EXPERIMENTAL-EVIDENCE FOR SEX-BASED PALATABILITY VARIATION IN FOURWING SALTBUSH

Two small-plot grazing trials were conducted in the spring of 1996 and the winter of 1997 to determine whether sheep would differentially gr aze fourwing saltbrush [Atriplex canescens (Pursh) Nutt,] on the basis of shrub sex in a uniform garden. Consumption was determined using an Australian method of leaf tagging in conjunction with the Adelaide Te chnique of biomass estimation. The results confirmed anecdotal field o bservations that herbivores prefer to graze the male shrub during late spring, No sex based preference was apparent during winter, We sugges t that differences in physiological vigor and/or chemistry may influen ce relative palatability of the sexes through time. Results of these e xperiments contrast with those for an Australian member of the genus ( A. vesicaria Hew. ex Benth.), for which it was found that the female w as the preferred phenotype throughout the year.