B106-04
Beyond Carbon Flux Partitioning: Inferring the Dynamic Non-structural Carbon Storage and Carbon Allocation at the Canopy Scale from Continuous Fluxes

Tuesday, 15 December 2020: 20:42
Virtual
Guofang Miao1, Asko Noormets2, Michael Gavazzi3, Bhaskar Mitra4, Jean-Christophe Domec5, Ge Sun6, Steven McNulty6 and John S King4, (1)Fujian Normal University, School of Geographical Sciences, Fuzhou, China, (2)Texas A&M University, Department of Ecology and Conservation Biology, College Station, TX, United States, (3)USDA Forest Service, EFETAC Research Triangle Park, Raleigh, NC, United States, (4)North Carolina State University, Department of Forestry and Environmental Resources, Raleigh, NC, United States, (5)Bordeaux Sciences Agro, UMR 1391 INRA-ISPA, Gradignan, France, (6)USDA Forest Svc, Eastern Forest Environmental Threat Assessment Center, Raleigh, NC, United States
Recorded Presentation
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.

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