Comparing the efficiency of intensity-based forest inventories with sampling-error-based forest inventories
2014
Strimbu, Bogdan M.
Forest resources can be assessed using two ground measurements approaches: one centred on preset intensity and the other centred on sampling error. The objective of the present research is to evaluate the efficiency of the two sampling approaches using a factorial design, the factors being intensity, area, sampling error and coefficient of variation. Overall, an inventory executed using sampling error is likely more efficient than using a preset intensity (i.e. 89 per cent of the investigated cases). For small tracts (i.e. ≤5 ha) or tracts with one stratum, forest inventories using preset intensities are more efficient, but mainly for reduced intensities (i.e. 5 per cent). For larger tracts and moderate variability (i.e. coefficient of variation ≤30 per cent), resource estimation based on sampling error is more efficient than the intensity-based, especially when the tract is stratified. Stratified random sampling inventories are almost always more efficient than 10 per cent intensity cruises, and, in 90 per cent of the cases, 5 per cent cruises. For balanced strata, the efficiency is so large that tracts with same size but different variability are indistinguishable, from sampling efficiency perspective. Therefore, a preliminary cruise can focus on attributes that are not the objective of the inventory but are related to the attributes of interest, easy, fast and accurate to measure, such as diameter at breast height, basal area or tree height.
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