A 3-PHASE SAMPLE DESIGN FOR FEDERAL-FORES T-INVENTORY

There are strong limitations concerning an increase in the efficiency of the Federal Forest. Inventory based on cluster samples. The spatial extension of the clusters is too large for consideration of changing heterogeneity of forest, stands planing the sampling design. Furthermo re, the intercorrelation between samples at the edges of a cluster dec reases the efficiency of this kind of sampling. For this reason, a 3-p hase sampling procedure based on terrestrial surveys in single sample plots was developed. Forest area and standing volume were chosen as th e main inventory characteristics. For the first phase of the sampling design, a stratification into forest and non-forest by satellite data is designated. The 1 km x 1 km grid contains the southwestern edges of the clusters of the Federal Forest Inventory. In the second phase sub samples from the first phase sample points are selected. The expected standard error of the forest area estimations in the Federal Republic of Germany by this 2 phase sampling for stratification is at 0.7%, max imally. For the third phase, each area class of the first phase is fur ther stratified into growth zones and age classes. Again, in every str atum a subsample of the second phase sample points is chosen. Each sam ple point selected the third time is the center of a terrestrial sampl e plot. The sampling density can be reduced in younger stands. With 61 08 sample plots in the entire Federal Republic of Germany, the same sa mpling error can be achieved as with the survey of approximately 6000 clusters including 15000 sample plots.