Poster Session # 15: Plant Ecology.

Wednesday, August 6 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.

Larrea tridentata defense of root territory in the Mojave Desert.

Hartle, R. Todd*,1, 1 University of Nevada, Reno, Reno, Nevada, USA

ABSTRACT- Larrea tridentata roots have been shown to exclude the roots of other Larrea or of another Mojave Desert shrub, Ambrosia dumosa, from a soil zone surrounding the Larrea roots (Mahall and Callaway 1991, 1992). The existence of root zone territory defense could explain field observations of unequal distribution and community structure in desert shrubs (Fonteyn & Mahall 1978, 1981; Brisson & Reynolds 1994), as well as add supporting evidence to the theory of allelopathy. In the spring of 2002, I developed a field method based on a phenomenon called hydraulic redistribution (formerly hydraulic lift) (Richards & Caldwell 1987; Yoder & Nowak 1999) In this method, I looked at paired shrubs, including Larrea with Larrea, Ambrosia with Ambrosia, and Larrea with Ambrosia, and tested whether the second shrub of the pair (receiver shrub) had access to the soil immediately surrounding the roots of the first shrub (donor shrub). Using hydraulic redistribution to place deuterated water (D2O) into the soil immediately surrounding the roots of the donor shrubs, I sampled the tissue of the receiver shrub and tested it for the presence of the deuterated water. The results of this study not only add to our knowledge of belowground interactions among Mojave Desert shrubs, but also add significantly to the evidence on the concept of territory defense in the plant kingdom, i.e. that plants actively defend soil resources for their exclusive use.

Key words: root, territory defense, Larrea tridentata, Ambrosia dumosa