Table 1 Synoptic comparison of the 6 NFI surveys under review according to major sampling and inference criteria. aThe American NFI is termed Forest Inventory and Analysis, bKMD: knight’s move design, cUSS: Unaligned systematic sampling, dSU: sampling unit
From: Take five: about the beat and the bar of annual and 5-year periodic national forest inventories
NFI survey | Geometric design | Periodicity | Paneling geometry | USS conditionc | Distance between panel SUd | SU status (field plot) (+ cluster SU number and between-Su distance) | Estimation framework | Reference |
|---|---|---|---|---|---|---|---|---|
French NFI | Square grid | 5 years | Squared sub-grids (KMDb), 5 panels | Yes, su location randomization within cells | 2√5 km (4.5 km) | Semi-permanent su (5 years) | Moving-average estimator (5 years) | Vidal et al. 2005 Bouriaud et al. 2023 |
Polish NFI | Square grid | 5 years | Squared sub-grids (KMD), 5 panels | No | 4√5 km (9 km) | Permanent cluster (5 su, 400 m) | Moving-average estimator (5 years) | Michalak & Zajączkowski (2010) Talarczyk (2014) |
US FIAa | Hexagonal grid | 5 years (+ variations) | Parallelogram-shaped sub-grids (KMD), two directions (unaligned) | Yes, su location randomization within cells | 17/11.3 km in the two panel directions | Permanent cluster (4 su, 36.5 m) | Multiple estimators including the moving-average estimator (5-years) and the time-independent estimator | Bechtold & Patterson (2005) Westfall et al (2022) |
Norwegian NFI | Square grid | 5 years | Latin squares, 5 panels | Yes, randomization of panel cell location | 9/37 km between cluster centers (min, max) | Permanent cluster (9 su,3 km) | Moving-average estimator (5 years) Single-panel estimation at a country level | Breidenbach et al. (2020) |
Swedish NFI | Strips and parallelogram-shaped grid | 5 years | Parallel bands of parallelogram-shaped cells (two directions, unaligned) | No for permanent su, 2 positions for temporary su | 4√5/√5 km (9/2.2 km) in the two permanent panel directions variable for temporary strips | Temporary and permanent clusters (8 to 12 su, 200 to 600 m depending on regions) | Moving-average estimator, weighting of estimations from permanent and temporary samples | Ranneby et al. 1987 Fridman et al. 2014 |
Romanian NFI | Rhomboid grid | 5 years | Parallelogram-shaped sub-grids (one single direction) 4 panels | No | 4√5 km (9 km) 2√13 km (7.2 km) in the two panel directions | Permanent cluster (4 su, 250 m) | Full cycle (time independent) Single panel estimations | Bouriaud et al. 2020 |