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Observations on Symphoricarpos occidentalis (Buckbrush) as forage in Billings County, North Dakota, 2005-2006.

Introduction. Dickinson State University maintains a small study area (approximately 0.75 x 0.75 x 0.45 km) in the badlands of western North Dakota east of the town of Medora. The study area is bounded to the north by 1-94 and to the southeast by Business 94. A small grassland butte is located to the northeast and a dry woodland draw is to the southwest. In 1987 a deer exclosure was constructed under the direction of Professor Myron Freeman west of the present woodland draw. A 30 m transect line (transect D) bisects this moderately wooded exclosure into northeast and southwest. This transect extends 15 m to the west (transect E) and 15 meters to the east (transect C) into unenclosed grassland. The west endpoint of a 15 m east-west woodland transect (transect B) is located 51.3 m from the northeast cornerpost of the exclosure along an 168[degrees] line of azimuth (the woodland edge occurs 26.8 m from this post). The north endpoint of a north-south woodland transect (transect A) is located 10 m east of transect B. Over the course of one year (September 2005-August 2006) monthly observations were made of Symphoricarpos occidentalis (buckbrush) along these transects. These observations provide a record that deer and cottontail utilized buckbrush as forage during fall and winter.

Observations/Discussion. The woodland draw is a Fraxinus pennsylvanica/Prunus virginiana (green ash/chokecherry) habitat with buckbrush extending from the woodland into the surrounding grasslands. The dominant grasses associated with the buckbrush are Poa pratensis (Kentucky bluegrass) and Bromus inermis (smooth brome). Observations include bones and antlers of Odocoileus hemionus (mule deer) as well as antler rubs, bedding sites, fecal pellets, and tracks in both the grassland and woodland draw. Sylvilagus floridanus (cottontails) were observed as well as their fecal pellets, tracks, and trails in both the grassland and woodland draw (including the exclosure).

Fieldwork October 15 and 22, 2005 consisted of identification and counts of vegetation intersecting each transect line. 30 buckbrush samples from each transect were randomly selected for morphometric data. Transect B had the lowest berry/flower counts (A: mean berry 4.61, 8.24 SD; mean flower 1.29, 2.34 SD; B: 0.34, 1.62 SD, 0.06, 0.35 SD; C: 3.72, 5.42 SD; 1.42, 3.38 SD; D: 2.84, 6.97 SD, 4.75, 7.57 SD; E: 6.44, 10.30 SD; 18.11, 16.74 SD). Transect B was highest in frayed and truncated foliage stem counts (A: 11, 5; B: 18, 3; C: 5, 1; D: 1, 4; E: 1, 3). Frayed stem evidence of deer browsing coincides with observations of deer fecal pellets, tracks, and a bedding site within 2 meters of B. Foliage browsing would result in a decrease of berries/flowers. Grassland (C, E) and lesser or no browsed similar woodland (A, D) provide partial control for potentially confounding factors (competition, nutrients, and sunlight).

On January 22, 2006 the study area was covered by approximately 10-15 cm of packed snow with 1 cm unpacked snowcover from the previous 24 hours. Cottontail fecal pellets and tracks (oriented toward sheared stems) were present on the new snow. The stems were sheared at 45[degrees] angles ([+ or -] 15[degrees]) to within 5 cm of the snow. Number and condition of buckbrush were evaluated on May 16, 2006 as total #, frayed #, and sheared # (A: 35, 10, 19; B: 22, 0, 15; C: 25, 11, 4; D: 117, 0, 78; E: 38, 18, 10). Stem shearing is attributed to cottontails. The frayed upper stems attributed to deer browsing do not occur in the exclosure and these numbers are presumably reduced in this May transect data due to the cottontail shearing. Overstory density was estimated on June 22, 2006 with a spherical densitometer at mid-transect (A: 17; B: 46; C: 0; D: 79; E: 0%). Evidence indicates feeding preference in dense overstory transects by cottontails (stem shearing--A, B, D), and deer (October fraying of foliage stems--A & B).

Conclusion. Herbaceous plants dominate the preferred diet of deer and cottontails during the growing season. The transition to woody plants occurs as seasonal weather conditions worsen. At extreme conditions, snow cover severely limits foraging opportunities. The most parsimonious interpretation of the October observations at transect B (frayed stems, fecal pellets, tracks, and bedding impressions) suggest deer browsed the upper foliage, and reduced the berry/flower count by mid-fall (although other factors may contribute--growing conditions, bird foraging). January observations (stems sheared at an angle to near snow-level, fecal pellets, and tracks) provide a record that cottontails fed on entire buckbrush (B and D). Both herbivores preferentially foraged in the denser overstory transects in these observations. Cottontails utilized stems of the plant as winter progressed.

James McAllister * Department of Science, Columbia College, Columbia, MO 65216

Jay Johnson Natural Resources Management, North Dakota State University, Fargo, ND 58105
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Author:McAllister, James; Johnson, Jay
Publication:Proceedings of the North Dakota Academy of Science
Article Type:Report
Geographic Code:1U4ND
Date:Apr 1, 2008
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