microscale distribution of neighbouring plant roots in fertile soil microsites

Proliferation and distribution of roots in fertile soil microsites were evaluated in the field for three perennial Great Basin species from soil samples frozen in situ. A chemical determination allowed the identification of fine roots of grass and shrub in soil samples containing roots of the shrub, Artemisia tridentata (Rydb.) Beetle, with either Pseudoroegneria spicata (Pursh) A. Love or Agropyron desertorum (Fisch. ex Link) Schult. Root proliferation of the shrub was considerably influenced by the species of grass roots in the patches; root densities of Artemisia were generally two to three times more abundant with Pseudoroegneria than when with Agropyron. There was also a greater tendency for roots of Artemisia and Pseudoroegneria to segregate (avoid one another) in comparison with the combination of Artemisia and Agropyron. Interference at the level of individual roots is suggested. The species also reacted to the fertile microsites differently; only Agropyron exhibited a significant proliferation compared to control microsites. In general, Agropyron had greater root densities than Pseudoroegneria. Root densities of the three species in fertile and control patches were not proportional to exploitation of P (Caldwell, Manwaring & Jackson, 1991). Roots of the shrub were four to 10 times more effective in P acquisition per unit root length than the grass species.