Drought is perhaps the most common environmental
stress that soil microorganisms experience. One third of
the earth’s cover is arid, semi-arid, or seasonally arid
(Mediterranean, dry tropical forest, and so on [Gurevitch
et al. 2002]) and other ecosystems experience
regular drought and episodic dry/rewetting cycles as
well. As soils dry, substrate diffusion becomes limited
and microbes may experience resource limitation that
can slow biogeochemical process rates (Stark and
Firestone 1995). However, decreasing water potentials
impose direct physiological stress that forces microbes to