Great Basin Naturalist


Blackbrush (Coleogyne ramosissima Torr.) is a dominant desert shrub in a distinct mid-elevational vegetation belt between creosote bush–bursage (Larrea tridentata–Ambrosia dumosa) shrubland below and big sagebrush–pinyon pine–Utah juniper (Artemisia tridentata–Pinus monophylla–Juniperus osteosperma) woodland above in the Mojave Desert. Seed germination patterns of blackbrush seeds collected from 2 elevations (1200 and 1550 m) in 5 mountain ranges within the blackbrush shrublands were investigated. Morphological features of blackbrush seeds, including weight, length, and width, were not significantly different (P > 0.05) among elevations and mountain ranges in the Mojave Desert. Germination of blackbrush seeds was optimal when preceded by a prechill period of 4–6 wk. Seeds incubated at room temperature germinated poorly. Seeds collected at warm, low-elevation sites appeared to be less dormant (required less prechill time), germinated faster, and showed a higher overall germination response; watering at 2-wk intervals revealed the greatest germination. Some ecotypic variation among populations establishing at different elevations was evident with regard to dormancy duration and germination response at certain constant temperatures.