We tested the utility of a low-level radiocarbon
(14C) pulse-chase label for quantifying carbon allocation patterns
and the contributions of different components to total ecosystem respiration at
ambient CO2 concentrations in a black spruce forest stand in central
Manitoba, Canada. Approximately .01 moles of CO2
that was isotopically enriched in 14C to ~100,000 times background
atmospheric 14C levels was introduced into the headspace of a 37,000
L translucent dome enclosure. Over a one
hour period, ~70% of this label was photosynthetically assimilated by the
enclosed vegetation. The label application produced a 14C signature
well below regulated health standards, and was easily detectable with
Accelerator Mass Spectrometry (AMS). We followed the allocation and timing of
labeled photosynthetic products by measuring the amount and 14C
content of CO2 respired from different ecosystem components over the
following 30 days.
Author: M.S. Carbone, C.I. Czimczik, K.E. McDuffee, S.E. Trumbore (mcarbone at uci dot edu)
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