Journal of Range Management, Volume 41, Number 4 (July 1988)

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Journal of Range Management, Volume 41, Number 4 (July 1988) Complete digitized issue.

Winterfat diaspore morphology

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Winterfat diaspore morphology Booth, D. T. Diaspores are disseminules specialized for dispersal and for other functions contributing to seedling establishment and seedling vigor. The winterfat (Eurotia lanata) diaspore consists of hairy bracts enveloping a utricle. Testa, embryo, and perisperm make up the enclosed seed. This general diaspore morphology also occurs in Atriplex and Grayia. The potential for seedling establishment is not equal between diaspores and diaspore subunits; therefore, authors should take care to use terminology that refers to the correct entity.

Vigor of needleandthread and blue grama after short duration grazing

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Vigor of needleandthread and blue grama after short duration grazing Reece, P. E.; Bode, R. P.; Waller, S. S. Grazing treatments were applied to pastures in western Nebraska from 1980 through 1983 to examine the influence of short duration grazing (SDG) on plant vigor. The 3 treatments were: (1) 4 years of SDG, (2) 3 years of SDG followed by 1 year of rest, and (3) 4 years of rest. Total nonstructural carbohydrate (TNC) concentrations of stem bases, mean tiller weight, and tiller number/plant of etiolated growth, and paired differences in spring growth between covered and uncovered plants were used to evaluate vigor of needleandthread (Stipa comata Trin. & Rupr.) and blue grama [Bouteloua gracilis (HBK) Lag. ex Griffiths]. Two 7-pasture, 1-herd SDG systems were used. Length of use and deferment periods, stocking density, stocking rate, and sequence of pasture use were constant throughout the study. Grazing treatments reduced the vigor of both study species, but the vigor of blue grama was more sensitive to treatments than needleandthread. Levels of TNC in needleandthread were not affected by grazing treatments. Concentrations of TNC in blue grama recovered to levels of ungrazed plants after 1 year of rest in some but not all pastures. Grazing increased the number of tillers/plant, but reduced total organic reserves of both species as measured by etiolated growth. Assimilates produced in early spring growth appeared to be more important for tiller initiation in plants that had been grazed than in ungrazed plants.

Vegetation response to the Santa Rita grazing system

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Vegetation response to the Santa Rita grazing system Martin, S. C.; Severson, K. E. Changes in vegetation under yearlong grazing were compared with those under the Santa Rita grazing system, a rotation system designed for southwestern US rangelands where 90% of the forage is produced in mid- to late-summer. The study was conducted on the Santa Rita Experimental Range near Tucson, Arizona, from 1972 to 1984. In 1984 there were no differences (P<0.05) in grass densities (16 vs. 17 to 18 plants/m2), forb densities (0.6 vs 0.7 to 1.4 plants/m2), shrub densities (2.0 vs 1.9 to 2.4 plants/m2), or shrub cover (20 vs 21 to 26%) on pastures grazed yearlong or in the Santa Rita rotation, respectively. Lack of response to grazing schedules is attributed to initial plant densities near the maximum the sites could support and to moderate grazing during the study period. Average herbage yields of pastures were not related significantly to grazing treatments but correlated strongly (r = 0.909) with long-time summer rainfall means. Results support the observation that rotation grazing may not improve ranges that are in good condition. It is concluded, however, that the Santa Rita Grazing System may accelerate recovery of ranges in poor condition.