PARENT SESSION
Poster Session #53: Plant Competition.
Thursday, August 8. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC

A field study of plant territory defense in Mojave Desert shrubs.

Hartle, R. Todd^*,1, Nowak, Robert¹, ¹ University of Nevada, Reno, Reno, NV

ABSTRACT- Mahall and Callaway (1991, 1992) demonstrated, in laboratory experiments, that Larrea tridentata roots exclude the roots of other Larrea or of another Mojave Desert shrub, Ambrosia dumosa, from a soil zone surrounding the Larrea roots. The defense of root territory could explain several field observations of unequal distribution and community structure in these desert shrubs (Fonteyn &Mahall 1978, 1981; Brisson &Reynolds 1994), as well as add supporting evidence to the theory of allelopathy. I investigated root territory defense under field conditions with mature Larrea and Ambrosia shrubs in the Mojave Desert near Mercury Nevada. 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) has access to the soil immediately surrounding the roots of the first shrub (donor shrub) in the pair. I used a phenomenon called hydraulic redistribution (formerly hydraulic lift) (Richards &Caldwell 1987; Yoder &Nowak 1999) to place deuterated water (D₂O) into the soil immediately surrounding the roots of the donor shrub in my pairs, and 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 for allelopathic interactions among plants and demonstrate the concept of territory defense in the plant kingdom.

KEY WORDS: territory defense, root, Mojave Desert, Larrea tridentata