HR: 14:30h
AN: B43A-03    [Abstracts]
TI: Base Metal Cycling in a Tropical Montane Forest in Ecuador
AU: * Wilcke, W
EM: wolfgang.wilcke@uni-mainz.de
AF: Geographic Institute, Johannes Gutenberg University Mainz, 55099 Mainz, Germany
AU: Boy, J
EM: j.boy@geo.uni-mainz.de
AF: Geographic Institute, Johannes Gutenberg University Mainz, 55099 Mainz, Germany
AU: Knuth, J
EM: jana.knuth@uni-mainz.de
AF: Geographic Institute, Johannes Gutenberg University Mainz, 55099 Mainz, Germany
AU: Valarezo, C
EM: cvalarezo@softhome.net
AF: Area Agropecuaria y de Recursos Naturales Renovables, Programa de Agroforestería, National University of Loja, Ciudadela Universitaria Guillermo Falconi, Loja, Ecuador
AB: Earlier work had shown that Ca and Mg deposited from the atmosphere were partly taken up by the canopy of an Ecuadorian mountain forest at the western rim of the Amazon basin and that both elements were immobilized during incubation of acid soil organic layer material. We therefore determined all base metal fluxes from atmospheric input through the forest ecosystem to output with surface runoff in three small catchments under tropical montane forest between 1850 and 2200 m above sea level. We found a large interannual variation in the deposition of Ca and Mg from the atmosphere. This variation was related with the ENSO cycle. During La Nina conditions, Saharan dust was transported via the Amazon basin to our study site. Our ecosystem responded by accumulation of base metals likely because of nutrient accretion by increased growth. During strong forest fires in the Amazon basin, increased acid input was observed at our study site. This resulted in the export of base metals and counteracted the base metal accumulation during years of high base metal input. Base metal loss was promoted by fast near-surface flow flushing the base metal-enriched surface layers of the soil (particularly the organic layer) during rainstorms. Base metal loss during baseflow conditions was attributed to the weathering of the Ca- and Mg-poor bedrock and an unavoidable leaching of Ca and Mg with a similar size as weathering. The low availability of Ca and Mg in the studied ecosystem and the positive response of the studied forest to Ca and Mg inputs suggests that at this probably neither N- nor P-limited site base metals played a key role for forest performance. As the Ca and Mg cycles seem to be linked to large-scale events such as the ENSO phenomenon, forest burning in the Amazon basin, and climatic changes (particularly those influencing the storm frequency and intensity and thus the importanc of near-surface flow), future environmental change might have an impact on the stability of the precious, highly biodiverse north Andean mountain forests.
DE: 0400 BIOGEOSCIENCES
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 0461 Metals
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
SC: Biogeosciences [B]
MN: 2007 Joint Assembly