Description:
<jats:title>Summary</jats:title><jats:p>
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<jats:list-item><jats:p>Nonstructural carbon (<jats:styled-content style="fixed-case">NSC</jats:styled-content>) reserves act as buffers to sustain tree activity during periods when carbon (C) assimilation does not meet C demand, but little is known about their age and accessibility; we designed a controlled girdling experiment in the Amazon to study tree survival on <jats:styled-content style="fixed-case">NSC</jats:styled-content> reserves.</jats:p></jats:list-item>
<jats:list-item><jats:p>We used bomb‐radiocarbon (<jats:sup>14</jats:sup>C) to monitor the time elapsed between C fixation and release (‘age’ of substrates). We simultaneously monitored how the mobilization of reserve C affected δ<jats:sup>13</jats:sup><jats:styled-content style="fixed-case">CO</jats:styled-content><jats:sub>2</jats:sub>.</jats:p></jats:list-item>
<jats:list-item><jats:p>Six ungirdled control trees relied almost exclusively on recent assimilates throughout the 17 months of measurement. The Δ<jats:sup>14</jats:sup>C of <jats:styled-content style="fixed-case">CO</jats:styled-content><jats:sub>2</jats:sub> emitted from the six girdled stems increased significantly over time after girdling, indicating substantial remobilization of storage <jats:styled-content style="fixed-case">NSC</jats:styled-content> fixed up to 13–14 yr previously. This remobilization was not accompanied by a consistent change in observed δ<jats:sup>13</jats:sup><jats:styled-content style="fixed-case">CO</jats:styled-content><jats:sub>2</jats:sub>.</jats:p></jats:list-item>
<jats:list-item><jats:p>These trees have access to storage pools integrating C accumulated over more than a decade. Remobilization follows a very clear reverse chronological mobilization with younger reserve pools being mobilized first. The lack of a shift in the δ<jats:sup>13</jats:sup><jats:styled-content style="fixed-case">CO</jats:styled-content><jats:sub>2</jats:sub> might indicate a constant contribution of starch hydrolysis to the soluble sugar pool even outside pronounced stress periods (regular mixing).</jats:p></jats:list-item>
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