282
6. Habeck (1994) used survey data and presentday sampling to quantify successional changes in
ponderosa pine-Douglas fir forests in western
Montana following altered fire regimes.
19.7 Repeat Photography
Repeat photography involves relocating the site of
an early photograph and taking a new photograph
of the same scene from the same camera position
(G. F. Rogers et al., 1984). Both ground and aerial
photographs have been repeated to evaluate
changes in landscapes following settlement (Bahre,
1991). The photographs are points in time with spatial extents ranging from a few hectares (ground
photographs) to kilometers (aerial photographs).
Historical photographs, if taken prior to settlementinduced changes, can serve as benchmark records
of landscape condition, and their depiction of landscapes may have an element of impartiality because
they were made for purposes other than studying
landscape change (G. F. Rogers et al., 1984). However, repeat photography has a number of limitations. Ground photographs are unlikely to be spatially or temporally representative samples of a
region because they are fairly recent points in time
that cover only a small portion of the total surface
area in a region (Bahre and Shelton, 1993). They
are also the result of the photographer's bias in selecting sites to photograph (G. F. Rogers et aI.,
1984). Some historical photographs used for repeat
photography studies were taken after settlement activities had already affected an area (e.g., Hastings
and Turner, 1965; Gruell et aI., 1982). In addition,
land-use histories are not usually available for the
sites rephotographed, leading to difficulties in ascribing landscape changes to particular causes
(Bahre, 1991). Repeated aerial photography has the
advantage of enabling measures of areal cover to
be made and providing continuous coverage over
large areas. However, the time spans between repeated aerial photographs are short, because the
first vertical aerial photographs were not taken in
many areas until the 1930s (Bahre and Shelton,
1993).
EXAMPLES
1. Johnson (1987) repeated photographs taken
in presettlement Wyoming grassland as part of the
Hayden expedition of 1870 and concluded that, although sagebrush steppe, wooded areas, and riverbottoms had experienced changes in the intervening years since 1870, grassland-dominated areas
had remained fairly stable.
Methods for Determining Historical Range of Variability
2. Progulske (1974) repeated photographs taken
during the Custer Expedition in 1874 to the Black
Hills, South Dakota. The expedition photographs
documented landscape conditions prior to settlement.
3. Bahre and Bradbury (1978), Gehlbach (1981),
and Humphrey (1987) repeated photographs taken
in the early l890s of the international boundary
markers between the United States and Mexico to
determine vegetation changes and erosion effects.
The photographs provide a more systematic sample
of the vegetation than is present in most historical
photographs because the markers are evenly spaced
along the border (Bahre, 1991).
4. Rogers (1982) matched photographs taken in
the Bonneville area of Utah and Idaho between
1868 and 1916. Because all the historical photographs were taken following settlement, changes
prior to domestic livestock grazing could not be
documented, but the comparisons were used to understand changes under continuous grazing since
settlement. Trends included increasing prevalence
of weedy annuals and increases in woody species
such as juniper and oak.
5. Historical photographs taken between 1880
and 1915 in the Colorado Front Range were rephotographed and the comparisons supplemented with
plot data collected on 24 forest stands (Veblen and
Lorenz, 1991). Increasing conifer density was
noted, especially in montane stands, and young
ponderosa pine trees invaded fonner grasslands.
Changes were attributed to a more mesic climate,
overgrazing, and fire suppression.
6. Analyses of matches to photographs taken between 1873 and 1915 of subalpine forests in western Colorado were combined with tree-ring
chronologies to distinguish patterns of mortality due
to spruce beetle attack, fire, and wind (Baker and
Veblen, 1990). Complex interactions among the disturbance agents produced a spatially heterogeneous
mosaic of disturbance-created patches in the forest.
7. Veblen and Markgraf (1988) considered evidence from comparisons of 35 historical photographs
taken between 1883 and 1913 of the forest-steppe
ecotone in northern Patagonia, Argentina, along with
pollen, tree-ring, and forest-stand structure analyses
to evaluate vegetation changes at the ecotone over
the past 100 years.
8. Lehmkuhl et al. (1994) used historical (1932
to 1959) and current (1985 to 1992) aerial photographs to detennine HRV in vegetation composition and structure in six basins in eastern Oregon
and Washington as part of the Eastside Forest
Ecosystem Health Assessment (Everett et aI.,
1994). Changes in landscape pattern, wildlife habi-
6. Habeck (1994) used survey data and presentday sampling to quantify successional changes in
ponderosa pine-Douglas fir forests in western
Montana following altered fire regimes.
19.7 Repeat Photography
Repeat photography involves relocating the site of
an early photograph and taking a new photograph
of the same scene from the same camera position
(G. F. Rogers et al., 1984). Both ground and aerial
photographs have been repeated to evaluate
changes in landscapes following settlement (Bahre,
1991). The photographs are points in time with spatial extents ranging from a few hectares (ground
photographs) to kilometers (aerial photographs).
Historical photographs, if taken prior to settlementinduced changes, can serve as benchmark records
of landscape condition, and their depiction of landscapes may have an element of impartiality because
they were made for purposes other than studying
landscape change (G. F. Rogers et al., 1984). However, repeat photography has a number of limitations. Ground photographs are unlikely to be spatially or temporally representative samples of a
region because they are fairly recent points in time
that cover only a small portion of the total surface
area in a region (Bahre and Shelton, 1993). They
are also the result of the photographer's bias in selecting sites to photograph (G. F. Rogers et aI.,
1984). Some historical photographs used for repeat
photography studies were taken after settlement activities had already affected an area (e.g., Hastings
and Turner, 1965; Gruell et aI., 1982). In addition,
land-use histories are not usually available for the
sites rephotographed, leading to difficulties in ascribing landscape changes to particular causes
(Bahre, 1991). Repeated aerial photography has the
advantage of enabling measures of areal cover to
be made and providing continuous coverage over
large areas. However, the time spans between repeated aerial photographs are short, because the
first vertical aerial photographs were not taken in
many areas until the 1930s (Bahre and Shelton,
1993).
EXAMPLES
1. Johnson (1987) repeated photographs taken
in presettlement Wyoming grassland as part of the
Hayden expedition of 1870 and concluded that, although sagebrush steppe, wooded areas, and riverbottoms had experienced changes in the intervening years since 1870, grassland-dominated areas
had remained fairly stable.
Methods for Determining Historical Range of Variability
2. Progulske (1974) repeated photographs taken
during the Custer Expedition in 1874 to the Black
Hills, South Dakota. The expedition photographs
documented landscape conditions prior to settlement.
3. Bahre and Bradbury (1978), Gehlbach (1981),
and Humphrey (1987) repeated photographs taken
in the early l890s of the international boundary
markers between the United States and Mexico to
determine vegetation changes and erosion effects.
The photographs provide a more systematic sample
of the vegetation than is present in most historical
photographs because the markers are evenly spaced
along the border (Bahre, 1991).
4. Rogers (1982) matched photographs taken in
the Bonneville area of Utah and Idaho between
1868 and 1916. Because all the historical photographs were taken following settlement, changes
prior to domestic livestock grazing could not be
documented, but the comparisons were used to understand changes under continuous grazing since
settlement. Trends included increasing prevalence
of weedy annuals and increases in woody species
such as juniper and oak.
5. Historical photographs taken between 1880
and 1915 in the Colorado Front Range were rephotographed and the comparisons supplemented with
plot data collected on 24 forest stands (Veblen and
Lorenz, 1991). Increasing conifer density was
noted, especially in montane stands, and young
ponderosa pine trees invaded fonner grasslands.
Changes were attributed to a more mesic climate,
overgrazing, and fire suppression.
6. Analyses of matches to photographs taken between 1873 and 1915 of subalpine forests in western Colorado were combined with tree-ring
chronologies to distinguish patterns of mortality due
to spruce beetle attack, fire, and wind (Baker and
Veblen, 1990). Complex interactions among the disturbance agents produced a spatially heterogeneous
mosaic of disturbance-created patches in the forest.
7. Veblen and Markgraf (1988) considered evidence from comparisons of 35 historical photographs
taken between 1883 and 1913 of the forest-steppe
ecotone in northern Patagonia, Argentina, along with
pollen, tree-ring, and forest-stand structure analyses
to evaluate vegetation changes at the ecotone over
the past 100 years.
8. Lehmkuhl et al. (1994) used historical (1932
to 1959) and current (1985 to 1992) aerial photographs to detennine HRV in vegetation composition and structure in six basins in eastern Oregon
and Washington as part of the Eastside Forest
Ecosystem Health Assessment (Everett et aI.,
1994). Changes in landscape pattern, wildlife habi-