An examination of the accuracy of the data collected from the yield research plots of the Forest Research Institute
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
The work described in this thesis arose from a concern that the data being obtained from the yield research plots maintained by the Forest Research Institute of the New Zealand Forest Service were inadequate for present day yield research. This was partly because some of the data were considered to be inaccurate and partly because of deficiencies in the types of data being collected. It was thought that one solution to the problem would be to give each plot a detailed final measurement to obtain additional data to supplement those collected during the life of the plot. The first section of the thesis describes the methods of data collection and processing used for the plots, and includes a detailed comparison between data available in the plot records and data obtained from a detailed stem analysis of each of the trees in two of the plots. It is shown that there are errors in both the basic and the computed data, the errors being such that the data are considered unsuitable for detailed research into methods of constructing growth models, particularly those models based on the growth of individual trees. Further analysis of the data collected for the first part of the study suggested that it is feasible to perform a final measurement of each plot during which selected sample trees would be subjected to a stem analysis. The results indicate that a minimum of ten trees per plot should be selected and that sample points should be located near the base of every second annual shoot in each tree. Not only would such a procedure provide accurate data on the growth of individual trees, but it would enable a reduction to be made in the amount of measurement necessary during the life of a plot, thereby reducing the cost of the periodic remeasurements.