Critical mule deer (Odocoileus hemionus) winter ranges in southeastern Utah dominated by Wyoming big sagebrush (Artemisia tridentata var. wyomingensis [Beetle and A. Young] Welsh) have developed dense cheatgrass (Bromus tectorum L.) understories. These communities are currently characterized by predominately mature to decadent stands of sagebrush with few perennial grasses and forbs. Sagebrush seedlings and perennial grasses compete for limited resources with annual grasses and forbs. To determine the affects of cheatgrass control on sagebrush growth and reproductive characteristics, imazapic (PLATEAU®, AC 263,222) herbicide was sprayed at 438.5 ml/ha with water and methylated seed oil during active fall growth of cheatgrass in 2002. Sagebrush growth and reproductive variables were measured on browsed and unbrowsed (caged) plants on sprayed and non-sprayed paired plots on 6 sites. Cheatgrass and other annual forb pretreatment cover was reduced from 23% to less than 3% the first year after the herbicide treatement and only increased to 4% the second year. Soil moisture on the treated plots was available at 15, 30, and 60 cm for several days to several weeks longer than on the control plots depending on the depth in the soil and year. Annual leader growth and flowering seedstalk length were similar on unbrowsed and browsed shrubs, but the number of seedstalks per plant was decreased by browsing. The number of sagebrush flowering seedstalks was significantly reduced by the herbicide the first year after the treatment, but recovered by the second year. The decrease in flowering seedstalks per sagebrush reduced the number of sagebrush seedlings observed the second year after the treatment (control = 81,800 seedlings/ha and treated = 16,700 seedlings/ha). Both seedstalk length (treated = 13.4 cm and control = 11.2 cm) and annual leader growth (treated = 6.2 cm and control = 5.3 cm) were greater on treated plots than control plots. Overall, imazapic can provide a window of cheatgrass and annual forb control to allow big sagebrush seedlings and perennial grasses and forbs to establish.

Herbivory and plant competition affect sexual reproduction of plants in various ways. Exclusion of mule deer (Odocoileus hemionus) and cattle, removal of plant competition (both inter- and intraspecific), and all combinations of the above treatments were used to examine the individual and combined affects on Artemisia tridentata ssp. wyomingensis (Wyoming big sagebrush) reproduction. Reproduction of Artemisia tridentata ssp. wyomingensis was divided into hierarchical levels of the number of: (1) modules per current-year ' s growth (CYG), (2) nodes per module, (3) inflorescence heads per node, (4) achenes per inflorescence head and (5) percent viable achenes. Counts at hierarchical levels were made to determine the level affected by the treatments. Deer herbivory significantly reduced reproduction at the reproductive-module-per-CYG-vegetative-biomass hierarchical level, while plant competition (both inter- and intraspecific) significantly reduced reproduction at the nodes-per-reproductive-module level and at the inflorescence-heads-per-node level. Cattle presence had neither a beneficial nor detrimental influence on reproduction during this two-year study. The combined effects of release from deer herbivory and from plant competition on reproduction was more than additive because these biotic interactions affected nested hierarchical levels.

Big sagebrush (Artemisia tridentata) is one of the ecologically most important shrub species in western North America. The species serves as a major source of food and habitat for the near-threatened sage grouse and various other fauna. Habitat loss due to a combination of disturbances followed by establishment of invasive plant species is considered as a serious threat to sustainability of the big sagebrush ecosystem. Because of its importance, restoration of this species is very crucial to those dependent on big sagebrush community. However, restoration of big sagebrush carried out by using diverse seed source can lead to imbalance and degradation in the native ecosystem. Therefore, restoration works aided by understanding of adaptive traits of big sagebrush using molecular markers will aid successful restoration. The major objective of this research was to create a substantial resource of nuclear sequence data and identify markers that can be used in future studies in big sagebrush. We report the development and annotation of the first expressed sequence tag (EST) collection for big sagebrush based on 454 sequencing of leaf tissue. Expressed genes of subspecies tridentata and vaseyana were sequenced using the 454 GS-FLX titanium platform, which produced 823,392 reads with an average read length of 404 bp and 702,001 reads with an average read length of 333 bp for sspp. tridentata and vaseyana, respectively. Assembly of the reads resulted in 212,102 consensus sequences in ssp. tridentata and 199,439 in ssp. vaseyana. A combined assembly of both subspecies sequences generated 29,541 contigs with an average length of 796 bp and 275,866 singletons with an average length of 370 bp. A BLASTx search against the non-redundant (NR) protein database using the contigs obtained from a combined assembly resulted in 21,436 sequences with significant blast alignments (≤ 1e-15). Gene Ontology (GO) IDs were assigned to 18,397 sequences. A total of 20,952 SNPs were detected between the two subspecies and 1,182 SNPs were confirmed in tetraploid ssp. wyomingensis. In addition, 1,003 and 507 SSRs were detected in ssp. tridentata contigs and ssp. vaseyana contigs, respectively.