Browsing Journal of Range Management, Volume 54, Number 2 (March 2001) by Title
Now showing items 15-18 of 18
Technical Note: A simple method for preparing reference slides of seedMicrohistological analysis has become the most commonly used and successful method for determining micromammal diets. However, this technique has a number of limitations, particularly when used on fecal samples where identification of some items is difficult. This method underestimates those nearly unrecognizable plant parts in the diet, such as seed, and overestimates easily identifiable parts, such as leaf epidermis. In this note we describe a simple technique that uses a macerating solution of 17.5% NaHCO3 for preparing reference slides of seeds. Advantages of the proposed method are discussed and compared with Jeffrey's technique.
Technical Note: Early harvest of squirreltail seedSquirreltail (Sitanion hystrix (Nutt. J. G. Smith), a native, cool-season perennial bunchgrass of the Intermountain West has been shown to reinvade degraded rangelands invaded by exotic annual weeds. However, one limitation to mechanical seed collection of this species is the disarticulating nature of the rachis at seed maturity. The purpose of this research was to determine if early harvest of the inflorescence before disarticulation would result in viable seed. After anthesis, seeds were collected weekly in 1995 and about every 10 days in 1996 at a research site near Prineville, Oregon. Seeds were germinated for 21 days at a constant temperature of 20 degrees C. Germinable seeds were present at all collection dates from late anthesis to seed shatter in 1995, and all but early anthesis in 1996. Total germination, rate of germination and seed weight increased as seeds were collected later in the summer. Collection of squirreltail seed when a majority of seed awns have moved from a reddish to a divergent, straw colored appearance resulted in germination properties similar to fully mature seed. This occured about 1 week prior to the onset of seed head disarticulation.
Technical Note: Physical and chemical comparisons between microphytic and non-microphytic soil seedbedsIn arid and semi-arid climates, the physical and chemical nature of the soil seedbed greatly effects success or failure of plant recruitment. We hypothesized that the presence or absence of microphytic soil crusts may influence the character of soil seedbeds. To test this hypothesis, we compared chemical and physical attributes of the soil seedbed (0-6 cm) between adjacent areas of well-expressed microphytic soil crusts and non-microphytic soil surfaces for 2 sites on granitic alluvial fans in north-western Nevada. As compared with non-microphytic areas, microphytic soil seedbeds were finer-textured and contained more DTPA-extractable Mn, Cu, and Zn. Further research should examine in greater detail the role of microphytic soil surfaces in eolian dust entrapment, its relationship to nutrient deposition, and the interaction with seed recruitment.
Vegetation and water yield dynamics in an Edwards Plateau watershedWoody cover, when expressed at the scale of the 207 km2 Cusenbary Draw basin, remained unchanged (approximately 23%) from 1955 to 1990. When expressed at the scale of range sites, woody cover declined on sites with relatively high production potential and increased on sites with relatively low production potential. Change in woody cover distribution at sub-range site scales, increased low and high woody covers and decreased intermediate woody cover, would be expected to lead to increased water yield at the basin scale because there was an apparent threshold woody cover (approximately 20%) above which simulated evapotranspiration (ET) changed little with increasing woody cover. This potential increase, however, was more than offset by the decreased water yield due to increased ET loss associated with compositional changes of woody vegetation from oak to juniper. A set of woody cover-ET regression curves was developed for different range sites based on simulation studies using the SPUR-91 hydrologic model. Based on these woody cover-ET regression curves and GIS analysis, no brush management would result in a 35% decrease in water yield, while a hypothetical brush management cost-share program would increase water yield by 43% over the 1990 level. Benefits in water yield and forage production from brush management differ in different range sites. A brush management cost-share program that preferentially allocated brush management to sites with deep soil and the highest forage production potential increased water yield by 50%, compared to a 100% increase if brush management were preferentially allocated on sites with shallow soil and highest water yield potential. These model results illustrate that the spatial scale of assessment and spatial distribution of brush management among range sites should be important concerns associated with developing and evaluating brush management policies.