Browsing Journal of Range Management, Volume 49, Number 3 (May 1996) by Title
Now showing items 13-16 of 16
Season and sex influences on botanical composition of cattle diets in southern New MexicoWe conducted a study in southern New Mexico to determine seasonal variation in botanical diet composition of cattle and to compare cow and steer diets. The climate and vegetation is typical of semidesert grassland. Fecal samples were obtained from a group of cows and steers during spring, summer, fall, 1989; winter and summer, 1990. Results showed that cattle diets were highest in grass content during spring (57%), summer (78%), and winter (54%), while fortes comprised the highest proportion of cattle diets during the fall (47%). Shrubs were moderately important during winter (18%). Dropseeds (Sporobolus spp.), black grama (Bouteloua eriopoda [Torr.] Torr.), threeawn species (Aristida spp.), and leatherweed croton (Croton pottsii [Klotzch] Muell. Arg.) were key forage species for cattle. The importance of these species varied with season, availability, physiological stage, and presence of other species. Differences between cow and steer diets varied with season. The relative similarity ranged from 70% (fall) to 90% (summer). The lower fall similarity compared to that in the summer might be related to physiological variation or past differences in grazing experience between cows and steers. For practical purposes, steer diets might generally be used to represent cow diets, but caution should be exercised during periods of low forage quality.
Seasonal grazing of Columbia milkvetch by cattle on rangelands in British ColumbiaThere is a dearth of knowledge on the selection and utilization of Columbia milkvetch (Astragalus miser Dougl. ex Hook. var. serotinus) by grazing livestock on rangelands in British Columbia. Four grazing trials were conducted with cattle on Columbia milkvetch range in southern interior British Columbia. In the first 2 trials during 1990 and 1991 cattle grazed an upper grassland site in late spring. In 1992 and 1993, the animals grazed a lodgepole pine forest site during early summer. The density of Columbia milkvetch and its basal area were similar at both locations. The Columbia milkvetch was not a preferred species on the grassland site as indicated by the bite count technique that determined its percentage in the diet. Consumption of Columbia milkvetch increased gradually as other forage species were preferentially selected and depleted. On the grasslands, consumption of Columbia milkvetch by individual animals did not show an addictive pattern. At the forest site, utilization of Columbia milkvetch was determined on a weekly basis during 1992 and on a biweekly basis during 1993 by paired plots. In contrast to the grassland site, Columbia milkvetch was a preferred species at the forest site where it was utilized to a greater extent than grasses or other forbs. Approximately 80% of the Columbia milkvetch was utilized during 1992 and 60% during 1993, which was significantly greater than the utilization of grasses or other forbs. Forage nutrient analysis at the forest site indicated Columbia milkvetch had higher crude protein and lower ADF content than other forages but it caused livestock poisoning in 1993.
Shrub-grassland small mammal and vegetation responses to rest from grazingBetween 1989-1991, I studied the effects of livestock grazing on vegetation and small mammals in semiarid shrub-grassland habitats of south-central Utah. Responses were measured at 2 spatial habitat scales; patches and macrohabitats. Patch-scale data were obtained from 4 small (<1 ha) livestock exclosures and nearby grazed areas. Macrohabitat-scale data were collected at 4 actively grazed sites and 4 comparable, excellent condition sites, ungrazed for 30+ years. Ungrazed patch and macrohabitat sites had more surface litter, greater perennial grass cover, and taller perennial grass plants, but treatment response varied among sites. Small mammal responses were apparent only at the macro-habitat scale, where ungrazed sites had 50 % greater species richness and 80% higher abundance. Small mammal reproductive activity and biomass were not affected by rest from grazing at either scale. Small mammal community composition varied greatly among sites and within treatments. This variability has important implications for ecological monitoring efforts involving these species.
Soil water effects on growth and nutrition in upland pasturesNormally the oceanic climate of Scotland maintains soils at low levels of soil water deficit. Field data for such a year are presented and compared with those for an unusually dry year, with the objective of assessing to what degree dry spells might limit herbage production in upland pastures. One meter square plots were sampled on selected dates on reseeded pastures growing on each of 3 cambisols, each derived from different parent materials. The swards were unfertilized and maintained at nominal heights of 2, 4, 7, and 10 cm by cutting every 2 or 3 weeks to manipulate growth and demand for P and N. Overall yield was 25 to 50% lower in the dry year compared with an average year. Peaks and troughs in growth rates, measured as yield at each cutting, and in P and N content, corresponded to changes in soil water deficit in the top meter of soil. The linear correlation coefficient between soil water deficit and growth rate was -0.894 (P = 0.001). Although there was some variation in volumetric water content between soils, soil water deficits were similar in all the cambisols. Yields and nutrient contents were generally similar for herbage harvested from the 2 soils having basic parent material (one a eutric and one a dystric cambisol) and lower on the dystric cambisol derived from schists. The effects of water content largely over-rode cutting treatments, demonstrating that dry spells occasionally occurring in the oceanic climate of Scotland can significantly affect grassland production.