Germination of green and gray rubber rabbitbrush and their establishment on coal mined land

Abstract

The objectives of this study were to: (1) determine the effects of temperature and water stress on germination, and; (2) evaluate effects of seeding date on emergence and survival of green and gray rubber rabbitbrush (Chrysothamnus nauseosus (Pallas) Britt. subsp. graveolens (Nutt.) Piper. and Chrysothamnus nauseosus (Pallas) Britt. subsp. nauseosus (Nutt.) Piper.). Seeds of both shrubs were incubated at 10, 20, and 30 degrees C in a gradient of osmotic potentials ranging from 0.0 to -1.5 MPa. Seedings were also made in the field on seeding dates over a period of 3 years. Total germination and germination rate declined as temperatures and osmotic potentials decreased; they were highest for both shrubs at 20 and 30 degrees C and lowest at 10 degrees C. Under field conditions seedling populations were limited by low emergence and survival relative to viable seed planted. Emergence and survival of seedlings were highest in an exceptionally wet year, declining in subsequent years that were drier. Emergence ranged from 0 to 6.9% and 0 to 7.1% and survival of emerged seedlings ranged from 6.6 to 55% and 0 to 60% for green and gray rubber rabbitbrush, respectively. Survival of green rubber rabbitbrush was highest from mid-spring plantings, but no distinctively favorable seeding date was found for gray rubber rabbitbrush. Results suggest that seeds of these shrubs should be planted prior to or during periods when seedbed temperatures are in the 20 to 30 degrees C range and soil moisture is expected near its seasonal high.