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• 34 • <br />depths of ploughing were moderate to shallow during this early drought <br />period of land manipulation. Robert Lang produced a piasters thesis in <br />1941 at the University of Wyoming on abandoned farmland succession from <br />1936 onward and has followed up his earlier work with a Wyoming Agricul- <br />tural Experiment Station Bulletin in 1945 and a further paper on changes <br />through 1965 in a 1973 Journal of Range Management. Lang's record serves <br />as a remarkably timely and fortuitous record of natural plant succession <br />under conditions of both grazing pressure and within exclosures that were <br />fenced and maintained from 1941 through 1965. Lang's work shows that, in some <br />sites under conditions of climatic variability and grazing pressure <br />that are normal for the Powder River Basin area and typical for the coal <br />region of northeastern Wyoming and southeastern Montana, after 9 years <br />vegetative cover co.~nprised only slightly over 3 percent and was but 50 <br />percent of that found on adjacent undisturbed but grazed lands. In 1965, <br />nearly 30 years after the original vegetation surveys were begun, Lang <br />found that range conditions had not improved over those reported >n 1941 <br />and 1945 but had actually deteriorated by 35 percent. Lang attributed this <br />to overgrazing but on study plots that were established on unfarmed lands <br />subject only to grazing pressure, his data show that over the same period <br />of time vegetative cover conditions increased by 10 to 20 percent. This <br />may be due to changes in grazing pressure over the past three decades, or <br />equally probably, due to the increased moderation of climatic extremes <br />that has characterized the late forties through sixties (cf Bureau of Re- <br />clamation, 1974, p. I-116-117). A reduction of cover of 35 percent from <br />