Controls on aboveground net primary productivity & the partitioning of canopy and wood production in tropical rainforests Florian Hofhansl, & Wolfgang Wanek ATBC 2013 San José, Costa Rica
Climatic Controls Introduction – Global carbon cycle Potential net primary production (NPP) Tropical Forests: 12% of Earth's land surface 25% of the world's biomass C 40% of terrestrial NPP Source: Schuur, E. Productivity and global climate revisited: The sensitivity of tropical forest growth to precipitation. Ecology, 84, 1165–1170.
Climatic Controls Introduction – Global carbon cycle Temperature Precipitation Climatic drivers: Mean annual temperature (MAT) Mean annual precipitation (MAP) Source: Schuur, E. Productivity and global climate revisited: The sensitivity of tropical forest growth to precipitation. Ecology, 84, 1165–1170.
Climate Projections Introduction – Global carbon cycle Expected changes: Drought frequency Precipitation intensity à Temperature à Source: IPCC - Climate Change 2007: Working Group I: The Physical Science Basis
Methodology Net primary production Net primary production (NPP): (NPP): Aboveground NPP - Canopy production (47%) - Wood production (53%) Belowground NPP Source: Malhi, Y..et al. (2011). The allocation of ecosystem net primary productivity in tropical forests. Philosophical Transactions of the Royal Society B: Biological Sciences, 366, 3225–3245.
Methodology Net primary production (NPP): Aboveground NPP - Stem increment (ABI) - Litter fall (LF) Relationship explained ABI ~ 60% LF ~ 40% à about 50% undetermined à
Methodology 30 Number of studies (ISI): • Net primary production 6,833 • Stem increment 23,116 8,474 • Litter fall • Stem increment & Litter fall < 1% measured both !!! Source: ISI webofknowledge.com
Local Study Tropical Field Station La Gamba: (since 2005) Topographic positions: - Ridge - Slope - Ravine Stem increment (DBH>10 cm) Litter fall (n=15 per site) www.univie.ac.at/bdef
Local Controls Introduction – Global carbon cycle Climatic controls: ANPP No sign. effect Stem increment (ABI) Precipitation Litter fall (LF) Drought and Temperature à à à à à à Different Controls ABI / LF Source: Hofhansl et al. (2013) Climatic controls on aboveground net primary productivity and the partitioning between canopy and wood production (in preparation).
Global Study >100 sites , S-America (62), Asia (26), Hawaii (12), Africa (3), Australia (2) Parameters : MAT, MAP, DSL, CLD, Soil N:P, Litter N:P, Foliar N:P
Global Controls Introduction – Global carbon cycle Classification Tree (CART): MAT All forest sites (n=105) MAP Lowland Sites (>21.65°C) Soil N:P ratio Montane Sites (<21.65°C) Source: Hofhansl et al. (2013) Climatic controls on aboveground net primary productivity and the partitioning between canopy and wood production (in preparation).
Global Controls Introduction – Global carbon cycle Structural equation model (SEM): Overall Model Lowland Model Montane Model ABI LF ABI LF ABI LF ANPP ANPP ANPP Source: Hofhansl et al. (2013) Climatic controls on aboveground net primary productivity and the partitioning between canopy and wood production (in preparation).
Temperature Introduction – Global carbon cycle MAT Effect Overall Lowland Montane + + ANPP + % WP
Precipitation Introduction – Global carbon cycle MAP Effect Overall Lowland Montane + ANPP + + % WP
Soil N:P ratio Introduction – Global carbon cycle Soil N:P ratio Effect Overall Lowland Montane - - ANPP - - % WP
Conclusion Conclusion • Local Controls on ANPP differ for canopy & wood production • Global Controls on tropical ANPP: MAT à (+) overall and montane ANPP, overall %WP MAP à (+) lowland ANPP, lowland & overall %WP Soil N:P à ( − ) overall and montane ANPP and %WP • Global change effects: MAT à enhance productivity of montane forests MAP à alter C-sequestration potential of lowland forests Soil N:P à N-deposition might decrease tropical productivity
Acknowledgements Team of the Tropical Research Station La Gamba: Victor Cruz-Garcia, Luis Sanchez-Jimenez, Eduardo Arauz- Suarez Co-Workers: Sigrid Drage, Nina Hinko, Eva-Maria Pölz, Daniel Schaber Supervisors: Wolfgang Wanek, Andreas Richter, Roland Albert, Veronika Mayer, Anton Weissenhofer, Werner Huber Ministerio de Costa Rica: MINAE (Ministerio Nacional de Ambiente y Energia) www.univie.ac.at/bdef
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