Abundance and Size Distribution of Cavity Trees in Second-Growth and Old-Growth Central Hardwood Forests
In central hardwood forests, mean cavity-tree abundance increases with increasing standsize class (seedling/sapling, pole, sawtimber, old-growth). However, within a size class, the number of cavity trees is highly variable among 0.1-ha inventory plots. Plots in young stands are most likely to have no cavity trees, but some plots may have more than 50 cavity trees/ha. Plots in old-growth stands often had 25 to 55 cavity trees/ha, but individual plots ranged from 0 to 155/ha. The Weibull probability density function was used to mathematically describe the variation in cavity-tree abundance for plots in stands of differing size (or age) class. A graph of the cumulative probability of cavity-tree abundance is a particularly easy way for managers to estimate the probability that a stand of a given size class will have any specified number of cavity trees per hectare. Results for individual plots or stands can be combined to estimate cavity abundance probabilities for landscapes. Because the results are presented in terms of plot-size classes (or age classes), this approach to cavity tree estimation is compatible with relatively simple forest inventory systems.