Ecosystem carbon transit versus turnover times in response to climate warming and rising atmospheric CO<sub>2</sub> concentration
<p>Ecosystem carbon (C) transit time is a critical diagnostic parameter to characterize land C sequestration. This parameter has different variants in the literature, including a commonly used turnover time. However, we know little about how different transit time and turnover time are in r...
Main Authors: | , , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2018-11-01
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Series: | Biogeosciences |
Online Access: | https://www.biogeosciences.net/15/6559/2018/bg-15-6559-2018.pdf |
Summary: | <p>Ecosystem carbon (C) transit time is a critical diagnostic parameter to
characterize land C sequestration. This parameter has different variants in
the literature, including a commonly used turnover time. However, we know
little about how different transit time and turnover time are in representing
carbon cycling through multiple compartments under a non-steady state. In this
study, we estimate both C turnover time as defined by the conventional
stock over flux and mean C transit time as defined by the mean age of C mass
leaving the system. We incorporate them into the Community
Atmosphere Biosphere Land Exchange (CABLE) model to estimate C turnover time
and transit time in response to climate warming and rising
atmospheric [CO<sub>2</sub>]. Modelling analysis shows that both C turnover
time and transit time increase with climate warming but decrease with rising
atmospheric [CO<sub>2</sub>]. Warming increases C turnover time by 2.4 years
and transit time by 11.8 years in 2100 relative to that at steady state in
1901. During the same period, rising atmospheric [CO<sub>2</sub>] decreases C
turnover time by 3.8 years and transit time by 5.5 years. Our analysis shows
that 65 % of the increase in global mean C transit time with climate
warming results from the depletion of fast-turnover C pool. The remaining
35 % increase results from accompanied changes in compartment C age
structures. Similarly, the decrease in mean C transit time with rising
atmospheric [CO<sub>2</sub>] results approximately equally from replenishment
of C into fast-turnover C pool and subsequent decrease in compartment C age
structure. Greatly different from the transit time, the turnover time, which
does not account for changes in either C age structure or composition of
respired C, underestimated impacts of warming and rising atmospheric
[CO<sub>2</sub>] on C diagnostic time and potentially led to deviations in
estimating land C sequestration in multi-compartmental ecosystems.</p> |
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ISSN: | 1726-4170 1726-4189 |