It is common knowledge that white pine, Pinus strobus L., was an important component of the primeval forests in northwestern Pennsylvania. It appears that the species generally occurred as scattered individuals in mixture with hemlock and hardwoods but occasionally formed pure or nearly pure stands. In view of the inability of white pine to satisfactorily reproduce and develop under dense canopies of species such as hemlock, beech and sugar maple, the question naturally arises as to how it originated in the virgin stands. Did the virgin white pine originate on relatively open forest sites, as pure pine stands commonly do today, or did it develop under relatively open forest canopies? Heretofore, so far as is known to the writers, there has been no direct attempt to answer this question.The methods employed in the investigation here reported consisted essentially in comparing stem and basal branch features of pines which developed in virgin forest stands with the features of pines now developing ( 1) on open sites such as clear cut or old field areas and ( 2) on sites which support a somewhat open forest stand (density usually 0.3 to 0.6, which appears to be about the maximum density under which white pine is capable of development). All trees employed in the study developed on similar welldrained soils in the same general climatic region.Data representing virgin forest conditions were obtained from two localities in northwestern Pennsylvania, namely, Heart's Content and Ludlow. At Heart's Content the pine occurred as scattered individuals in a virgin hemlockbeech stand. Based on the number of individuals in the dominant tree class white pine had an abundance of approximately 11 per cent ; there were about 7 pine trees per acre. At Ludlow the virgin stand contained a considerably larger proportion of pine; in fact it must have approached a pure pine forest over portions of the area. The average number of pine trees per acre was about 20. From the standpoint of size the pines in these two virgin stands were similar.
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