2002-07-08_GENERAL DOCUMENTS - M2002004 (3)

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while Bai et al. (1997) reported 3100 -4500 seeds g' for five Wyoming collections. Sagebrush seed availability and quality are very dependent upon yearly climatic conditions because most of the seed used in land reclamation are collected from native stands. However, more emphasis and interest is being directed toward seed production under cultivated field conditions and irrigation, which will ensure a more consistent quality and availability of seed. Seed availability will become a more important consideration in the future because demand for Wyoming big sagebrush seed has increased dramatically over the last few years as land management agencies attempt to revegetate large land areas affected by fire and invasive species. However, with good sound planning and use of good cultural practices by these agencies, the impact on seed availability and cost could be greatly reduced. Harvesting seed from native big sagebrush stands requires careful observation and timing. Young and Young (1992) reported that seed needs to be harvested as soon after seed ripening as possible. In fact, Walton et al. (1986) believe that viable, ripe seeds will fall from the seed stalks within the first seven days after ripening. However, Bai et al. (1997) found significant amounts of viable Wyoming big sagebrush seed in the seed stalks in February. These inconsistent findings may be associated with variance in climate and seed quality between eco- regions. Seed processing by using a debearder is common and has been found to have no detrimental effects on seed germination (percentage or rate), seedling vigor, or shelf - life (Booth et al. 1997). However, seed storage is a topic in which much additional research is needed to fully understand the effects of the various environmental conditions utilized for seed storage. Bai et al. (1997) and Shaw and Booth (1999) found a full range of seed responses to various seed storage conditions, leaving one to conclude that no single seed storage protocol has been shown to be superior or is used as a standard. Germination of big sagebrush is believed to be genetically regulated and has evolved to ensure its survival under the wide range of climatic conditions exhibited within its wide geographical distribution in the western -U.S. (Meyer and Monsen 1992). Monsen and Meyer (1990) and Shaw (1994) stated that understanding specific germination requirements for a subspecies is essential to developing an appropriate seedbed ecology (seedbed preparation, planting methods, equipment, mulch) that will enhance germination and establishment. Big sagebrush seed has been reported to have a 40 relatively short lived viability of only a few months (Young and Evans 1989); however, researchers have shown Wyoming big sagebrush to have some seed dormancy (McDonough and Harniss 1974; Booth et al. 1997). Soil moisture has been shown to be a critical factor in big sagebrush germination and germination rate (Sabo et al. 1979; Walton et al. 1986). Schuman and Booth (1998) and Schuman et al. (1998) have shown that good quality Wyoming big sagebrush seed broadcast on the soil surface with some type of mulch may persist for at least four years with additional natural recruitment occurring as "safe sites" develop and temperature and soil moisture conditions become optimum for seed germination and seedling development. In fact, Cawker (1980) and Lyford (1995) concluded that inadequate moisture is the predominant factor in determining big sagebrush mortality during and after the first growing season. Therefore, it is not surprising that Maier (1999) found above average December and January precipitation (following year of establishment) positively correlated to big sagebrush establishment in Wyoming. Weldon et al. (1959) reported that light level was critical to sagebrush seed germination; hence, seeds on the surface of the soil can readily experience wide moisture conditions. Seedbed Considerations In the last two decades much research has evaluated the role and effect of the seedbed on big sagebrush establishment (Schuman et al. 1998; Robertson 1972; Monsen and Meyer 1990). Schuman et al. (1998) found that some type of mulch (surface straw mulch or stubble mulch) greatly increased the establishment of big sagebrush on mined lands. They concluded that the mulch reduced soil water evaporation, reduced diurnal temperature fluctuations, and aided in the development of "safe sites" for sagebrush to germinate and become established (Schuman et al. 1998; Schuman et al. 1980). "Safe site" development is not simply a modification of microclimate factors but also includes mycorrhizal inoculum that will enhance seedling development and survival. The stubble mulch also increased soil moisture conservation by trapping snow during the winter months (Schuman et al. 1980) which will greatly aid seed germination and seedling development. Monsen and Meyer (1990) also found that big sagebrush germination and establishment was enhanced by snow management through placement of snow fencing to increase the probability of snow drifting on direct seeded plots. Schuman et al. (1998) also found that direct placed topsoil significantly increased first year sagebrush seedling densities on mined land compared to topsoil that had been stockpiled for 5 years. They concluded that the improved sagebrush seedling density was attributed to