Ecological Studies in the Tension Zone between Prairie and Woodland

Upon the completion of a series of investigations in southeastern Washington and adjacent Idaho, in which there was found to be a direct relation between the available water content of the soil and the evaporating power of the air as succession progressed from grassland through scrub to forest, the senior writer moved to Minneapolis, Minnesota. Here such excellent conditions of prairie invaded by scrub and followed by forest offered themselves for study that the services of the junior author were enlisted and an analysis of the situation attempted. Later this study was supplemented by similar work carried on at Lincoln, Nebraska. The time-worn controversy as to the origin of the prairies and the absence of trees from this great area of grassland has been a favorite theme for the layman and amateur as well as for the scientist. However, we need not concern ourselves here with a general discussion of the literature. A comprehensive bibliography including papers up to 1911 is given by Shimek; and Clements (1916) summarizes the successional work in the Prairie-Plains Climax. Notwithstanding the fact that the exact methods of permanent quadrat and factor measurements of modern ecology are rapidly replacing the earlier type of observation and deduction, few quantitative data looking towards a solution of the prairie-forest problem are yet available