FOREST LITTER DECOMPOSITION AS AFFECTED BY EUCALYPTUS STAND AGE AND TOPOGRAPHY IN SOUTH-EASTERN BRAZIL 1

摘要

Forest litter decomposition is a major process in returning nutrients to soils and thus promoting wood productivity in the humid tropic. This study aimed to assess decomposition of eucalypt litter in the Rio Doce region, Brazil. Leaf litter was sampled under clonal eucalypt stands aged 2, 4 and 6 years on hillslopes and footslopes. Soil and soil+litter samples were incubated at two levels of soil moisture, temperature and fertilization. C-CO 2 emissions from soil measured during 106 days were higher at 32 ?°C than at 23?°C, mainly for the 2-yr-old stand on footslope. When leaf litter was added on soils, C-CO 2 emissions were eight times higher, mainly on footslopes, with no effect of stand age. Leaf decomposition in situ, assessed with a litterbag experiment showed a mean weight loss of at least 50% during 365 days, reaching 74% for 2 yr-old stands on footslopes. In comparison with data from the native forest and the literature, no apparent restrictions were found in eucalypt litter decomposition. Differences between in vitro and in situ results, and between eucalypt and native forest, were most likely related to the response of diverse decomposer communities and to substrate quality.