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Water is generally considered to be the major limiting factor for perennial shrub growth in the Mojave Desert, USA. However, the responses of active fine roots to soil moisture and microsite differed among Ambrosia dumosa, Ephedra nevadensis, Larrea tridentata, and Lycium pallidum, suggesting differences in root foraging strategies. Ambrosia and Ephedra had a positive linear relationship between active fine root lengths and soil moisture and more roots under the canopy, whereas Larrea had a negative linear relationship and more roots in the interspace. Lycium did not show a significant root/water relationship or significant differences between canopy and interspace microsites. (C) 2003 Elsevier Science Ltd. All rights reserved.