Temperature sensitivity of soil organic matter fractions

It is uncertain how the projected global warming will affect global carbon cycles and specifically soil carbon stocks.  Soil organic matter (SOM) acts as a reservoir that contains two to three times as much carbon as the atmosphere with temperature being a controlling factor in this reservoir’s turnover.  This may cause the projected climate change to have a considerable effect on SOM stocks.  SOM is composed of heterogeneous materials with varying turnover times and there has been considerable debate about the effect of increased temperature on the decomposition rate of these different SOM fractions.  The purpose of this research was to understand how these different fractions respond to increased temperature. Our research utilized soil incubations, land use change, and shifts in plant-derived ¹³C signatures to alter the balance of labile versus resistant soil C on twelve soils at six different locations across a latitudinal gradient from Canada to Brazil.  Results from our ¹³C signatures of our soil incubation experiment comparing Q₁₀ temperature coefficients indicate that the more resistant SOM is most sensitive to a given temperature increase.  These results indicate that at warmer global temperatures we may lose a considerable amount of SOM due to increased decomposition, potentially causing a positive feedback loop to the atmosphere.