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Table 4 Two-sample Kolmogorov-Smirnov D statistic and P-values to test significance of difference between the distributions of topographic metrics among unburned islands within fires in the Inland Pacific Northwest from 1984 to 2014 based on their degree of persistence and fire regime group (FRG). The topographic metrics used for analysis were Topographical Position Index (TPI; Weiss 2001), Topographic Wetness Index (TWI; Beven and Kirkby 1979), Terrain Ruggedness Index (TRI; Riley et al. 1999), slope, the cosine of the aspect (CosAsp), and the transformed aspect (TRASP; Roberts and Cooper 1989)

From: Characterizing persistent unburned islands within the Inland Northwest USA

FRG TPI TWI TRI Slope CosAsp TRASP Number of observations
D P D P D P D P D P D P
All 0.0425 <0.0001 0.0689 <0.0001 0.1108 <0.0001 0.1030 <0.0001 0.0483 <0.0001 0.0492 <0.0001 n1 = 30 000 n2 = 30 000
I 0.1077 <0.0001 0.1352 <0.0001 0.1847 <0.0001 0.1747 <0.0001 0.0544 <0.0001 0.0508 <0.0001 n1 = 4 006 n2 = 4 667
II 0.1421 <0.0001 0.0736 0.1234* 0.2696 <0.0001 0.2719 <0.0001 0.0992 0.0126** 0.0562 0.3906* n1 = 939 n2 = 354
III 0.048 <0.0001 0.0751 <0.0001 0.1253 <0.0001 0.1164 <0.0001 0.0748 <0.0001 0.0799 <0.0001 n1 = 8 978 n2 = 10 097
IV 0.0412 <0.0001 0.0726 <0.0001 0.1118 <0.0001 0.1016 <0.0001 0.0475 <0.0001 0.0305 <0.0001 n1 = 15 136 n2 = 13 854
V 0.0804 0.0035 0.0748 0.0082 0.058 0.0736* 0.0625 0.0429** 0.1256 <0.0001 0.1215 <0.0001 n1 = 941 n2 = 1 028
  1. *Indicates P > 0.05
  2. **Indicates P > 0.01