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Carbon and Nitrogen Storage in a Tallgrass Prairie Soil
Belay-Tedla, A., Zhou, X., Su, B., Wan, S. and Luo, Y. 2009. Labile, recalcitrant, and microbial carbon and nitrogen pools of a tallgrass prairie soil in the US Great Plains subjected to experimental warming and clipping. Soil Biology & Biochemistry 41: 110-116.

The authors write that "the stability of carbon (C) and nitrogen (N) in soil organic matter (SOM) to perturbations such as global warming is critically important," because, as they continue, "on a global scale, the soil contains 1500 Pg (1 Pg = 1015 g) of organic carbon and 300 Pg of total nitrogen" in its uppermost meter, so that "relatively small changes in the amounts of soil C and N may therefore bring about substantial effects on atmospheric concentrations," which in the case of the carbon contained in CO2 may feed back either positively or negatively to enhance or reduce the original global warming.

What was done
In a study designed to explore these interactions within a specific biome, Belay-Tedla et al. "used sulfuric acid hydrolysis to quantify changes in labile and recalcitrant C and N fractions of soil in a tallgrass prairie ecosystem that had been continuously warmed with or without clipping for about 2.5 years," conducting their work in "an old-field tallgrass prairie abandoned from agriculture 30 years ago and without grazing during the past 20 years" at a location within the Great Plains Apiaries of McClain County, Oklahoma, USA, where infrared heaters suspended 1.5 m above the ground warmed half of the plots 24 hours a day, 365 days a year, for the 2.5-year period, increasing the daily mean air temperature at 25 cm above the ground by 1.1C and soil temperature at 2.5-cm depth by 2.0C.

What was learned
The work of the five researchers revealed, as they describe it, "significant increases in both labile C and N (including microbial biomass) pools in response to experimental warming," which "largely resulted from increased above- and below-ground biomass." They also observed "a possible shift to a fungi-dominated microbial community," noting that "such a shift could favor soil C storage" as well. In addition, they found evidence suggesting that "warming increased the percentage of total N for microbial biomass N," which "enhanced N use efficiency," in their words, "may be conducive for a continued supply of organic inputs."

What it means
Belay-Tedla et al. conclude that their combined findings favor "long-term N retention and C accumulation in soils, leading to negative feedbacks of terrestrial ecosystems to climate warming."

Reviewed 8 April 2009