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 Temperate Grasslands

North America Prairie, Great Plains Grasslands Eurasia Steppe South America Pampas

Subtropical to Tropical Grasslands

South America Cerrado, Llanos Africa Savanna, Veldt Australia Mitchell Grasslands Prairie

From the historic French word for a tree-less meadow or pasture co-dominated by perennial grasses and forbs. Generally used by North American ecologists to describe a tree-less vegetation of grasses, dicotyledonous herbs, and small shrubs.

Steppe

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)

Subtropical to Tropical Grasslands

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 pampas prairie

steppe 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”

Grazing: feeding primarily on grasses and grass-like plants

Browsing: feeding primarily on forbs (dicotyledonous herbs) and shrubs

Mixed Browsing and Grazing Grazers

American Bison diet 90 – 95 % grasses 4 – 6 % forbs and shrubs 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

Grazing Fire

reduce competition enhance seed germination return nutrients to the soil remove or kill shrub and tree seedlings

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 Deschampsia cespitosa Festuca californica California oatgrass hair grass California fescue

Carex tumulicola Ranunculus californicus Iris douglasiana foothill sedge California buttercup Douglas iris 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. Fire

Clements emphasized the role of over-grazing, but ignored that fire promotes the establishment and persistence of needle-grass.

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+ 19th Century, Coast and Coast Ranges

Spring months: grasses and many wildflowers; forage

Summer months: few grasses, few wildflowers; forage sometimes sparse or completely absent

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

Brassica nigra black mustard Avena fatua wild oat

Avena sativa culitvated oat Medicago polymorpha burr clover Hordeum murinum wall barley

Malva parviflora cheeseweed

Erodium cicutarium Bromus diandrus redstem filaree ripgut brome

Bromus hordeaceus smooth brome 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.

Pre-European vegetation of the Great Central Valley, especially the San Joaquin Valley with clay soils, probably was not dominated by grasses.

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. 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 ?