Grasslands and Prairies

Grassland

Dominated by grasses (Poaceae) and

grass-like plants (sedges, rushes)

30 – 40 % of world land surface

Climate composed of moderate

precipitation (10 - 50 inches/yr) and

periodic drought

Other environmental factors

Fire

Grazing

Major Global Grasslands

North America Prairie, Great Plains Grasslands

Eurasia Steppe

South America Pampas

Temperate Grasslands

Subtropical to Tropical Grasslands

South America Cerrado, Llanos

Africa Savanna, Veldt

Australia Mitchell Grasslands

From the historic French word for a tree-less meadow or

pasture co-dominated by perennial grasses and forbs.

Prairie

Steppe

Generally used by North American ecologists to describe a

tree-less vegetation of grasses, dicotyledonous herbs, and

small shrubs.

From the Russian word “степ” for an extensive, flat

grassland.

Sometimes used by North American ecologists to describe

a grassland composed of short statured, perennial grasses

or bunch grasses.

Temperate Grasslands

Cold season alternating with Warm to Hot season

10 – 35 inches of annual precipitation alternating with

drought

Deep, porous soils (e.g., loess)

Cool to Warm seasons alternating with Warm to Hot

seasons

20 – 50 inches of annual precipitation alternating with

drought

Soils vary from deep to thin, porous to clay

Subtropical to Tropical Grasslands

pampas

steppe

prairie

savannah

Adaptations

perennial, cespitose habit

thin, narrow leaves that grow from the base

deep, compact root systems

G G G G G G G G G

Fire

“Grazing”

Mixed Browsing and Grazing

Grazing: feeding primarily on

grasses and grass-like plants

Browsing: feeding primarily on

forbs (dicotyledonous herbs)

and shrubs

American Bison diet

90 – 95 % grasses

4 – 6 % forbs and shrubs

Grazers

Mule Deer diet

4 – 15 % grasses

15 – 30 % forbs

75 – 90 % shrubs

Pronghorn diet

5 – 45 % grasses

25 – 50 % forbs

10 – 60 % shrubs

Elk diet

45 – 60 % grasses

11 – 40 % forbs

25 – 30 % shrubs

Grazing and Fire Remove Biomass

reduce competition

enhance seed germination

return nutrients to the soil

remove or kill shrub and tree seedlings

Grazing

Fire

Coastal Prairie

northern coastal California north to southern Oregon

highest plant species diversity among California

“grasslands”, composed of a mixture of grasses, sedges,

and forbs

deep, porous, sandy soils of low-lying valleys

historically promoted by Native American burning practices

and grazing by elk

Danthonia californica

California oatgrass

Deschampsia cespitosa

hair grass

Festuca californica

California fescue

Iris douglasiana

Douglas iris Carex tumulicola

foothill sedge

Ranunculus californicus

California buttercup

California Grasslands

Frederick Clements’ (1934) “Bunchgrass-Grazing”

hypothesis.

Bunchgrasses once dominated the Great Central

Valley and adjacent foothills but were eliminated by

excessive livestock grazing and too frequent fires.

Needle grass (Stipa, Nassella)

Bunchgrass Steppe

Clements based his hypothesis on "relict" stands of native

bunchgrasses he found along railways and outside of fenced

pastures.

He assumed that the original vegetation was like that of

central North America, i.e. composed of perennial grasses.

Clements emphasized the role of over-grazing, but ignored

that fire promotes the establishment and persistence of

needle-grass.

Fire

Proponents of the bunchgrass-grazing hypothesis tended to

ignore historical observations and the significance of alien

Mediterranean invasive species.

18th Century Expeditions and Observations

Gaspar de Portolá Expeditions, 1769-1770, 1772

Fr. Juan Crespí, Miguel Costansó, Pedro Fages

Juan Bautista de Anza Expeditions, 1774, 1776

● observed burning by Native Americans, which enhanced

open habitats and barren areas or areas dominated by

grasses

● described open areas using words (pasto, yerbas, zacate)

that often referred to forage or dry herbaceous vegetation

● observed herbivores that are now known to be deer,

pronghorn, and elk

19th Century Expeditions and Observations

Gabriel Moraga, 1806 (Fr. Pedro Muňoz)

Thomas Coulter, 1832 - 1834

Pacific Exploring (Wilkes) Expedition, 1838 – 1842

John C. Fremont, 1844, 1848

Edwin Bryant, 1848

William P. Blake, Pacific Railroad Survey, 1853-1854

William H. Brewer, California Geological Survey, 1860 – 1864

John Muir, 1870+

Spring months: grasses and many wildflowers;

forage

Summer months: few grasses, few wildflowers;

forage sometimes sparse or completely absent

19th Century, Coast and Coast Ranges

19th Century, Interior Valleys (San Joaquin)

Spring months: vast wildflower displays; grasses and

forage rarely mentioned, except along rivers.

Summer months: herbaceous vegetation dried, no

forage, landscape often described as barren or destitute

California in 1850

California Grasslands

California Valley Grassland

Annual Grassland

western San Joaquin Valley Hungry Valley

Considered by ecologists as a unique grassland, because

it is dominated almost entirely by invasive, alien species

from European Mediterranean.

Annual Grasslands

Dominated almost exclusively by

alien, Mediterranean annuals

Avena fatua

wild oat

Avena sativa

culitvated oat

Brassica nigra

black mustard

Medicago polymorpha

burr clover

Bromus diandrus

ripgut brome

Bromus hordeaceus

smooth brome

Hordeum murinum

wall barley

Malva parviflora

cheeseweed

Erodium cicutarium

redstem filaree

Mediterranean Invasive Annuals

Arrived in California during the late 18th and 19th

centuries

Pre-adapted to California’s climate but differing

from the native California flora by their advantage

in having

rapid seed dispersal

recruitment from seeds at high densities

rapid early season growth rate

Most invasive annuals, however, have relatively low

seed longevity as compared to native annuals

Carrizo Plain

Carrizo Plain National Monument, a “remnant of the

Central Valley’s former vast grassland”

Carrizo Plain - Carrisa Plains

1850. First settlement by sheepherders (Saucito Ranch)

1853. US Railroad Survey names “Llano Estero” and “Carrizo

Ranch”

1876+ Sheep and cattle grazing; potato, wheat, and barley

farming.

1940s Farms and ranches begin to fail

1980+ Federal land acquisitions

2001. Carrizo Plain National Monument established

Saucito Ranch, Soda Lake,

Temblor Range

Carrizo Plain

Completely enclosed basin with alkaline clay or clay

loam soils

Vegetation a complex mosaic of:

Atriplex polycarpa (allscale saltbush) shrubland,

and

annual Mediterranean grassland

Scattered Stipa (Nassella) and Poa secunda bunch

grass mixed with Juniper-Ephedra shrubland

occurs on adjacent slopes and hills.

Great Valley Grasslands State Park

wetlands, sloughs, and floodplain of the San

Joaquin River east of Gustine, Merced County

California’s Grasslands

Original grasslands are not as extensive as

previously thought.

Coastal grasslands and prairies may have been

significantly influenced by Native American

burning practices. In the absence of fire, such

grasslands are subject to invasion by shrublands

and forest trees.

Pre-European vegetation of the Great

Central Valley, especially the San Joaquin

Valley with clay soils, probably was not

dominated by grasses.

California’s Grasslands

Some landscapes previously thought to be

grasslands actually may have been

composed of dicotyledonous annuals

(forbs).

The most common, widespread grasslands

in California are effectively dominated by

alien, Mediterranean grasses and forbs.

prairies ?

wildflower prairies ?

wildflower meadows ?

forblands ?