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Global patterns in carbon flux and partitioning

Carbon allocation plays a critical role in forest ecosystem carbon cycling by shifting the products of photosynthesis between respiration and biomass production, ephemeral and long-lived tissues, and aboveground and belowground components.  As a primary control on terrestrial carbon storage and forest ecosystem carbon dynamics, carbon allocation is a dynamic balance among total ecosystem carbon input (gross primary production), carbon fluxes and  partitioning of GPP to individual components, and carbon loss.  Some of our recent work on carbon allocation has focused on global syntheses of available data in forest ecosystems. This work is designed to inform terrestrial ecosystem models by examining general patterns in carbon flux and partitioning, and their response to variables such as resource availability, stand age, competition, and climate change.

Figure 2. Hypothesized relationship between mean annual temperature and the partitioning of GPP (carbon flux as a fraction of GPP) to aboveground vs.  belowground (top panel).  While GPP, aboveground C flux, and belowground C flux all increase with MAT, the slopes of the aboveground and belowground  relationships differ because the factors constraining GPP change as MAT increases (bottom panel).  At colder sites, air temperature presents the strongest  limitation to GPP, and belowground resource supply (e.g., nutrients and water) is high by comparison.  Conversely, at warmer sites, air temperature constraints are  alleviated and belowground resource supply exerts a stronger limitation to GPP.  As a result, partitioning of GPP to belowground increases at higher MAT (from  Litton and Giardina 2008).

Publications to Date

Ise T, Litton CM, Giardina CP, Ito A (2010) Comparison of modeling approaches for carbon partitioning: Impact on estimates of global net primary production and equilibrium biomass of woody vegetation from MODIS GPP. Journal of Geophysical Research-Biogeosciences, 115, G04025, doi:10.1029/2010JG001326. (PDF)

Litton CM, Giardina CP (2008) Belowground carbon flux and partitioning: Global patterns and response to temperature (Invited article). Functional Ecology 22: 941-954. (PDF)

Litton CM, Raich JW, Ryan MG (2007) Review: Carbon allocation in forest ecosystems. Global Change Biology, 13, 2089-2109. (PDF)