A study for several sites showed that storage of organic matter and N in uncultivated soils increased greatly with increasing alt. As a result of cultivation, often ombined with fire to clear the soil surface, losses of N occurred. The estimated rate of hydrogen-ion production by excessive nitrification was compared with the buffering capacity of the soil, showing that soil acidification could proceed for decades. The consequences of these periods of acidification are discussed, viz. depressed biomass production, changed composition of the secondary forest, and increased soil wetness.