Selection of Forest Inventory Cycle Length Based on Growth Rate and Measurement Variability

Abstract

As pressures on forest resources mount, there is an increasing need for up-to-date information on which sound management and policy decisions can be made. This is evident in the adoption of shorter inventory cycle lengths for national forest inventories in the past few decades. While these intensified efforts are meritorious, substantial efficiency can be lost if cycle lengths are too short in relation to growth in the population. Specifically, if growth is small in relation to measurement variation, the signal-to-noise ratio is small and considerable expense is incurred to obtain data of limited usefulness. To address this issue, the relationships between measurement variation and growth rates were examined across a spatial gradient in the eastern United States. As tree measurements are often not used directly, these relationships were also analyzed in the context of tree biomass prediction models of varying complexity. The results indicated that for latitude range N 30 –38 degrees, where many fast-growing plantations are found, cycle lengths as short as 3 years may be acceptable if the biomass model only relies on tree diameter; however, increased cycle lengths should be chosen for more northerly latitudes. Longer cycle lengths are also suggested when employing more complex biomass models requiring additional inputs such as tree height and crown ratio, which are subject to higher levels of measurement variability. The methods provide a framework for determining cycle lengths that may considerably improve the efficiency and effectiveness of ongoing forest inventory and monitoring efforts.

Citation

Westfall, James A. 2015. Selection of Forest Inventory Cycle Length Based on Growth Rate and Measurement Variability. Forest Science. 61(1): 17-24. https://doi.org/10.5849/forsci.13-202.