Fig. 3
From: Whitebark pine encroachment into lower-elevation sagebrush grasslands in southwest Montana, USA
Historical (1953 to 1954) and current (2018) aerial photographs showing both upper and lower forest margins at the three sites sampled during the 2017 and 2018 field seasons in southwest Montana, USA: (a) Harkness 1953, (b) Harkness 2018, (c) Jeff Davis 1953, (d) Jeff Davis 2018, (e) Morrison 1953, and (f) Morrison 2018. Encroachment is evident in the 2018 photos. Data available from the US Geological Society, USGS Aerial Single Frame Archive, at earthexplorer.usgs.gov