West, this species was selected for study. The investigations were designed to determine its response to various intensities, frequencies, and seasons of herbage removal under favorable (artificially watered) and unfavorable (arid) environment. The responses were evaluated on the basis of forage yield, chemical composition of herbage, apparent vigor, seed production, root yield, and root reserves. • REVIEW OR LITERATURE The effect of frequency and intensity of clipping on the yield and vigor of various pasture and range plants has received considerable study. These investigations have dealt with a great variety of conditions and methods and in general they show that yield and vigor decrease as frequency or intensity of clipping is increased (
This article is published out of the order determined by the receipt of the manuscript at the expense of funds other than those of the Ecological Society of America.
D URING the past decade much attention has been given to the great range lands of the West. These lands are inherently low in productivity because of aridity. Abnormal drought and constantly heavy use by livestock have caused the vegetation over much of the area to become greatly depleted. The forage has decreased in quantity, but more serious in many cases is the decrease~ in quality. Valuable species have been replaced by less valuable or even worthless ones. Because of the serious nature of these changes a number of ecological studies have been conducted on native grass to determine the reason for range deterioration.The studies were made during the summer of 1938 in southern Cache Valley, Utah. The observed range occupies the benches and foothills above the more moist valley floor and is roughly comparable to the northern intermountain grasslands.Originally bunch wheat grasses, Agropyron inerme (Scribn. and Smith) Rydb. and Agropyron spicatum (Pursh) Scribn. and Smith, were apparently dominant on the benches and alluvial fans. 3 Sagebrush, Artemisia tridentata Nutt., was generally subdominant to the grass but dominated the vegetation on some exposed slopes.The present abundance of sagebrush on the heavily-grazed benchland and the sparsity of bunch wheat grass suggest invasion of sagebrush into climax grassland. Bunch wheat grass is scarce or lacking in many places along the benches. That this grass had been dominant is evidenced by the presence of an almost pure stand of wheatgrass on one side of a range division fence and almost pure sagebrush or sagebrush-weed on the other (Fig. r). On parts of the range where grazing has been more moderate wheatgrass is still abundant, but it has undergone considerable reduction in number and size of plants.The question naturally arises as to the causes within the plant which led to the disappearance or severe reduction of the wheatgrasses under current grazing practices. Investigators have recognized the importance of food accumulations in .the economy of the plant; but other than the work done by McCarty (7, 8, 9) 4 and Aldous (r), little investigation of carbohydrate relationships of range forage species has been undertaken. This phase of the problem has to do with the permanence of the climax plants and the sustained yield of forage from year to year. Closely allied are the relationships of underground parts to longevity and forage yield. Because roots are less apparent and more difficult to study, they are often neglected in the consideration of a plant.
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