Figure 1.

Conceptual models indicating possible scenarios for mixing of nonstructural carbon (NSC) across tree ring boundaries. In the case where there is complete mixing of ‘old’ (stored) NSC and ‘new’ (recent photosynthetic assimilates) NSC across the radial profile, the measured age of extracted NSC should be constant with depth, that is, across rings of different ages (a). When there is no mixing of old and new, and NSC is effectively ‘locked’ into the ring in which it is first deposited, then the measured age of extracted NSC should increase in parallel with ring age (b). However, if younger NSC ‘mixes in’ to older rings, the age of NSC should always be younger than the ring age (c), whereas if older NSCs ‘mixes out’ to younger rings, the age of NSC should always be older than the ring age (d). Intermediate cases are possible, for example, partial mixing would be characterized by young rings where the NSC is older than the ring age, and old rings where the NSC is younger than the ring age. The dashed line indicates the 1:1 line, and the orange line indicates the mixing scenario.