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? “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 “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

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 10% GPP Ranges from 0-1 or 0-100% What models use! Turnover Flux GPP

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

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

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 partitioning to wood and decreased partitioning to TBCA Litton, Raich, Ryan. 2007. Global Change Biol. 13: 2089- 2109

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

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 and increased GPP increases 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