Abstract
Abstract. The flux of carbon dioxide from the soil to the atmosphere (soil respiration) is one of the major fluxes in the global carbon cycle. At present, the accumulated field observation data cover a wide range of geographical locations and climate conditions. However, there are still large uncertainties in the magnitude and spatiotemporal variation of global soil respiration. Using a global soil respiration data set, we developed a climate-driven model of soil respiration by modifying and updating Raich's model, and the global spatiotemporal distribution of soil respiration was examined using this model. The model was applied at a spatial resolution of 0.5°and a monthly time step. Soil respiration was divided into the heterotrophic and autotrophic components of respiration using an empirical model. The estimated mean annual global soil respiration was 91 Pg C yr−1 (between 1965 and 2012; Monte Carlo 95 % confidence interval: 87–95 Pg C yr−1) and increased at the rate of 0.09 Pg C yr−2. The contribution of soil respiration from boreal regions to the total increase in global soil respiration was on the same order of magnitude as that of tropical and temperate regions, despite a lower absolute magnitude of soil respiration in boreal regions. The estimated annual global heterotrophic respiration and global autotrophic respiration were 51 and 40 Pg C yr−1, respectively. The global soil respiration responded to the increase in air temperature at the rate of 3.3 Pg C yr−1 °C−1, and Q10 = 1.4. Our study scaled up observed soil respiration values from field measurements to estimate global soil respiration and provide a data-oriented estimate of global soil respiration. The estimates are based on a semi-empirical model parameterized with over one thousand data points. Our analysis indicates that the climate controls on soil respiration may translate into an increasing trend in global soil respiration and our analysis emphasizes the relevance of the soil carbon flux from soil to the atmosphere in response to climate change. Further approaches should additionally focus on climate controls in soil respiration in combination with changes in vegetation dynamics and soil carbon stocks, along with their effects on the long temporal dynamics of soil respiration. We expect that these spatiotemporal estimates will provide a benchmark for future studies and also help to constrain process-oriented models.
Highlights
The carbon balance of terrestrial ecosystems is the result of the balance between carbon uptake by plants and carbon loss by plant and soil respiration (Beer et al, 2010; Luyssaert et al, 2007; Malhi et al, 1999; Le Quéré et al, 2009, 2014; Trumbore, 2006)
Our analysis provides additional data to support an increasing trend for global RS, even though a new model was applied for this study, and supports the assumption that the soil carbon flux from soil to the atmosphere is increasing in response to climate change
We estimated the spatiotemporal variation of global RS using a global soil database, SRDB, and a semiempirical model
Summary
The carbon balance of terrestrial ecosystems is the result of the balance between carbon uptake by plants and carbon loss by plant and soil respiration (Beer et al, 2010; Luyssaert et al, 2007; Malhi et al, 1999; Le Quéré et al, 2009, 2014; Trumbore, 2006). The value of the balance, i.e., whether terrestrial ecosystems act as sinks or sources of carbon, has been a subject of considerable interest for studies of climate change. Accurate evaluations of each sink/source component and their response to environmental factors are essential for understanding future changes in the terrestrial carbon balance. S. Hashimoto et al.: Global spatiotemporal distribution of soil respiration
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