Transcript California Grasslands: Biodiverse Landscapes in a Biodiverse Region

California Grasslands:
Biodiverse Landscapes
in a Biodiverse Region
Source: sonoma.edu/preserves/prairie
Photo Credit: D. Immel-Jeffery 2010
GLOBAL HOTSPOTS OF BIODIVERSITY
Mittermeier et al. 1999
North
Coast/Klamath
 14 million acres
 40% of California’s
total runoff (10 major
coastal rivers)
 Rugged forested
mountains (3,0008,000 ft)
The Global Domination of
Grasses
• Grasses evolved in the late Jurassic (part
of the “abominable mystery”)
• Grasses co-evolved with and are
incredibly resistant to disturbance
• Grasslands cover 33-41% of the earth’s
terrestrial surface
Source: sonoma.edu/preserves/prairie
Photo Credit: D. Immel-Jeffery 2010
Definitions
• Grasses: members of the family Poaceae; not
forbs, shrubs, vines, rushes or sedges
• Grasslands are composed primarily of annual
and perennial grasses and forbs (from the
Greek Phorbe, or fodder)
• Savannah: grassland with widely spaced trees
• Prairie: grassland in a moderately dry
temperate region; from the French prata,
meadow (Lincoln, et al. 1998). First used by
French trappers on the North American Great
Plains.
Source: sonoma.edu/preserves/prairie
Photo Credit: D. Immel-Jeffery 2010
Prairies and Carbon Sequestration
• Prairies remove more
carbon from the
atmosphere than any other
ecosystem in the United
States
• Root die-back (from
grazing, mowing) deposits
carbon in the soil
• Annual cycles of deposition
and re-growth create an
incredibly effective carbon
pump
Photo Credit: Mark Stromberg
Illustration courtesy of the Hastings Natural History Reserve
California’s Coastal Prairies
• Unlike other North American
grasslands, coastal prairies grow
in California’s “fog belt”, which
shapes species composition
• May have been dominated by
wildflowers instead of grasses
(Minnich 2008; Holstein 2011)
• Early explorers, and early
naturalists such as John Muir,
documented wildflower-rich
prairies (see Lulow & Young
2011).
Source: Wikimedia Commons
Photo Credit: NASA
• Coastal prairies occur in a
patchwork with scrub and
forests
• Continued disturbance
maintains prairie species
composition and extent (with a
caveat)
• Disturbance processes include
grazing, fire, digging,
wallowing—not interchangeable
California’s Coastal Prairies
Support:
• Approximately 40% of California’s native
plant species (Wigand 2007)
• An incredibly rich flora, including 80
endemic species (Ford and Hayes 2007)
• Long-lived perennial bunchgrasses (e.g.
Festuca californica, F. idahoensis,
Danthonia californica): some are over 200
years old
Source: sonoma.edu/preserves/prairie
Photo Credit: National Park Service
California’s Coastal Prairies
Support:
• Over 30% of the diversity of vegetation
types in Sonoma and Marin Counties
• The most biodiverse grassland in North
America—more than twice the species
found in areas of the Great Plains
(Stromberg, et al. 2001; Wigand 2007)
Source: sonoma.edu/preserves/prairie
Photo Credit: National Park Service
California’s Coastal Prairies:
Carbon Sequestration
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Obligate summer dormancy of perennial
bunchgrasses: maintains carbon pump even
in the absence of other disturbance (e.g.
Zhou 2012)
Soil organic matter of Marin coastal prairies is
approximately 50% carbon
Certain short-rotation, intensive grazing
practices increase the amount of carbon
removed from the atmosphere and stored in
Source: sonoma.edu/preserves/prairie
the soil (Jasper 2008)
Photo Credit: National Park Service
California’s Coastal Prairies:
Erosion
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•
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Deep-rooted perennial grasses capture, filter
and store water, anchoring the soil in place
Perennial grasses provide erosion control
throughout the year, long after annual plants
die
Perennial grasses take advantage of early
autumn rains, greening up and absorbing
water before the annual seeds have a chance
to germinate.
Source: sonoma.edu/preserves/prairie
Photo Credit: National Park Service
Grassland birds are the most threatened group
of birds in the United States (Rao, et al. 2008).
Source: sonoma.edu/preserves/prairie
Photo Credit: Wikimedia Commons
Grassland birds (e.g. grasshopper sparrow and
savannah sparrow) need open spaces
between bunchgrasses to forage and build
their nests. Prairies dominated by invasive
annuals, with few native bunchgrasses, are
poor habitat for grassland birds (Grassland
Birds Need More than Grass, Hastings Natural
History Reserve).
Source: sonoma.edu/preserves/prairie
Photo Credit: Jim Coleman
• Wildflowers that grow among grasses are
an essential food source along with the
insects that the plants attract
• Poorly managed grazing can destroy
nests by trampling and reducing protective
cover (Unitt 2008)
Source: sonoma.edu/preserves/prairie
Photo Credit: Jim Coleman
Grassland Wildlife Resources:
Raptors
• Northern Harrier (nesting sites, hunting
areas)
• Red-tailed Hawk (hunting areas)
• White-tailed Kite (hunting areas)
Source: sonoma.edu/preserves/prairie
Photo Credit: Wikimedia Commons
Invasive species, land development, and other
human-related activities have reduced
California’s coastal grasslands by 90%.
California grasslands are among the most
endangered ecosystems in the United States
(Noss and Peters 1995).
Source: sonoma.edu/preserves/prairie
Photo Credit: D. Immel-Jeffery 2010
Coastal Prairie Threats
• Habitat Conversion and
Fragmentation
• Invasive Species
• Reduced Disturbance
• Altered watershed
hydrology
• Limited knowledge and
under-appreciation
• Air pollution
• Climate Change
Source: sonoma.edu/preserves/prairie
Photo Credit: K. Kraft 2009
Over 24% along California’s north
(Bay area) coast has been
urbanized, the most of any other
major plant community in the
United States (Ford and Hayes
2007; Loveland and Hutcheson
1995)
Source: sonoma.edu/preserves/prairie
Photo Credit: K. Kraft 2009
•
•
•
Nitrogen deposition from auto exhaust
has been linked to the increase of
Italian ryegrass (Festuca perennis) in
serpentine grasslands in the Bay Area
(Harrison and Viers 2007)
Nitrogen pollution can negatively affect
microbial activity, decreasing the rate
of decomposition of organic matter
Automobile pollution from Highway
101 has been cited as a threat to the
endangered Checkerspot butterfly
(Eilerin 2006).
Source: sonoma.edu/preserves/prairie
Photo Credit: K. Kraft 2009
Invasive Species
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Form monocultures
Decrease biodiversity
Alter vegetation structure
Impact ecosystem processes
Impact rare or endangered species
Threaten wildlife resources*
Threaten rare or endangered
ecosystems
Source: sonoma.edu/preserves/prairie
Photo Credit: Wikimedia Commons
•
•
Many non-native, annual grasslands still harbor a variety
of native species, depending on their use history. The
proportion of native plants can range up to 50% or more
(Biswell 1956).
Annual grasslands continue to be utilized by grassland
dependent birds and other animals (CPEFS 2010; Ford
and Hayes 2007; Kie 2005).
Source: sonoma.edu/preserves/prairie
Photo Credit: Ryan DiGaudio
Invasive Species: Ecosystem
Engineers
• Create conditions that
increase their own
survival while reducing
that of their competitors
• Conditions persist even
after the invasive species
is removed (e.g. soil
chemistry changes,
hybridization with native
species, hydrological
changes)
Source: Wikimedia Commons
REDUCED DISTURBANCE:
Grazing , Fire, Digging
GRAZING
By the late Pleistocene (10,000 BP to 1.6 MYBP), California grasslands
supported one of the greatest wildlife assemblages on the Earth. The diversity
and abundance of pre-historic grazers, browsers, predators and scavengers
may be one of the greatest in the world exceeding that of East Africa
(Edwards 2007).
Zebras:
Horses :
Llamas:
Deer:
Pronghorns:
Oxen:
Mammoths:
Sloths:
Bison:
Camels:
Tapirs:
Pigs:
(Dolichohippus sp.) , (Pliohippus sp.)
Giant horse, Western horse, Three-toed horse
Large-headed llama
Brachyodont deer, Mule deer, Elk
Pacific pronghorn, antelope or four-horned pronghorn,
Pronghorn
Shrub ox, Woodland musk ox
Columbian mammoth, American mastodon
Harlan’s ground sloth, Shasta ground sloth, Jefferson’s ground
sloth
Ancient or Ice Age bison
Large or western camel
Tapir
Flat-headed peccary
SOIL DISTURBANCE
Examples: Gophers, Bears, Pigs,
Ground Squirrels, Insects
Caveat: These species are also
grazers!!!
At a density of 23 per acre,
Botta’s pocket gophers
decreased the forage yield by
25% in annual-dominated
rangelands in the California
foothills.
(Case 2008)
GOPHERS
• 4 to 18 inches below the surface,
deeper branches 5 - 6 ft
• up to 200 yards of tunnels
• up to 300 soil mounds per animal
per year
• up to 2 1/4 tons of earth moved per
gopher each year
• up to 46 3/4 tons per acre per year
for a population of 50 pocket
gophers
• Tend to increase in ungrazed sites
(Case 2008)
Grazing Adaptations
• Stimulates growth of tillers, rhizomes and
stolons
• Detachable stems transported (with
uneaten seed) to new areas—example:
Danthonia californica
• Seeds germinate when trampled into the
ground
• Seeds take advantage of grazers’ fertilizing
manure
FIRE
Fire
prevents
invasion by
trees and
shrubs
Grey Hayes citing: Hatch, D. A., J. W. Bartolome, J. S. Fehmi, and D. S. Hillyard. 1999
Fire affects grass
species differently
Grey Hayes citing: Hatch, D. A., J. W.
Bartolome, J. S. Fehmi, and D. S. Hillyard. 1999
Effects of Fire on Coastal
Grasslands
• Removes thatch, shrub seedlings, and tree
seedlings
• Recycles nutrients
• Destroys pathogens
• Creates openings for grassland species
• Increases flowering among some species (e.g.
Chlorogalum and Brodiaea spp.)
• Caveat: fire effects depend on fire intensity,
frequency, pattern and season
GRAZING, FIRE & SOIL DISTURBANCE
• Shrub clearance
• Tolerant grassland species
DISTURBANCE THEN AND NOW
Significant environmental
changes:
Invasive species
Nitrogen
Habitat patchiness
Climate
Disturbance processes will have different effects
because the environment has changed