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Internal Respiration of Amazon Tree Stems Greatly Exceeds External Co2 Efflux : Volume 9, Issue 8 (27/08/2012)

By Angert, A.

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Book Id: WPLBN0003972164
Format Type: PDF Article :
File Size: Pages 35
Reproduction Date: 2015

Title: Internal Respiration of Amazon Tree Stems Greatly Exceeds External Co2 Efflux : Volume 9, Issue 8 (27/08/2012)  
Author: Angert, A.
Volume: Vol. 9, Issue 8
Language: English
Subject: Science, Biogeosciences, Discussions
Collections: Periodicals: Journal and Magazine Collection, Copernicus GmbH
Publication Date:
Publisher: Copernicus Gmbh, Göttingen, Germany
Member Page: Copernicus Publications


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Muhr, J., Santillan, J. R., Kraemer, G., Muñoz, W. A., Angert, A., Juarez, R. N.,...Mazeh, S. (2012). Internal Respiration of Amazon Tree Stems Greatly Exceeds External Co2 Efflux : Volume 9, Issue 8 (27/08/2012). Retrieved from

Description: The Institute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel. Respiration in tree stems is an important component of forest carbon balance. The rate of CO2 efflux from the stem has often been assumed to be a measure of stem respiration. However, recent work in temperate forests has demonstrated that stem CO2 efflux can either overestimate or underestimate respiration rate, because of emission or removal of CO2 by transport in xylem water. Here we used the ratio between CO2 efflux and O2 influx in stems of tropical forest trees to better understand respiration in an ecosystem that plays a key role in the global carbon cycle. This ratio, which we defined here as apparent respiratory quotient (ARQ), is expected to equal 1.0 if carbohydrates are the substrate for respiration, and the net transport of CO2 in the xylem water is negligible. However, using a stem chamber approach to quantifying ARQ we found values of 0.66 ± 0.18. These low ARQ values indicate that a large portion of respired CO2 (~35%) is not emitted locally, and is probably transported upward in the stem. ARQ values of 0.21 ± 0.10 were found for the steady-state gas concentration within the tree, sampled by in-stem equilibration probes. These lower values may result from the proximity to the xylem water stream. In contrast, we found ARQ values of 1.00 ± 0.13 for soil respiration. Our results indicate, for the first time, the existence of a~considerable internal flux of CO2in the stem of tropical trees. If the transported CO2 is used in the canopy as a substrate for photosynthesis, it could account for several percent of the C fixed by the tree, and perhaps serve as a mechanism that buffers the response of the tree to changing CO2 levels. Our results also indicate, in agreement with previous work, that the widely used CO2 efflux approach for determining stem respiration is unreliable. We demonstrate here a field applicable approach for measuring the O2 uptake rate, which we suggest to be a more appropriate method to estimate stem respiration rates.

Internal respiration of Amazon tree stems greatly exceeds external CO2 efflux

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