Forest inventories assisted by wall-to-wall airborne laser scanning (ALS), have become commonpractice in many countries. One major cost component in these inventories is the measurementof field sample plots used for constructing models relating biophysical forest attributes to metricsderived from ALS data. In areas where ALS-assisted forest inventories are planned, and in whichthe previous inventories were performed with the same method, reusing previously acquired fielddata can potentially reduce costs, either by (1) temporally transferring previously constructedmodels or (2) projecting field reference data using growth models that can serve as field reference data for model construction with up-to-date ALS data. In this study, we analyzed these twoapproaches of reusing field data acquired 15 years prior to the current ALS acquisition to estimatesix up-to-date forest attributes (dominant tree height, mean tree height, stem number, stand basalarea, volume, and aboveground biomass). Both approaches were evaluated within small standswith sizes of approximately 0.37 ha, assessing differences between estimates and ground referencevalues. The estimates were also compared to results from an up-to-date forest inventory relyingon concurrent field- and ALS data. The results showed that even though the reuse of historicalinformation has some potential and could be beneficial for forest inventories, systematic errors mayappear prominent and need to be overcome to use it operationally. Our study showed systematictrends towards the overestimation of lower-range ground references and underestimation of theupper-range ground references.
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