An incubation method to determine the age of available nonstructural carbon in woody plant tissues.

This article focuses on comparing two methods—an established extraction method and a novel incubation method—for measuring radiocarbon (∆¹⁴C) in nonstructural carbon (NSC) pools of trembling aspen (Populus tremuloides Michx.) to infer the age and metabolic availability of stored photosynthate. The incubation method captures ∆¹⁴C from respired CO₂ of live tissue sections, reflecting metabolically available NSC, while the extraction method isolates soluble and insoluble NSC fractions but tends to overestimate carbon yield and includes non-reserve compounds, especially in older tissues like bark and heartwood. Results showed good agreement between methods in sapwood but significant discrepancies in bark and heartwood, where extraction-based ∆¹⁴C values were older and carbon yields were inflated, likely due to dead cells and non-metabolizable compounds. The study suggests the incubation method offers a potentially more accurate, cost-effective approach to assess the age and availability of NSC relevant for tree metabolism and resilience, though it requires rapid sample processing and has limitations such as potential microbial respiration contributions.