Fig. 4

Simulation of silver fir colonization in the frame of an evaluation trial (see also Table 2) with four spatial options. Colonization progress after 50 and 90 years is shown for one of the twenty simulation runs for each spatial option. The source, on the left (0.05 km × 1 km), is a silver fir stand (initial characteristics: basal area 23 m²/ha, 1980 stems/ha, age 40 years, dominant height 11 m); the colonized stand (2 km × 1 km) is a Scots pine stand (trees not shown, initial characteristics: basal area 10 m²/ha, 300 stems/ha, age 40 years, dominant height 11 m). Three spatial sampling schemes are compared to the complete grid (CG; 20,000 cells; cell limits are not shown): nine-cell groups every 100 m (100S sampling; 1,711 cells), or every 200 m (200S sampling; 435 cells) and orthogonal transects (TRS sampling; two transects, three-cell wide; the longest is along the colonization direction; 888 cells)