Beyond Carbon Flux Partitioning: Inferring the Dynamic Non-structural Carbon Storage and Carbon Allocation at the Canopy Scale from Continuous Fluxes
Abstract
Non-structural carbon (NSC) storage and carbon allocation play important roles in plant growth and survival under stress and disturbance. The availability of quantitative measurements limits our understanding of these internal processes. By contrast, recent advances in the measurement of photosynthesis and respiration have provided a large amount of flux data and improved our understanding of these biosphere-atmosphere interactions. Given the continuum of integrated processes in carbon cycling, the tight connection between ecosystem fluxes and internal physiology could provide information on NSC dynamics and carbon allocation, but has not been fully explored.
We propose a simple mass balance model that allows the derivation of NSC and carbon allocation at the canopy scale from eddy covariance and soil CO2 efflux measurements using a flux regression approach. The temporal decoupling of carbon inputs and losses is interpreted as allocation to NSC. Carbon translocation to above-/below-ground pools and the efficiency of conversion to structural biomass are calculated in the meantime. We applied this framework to two long-term monitored loblolly pine (Pinus taeda) plantations in North Carolina (AmeriFlux US-NC1 and US-NC2). As hypothesized, the young plantation had closely balanced assimilation and respiration fluxes and did not store NSC in years of typical growth. The mature plantation had a surplus of assimilates and stored a near-constant proportion as NSC. This pattern was altered in a drought year and the year that followed. The mature plantation stored more NSC in the aboveground pool, but had an NSC consumption in the roots in the drought year. Both the young and mature plantations stored a significant amount of NSC in the roots in the year after the drought. The inter-annual carbon translocation and conversion efficiency changed in the young plantation and while the more mature stand was relatively stable. The flux regression approach allows quantitation of internal fluxes that are difficult to be measured directly, and therefore, is useful in testing and validating ecophysiological and ecosystem models. However, independent measurements of NSC, as well as long-term studies spanning ecosystem gradients in age, stress or disturbance are necessary to validate and generalize the approach.- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMB106...04M
- Keywords:
-
- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0426 Biosphere/atmosphere interactions;
- BIOGEOSCIENCES;
- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 0438 Diel;
- seasonal;
- and annual cycles;
- BIOGEOSCIENCES