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The effects of clipping to a 2.54 cm (1 inch) height at 5 stages of development of western North Dakota mixed prairie were investigated. Soil moisture content at the beginning of the growing season had a greater effect on yields than did the clipping treatments. Observations from this two-year study indicate that soil moisture removal was not affected by the clipping treatments. Clipping significantly affected peak yields by needle-and-threadgrass (Stipa comata) and the Carex species during 1977; and the miscellaneous grasses (Agropyron smithii and Agropyron subsecundum) during 1978, at the sandy loam site. No significant differences in yields were observed for the other species and groups at the sandy loam site, or, the species and groups at the loam site for the two-yearperiod. Late season livestock gains in western North Dakota may be improved if the amount of blue grama (Bouteloua gracilis), the dominant palatable warm-season shortgrass, could be increased without decreasing the overall productivity of the range. Whitman (1953) reported that normal grazing usage results in a cover which is probably of greater grazing value than the completely protected cover. Employing a deferred and rotation system, Sarvis (1923) reported greater total gains on fewer acres when compared to a continuous grazing system. Under the deferred and rotation system, the vegetation was allowed to mature periodically before being subjected to grazing again. A new system of ranching, referred to as the Short Duration Grazing or SDG system, was developed in Rhodesia in 1964 (Goodloe 1969). This system consists of a high intensity-low frequency harvesting of the forage, even with intensive harvesting range conditions improved under the semiarid climate where the SDG system was developed. The present study was designed to determine the effect of intensive harvesting on the developmental stages of Northern Great Plains mixed prairie. Clipping results in more severe injury to grass stands than does defoliation from normal grazing use (Whitman et al. 1961). Although clipping does not directly duplicate the effects of grazing, considerable information may be gained by the reactions of species to foliage removal (Sarvis 1923). The effects of clipping on the Northern Great Plains have been reported by different authors. In South Dakota, Black et al. ( 1937) reported that frequency of clipping buffalo grass (Buchloe dactyloides) and blue grama appeared to have little effect on yield. Total production of buffalo grass, blue grama, western wheatgrass (Agropyron smithii), plains bluegrass (Poa arida), and six weeks fescue (Festuca octoflora) was greatest when clipped at 40-day intervals. Total production by all plants was also greatest when clipped at 40-day intervals. Two vegetation types in western North At the time of the research, authors were graduate student and chairman, Botany Department, North Dakota State University, Fargo, 58105. Holderman's present address is Ozark Francis National Forests, P.O. Box 1008, Russellville, Arkansas 72801. This report is a contribution of North Dakota Agricultural Experiment Station. Published with approval of the Director as Journal Paper No. 1091. Manuscript received October 19, 1979. Dakota, a western wheatgrass-blue grama type, and a needle-andthreadgrass (Stipa comata)-blue grama-sedge (Carex spp.) type were studied by Whitman and Helgeson (1946). Average yields for blue grama decreased in both vegetation types when clipped twice during a season to a height of 1.27 cm (1/2 in). Needle-andthreadgrass decreased under all clipping treatments in height, yield, and basal area. Average yields for western wheatgrass were maintained under single clipping to a height of 3.81 cm (1 1/2 in) and 7.62 cm (3 in), but decreased under double clipping. Sarvis (1923) reported blue grama was benefited by frequent clipping while needle-and-threadgrass decreased in relation to clipping frequency. Heinrichs and Clark (1961) in Saskatchewan, and Whitman et al. (1961) at Dickinson, North Dakota, reported that yields of green needlegrass (Stipa viridula) increased when clipped 2 or 3 times a year compared to annual clipping. These studies applied periodic and/or annual clipping treatments. The present paper reports the response of Northern Great Plains mixed prairie to intensive clipping at five stages of development, with respect to peak yields and basal cover of selected species and groups, and the seasonal removal of soil moisture in the profile. Description of Study Locations This study was carried out on two major range sites in western North Dakota. Vegetation of the region is mixed grass prairie as described by Weaver and Clements (1938). Study site I is located approximately 9.6 km (6 miles) northwest of the city of Dickinson on a sandy loam of the Vebar-Parshall-Arnegard toposequence (Larson et al. 1968). Dominant perennial grasses are needle-andthreadgrass, green needlegrass, blue grama, prairie Junegrass (Koeleria cristata), and Sandberg bluegrass (Poa secunda). The miscellaneous grasses are dominated by western wheatgrass and bearded wheatgrass (Agropyron subsecundum). Major Carex species are C. filifolia, C. eleocharis, and C. heliophila. Study site 2 is located approximately 14.4 km (9 miles) southeast of the town of Medora on a loam soil similar to the Shambo series (U.S. Dep. Agr. Forest Serv. 1971; and personal communication with Ken Thompson, Soil Conserv. Serv., Dickinson, N.D.). Dominant perennial grasses are western wheatgrass, blue grama, prairie Junegrass, and needle-and-threadgrass. The miscellaneous grasses are dominated by green needlegrass (Stipa viridula) and Sandberg bluegrass (Poa secunda). Major Carex species are C.filifolia, C. eleocharis, and C. heliophila. Scientific and common names follow Stevens (1963). Abbreviated scientific names follow the Range Analysis Handbook U.S.F.S. (1977). The climate of the region is semiarid with an annual precipitation between 40.13 cm (15.80 inches) and 42.06 cm (16.56 in), 75% of which falls during the growing season April through September. Experimental Procedures The experimental plots were randomly located with three repli188 JOURNAL OF RANGE MANAGEMENT 34(3), May 1981 This content downloaded from 157.55.39.55 on Sun, 12 Jun 2016 05:40:36 UTC All use subject to http://about.jstor.org/terms cates of eight treatments on each of two study sites. Plot size was 10.1 m by 11.9 m (33 ft by 39 ft) with four rows of six plots. Plots were subdivided into six 3.96 m by 5.03 m (13 ft by 16.5 ft) subplots, half of which were randomly selected to be sampled for above ground biomass in alternating years. Six-foot alley ways were left between plots to facilitate movement. Five of the treatments were clipping trials, two were herbicide trials, and one the control which received no treatment. This paper reports only the results of the |
