Introduction and evaluation of possible indices of stand structural diversity

Stand structural diversity is useful in forecasting growth and can be indicative of overall biodiversity. Many variables that indicate structural diversity can be measured. However, species, diameter, and height are commonly measured and indicate changes in vertical and horizontal stand structure. Indices based on the distribution of basal area per hectare by diameter, height, and species were derived and evaluated by applying them to simulated and actual data sets with a wide variety of stand structures. Extending the Shannon index of diversity to proportions by species, diameter, and height resulted in reasonable results with more diverse structures having higher values. However, diameter and height ranges must be divided into classes to use these indices. A new index based on the variances of the target stand, relative to the variance of a uniformly distribution stand, showed similar diversity measures to that of the Shannon index, without the need for dividing the diameter and height data into classes. Examination of these indices for use in growth and yield modelling of complex stands is needed.