2002-07-08_GENERAL DOCUMENTS - M2002004 (4)

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natural sagebrush stand establishment. This study evaluated stands of the Wyoming, basin (vaseyanna), and mountain (tridentata) subspecies from locations thorough out Wyoming. Significant findings include stands are generally even -aged and establishment is episodic. Mean stand ages of Wyoming big sagebrush in northeast and central Wyoming are approximately 26 to 32 years. This is 3 to 4 times older than the mean fire- free interval of 8 years for these areas. Irregular pulses of recruitment appear to be characteristic of big sagebrush stands in Wyoming. This study further found that above average December and January precipitation following initial establishment of Wyoming big sagebrush seedlings was a common occurrence associated with stand establishment. It would appear that the deeper snow cover associated with the above- average precipitation at that time of year provides protection from winter desiccation as well as additional soil moisture during the spring growing season. For basin big sagebrush, there was higher recruitment in those years with higher than average June precipitation during the first growing season, followed by higher than average precipitation in March, May and June of the second growing season. Mountain big sagebrush did not follow this pattern as precipitation in the higher mountain environments means lower temperatures, not conducive to germination and growth at those times of the year. Perryman et al. (1999) further found that big sagebrush stand age might be estimated by stem diameter measurements of the larger plants within the stand with reasonable accuracy. They obtained good correlation with approximately 1 mm of diameter per year. A second study, The Influence of Post - harvest and Pre - planting Seed Treatment on Sagebrush Seedling Vigor, was initiated in 1993 (Booth et al. 1996). Analyses were performed on big sagebrush seeds collected from several locations during the late winter. Processing through a 48 -inch commercial debearder did not appear to reduce seed quality. Moisture percentages in the seed ranged from 2.3 to 9.0% and seed weights ranged from 0.022 to 0.032 g/100 seeds. Germination percentages were highest, and germination most rapid, from the heavier seeds. This study also evaluated moisture uptake (hydration) by big sagebrush seed in storage during a 15 -day period at 2 °, 5 °, 10 °, and 15 °C. Hydration occurred slowly at the cooler temperatures while the maximum rate of hydration occurred at 10 °C. The differences in hydration rates did not appear to influence germination or seedling vigor in laboratory tests. Big sagebrush seeds, when exposed to seven water potentials ranging from 0.00 to —1.5 MPa, exhibited greatest germination at 0.00 Mpa. The authors also observed that the pericarp reduces water uptake and that pericarp removal enhanced germination between —0.50 and —1.00 Mpa. Booth et al. (1996) recommended, however, not to remove the pericarp, as they believed it is important in retaining seed viability in the soil until more favorable soil moisture conditions occur. They implied normal seed