Prof. Sean M. Schaeffer

Dryland ecosystems cover much of the Earth’s land surface and may have highly variable weather and climate, making them sensitive to climate changes that alter soil water. In ecosystems with Mediterranean climates, cycles of carbon (C) and nitrogen (N) may be particularly sensitive to shifts in rainfall; the rainy winters support plant growth and C-inputs into soils, but summers are dry and plant C inputs decrease as many plants senesce. Coincident shifts in microbial processes remain relatively under studied but maybe just as critical to biogeochemical cycling. Drought imposes both physiological and physical stress on microbes, and the mechanisms by which they respond to stress can affect C release and storage, and N availability and loss. Here, we will discuss microbial stress response and the implications for large scale changes in biogeochemistry in arid lands, particularly Mediterranean, and other agroecosystems. We find that the length of drought is proportional to the accumulation of organic C and inorganic N with relatively higher bioavailability that can be rapidly mobilized by microbes upon rewetting. Rewetting may also induce a commensurate release of carbon dioxide and nitrous oxide.