Abstract
Background and aimsPriming effect (PE) plays an important role in modifying the decomposition of soil organic matter (SOM), but large uncertainties remain in the temperature effect on PE mainly due to the variation in SOM stability.MethodsWe tested the temperature effect on PE of the relatively stabilized SOM by incubating soils collected from a bare fallow (representing the relatively stabilized SOM) and its adjacent old field (containing both stabilized SOM and labile SOM) at 10 and 20 °C for 815 days. We used a natural 13C abundance tracer method for measuring the PE.ResultsPositive PE was observed in all treatment combinations when maize leaf litter was added. The temperature sensitivity of PE in the bare fallow soil and the old field soil was quite different: increasing temperature significantly enhanced the magnitude of PE in the bare fallow soil, but had no effect on it in the old field soil. The increase of microbial biomass C by litter addition was higher in the bare fallow soil than in the old field soil. Furthermore, for litter-treated soil, temperature increase significantly increased net N mineralization rate throughout the incubation in the bare fallow soil, but had minor effect on it in the old field soil at the end of incubation.ConclusionsOverall, this study demonstrates that PE of the relatively stabilized SOM is sensitive to temperature, which may be mainly driven by greater microbial growth and demand for N.
Highlights
Soil organic matter (SOM) is the largest reservoir of carbon (C) storage in terrestrial ecosystems and its mineralization produces a major carbon dioxide (CO2) flux into the atmosphere (Lal, 2008)
For maize leaves-treated soil, temperature increase significantly increased the rate of microbial N mining throughout the incubation in the bare fallow soil, but had minor effect on microbial N mining in the old field soil at the end of incubation
We conclude that the priming effect of the relatively stabilized soil organic matter (SOM) was sensitive to temperature increase, which may be mainly driven by greater microbial growth and microbial demand for N
Summary
Soil organic matter (SOM) is the largest reservoir of carbon (C) storage in terrestrial ecosystems and its mineralization produces a major CO2 flux into the atmosphere (Lal, 2008). The intermediate and stable C pools can be collectively described as a relatively stabilized C pool with a turnover time from decades to centuries or more (Anderson and Paul, 1984; Jenkinson and Rayner, 1977; Trumbore et al, 1989). This relatively stabilized C pool is the major component of SOM stocks (Davidson and Janssens, 2006) and its vulnerability to the PE can significantly impact the global C cycle (Derrien et al, 2014). The absence of an adequate understanding on the PE of the relatively stabilized SOM leads to a debate on the temperature sensitivity of PE (Ghee et al, 2013; Frøseth and Bleken, 2015; Lyu et al, 2019)
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