 3.7 to 6.6Mg C ha(-1)/year, respectively). Parota and rosa morada with no herbs control had higher contributions from PR and SOC (70 and 64Mg C ha(-1.)). SOC changes were simulated with a model efficiency value of 90% and an R-2 of 0.90. The simulated rate of SOC change (Mg ha(-1)/year) 40 years after LUC to plantations with tropical forest species without herbs and shrub control was higher and positive, between 0.1 and 0.7, while in the plantations with control, it was -0.2 to 0.3.