Abstract
Increases in respiration rates following management activities in croplands are considered a relevant
anthropogenic source of CO2. In this paper, we quantify the impact of management events on cropland
respiration fluxes of CO2 as they occur under current climate and management conditions. Our findings
are based on all available CarboEurope IP eddy covariance flux measurements during a 4-year period
(2004–2007). Detailed management information was available for 15 out of the 22 sites that contributed
flux data, from which we compiled 30 types of management for European-scale comparison. This allowed
us to address the question of how management activities influence ecosystem respiration. This was done
by comparing respiration fluxes during 7, 14, and 28 days after the management with those observed
during the matching time period before management.
Median increases in respiration ranged from +83% (early season tillage) to -50% (rice paddy flooding
and burning of rice residues) on the 28 days time scale,whenonlymanagementtypes with aminimumof 7
replications are considered. Most management types showed a large variationamongevents and between
sites, indicating that additional factors other than management alone are also important at a given site.
Temperature is the climatic factor that showed best correlation with site-specific respiration fluxes.
Therefore, the effect of temperature changes between the time periods before and after management
were taken into account for a subset of 13 management types with adequate statistical coverage of at least
5 events during the years 2004–2007. In this comparison, late-season moldboard ploughing (30–45 cm)
led to highest median increase in respiration on the 7 days timescale (+43%), which was still +15% in
the 28 days comparison. On average, however, management-induced increases in respiration losses from
croplands were quite moderate (typically <20% increase over 28 days).
An assessment of extreme values in daily respiration fluxes using the Gumbel distribution approach
revealed that sites with larger average respiration fluxes also experience the larger extremes in respiration
fluxes. This suggests that it is very unlikely that sites that generally have low respiration rates will have
exceedingly high respiration rates as a result of certain specific management events.
anthropogenic source of CO2. In this paper, we quantify the impact of management events on cropland
respiration fluxes of CO2 as they occur under current climate and management conditions. Our findings
are based on all available CarboEurope IP eddy covariance flux measurements during a 4-year period
(2004–2007). Detailed management information was available for 15 out of the 22 sites that contributed
flux data, from which we compiled 30 types of management for European-scale comparison. This allowed
us to address the question of how management activities influence ecosystem respiration. This was done
by comparing respiration fluxes during 7, 14, and 28 days after the management with those observed
during the matching time period before management.
Median increases in respiration ranged from +83% (early season tillage) to -50% (rice paddy flooding
and burning of rice residues) on the 28 days time scale,whenonlymanagementtypes with aminimumof 7
replications are considered. Most management types showed a large variationamongevents and between
sites, indicating that additional factors other than management alone are also important at a given site.
Temperature is the climatic factor that showed best correlation with site-specific respiration fluxes.
Therefore, the effect of temperature changes between the time periods before and after management
were taken into account for a subset of 13 management types with adequate statistical coverage of at least
5 events during the years 2004–2007. In this comparison, late-season moldboard ploughing (30–45 cm)
led to highest median increase in respiration on the 7 days timescale (+43%), which was still +15% in
the 28 days comparison. On average, however, management-induced increases in respiration losses from
croplands were quite moderate (typically <20% increase over 28 days).
An assessment of extreme values in daily respiration fluxes using the Gumbel distribution approach
revealed that sites with larger average respiration fluxes also experience the larger extremes in respiration
fluxes. This suggests that it is very unlikely that sites that generally have low respiration rates will have
exceedingly high respiration rates as a result of certain specific management events.
| Originalsprog | Engelsk |
|---|---|
| Tidsskrift | Agriculture, Ecosystems & Environment |
| Vol/bind | 139 |
| Sider (fra-til) | 346-362 |
| Antal sider | 17 |
| ISSN | 0167-8809 |
| DOI | |
| Status | Udgivet - 15 nov. 2010 |
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