An analysis of mortality inventory tally using large plots compared to tally using small plot clusters

During an inventory to assess spruce bark beetle impact on the Kenai Peninsula in south-central Alaska, 5-year mortality estimates were made for all growing-stock trees on 0.6 ha areas, on 0.4 ha areas, and on a cluster of four 1/60-ha subplots. The analysis of the results of the comparison between cluster data and the larger plot data highlighted some of the problems associated with trying to assess tree mortality from small plots. Based on the large chi square values observed in these tests, there seems to be a strong case for taking a mortality plot that is larger than the four 1/60-ha plots tested here. For the population under study, the smaller plots do not capture the highly variable distribution nature of mortality as well as the two larger plots evaluated.