Grazing Intensity Research in the Missouri Coteau of North Dakota


 

Plant Community Dynamics


Changes in the plant community are monitored by sampling the frequency of occurrence, density per unit area and percent basal cover of all plant species as well as sampling the weight of herbage produced. Frequency data was collected each year of the study. Density was collected on forbs and shrubs in 1988 and 1990 to 2002 and on cespitose (bunchgrasses) from 1992 to 2002. Basal cover was sampled on plant species in 1988, 1990, 1992, 1993, 1996, 1999, and 2002 and basal cover of litter and bare ground was sampled in 1996, 1999 and 2002. The change in abundance of species between years was determined for each site. The arcsine transformation was applied to frequency and basal cover data to convert it from a binomial distribution to a nearly normal distribution. Analysis of variance was performed to determine if there was a change in species abundance across all sites, which might indicate a response to weather, or if there was a change in response to the different grazing treatments. All tests were performed at the P=0.05 level. Table 8 lists plant species that appear to be favored by no grazing or light grazing. Table 9 lists species that appear to be favored by moderate grazing and table 10 lists species that appear to be favored by heavy grazing. An asterisk marks species in Table 10 which appear to be invasive. These are species that have not been found or are extremely rare on the ungrazed or lightly grazed treatments. On overflow sites, total forb density and total plant density (includes forbs, bunchgrasses and shrubs but not rhizomatous grasses) have become greatest on the extreme and heavy treatments and least abundant on the ungrazed treatment and total plant basal cover has increased on the extreme treatment. On silty sites, total forb density and total plant density increase as the grazing intensity increases. Also on silty range sites total plant basal cover has decreased on the ungrazed and lightly grazed treatments between 1992 and 1999 and increased on the extreme and heavy treatments between 1996 and 1999. In addition to the changes listed for plant species, litter has decreased and bare ground has increased on both silty and overflow range sites under heavy grazing.


Table 8. Plant species that appear to be favored by no grazing or light grazing (P≤ 0.05).

 

Overflow Range Sites

 

Bromus inermis

smooth brome

Helianthus rigidus

stiff sunflower

Rosa arkansana

prairie rose

Solidago mollis

soft goldenrod

Silty Range Sites

 

Artemisia absinthium

wormwood

Helianthus rigidus

stiff sunflower

Medicago sativa

alfalfa

Melilotus officinalis

yellow sweetclover

Poa pratensis

Kentucky bluegrass

Polygonum convolvulus

wild buckwheat

Psoralea esculenta

breadroot scurf-pea

Tragopogon dubius

goat's beard



Table 9. Plant species that appear to be favored by moderate grazing (P≤ 0.05).

 

 

Overflow Range Sites

Ambrosia psilostachya

western ragweed

Anemone cylindrica

candle anemone

Aster simplex

panicled aster

Campanula rotundifolia

harebell

Carex lanuginosa

wooly sedge

Galium boreale

northern bedstraw

Glycyrrhiza lepidota

wild licorice

Juncus balticus

Baltic rush

Poa pratensis

Kentucky bluegrass

Sisyrinchium montanum

blue-eyed grass

Solidago rigida

stiff goldenrod

 

Silty Range Sites

Agropyron repens

quackgrass

Ambrosia psilostachya

western ragweed

Artemisia dracunculus

green sagewort

Artemisia ludoviciana

cudweed sagewort

Bromus inermis

smooth brome

Carex filifolia

thread-leaved sage

Cirsium flodmanii

Flodman’s thistle

Comandra umbellata

comandra

Dichanthelium wilcoxianum

Wilcox dichanthelium

Erysimum inconspicuum

smallflower wallflower

Geum triflorum

prairie smoke

Lactuca oblongifolia

blue lettuce

Orthocarpus luteus

owl clover

Psoralea argophylla

silver-leaf scurf-pea

Ratibida columnifera

prairie coneflower

Rosa arkansana

prairie rose

Sisyrinchium montanum

blue-eyed grass

Solidago missouriensis

Missouri goldenrod

Solidago mollis

soft goldenrod

Solidago rigida

stiff goldenrod



Table 10. Plant species that appear to be favored by heavy grazing (P≤ 0.05).

 

 

Overflow Range Sites

  Achillea millefolium

western yarrow

  Agropyron caninum

slender wheatgrass

  Agropyron smithii

western wheatgrass

  Agrostis hyemalis

ticklegrass

  Androsace occidentalis

western rock jasmine

  Artemisia ludoviciana

cudweed sagewort

  Astragalus agrestis

field milk-vetch

  Aster ericoides

heath aster

  Bouteloua gracilis

blue grama

* Buchloe dactyloides

buffalograss

  Carex heliophila

sun sedge

  Carex obtusata

sedge

  Cerastium arvense

prairie chickweed

  Cirsium flodmanii

Flodman's thistle

  Conyza canadensis

horse–weed

  Draba nemorosa

yellow whitlowort

  Erysimum inconspicuum

smallflower wallflower

  Euphorbia serpyllifolia

thyme-leaved spurge

  Geum triflorum

prairie smoke

  Grindelia squarrosa

curly-cup gumweed

* Lithospermum incisum

yellow puccoon

* Medicago lupulina

black medic

   Oxalis stricta

yellow wood sorrel

   Penstemon gracilis

slender beardtongue

   Polygonum convolvulus

wild buckwheat

* Polygonum ramosissimum

bushy knotweed

   Potentilla norvegica

Norwegian cinquefoil

* Potentilla pensylvanica

Pennsylvania cinquefoil

   Ratibida columnifera

prairie coneflower

   Solidago missouriensis

Missouri goldenrod

  Stipa viridula

green needlegrass

  Taraxacum officinale

common dandelion

* Trifolium repens

white clover

  Vicia americana

American vetch

  Viola pedatifida

larkspur violet

 

Silty Range Sites

   Achillea millefolium

western yarrow

   Agropyron smithii

western wheatgrass

* Agrostis hyemalis

ticklegrass

  Androsace occidentalis

western rock jasmine

  Artemisia frigida

fringed sagewort

  Bouteloua gracilis

blue grama

  Carex eleocharis

needle-leaved sedge

  Carex heliophila

sun sedge

  Carex obtusata

sedge

  Cerastium arvense

prairie chickweed

  Chenopodium desiccatum

narrow-leaved goosefoot

  Draba nemorosa

yellow whitlowort

  Erysimum asperum

western wallflower

  Euphorbia serpyllifolia

thyme-leaved spurge

  Grindelia squarrosa

curly-cup gumweed

  Hedeoma hispidum

rough false pennyroyal

* Juncus interior

inland rush

  Koeleria pyramidata

junegrass

  Lepidium densiflorum

peppergrass

 *Medicago lupulina

black medic

  Oxalis stricta

yellow wood sorrel

  Plantago patagonica

wooly plantain

* Polygonum ramosissimum

bushy knotweed

   Potentilla norvegica

Norwegian cinquefoil

  Potentilla pensylvanica

Pennsylvania cinquefoil

  Symphoricarpos occidentalis

buckbrush

  Taraxacum officinale

common dandelion

  Vicia americana

American vetch

* Invaders, these species have not been found, or are extremely rare, on the ungrazed and lightly grazed treatments.



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