Introduction
Sagebrush species (Artemisia spp.) occupies roughly 62 million hectares in the
western United States (Kuchler, 1970; Miller and others,1994; West and Young, 2000).
Treatment of sagebrush communities with a herbaceous understory have shown a
significant increase in herbaceous vegetation recovery (Davies and other, 2007a; Harniss
and Murray, 1973). The key to having a successful treatment in sagebrush communities is
the intact understory of desired bunch grasses. Without the desired bunch grasses there is
an increased risk for vegetation to become dominated by exotic annuals (Blaisdell, 1953;
Peek and other, 1979; Davies and others, 2011). It is understood that sagebrush
communities’ treatments need to be studied further due to the importance of sagebrush
has for wildlife habitat and livestock operations (Connelly and others, 2000; Shipley and
others, 2006).
The objective is to monitor Wyoming big sagebrush’s (Artemisia wyomingenis)
response to mowing, and forecast future vegetation in ten, fifteen, twenty, and twenty five
years. A current site description will provide insight to current vegetation; a mow scenario
will provide how the plant community will change.
Description
Emblem Bench is seventy two kiolometers south of Powell, Wyoming. Historically,
the area was used for sheep grazing, and wild horses, today is used by cattle, wildlife and
occasional wild horses. The Bureau of Land Management (BLM) manages most the bench.
Parts of Emblem Bench have been cultivated into sugar beets, peas, or alfalfa for seed.
Temperature varies on the bench between -13-30oC , precipitation also fluxes from
0-3.2 centimeters for last year. The months receiving the most precipitation were May and
June, and July receiving the highest temperature (weatherchannel). Vegetation currently
consists of bottlebrush squirrel tail (Elymus elymoides), sandberg bluegrass (Poa secunda),
bluebunch wheatgrass (Pseudoroegneria spicata). Shrubs that dominate the area are;
Wyoming big sagebrush (Artemisia tridentate) and plains prickly pear cactus (Opuntia
polyacanth) (Table 1, Figure 1). The understory is in tacked and little to no presents of
exotic annuals. The rancher that has the permit is on a restrotional grazing program.
Scenario
In 2006 the BLM used a range mower and mowed five foot stripes, creating a mosaic
of the landscape. The BLM have permanent plots that were left untreated. They then
created new monitoring plots in the mowed areas (Table 2, Figure 2). I hypothesize that
mowing will (1) increase grass production the first few years, (2) decrease shrub cover and
density at first, and (3) have an increase in annual forbs the first year.
Five years post mow
Vegetation five years after mow (2011) there is a still a strong litter layer present.
Bunch grasses have a increase in new seed recruitment. Native annual forbs increased
(Davis et. al. 2011a). There is no present of exotic annuals, there are small sagebrush plants
sprouting. There is little to no bare ground, lichens and mosses have increased. Soil
stability has not changed but few samples were found to be hydrophobic. But infiltration
not affected.
Ten years post mow
Vegetation in 2016 did not have increase in species diversity. There is a litter layer
present but there is more bare ground between patches of litter. Bunchgrasses are still
present and are starting to increase in size. There few annuals present but in significant
numbers. Mosses and lichens have decreased (Davis et. al. 2013). Soils are no longer
hydrophobic, but are still stable.
Fifteen years post mow
Year 2021 vegetation has lost some diversity. The presents of Brassica has
decreased, Pseudoroegneria spicata has become the dominate bunch grass. Elymus
elymodes has seen a decline and is found closest to reestablishing sagebrush. Sagebrush
plants have grown and have an average height of 6 inches. Bare ground has increase, with
lichen being present at the bases of bunch grasses and shrubs. Litter from the mow is
mostly absent. Only indication of mowing is a mosaic across landscape with few sagebrush
skeletons. Soil stability has started to show improvement, and increase in soil nutrients
(Young and Allen, 1997).
Twenty years post mow
At year 2026 plant community is still staying the same. Sagebrush has grown and
becoming the dominate plant. Pseudoroegneria spicata has dominate grass with Elymus
elymodes present in sagebrush plants. There is little to no present of annual forbs.
Bareground has a soil crust starting to form from carbonates, decreasing water infiltration.
The lines from the mosaic are still present but not as abrupt and clear.
Conclusion
Mowing Wyoming big sagebrush did not increase grass production or density (Davis
et. al. 2011a). Mowing is an effective way to reduce sagebrush cover, and increase soil
nutrients. Annual forbs favored opening of the canopy. Exotic annuals also favored opening
the canopy but can be at a manageable level. Seed germination density increased in the
mowed areas because of the litter. Litter moderates the soil temperature making a
microclimate for better seed germination (Evans and Young, 1970, 1972). Davis (2013)
found native grass did not responded as well but longer term studies are needed. Mowing
does not increase plant diversity of Wyoming big sagebrush.
The goal to decrease sage brush cover was met, but native production did not have
increase as hoping. Davis (2013) advises against large scale mow treatments. Large scale
removal of sagebrush cover could have negative impacts on other wildlife species.
Important part of mowing sagebrush communities is to have an intact understory. A
degraded understory has shown to increase density undesirables (Davis 2013). Longer
term studies are required in order to better predict plant production and density of native
plants.
Cover Estimates by Species
Species
ARTRW8
BOGR2
BRASS2
ELEL5
HECO26
OPPO
POSE
PSSP6
Scientific
Artemisia tridentata Nutt. ssp. wyomingensis Beetle & Young
Bouteloua gracilis (Willd. ex Kunth) Lag. ex Griffiths
Brassica L.
Elymus elymoides (Raf.) Swezey
Hesperostipa comata (Trin. & Rupr.) Barkworth
Opuntia polyacantha Haw.
Poa secunda J. Presl
Pseudoroegneria spicata (Pursh) Á. Löve
Common
Wyoming big sagebrush
BLUE GRAMA
mustard
BOTTLEBRUSH SQUIRRELTAIL
needle and thread
PLAINS PRICKLYPEAR
BIG BLUEGRASS
bluebunch wheatgrass
Table 1: Foliar cover by species before mow treatment
Year
2013
2013
2013
2013
2013
2013
2013
2013
Average Annual
Foliar Cover %
22.0
1.0
1.0
2.0
6.0
4.0
3.0
15.0
Cover Estimates by Species
Species
ARENA
ARTRW8
BOGR2
ELEL5
HECO26
OPPO
PHHO
POSE
PSSP6
SPCO
Scientific
Arenaria L.
Artemisia tridentata Nutt. ssp. wyomingensis Beetle & Young
Bouteloua gracilis (Willd. ex Kunth) Lag. ex Griffiths
Elymus elymoides (Raf.) Swezey
Hesperostipa comata (Trin. & Rupr.) Barkworth
Opuntia polyacantha Haw.
Phlox hoodii Richardson
Poa secunda J. Presl
Pseudoroegneria spicata (Pursh) Á. Löve
Sphaeralcea coccinea (Nutt.) Rydb.
Common
sandwort
Wyoming big sagebrush
BLUE GRAMA
BOTTLEBRUSH SQUIRRELTAIL
needle and thread
PLAINS PRICKLYPEAR
HOODS PHLOX
BIG BLUEGRASS
bluebunch wheatgrass
SCARLET GLOBEMALLOW
Year
2013
2013
2013
2013
2013
2013
2013
2013
2013
2013
Table 2: Foliar cover by species four years after mow treatment
Figure 1: Study area day of burn (summer 2006). Photo by Jack Mononi BLM
Average Annual
Foliar Cover %
1.0
11.0
1.0
1.0
15.0
2.0
1.0
1.0
12.0
5.0
Figure 2: study area 2010, four years after mow treatment. Photo by Jack Mononi BLM
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