Treesearch

Successful natural regeneration of Engelmann spruce in small clearcut openings depends on weather and aspect and is modified by cultural treatments. Small clearcut openings (1-2 ha) can be successfully regenerated on north aspects with mineral soil seedbeds and shade. On south aspects, shade is absolutely essential for any survival. However, successful natural regeneration is not likely regardless of cultural treatments. Drought is the most serious cause of mortality; but clipping by birds, frost heaving (north aspect), heat girdle (south aspect), and snowmold (north aspect) caused...

Differential scanning calorimetry has been applied to three woody laboratory fuels studied in current wild/and fire modeling research. The heat required to increase a fuel's temperature to ignition is an important modeling parameter affecting the rate of fire spread. Below 200° C, ground fuel-stick samples had similar heat requirements, but above 200° C the heat of preignition varied up to 19 percent among fuels. Therefore, these variations can affect fire spread rates similarly to variations in moisture content. A consistent set of data is provided for calculating the heat of preignition....

This proceedings, second in a series of publications of wildland shrub symposia, brings together current knowledge of plants belonging to the chenopod family. Topics addressed by the 46 papers include distribution, systematics, genetics, ecological relationships, physiology, seed technology, animal relationships, and revegetation techniques.

The mountain pine beetle, Dendroctonus ponderosae Hopkins, exhibits variations in morphology, behavior, and physiology over its extensive range. Morphological variation is seen in size differences in beetles from different localities and in the surface sculpturing of various body parts. There are also apparent differences in host selection among populations. While this insect attacks most species of pines in western North America, beetle populations in mixed pine stands may concentrate on one host species (Barker et al. 1971, Wood 1963). This diversity is reflected in the taxonomic history...

During a 2-year study of the fish and macroinvertebrates of a third-order montane stream, a severe drought in the first year resulted in a temporary cessation of surface flow. Flow was continuous during the second year. Some taxa (e.g. Ophiogomphus severus) exhibited higher density during the drought year, others declined in abundance during low flow (e.g. Baelis spp.), whereas a few (e.g. Tricorythodes minuius) appeared unaffected. Total macroinvertebrate density decreased by 50% during the low flow year compared to the normal flow year. Mayflies were most severely affected, but also...

This report summarizes information on distribution, botanical description, habitat conditions, life history, special uses, and genetics of Engelmann spruce.

Accurate, low cost measurements of forage utilization by livestock are essential in range management and the evaluation of grazing systems. However, because of difficulty in making these measurements, visual estimates often are substituted for measured values. To help land managers better determine use, range utilization calculating charts (Crafts 1938, NRCAB 1962) have been revised into a utilization gauge. Height-weight distributions of two additional southwestern grasses have been measured and incorporated into this gauge.Grass gauges are currently available through Colorado State...

The extent of Marssonina leaf blight (Marssonina populi) on quaking aspen (Populus tremuloides) was observed in northern Utah and adjacent States in 1981 aand 1982. Area of the epidemic and symptoms of the disease are described. On 1,000 acres (405 hal) in northern Utah, infection levels were 6 percent slight, 12 percent light, 32 percent moderate, 16 percent moderately heavy, and 34 percent heavy.

Daily activity budgets of male and female Abert's Towhees (Pipilo aberti) were measured in 1980 during the reproductive cycle and then converted into energy budgets to determine the relative demands of different nesting phases. Mean daily energy expenditures (DEEtot) in males reached a seasonal maximum of 126.7 kJ, or 2.16 times basal metabolic rate (BMR), in the prenesting phase. Thermoregulatory demands accounted for higher energy expenses in this phase. The cost for females was also high in the pre nesting phase but was exceeded by DEEtot in the egg-laying phase. Average DEEtot was at a...

Abert's Towhee (Pipilo aberti) is restricted to desert riparian zones of Arizona and bordering states (Phillips et al., The Birds of Arizona, Univ. Arizona Press, Tucson, Arizona, 1964). Its breeding behavior, communication, and physiological responses have been detailed by Marshall (Condor 62:49-64, 1960; pp. 620-622 in Proc. XIII Int. Omithol. Congr., Ithaca, New York, 1962; Condor 66:345-356, 1964), and Dawson (Univ. Calif. Publ. 2001. 59:81-124, 1954), but no information is available on annual productivity. Abert's Towhee is multibrooded, and therefore, the number of broods per season...