One of the assumptions of the impact of global warming is that soil-based decay processes that transform dead plant material back to atmospheric carbon dioxide (soil respiration) will accelerate at the higher temperatures projected to occur under global warming. Luo et al (2001) examine this assumption of a positive feedback between temperature and soil respiration and find that, in fact, the opposite is more likely to occur in tall grass prairie biomes. They observe that soil respiration for this ecosystem is a negative feedback to increasing temperature.
Luo, Y., S. Wan, D. Hui, and L. L. Wallace, 2001: Acclimatization of soil respiration to warming in a tall grass prairie. Nature, 413, 622-625.