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Clues from the Past about our Future
Expanding Agriculture and Population
Night Lights and Urbanization
Patterns in Plant Diversity
Baltimore-Washington Urbanization
Great Lakes Landscape Change
Upper Mississippi River Vegetation
Greater Yellowstone Biodiversity
Southwestern US Paleoecology
Palouse Bioregion Land Use History
Northeastern Forest Dynamics

Land Use History of the Colorado Plateau

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Chapter 9: Additional Figures - Landscape Changes in the Southwestern United States: Techniques, Long-term Data Sets, and Trends

Photo 1920s Photo 1988
Additional Figures 1 & 2 - (Older image is on the left.) Fire suppression could explain the shifting of local ecotones, for example as shown in H. E. Gregory's 1920s and Ray Turner's 1988 photographs of Bear's Ears in southeastern Utah. Note the expansion of mixed conifer forest, including Douglas-fir (Pseudotsuga menziesii), white fir (Abies concolor), and (Pinus ponderosa) from Bear's Ears down to level terrain of Elk Ridge.


Photo 1910 Photo 1982
Additional Figures 3 & 4 - In 1910, N. H. Darton recorded the progress of arroyo-cutting on San Vicente Wash, the stream that runs through the town of Silver City, New Mexico. A few years prior, arroyo-cutting had gouged a huge gully through Main Street (Alford 1982). An arroyo has been extended upstream and maintained during the past 85 years, indicating that recovery rates from channel entrenchment may take centuries.


Photo 1940 Photo 1982
Additional Figures 5 & 6 - Since World War II, ground-water withdrawals have reduced wetlands and riparian vegetation in southwestern valleys. Mining of ground water in the Tucson Basin, for example, destroyed mesquite forests in the bottomlands of the San Xavier Indian Reservation between 1940 and 1982. Such wholesale conversions of floodplains makes recovery from arroyo-cutting impossible on century time scales.


Photo 1890s Photo 1980s
Additional Figures 7 & 8 - Many southwestern floodplains, including the Rio Grande (Albuquerque, Las Cruces, El Paso), the Salt River (Phoenix), and the Santa Cruz River (Tucson) have been heavily urbanized. Compare these photographs of the Santa Cruz River floodplain in the 1890s and 1980s. Restoration of these downstream reaches are no longer possible, as is the case downstreams of dams (Collier et al. 1996).


Photo of surface fire in pine forest Additional Figure 9 - Low to moderate intensity surface fires burning through pine forests occasionally cause fire scars at the base of surviving trees. Subsequent fires readily reignite in the exposed wood and flowing resin at the older wound boundary.

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