Rising temperatures could lower water levels and lead to more breakdown of carbon in peat, leading to positive feedback, but other possibilities exist. For example, since peat pH is low, preventing breakdown, rising atmospheric carbon dioxide could raise soil water carbon dioxide concentrations, lowering pH and further delaying rerelease of stored carbon (negative feedback). Higher temperatures could speed growth of sphagnum moss, storing more carbon (negative feedback).
Work Step by Step
This is speculative— other scenarios could play out, especially given the great uncertainty in models. Use you imagination in connection with the information on sphagnum growth and on peat breakdown on p. 622.