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Cattle weights 4 Vegetation measurements 4 Climate and weather 5 Experimental results 5 Cattle weight gains 5 Weight gains per head 5 Weight gains per acre 8 Effects on the range vegetation 9 Changes in ground cover 10 Changes in composition 13 Changes in herbage production 13 Reaction of vegetation to 1954 drought. .. .14 Mechanical impact of concentrated stocking. .14 Summary 15 Common and botanical names of plants mentioned. .16 Early-and Late-Season Grazing Versus Season-Long Grazing of Short-Grass Vegetation on the Central Great Plains by Graydon E. Klipple Cattle that graze range vegetation of the short-grass association on the Central Great Plains usually produce much larger weight gains during May, June, and July than they do during August, September, and October. This has induced many cattle producers using short-grass rangelands to make large increases in the stocking of their range during the early period, and reduce the length of the grazing season. In this arrangement, steers are sold when the feed is utilized. In the 1940's the Rocky Mountain Forest and Range Experiment Station received numerous inquiries as to the amount of increase in cattle weight gains per acre that could be expected from this early accelerated stocking practice, and the effect of the practice upon the range vegetation. A study was made at the Central Plains Experimental Range 3 near Nunn, Colorado, to obtain information on these questions. This report summarizes results of the study. Operated at the time of the study by the Forest Service in cooperation with the Soil Conservation Service and the Crow Valley Livestock Cooperative Association on a portion of the northeastern Colorado Land Utilization Project. EXPERIMENTAL DESIGN Nine pastures were used: seven, approximately a half-section each, one, 400 acres, and one, 200 acres. They were divided into three blocks of three pastures each, with each block representing a different subtype of the short-grass association (table 1). These subtypes are typical of the short-grass vegetation of the Central Great Plains. Grazing Treatments Treatments were three different periods of grazing, designated as follows: Length of Approximate grazing period dates Season-long 6 months May 10-Nov. 10 Early grazing 3 months May 10-Aug. 10 Late grazing 3 months Aug. 10-Nov. 10 Cattle grazed in an early-grazed pasture were moved to the late-grazed pasture in the same block. Grazing treatments were randomized within blocks in 1943 and repeated without change each year from 1943 to 1952. All pastures were grazed as nearly as possible to the same intensity-removal of approximately 40 percent by weight of the l

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M ETHODS of making surveys of range land vegetation have been evolving slowly for a period of more than 30 years. Since the beginning, determination of density or spread of vegetation above the ground has been an integral part of survey procedure. Originally, density was estimated by the system common to the reconnaissance method of range surveying (3). 3 More recently a method of determining density known as the square-foot density or point-observationplot method has been developed by Stewart and Hutchings (4), and this method is now optional in standard range survey instructions (3). Questions and comments which have arisen asa result of the use of the optional ·square-foot density method in range surveys have emphasized a need for specific information on sampling intensity as reflected in number of plots required for an estimate within given limits of accuracy.This paper, based on sample plot data recorded from all major range vegetation types in Colorado, Wyoming, and the Black Hills region of South Dakota, deals with sampling intensity in relation to reliability of mean densities and forage factors secured by the squarefoot density method. It also presents the relationships between number of plots required for a reliable sample and (a) size of area sampled, (b) vegetation type, and (c) adequacy of sampling as determined by the purpose of the survey. SOURCE AND NATURE OF THE DATA A very considerable mass of data, obtained through the use of the square-foot density method of making range surveys, has been assembled by the Rocky Mountain Forest and Range Experiment Station. Observations on 4,620 plots were obtained in a general survey of range conditions throughout Colorado and Wyoming and in the Black Hills of South Dakota in October 1935. A forage inventory of Colorado and Wyoming, started in the spring of 1936, resulted in observations on 44,123 sample plots by November 1938. These data were supplemented by 24,476 sample plots which were established by various state and federal agencies• under careful supervision and coordination during 1936 and 1937.The basic data on all plots were recorded on Form 764b of the instructions for range surveys (3) or on similar forms. Species were listed by vegetation types and their densities were recorded directly in square feet or fractions thereof for each plot. Plot locations within any type area were determined by throwing a stone into the type to locate the first plot and by stripping or grid-ironing at a predetermined sampling interval until the necessary number of plots was established.