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Boy, J. (2009): <b>External drivers of biogeochemical cycles in a tropical montane forest in Ecuador</b> Johannes Gutenberg University Mainz, <i>phd thesis</i>

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Title: External drivers of biogeochemical cycles in a tropical montane forest in Ecuador
Short Name: Biogeochemical drivers
FOR816dw ID: 443
Publication Date: 2009-04-01
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Resource Owner(s):
Individual: Jens Boy
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Abstract:
Successful conservation of tropical montane forest, one of the most threatened<br/> ecosystems on earth, requires detailed knowledge of its biogeochemistry. Of particular<br/> interest is the response of the biogeochemical element cycles to external influences such<br/> as element deposition or climate change. Therefore the overall objective of my study<br/> was to contribute to improved understanding of role and functioning of the Andean<br/> tropical montane forest. In detail, my objectives were to determine (1) the role of longrange<br/> transported aerosols and their transport mechanisms, and (2) the role of short-term<br/> extreme climatic events for the element budget of Andean tropical forest.<br/> In a whole-catchment approach including three 8-13 ha microcatchments under<br/> tropical montane forest on the east-exposed slope of the eastern cordillera in the south<br/> Ecuadorian Andes at 1850-2200 m above sea level I monitored at least in weekly<br/> resolution the concentrations and fluxes of Ca, Mg, Na, K, NO3-N, NH4-N, DON, P, S,<br/> TOC, Mn, and Al in bulk deposition, throughfall, litter leachate, soil solution at the 0.15<br/> and 0.3 m depths, and runoff between May 1998 and April 2003. I also used<br/> meteorological data from my study area collected by cooperating researchers and the<br/> Brazilian meteorological service (INPE), as well as remote sensing products of the<br/> North American and European space agencies NASA and ESA.<br/> My results show that (1) there was a strong interannual variation in deposition of Ca<br/> [4.4-29 kg ha-1 a-1], Mg [1.6-12], and K [9.8-30]) between 1998 and 2003. High<br/> deposition changed the Ca and Mg budgets of the catchments from loss to retention,<br/> suggesting that the additionally available Ca and Mg was used by the ecosystem.<br/> Increased base metal deposition was related to dust outbursts of the Sahara and an<br/> Amazonian precipitation pattern with trans-regional dry spells allowing for dust<br/> transport to the Andes. The increased base metal deposition coincided with a strong La<br/> Niña event in 1999/2000. There were also significantly elevated H+, N, and Mn<br/> depositions during the annual biomass burning period in the Amazon basin. Elevated H+<br/> deposition during the biomass burning period caused elevated base metal loss from the<br/> canopy and the organic horizon and deteriorated already low base metal supply of the<br/> vegetation. Nitrogen was only retained during biomass burning but not during non-fire<br/> conditions when deposition was much smaller. Therefore biomass burning-related<br/> aerosol emissions in Amazonia seem large enough to substantially increase element<br/> deposition at the western rim of Amazonia. Particularly the related increase of acid<br/> deposition impoverishes already base-metal scarce ecosystems. As biomass burning is<br/> most intense during El Niño situations, a shortened ENSO cycle because of global<br/> warming likely enhances the acid deposition at my study forest.<br/> (2) Storm events causing near-surface water flow through C- and nutrient-rich<br/> topsoil during rainstorms were the major export pathway for C, N, Al, and Mn<br/> (contributing >50% to the total export of these elements). Near-surface flow also<br/> accounted for one third of total base metal export. This demonstrates that storm-event<br/> related near-surface flow markedly affects the cycling of many nutrients in steep<br/> tropical montane forests. Changes in the rainfall regime possibly associated with global<br/> climate change will therefore also change element export from the study forest.<br/> Element budgets of Andean tropical montane rain forest proved to be markedly<br/> affected by long-range transport of Saharan dust, biomass burning-related aerosols, or<br/> strong rainfalls during storm events. Thus, increased acid and nutrient deposition and<br/> the global climate change probably drive the tropical montane forest to another state<br/> with unknown consequences for its functions and biological diversity.
Literature type specific fields:
THESIS
Degree: phd
Degree Institution: Johannes Gutenberg University Mainz
Total Pages: 126
Metadata Provider:
Individual: Wolfgang Wilcke
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Download File: http://www.lcrs.de/publications.do?citid=443


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