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Controls on aboveground net primary production of tropical rainforests

Monday, 24 June 2013: 11:05
Americas B-C (Herradura San Jose)
Florian Hofhansl , Terrestrial Ecosystem Research, University of Vienna, Austria
Wolfgang Wanek , Terrestrial Ecosystem Research, University of Vienna, Austria
Aboveground net primary production (ANPP) of tropical forests is driven by soil fertility and climate, the latter receiving special attention as recent projections of global circulation models predict large tracts of tropics to become drier and warmer. Given the scarcity of manipulative experiments, global climate-ecosystem relations and interannual climate variations caused by El Niño Southern Oscillation have been used to assess potential responses of tropical ANPP to projected climate change. The focus of this study was to investigate how seasonal and interannual climate variations affect ANPP and the partitioning between canopy and wood production at three forest sites differing in topography and disturbance history in SW Costa Rica. In each of the three forests, wood production and fine litterfall were monitored at monthly time resolution since 2005. We moreover identify major drivers of tropical forest ANPP by integrating our results into a dataset of >100 tropical old growth forests where canopy and wood production have been reported respectively. Across all forest sites MAT was the strongest predictor of ANPP (0.31 Mg C ha-1 yr-1 per °C) but the response differed between lowland and montane forests. Our results suggest a shift in the allocation of biomass towards greater nutrient conservation (i.e. production of wood biomass) in more productive lowland forests, whereas nutrient recycling processes (i.e. production of canopy biomass) predominate in less productive, montane forests. We demonstrate that both ANPP components are sensitive to climate variation, both in a local and a global context, but that the controls differ for canopy and wood production. Climate change may therefore shift the balance between nutrient recycling (canopy production) and carbon sequestration (wood production) and thus adversely affect ecosystem functions of the tropical forest biome.
  • Hofhansl+04-4+June24.pdf (3.0 MB)