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>
Resource Description
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
License and Usage Rights:
Resource Owner(s):
Individual:
Jens Boy
Contact:
email:
boy <at> ifbk.uni-hannover.de
D-30419 Hannover
Germany
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
Contact:
email:
wolfgang.wilcke <at> kit.edu
Karlsruhe Institute of Technology
Institute of Geography and Geoecology
Reinhard-Baumeister-Platz 1
76131 Karlsruhe
Baden-Württemberg
Germany
