Invasive annual grasses, such as medusahead, can reduce forage production capacity and interfere with revegetation projects in California rangelands. Because of the taxonomic similarity to other more desirable grasses, achieving selective control of invasive annual grasses can be difficult. In selectivity trials conducted in Yolo and Siskiyou counties, CA, the herbicide imazapic gave control of many nonnative annual grasses yet provided some level of selectivity to specific perennial grasses used in revegetation projects throughout the western United States. The selectivity difference between newly seeded perennial and annual grasses was greater with PRE applications than with POST treatments. Both perennial and annual grasses within the tribe Hordeae were more tolerant to imazapic than other grass species. In addition, field experiments were conducted at three sites in northern California (Yuba, Yolo, and Lassen counties) and one in southern Oregon (Lake County) to test the response of imazapic to varying management conditions. Imazapic was applied PRE in fall (and also spring in Lake County) at rates from 35 to 210 g/ha on undisturbed rangeland, in comparison with rangeland cleared of standing plant material and thatch by either tillage, mowing and raking, or burning. Imazapic generally showed enhanced weed control when applied following disturbance. Rates as low as 70 g/ha, if combined with thatch removal, provided significant suppression of medusahead. In addition, disturbance alone generally reduced medusahead cover in the following year. Although imazapic showed potential for control of medusahead and other annual grasses, its selectivity window was relatively narrow.
Livestock grazing practices on public and private rangelands throughout the western United States are subject to increasing scrutiny. Much criticism arises from the tendency for livestock to concentrate in riparian areas and to disproportionately use the vegetation to the degree that riparian function and vegetation are compromised. The purpose of this synthesis article is to evaluate grazing-management strategies that encourage beef cattle to use forage resources away from riparian areas and areas where topographical features limit grazing use. Specifically, this paper evaluates individual management strategies and attempts to quantify the changes in distribution patterns and vegetation use. An effective strategy uses water development to encourage uniform distribution. Likewise, timing and duration of grazing have dramatic influences on cattle distribution in riparian and upland range areas. In general, early in the grazing season, when upland forage is green and growing, cattle tend to distribute more uniformly than later in the season, when upland vegetation is dormant and cattle disproportionately use riparian areas. In addition, early in the season, cattle grazing forested rangelands seem to prefer south-facing aspects with more open canopies when compared with late-season distribution patterns when concentration switches to northerly aspects, denser canopies, and more diverse diets. Other factors that appear to influence distribution include cow breed, age, and stage of production. In addition, recent research suggests that as cows age, distribution patterns change: Older cows have been reported to travel further from water than their younger contemporaries as long as adequate forage is available in the uplands. Additional research is needed on beef cattle selection, technological applications, efficient herding practices, supplementation strategies, and whole-range management systems that encourage the sustainable use of rangeland resources. Resumen En los pastizales pú blicos y privados del oeste de Estados Unidos las prá cticas de apacentamiento están sujetas a un creciente escrutinio. Una gran crítica surge de la tendencia del ganado a concentrarse en las áreas ribereñ as y utilizar en forma desproporcionada la vegetació n, al grado de que la funció n ribereñ a y la vegetació n se ven comprometidas. El propó sito de este artículo de síntesis es evaluar las estrategias de manejo del apacentamiento del ganado para carne que motivan al ganado a usar los recursos forrajeros fuera de las á reas ribereñ as y á reas donde las características topográ ficas limitan el uso mediante el apacentamiento. Específicamente, este articulo evalú a las estrategias individuales de manejo e intenta cuantificar los cambios en los patrones de distribució n y utilizació n dela vegetació n. Una de las estrategias má s efectiva es usar aguajes para propiciar una distribució n uniforme. Asi mismo, la época y duració n del apacentamiento tienen dramá ticas influencias en la distribució n del ganado relació n a las áreas ribereñ as...
The objective of this study was to test the combined effect of offstream water and trace mineral salt on cattle distribution in a riparian meadow and its adjacent uplands. From July 15 to August 26, 1996 and 1997, three treatments were each randomly assigned to one pasture in each of three blocks. Sixty cow/calf pairs were then randomly allotted to the grazed pastures. The treatments included 1) stream access and access to offstream water and trace-mineral salt (off-stream), 2) stream access and no access to offstream water or trace-mineral salt (no-offstream), and 3) ungrazed control. The response of cattle was measured through visual observations of cattle distribution, grazing activity and travel distance, cow/calf performance, and fecal deposit distribution. Distribution patterns of the cattle, measured as the distance of cattle from the stream, was characterized by a time of day x treatment x time in grazing period x year interaction (P < 0.05). No-offstream cattle began the day further from the stream than offstream cattle but consistently moved closer to the stream after the morning grazing period (0600 to 0900). Differences in distribution patterns between the two treatments were more pronounced early in the grazing period than late in the grazing period. Grazing activity, fecal deposit distribution, and travel distance of cattle were not affected by the presence of offstream water and trace-mineral salt. Cows and calves with offstream water and trace-mineral salt gained 11.5 kg and 0.14 kg/d more, respectively, than no-offstream cows and calves averaged across years (P < 0.05). Overall, cattle distribution patterns and cow/calf performance were influenced by the presence of offstream water and trace-mineral salt. Changes in distribution were most pronounced early in the grazing season.
To quantify the effects of season of use on beef cattle distribution relative to the riparian area, 52 cow/calf pairs were used to evaluate 1) early summer grazing (mid-June to mid-July), and 2) late summer grazing (mid-August to mid-September) during the summers of 1998 and 1999. Within a block, cow/calf pairs used during early summer were also used during late summer grazing periods. Pastures were stocked to achieve 50% utilization of herbaceous vegetation after a 28-day grazing trial. Livestock location and ambient air temperature were recorded hourly during two, 4-day periods in each season of use. Locations were transcribed to a geographical information system for the study area. Ocular vegetation utilization estimates, forage quality, and fecal deposits within 1-m of the stream were recorded post-grazing. During early summer, cattle were further from the stream (P < 0.01) than late summer, averaging 161 and 99-m, respectively. Cows were observed closer (P < 0.01) to the stream when ambient air temperatures were higher. Fecal deposits within 1-m of the stream were similar (P = 0.13) following early and late summer grazing. Forage quality varied (P < 0.01) between seasons, with early summer forages having lower dry matter, greater crude protein, lower fiber, and greater in situ dry matter disappearance compared with late summer forages. Utilization of riparian vegetation was lower and use of upland vegetation greater during early summer than late summer (P < 0.05). In summary, season of use affected cattle distribution relative to the riparian area, with late summer pastures having more concentrated use of riparian vegetation.
Livestock grazing in riparian areas is an important management issue on both private and public lands. A study was initiated in northeastern Oregon to evaluate the economic and ecological impacts of different cattle management practices on riparian areas. The effect of off-stream water and salt on livestock distribution and subsequent impact on riparian use, water quality, and livestock production was evaluated. A multi-period bioeconomic linear programming model is used to evaluate the long-term economic feasibility of this management practice with a riparian utilization restriction of 35% for a 300 cow-calf operation. The utilization restriction resulted in economically optimal herd sizes 10% smaller than the baseline herd size. With the management practice, cattle were distributed more evenly, consumed more upland forage before maximum riparian utilization was reached, and gained more weight. The economic impacts of these outcomes were increased with expected annual net returns to the ranch for the project ranging between $4,500 and $11,000 depending on cattle prices and precipitation levels.
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