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Dynamics of Green Ash Woodlands
in Theodore Roosevelt National Park

Study Area

TRNP was established in 1947 as the Theodore Roosevelt Memorial Park and received National Park status in 1978. The 18,756-ha South Unit (Fig. 1) encompasses a representative sample of the vegetative communities native to western North Dakota including approximately 427 ha of the Green Ash – Choke Cherry Habitat Type described by Hansen et al. (1995) (Westfall et al. 1993). These lands were extensively grazed by livestock and influenced by homesteading beginning in the 1980's (Severson 1981, Girard et al. 1987) but have not been farmed since the 1930's or grazed by cattle and sheep (Ovis aries) since the early 1950's (Theodore Roosevelt National Park 1984).

Fig. 1 - Map of South Unit of Theodore Roosevelt National Park

Figure 1.  Map of the South Unit of Theodore Roosevelt National Park with stand locations and the release site for introduced elk indicated.

Mule deer, white-tailed deer, and a few feral horses were present in 1947. Pronghorn, introduced in 1951, have established a migratory pattern with most of their annual range outside the TRNP boundary fence. Bison were reintroduced in 1956. Elk were introduced in 1985 (Sullivan 1988). Numbers of bison, horses, and elk are actively managed to maintain populations within specific numerical ranges via live capture and removal. No attempts have been made to manipulate deer or pronghorn numbers. Although precise counts were not available for all ungulate species during the 1985 to 1996 period, we estimated the mean densities of large herbivores during this period as: mule deer (0.03/ha), white-tailed deer (0.01/ha), bison (0.02/ha), elk (0.01/ha), pronghorns (<0.01/ha), and feral horses (<0.01/ ha).

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