Irvine T. Haig

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The principal object of the study was to determine the roles played by important physical factors of site, chiefly as these vary with overhead shade and hence are within the control of the silviculturist at the time of logging. No special effort was made to study the effect of biotic agents under natural conditions. Indeed, in order to insure as large a sample of seedlings as possible on which to follow losses caused by physical factors, biotic agents were discouraged wherever feasible. But as records of all mortality losses were kept by cause, some information was collected on the activity of biotic factors. Seedlings were classified as to cause of death only after a careful diagnosis and with knowledge of the important agents operating at the time death occurred. Certain check quadrats were used effectively in segregating causes; but the most satisfactory control came in instrumental measurement of important site . factors, including surface soil temperature and soil moisture. As a necessary adjunct in following the occurrence of critical soil moisture conditions, current measurements were made of root penetration.

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