Injury and Death or Recovery of Trees in Prairie Climate

Several years of decreasing precipitation initiated the 7 years of drought. By midsummer of 1934 it vas clear that the prairie region of the Middle West was undergoing the greatest drought since the beginning of its recorded weather history. The 12 months following June, 1933, was the driest weather period ever recorded not only for the Dakotas, Minnesota, Nebraska, Iowa, Illinois, and Missouri, but also drought in Kansas, Oklahoma, and Colorado was very severe (Kincer 1934). This intensely dry period, as well as those in several of the following years was accompanied by record-breaking temperatures, extremely low humidities, and exceptionally high rates of evaporation. These were the years also of high winds, swarms of grasshoppers, and great dust storms. Great losses were suffered by native trees both along the western margin of woodland and within the area of climax deciduous- forest. Where post- climax forest extends far westward along rivers and streams into the semi-humid and dry grassland climates, losses were extremely heavy (Fig. 1). These losses occurred (luring the past decade of drought despite the fact that in the prairie area and especially west of the Missouri River the more mesic species of trees are not found and only the more drought resistant kinds occur. Compensations for low water content of soil, high wind, and low humidit