Plot Level Estimation Procedures and Models

Abstract

Quantitative variable raw data recorded in the sample plots require pre-processing before the NFI estimators of totals and densities can be used to produce statistics. The objective of the plot level estimates is to estimate the variables of interest for each sample point expanded to the 1 km2 area of the cell that the point represents. The intensity and complexity of the computations vary considerably depending on the variable, the way it is obtained by the measured items (e.g., DBH measurement vs. basal area), whether all the items in the sample plot or only a subsample of them are measured, and the availability of models. The definitive result of the computations are tallies, volumes, biomass and carbon stocks but estimates of additional variables at intermediate steps may be needed (e.g., total tree height). This chapter describes the methods and the models used in INFC2015 for the estimation of the variables related to trees (e.g., tallies, basal area), small trees and shrubs (e.g., biomass, carbon stock), stumps (e.g., volume, biomass), stock variation (e.g., the wood annually produced by growth and that removed). Some of the models described were produced in view of the INFC needs, before and after it was established in 2001, while others were created during the NFI computation processes. Finally, the conversion factors needed to estimate the biomass of deadwood, saplings and shrubs were obtained through an additional field campaign of the second Italian NFI (INFC2005) and the following laboratory analyses.