Evaluation of Competition in the Rootzone of the Landscape of the Intermountain West

Current trends in population growth in states of the Intermountain West are resulting in increased stress being placed on a valuable and rapidly dwindling resource. Water demand in these semiarid states is increasing greatly as neighborhood residential and commercial properties increase in number. Considering the intense sunlight, dry winds and sparse rainfall, landscaping these properties is a challenging task. Turfgrasses, trees and flowering plants often require significant amounts of supplemental water to compensate growth conditions of the climate found in the Intermountain West region. In landscapes, species are often placed in very close proximity to one another, creating a situation in which plants must compete for scarce resources. Description and characterization of interactions between species in landscapes for these compounds can provide critical insight into proper selection of species more suitable to the local climate. Rooting volume can be a measure of a plant’s relative access to water and nutritional resources within the soil profile. Minirhizotron systems have been used successfully in assessing rooting extent and root viability in numerous species common to landscapes. A randomized split-block design experiment was performed investigating differences in rooting extent between combinations of two tree (Robinia pseudoacacia, Gleditsia triacanthos) and three turfgrass (Poa pratensis, Buchlöe dactyloides, Festuca arundinaceum) species. A minirhizotron system was used to obtain images for six months during summer 2006 and 2007 from depths of 1-30 cm under each tree-turfgrass rooting zone. Using RooTracker© 2.03, images were analyzed to determine combined total volume of turfgrass and tree roots. Our data suggests that significant differences in rooting extent exist among the turf-tree species combinations, with particular disparity between combinations with or without R. pseudoacacia (black locust) trees. With this in mind, use of black locust in landscapes with turfgrass may result in detriment to the turf cover as rooting is inhibited