An optimal cross-sectional sampling scheme for red oak borer scars within northern red oak boles

We selected three red oak borer infested northern red oak with varying heights along a latitudinal gradient throughout the Ozark and Ouachita National Forests in Arkansas. We cut the entire length of each tree bole into cross-sections ~5 cm thick, sanded top and bottom surfaces and dated all scars to the year of adult emergence within each bole. Currently, this procedure requires 200+ hours of processing time per tree. We wanted to devise a sampling strategy which minimized the number of cross-sections per tree necessary to obtain sufficient data concerning population patterns of the borer within oak dominant stands. Calculated normalized rise from the base indicated that the majority of scars, especially those recording earlier borer cohorts, occured between 0.1 and 0.5 on tree boles. We tested four potential strategies where the dated distribution of all scars within a particular section of the bole was tested against the distribution from the entire-tree. Dated scars within all strategies revealed a temporal distribution that was not significantly different from the entire-tree distribution tested separately for all three trees. Strategies including the lower 20% and 30% of host tree boles minimize labor efforts by 75-85% and proportional loss of data by 7-23%. Sampling the lower 20% of boles is favorable if study objectives are to determine patterns of red oak borer activity across larger geographic areas. However, sampling the lower 30% of boles may be favorable if activity within fewer stands is desirable as proportional loss of data is less.