Simulated Grazing Management Systems in Relation to Shrub Growth Responses

Abstract

Little rabbitbrush and snowberry plants were clipped for 5 years to simulate annual browsing at the same time each year, under deferred-rotation, alternate-rest, and rest-rotation grazing systems at each of three different intensities (30, 60, and 90% of herbage removal). The number of new sprouts was increased by some clipping treatments and all intensities of clipping in both species. Sprout length was reduced by all clipping schedules and intensities of clipping on little rabbitbrush but not on snowberry. Mortality of sprouts was high during their first year of growth. Carbohydrate reserves were lowered *for both species by some clipping schedules and by all intensities of clipping. This investigation was undertaken to determine the effects of intensity and time of clipping on the carbohydrate reserves and sprouting responses of two wildland shrubs. Little rabbitbrush (Chryso thamnus viscidiflorus (Hook .) Nutt .) and snowberry (Symphoricarpos vaccini&des Rydb.) were selected as representatives of the sprouting shrubs that are important browse plants for livestock and wild ungulates. Past research on shrub sprouting has been restricted mostly to the effects of burning, chemicals, and mowing or cutting. In such studies all of the top growth was removed to determine the effect of time of cutting and the resultant carbohydrate reserve levels on sprouting responses. We used clipping to deterrnine how browsing might be used to manipulate sprouting. Several researchers have reported a positive correlation between carbohydrate reserve levels in roots of woody plants and the degree of sprouting (Baker,

Carbohydrate Reserve, Phenology, and Growth Cycles of Nine Colorado Range Species

“…An index to proper frequency, intensity, and season of range use must ultimately depend upon the physiological state or condition of the plants within the various communities of the range vegetation. The total environment of the plant, including defoliation effects of grazing herbivores, is reflected in variations in plant morphological characteristics commonly used as indices of plant vigor, such as twig length, number and leafiness of reproductive culms and basal area (Cook et al 1958), herbage yield, leaf and seedstalk heights (Vogel and Van Dyne 1966, Mueggler 1967, and number and length of new sprouts or regrowth after defoliation (Willard andMcKell 1973, Trlica et al 1977). Alteration of individual plant physiological status, concurrent with these morphological changes, often results in community change including declines in productivity and undesirable botanical composition changes that lead to depressions in range condition.…”

Effect of Wildfires on Woody Species in the Monte Region of Argentina

“…Competition probably occurs between sprouts, with some having an advantage over others as evidenced by their continued growth. Willard and McKell (1973) reported the same phenomenon in snowberry (Symphoricarpos vaccinioides) and little rabbitbrush (Chrysothamnus viscidiforus) in which various amounts of sprout mortality were observed on shrubs which had been clipped to simulate grazing and also on intact plants which had been protected from grazing or other forms of herbage removal. Sprouts on algarrobo, calden, molle, and piquillin plants were all vigorously growing; thus it is assumed that little if any sprout mortality will occur in these species.…”

Influence of Grazing on Age-Yield Interactions in Bitterbrush

“…Other studies indicate that grazing during the spring and early summer is more detrimental to shrub vigor than grazing during late summer and fall; e.g., see McConnell and Garrison ( 1966) and Willard and McKell (1973). Therefore, season of use undoubtedly interacted with intensity of use and accentuated differences in grazing response on the two areas, but this did not interfere with our study objectives.…”