© 2003 Heron Publishing—Victoria, Canada
Modeling effects of hydrological changes on the carbon and nitrogen balance of oak in floodplains
Stephan A. Pietsch (1, 2), Hubert Hasenauer (1), Jiři Kučera (3) and Jan Čermák (3)
1. Institute of Forest Growth Research, University of Agricultural Sciences, Peter-Jordan-Straße 82, A-1190 Vienna, Austria / 2. Author to whom correspondence should be addressed (pietsch@edv1.boku.ac.at) / 3. Institute of Forest Ecology, Mendel University of Agriculture and Forestry, Zemedelská 3, 61300 Brno, Czech Republic / Received April 8, 2002; accepted November 9, 2002; published online July 1, 2003
Summary
We extended the applicability of the ecosystem model BIOME-BGC to floodplain ecosystems to study effects of hydrological changes
on Quercus robur L. stands. The extended model assesses floodplain peculiarities, i.e., seasonal flooding and water infiltration from the
groundwater table. Our interest was the tradeoff between (a) maintaining regional applicability with respect to available
model input information, (b) incorporating the necessary mechanistic detail and (c) keeping the computational effort at an
acceptable level. An evaluation based on observed transpiration, timber volume, soil carbon and soil nitrogen content showed
that the extended model produced unbiased results. We also investigated the impact of hydrological changes on our oak stands
as a result of the completion of an artificial canal network in 1971, which has stopped regular springtime flooding. A comparison
of the 11 years before versus the 11 years after 1971 demonstrated that the hydrological changes affected mainly the annual
variation across years in leaf area index (LAI) and soil carbon and nitrogen sequestration, leading to stagnation of carbon
and nitrogen stocks, but to an increase in the variance across years. However, carbon sequestration to timber was unaffected
and exhibited no significant change in cross-year variation. Finally, we investigated how drawdown of the water table, a general
problem in the region, affects modeled ecosystem behavior. We found a further amplification of cross-year LAI fluctuations,
but the variance in soil carbon and nitrogen stocks decreased. Volume increment was unaffected, suggesting a stabilization
of the ecosystem two decades after implementation of water management measures.
Keywords:
BGC-model, flooding, groundwater, Quercus
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