Main reason for sanitary/salvage felling. Reference: Forest Service Survey (MID 345: Ursache der Zwangsnutzung)

Code	Text	NFI2	NFI3	NFI4	NFI4b	NFI5
-1	n/a	x	x	x	x	x
0	no sanitary/salvage felling	x	x	x	x	x
1	insects	x	x	x	x	x
2	fungi	x	x	x	x	x
3	wind	x	x	x	x	x
4	snow load	x	x	x	x	x
5	avalanche	x	x	x	x	x
6	debris flow, landslide	x	x	x	x	x
7	flood	x	x	x	x	x
8	forest fire	x	x	x	x	x
9	loss of vitality	x	x	x	x
10	other causes	x	x	x	x	x
11	loss of vitality due to drought					x
12	other loss of vitality					x