Preestablished plant influences on antelope bitterbrush seedling recruitment and growth

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This study evaluated the influence of preestablished plant species distance, direction, and identity on antelope bitterbrush (Purshia tridentata Pursh) seedling establishment and biomass production. Antelope bitterbrush seeds were planted 10- and 20-cm away from the base of three preestablished plant species. Sowing antelope bitterbrush seeds 20-cm away from preestablished plant bases yielded 1.59 times greater seedling establishment than seeds sown 10-cm away, suggesting that established plants interfere with bitterbrush recruitment. Antelope bitterbrush seedling survival after 2 y of growth was greater than 96% for all treatments, suggesting that early growth phases were the primary bottlenecks to establishment. Antelope bitterbrush forage production decreased with proximity to preestablished plants. After 2 y of growth, antelope bitterbrush biomass was almost 3 times greater for plants grown without preestablished plant neighbors or with a preestablished grass (Elymus elymoides Raf.) than with preestablished forb species (Dalea candida Michx. ex Willd. or Gaillardia aristata Pursh). Inoculating preestablished plants with soil from native sites or arbuscular mycorrhizal fungi did not influence antelope bitterbrush establishment or growth. We suggest that plant trait complementarity and spatial relationships can be used to design seeding strategies to increase antelope bitterbrush establishment and forage production.