Herbivory Effects on Summer Drought Tolerance and Winter Survival of Wyoming Big Sagebrush Seedlings

Invasive species and fires have damaged many sagebrush habitats. Rehabilitation of these habitats requires reintroducing a keystone species, Artemisia tridentata (big sagebrush), which provides habitat and forage for many animals. Reestablishment of big sagebrush has proven difficult due to high seedling mortality. The purpose of this study was to determine herbivory effects on summer drought tolerance and winter survival of Wyoming big sagebrush ( A. tridentata ssp. wyomingensis ) seedlings. Seedlings outplanted at Kuna Butte-Idaho were exposed to different herbivory degrees by leaving them without tree-protectors or covering them with plastic or metal tree protectors. We measured survival, water potential, shoot size, and inflorescence occurrence to assess herbivory's effects on the seedlings. Herbivory in spring, presumably by ground squirrels, increased seedling mortality during summer, fall, and winter. A year and a half after outplanting, survival was 61.5, 82.4, and 89.7% for seedlings with no, plastic, and metal protectors, respectively ( p < 0.001). Herbivory also arrested flower development; the percentage of plants producing flowers was threefold higher in plants with than without protectors. Reduction in leaf area due to herbivory may have prevented accumulating sufficient carbon reserves, leading to higher susceptibility to drought and low temperatures.