Effects of slash-and-burn management on soil aggregate organic C and N in a tropical deciduous forest

Our study examined the effect of slash-and-burn management on the distribut ion of soil organic carbon (SOC) across water-stable aggregate size fractio ns. Macroaggregates(> 250 mu m) are an important source of SOC and soil org anic nitrogen in forest soil: they account for approximately 80% of the tot al C and N content. Slashing and burning did not destroy macroaggregates, b ut the SOC associated with macroaggregates decreased by 32% due to combusti on during burning. Fire also disrupted soil aggregate stabilization by chan ging the chemical nature of SOC. The largest changes were noted after the f irst growing season following fire: macroaggregates and associated C decrea sed 50% while microaggregates increased by the same proportion. The changes in organic C observed after the first growing season can be attributed to macroaggregate instability. (C) 1999 Elsevier Science B.V. All rights reser ved.