NITROGEN MINERALIZATION IN THE TROPICAL PEAT SWAMPS

摘要

The rate of daily net nitrification and net ammonification in the Badas peat swamp forest is low, averaging about 0.39 μ g N g~(-1) dry soil d~(-1) and 0.34 μ g N g~(-1) dry soil d~(-1), respectively, suggesting the rapid and tight cycling of mineral N between the organic and inorganic phase.The results supported the hypothesis that different peat swamp forest communities differ in the balance between nitrification and ammonification. Different peat swamp forest communities differ in their requirement of nitrate and ammonium. The results also imply that different tree species may have specific preferences of mineral N. Hydrological regime and its effects on water-table fluctuation and aeration are primary explanatory variables in the variation of nitrification and ammonification processes, supporting the hypothesis that environmental conditions are important factors in determining the N transformation rates. The occurrence of nitrification in the very acidic conditions of Badas peat swamp confirmed that nitrifiers were present and the nitrification process could take place under acidic condition. Acid-tolerant or acid-adapted strains of autotrophic as well as heterotrophic nitrifying and ammonifying bacteria may be responsible for regulating the relative dominance of nitrification and amonification pathways. The apparent ability of acidic, nutrient poor ecosystem to produce net N mineralization is clearly of practical significant, particularly with respect to usage of lime which is a common practice in acidic agricultural areas.