Factors controlling carbon sequestration in the soils of Puerto Rico

A study was conducted to determine which edaphic and climatic factors are most significantly associated with carbon sequestration in the soils of Puerto Rico. A database of 167 pedons was compiled containing seven qualitative and eleven quantitative variables for three soil depth layers (0-20, 20-50, 0-50 cm). Qualitative variables considered were the soil moisture regime, soil mineralogy, land use, parent material, and soil classification according to Soil Taxonomy. The effect of these variables on soil organic matter content was analyzed using analysis of variance (ANOVA) and cluster analysis. Within each soil layer, the amount of organic carbon sequestered was correlated with quantitative variables (clay and silt content, mean annual rainfall, mean annual air temperature, pH, extractable iron, and the ratio of rainfall to temperature).; The factors most related to organic carbon content were soil order, soil moisture regime and land use. Significant interactive effects of moisture regime x soil order and moisture regime x land use were also observed. Aquic soils sequestered more organic carbon than soils with udic and ustic regimes in all three layers. Also, forest soils sequestered more organic carbon than cropland and grassland in the three layers.; In kaolinitic and oxidic soils, sequestered carbon was best correlated to fine particles. Extractable iron was highly correlated to organic carbon in Vertisols and other soils of montmorillonitic mineralogy. Air temperature and rainfall were the best indicators of organic carbon accumulation for soils of mixed mineralogy.; Three GIS-based maps were produced to show the spatial distribution of organic carbon in the soils of Puerto Rico for the 0-30 and 0-100 cm soil layers. (Abstract shortened by UMI.)...