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Dynamics of Green Ash Woodlands
in Theodore Roosevelt National Park

Lynn R. Irby, Jack E. Norland, Mark G. Sullivan,
Jerry A. Westfall, Jr., and Paula Andersen

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Abstract: Green ash (Fraxinus pennsylvanica Marsh.) communities are valuable as sources of biological diversity and shelter for livestock in the Northern Great Plains. Excessive use of stands by livestock tends to convert these woodland communities to less valuable shrublands. We monitored 12 green ash stands in Theodore Roosevelt National Park (TRNP) from 1985 through 1996 to determine changes in species composition, plant density, and canopy coverage in green ash communities that were protected from livestock but exposed to foraging by native ungulates. Over the 12-year sampling period, density of choke cherry (Prunus virginiana L.) and Saskatoon service-berry (Amelanchier alnifolia Nutt.) in the tree stratum declined, shrub density showed no consistent trends, and canopy cover of grasses and forbs increased. The changes we observed were more likely attributable to succession and weather conditions than to impacts of native ungulates.

Key words: ecology, Fraxinus pennsylvanica Marsh., Green ash, North Dakota.

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This resource is based on the following source:

Irby, Lynn R., Jack E. Norland, Mark G. Sullivan, Jerry A. Westfall, Jr.,
     and Paula Andersen.  2000.  Dynamics of green ash woodlands in 
     Theodore Roosevelt National Park.  Prairie Naturalist 32(2):76-102.  

This resource should be cited as:

Irby, Lynn R., Jack E. Norland, Mark G. Sullivan, Jerry A. Westfall, Jr.,
     and Paula Andersen.  2000.  Dynamics of green ash woodlands in 
     Theodore Roosevelt National Park.  Prairie Naturalist 32(2):76-102.  
     Jamestown, ND: Northern Prairie Wildlife Research Center Online.  
     http://www.npwrc.usgs.gov/resource/plants/grashdyn/index.htm
     (Version 04MAR2002).

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Table of Contents

• Introduction
• Study Area
• Methods
  • Vegetation measurement
  • Independent variables
  • Analysis
• Results
  • Overall Changes
  • Changes between individual sampling periods
• Discussion
• Acknowledgments
• Literature Cited

Tables

• Table 1 -- Vegetation parameters included in analyses of change in green ash stands.
  
• Table 2 -- Independent variables used in analyses of changes in green ash stands
  
• Table 3 -- Wilcoxin's tests of changes in coverage and density.
  
• Table 4 -- Percent change in 18 vegetation categories expected to decline under heavy grazing pressure from elk.
  
• Table 5 -- Correlations between independent variables and percent change in 16 vegetation variables.
  
• Table 6 -- Summary of stepwise logistic regression analysis of changes in vegetation categories in shrub and ground strata for vegetation measurements.

Figures

• Figure 1 -- Map of South Unit of Theodore Roosevelt National Park.
  
• Figure 2 -- Mean temperatures for the summer and winter.
  
• Figure 3 -- Precipitation during the growing season and winter.
  
• Figure 4 -- Mean stems and standard errors for four plant categories.
  
• Figure 5 -- Mean stems and standard errors for five plant categories.
  
• Figure 6 -- Mean percent cover and standard errors for eight categories in the ground stratum.
  

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Lynn R. Irby, Mark G. Sullivan¹, and Jerry A. Westfall, Jr.², Fish and Wildlife Management Program, Ecology Department, Montana State University, Bozeman, Montana 59717
Jack E. Norland, Animal and Range Science Department, North Dakota State University, Fargo, North Dakota 58105
Paula Andersen, Theodore Roosevelt National Park, P.O. Box 7, Medora, North Dakota 58654

¹ Current Address: Montana Fish, Wildlife and Parks, Box 457, Malta, Montana 59538
² Current Address: U.S. Fish and Wildlife Service, 401 Ocean Heights Ave B6, Somers Point, New Jersey 08244

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