Microbial and nutrient activity in soils from three different subtropical forest habitats in Belize, Central America before and during the transition from dry to wet season

Significant variations were found in soil texture, levels of organic carbon, microbial biomass carbon, nitrate, and nitrification rates in the upper 20 cm of soil from three distinct Uplands forest, Cohune Palm forest, and Bajo forest habitats within the subtropical rainforest of Northwestern Belize. The Cohune Palm forest soils had the most organic carbon, microbial biomass carbon, nitrate, and highest nitrification rates, while the soils from the Bajo forests had the lowest levels of these parameters. The heterogeneity in the soil composition is even more significant given that the three habitats studied are part of the same 'forest' and are within 2 km of each other. The first rains at the beginning of the wet season had a rapid and significant effect on various components in the soil. A rapid increase in the microbial biomass carbon, organic carbon, and nitrification rates and a decrease in nitrate occurred in the soil from all three habitats within hours after what locals anecdotally consider the start of the wet season. The greatest percent change in all factors following the rains occurred within the soil from the Bajo forests, while the smallest percent change occurred within soil from the Uplands forest. There were also significant correlations found between soil moisture levels and organic carbon, microbial biomass carbon, and nitrification rates. The variations in the measured parameters were also associated with the amount of clay in the soil. It appears, then, that the amounts of moisture and clay are most critical soil composition factors which when combined with microbial biomass carbon, organic carbon, and nitrification rates may be good predictors of soil quality in these forests. (C) 2001 Elsevier Science B.V. All rights reserved.