In:
Biogeosciences, Copernicus GmbH, Vol. 16, No. 1 ( 2019-01-17), p. 177-191
Abstract:
Abstract. The ratio of CO2 efflux to O2 influx (ARQ,
apparent respiratory quotient) in tree stems is expected to be 1.0 for
carbohydrates, the main substrate supporting stem respiration. In previous
studies of stem fluxes, ARQ values below 1.0 were observed and hypothesized
to indicate retention of respired carbon within the stem. Here, we
demonstrate that stem ARQ 〈 1.0 values are common across 85
tropical, temperate, and Mediterranean forest trees from nine different
species. Mean ARQ values per species per site ranged from 0.39 to 0.78, with
an overall mean of 0.59. Assuming that O2 uptake provides a measure of
in situ stem respiration (due to the low solubility of O2), the overall mean
indicates that on average 41 % of CO2 respired in stems is not
emitted from the local stem surface. The instantaneous ARQ did not vary with
sap flow. ARQ values of incubated stem cores were similar to those measured
in stem chambers on intact trees. We therefore conclude that dissolution of
CO2 in the xylem sap and transport away from the site of respiration
cannot explain the low ARQ values. We suggest refixation of respired
CO2 in biosynthesis reactions as possible mechanism for low ARQ values.
Type of Medium:
Online Resource
ISSN:
1726-4189
DOI:
10.5194/bg-16-177-2019
DOI:
10.5194/bg-16-177-2019-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2019
detail.hit.zdb_id:
2158181-2