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Carbon Allocation in Forest Ecosystems

Carbon Allocation in Forest Ecosystems. Mike Ryan USDA Forest Service Rocky Mountain Research Station Creighton Litton California State University, Fullerton Jim Raich University of Iowa Pub available online: http://lamar.colostate.edu/~mryan/Publications. Why Allocation?.

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Carbon Allocation in Forest Ecosystems

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  1. Carbon Allocation in Forest Ecosystems Mike Ryan USDA Forest Service Rocky Mountain Research Station Creighton Litton California State University, Fullerton Jim Raich University of Iowa Pub available online: http://lamar.colostate.edu/~mryan/Publications

  2. Why Allocation? Large part of plant response to environment Mechanisms and response poorly understood Especially important for woody plants

  3. Progress in Understanding Allocation? “Our lack of knowledge on the processes governing the dynamic processes of carbon allocation…makes closure less reliable; Priority areas for future research…are carbon allocation…” - Landsberg et al 1991 Tree Physiology “What is not currently well understood is how plants allocate the products of photosynthesis – how much fuels metabolism (above- or below-ground), how much is used for tissue growth/repair (above- or below-ground), lost in ‘futile’ cycles, put aside for storage, or exported to symbiotic organisms” - Trumbore and Pataki, 2004, Workshop Report, Carbon Respired by Terrestrial Ecosystems

  4. An approach to allocation • Be clear about what we mean: ‘allocation’ • Measure flux of all major components • Use experiments to assess allocation shifts • Few studies so far • Even fewer for treatment effects

  5. Definitions - BIOMASS: 1) Patterns in existing biomass (for example, root:shoot) Litton, Raich, Ryan. 2007. Global Change Biol. 13: 2089-2109

  6. Definitions - Flux: 2) Amount of C to a component per unit time. For example, flux to wood and leaves (Mg/ha/yr) Stape, Binkley, Ryan FEM 2004

  7. Definitions - Partitioning: 3) Proportion of total used annually for a component: Annual flux/annual GPP Ranges from 0-1 or 0-100% What models use! GPP GPP 10% Flux Turnover

  8. Differences in the response of flux versus partitioning: 1 kg C/m2 = 10 MT C/ha = 20 MT/ha Ryan et al. Ecol. Monog. 2004 Partitioningshows large differences with fertility Fluxshows little difference with fertility

  9. Hypotheses • Flux and partitioning are related to biomass • Flux to all components increases with GPP • Partitioning to all components varies with fertility, forest age, competition • There are priorities for photosynthesis: (Waring, Weinstein ‘tipping bucket’ hypothesis)

  10. Measure the entire C budget and estimate GPP by sum GPP Foliage NPP Allometry + optical + litterfall Foliage Rs 4 - 13% 10 - 31% Measure-ments or N or biomass model Wood NPP Wood Rs Allometry 9 - 30% 4 - 25% TBCA by Carbon Budget Method TBCA: Root Production + Resp + Exudates + Mycorrhizae 25-62%

  11. Patterns in Biomass say little about flux and partitioning Litton, Raich, Ryan. 2007. Global Change Biol. 13: 2089-2109

  12. Flux for all components increases as GPP increases – ‘A rising tide lifts all boats…’ Litton, Raich, Ryan. 2007. Global Change Biol. 13: 2089-2109

  13. Respiration is strongly correlated with production for all components Slope of R:NPP is greater for fine roots and foliage than for wood Litton, Raich, Ryan. 2007. Global Change Biol. 13: 2089-2109

  14. Partitioning to respiration does not vary with forest age, fertility or temperature Litton, Raich, Ryan. 2007. Global Change Biol. 13: 2089-2109

  15. Partitioning • To wood and TBCA vary with resources and sometimes age • To foliage (and respiration) does not Litton, Raich, Ryan. 2007. Global Change Biol. 13: 2089-2109

  16. Partitioning varies with stand age Pines increase Partitioning to wood with age. Hawaii Eucalyptus did not. Litton, Raich, Ryan. 2007. Global Change Biol. 13: 2089-2109

  17. Partitioning does not change with competition Litton, Raich, Ryan. 2007. Global Change Biol. 13: 2089-2109

  18. Fertility increased partitioningto wood and decreased partitioningto TBCA Litton, Raich, Ryan. 2007. Global Change Biol. 13: 2089-2109

  19. Because partitioning to foliage is constant, foliage production may predict GPP Global data set Local Data Set: Hawaii Eucs, Ryan et al. 2004

  20. Site specific changes in partitioning are larger than inferred from global patterns Litton, Raich, Ryan. 2007. Global Change Biol. 13: 2089-2109

  21. No support for priority or ‘tipping bucket’ hypothesis • Resources increase GPP andincreased GPPincreases flux to all components

  22. Conclusions • Three facets: Biomass, flux, partitioning • Partitioning ≠ flux ≠ biomass • Partitioning and flux are related to GPP • No support for ‘priority’ system of allocation • Partitioning to respiration, foliage conservative

  23. Conclusions • Poorly understood: • Belowground biomass and soil C storage • Very few studies measure all components or respiration

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