Effects of shrub removal and nitrogen addition on soil moisture in sagebrush steppe

I monitored soil moisture profiles in sagebrush steppe in SE Idaho, USA, for 6 years, a period that included four consecutive years of drought. Recharge of soil moisture was primarily the result of winter and early spring precipitation, and soil moisture declined during the spring and summer growing season. Recharge was substantially lower during drought years, and a single year of average precipitation did not restore soil moisture to pre-drought levels. Relative to control plots, there was more soil moisture on shrub removal plots and less soil moisture on nitrogen addition plots, particularly at depths of 100–180 cm. These differences suggest that in this ecosystem shrubs extract more moisture from deeper in the soil profile than perennial grasses, and that increased nitrogen availability can significantly affect soil water balance.