Transcript RANGELANDS:

RANGELANDS:
• GRASSLANDS, DESERT
SHRUBLAND, AND SHRUB
WOODLAND
– Precipitation = 10-30 inches/yr
– 29% of US is rangeland
TAYLOR GRAZING ACT OF
1934
• 1. halt deterioration
• 2. improve range quality
• 3. stabilize rangeland economy
IMPORTANT WILDLIFE OF
THE GRASSLANDS
– Waterfowl (prairie potholes and marshes)
– Large ungulates (deer, elk, pronghorn)
– Smaller mammals and birds
GRAZING PERMIT
CONTROVERSY
– Nearly 5 million cattle and sheep graze on
80% of public rangelands annually
– Permits cost one-fifth that charged by
private landowners
– Federal subsidy = $100 million/yr over the
water subsidy they get
– In 45 National Parks, 150 National Wildlife
Refuges, and BLM lands
– http://www.sagebrushsea.org/pdf/factsheet
_Grazing_Economic_Contributions.pdf
GRAZING PERMIT
CONTROVERSY, continued
– Current fee doesn't even pay for
administration of program
– Ecosystem is being damaged by
overgrazing and miss-management:
wildlife suffer
– Ranchers benefit, but land belongs to
everyone
– The paradox persists. Why?
RANGELANDS
– Grasslands
– Desert Shrubland
– Shrub Woodland
– Tropical - Savanna, campos, llanos
– Temperate - prairie, steppes, pampas, veld
– Arctic - Tundra (mostly wetland too)
ECOLOGY OF
RANGELANDS
– Metabolic reserve = lower half of grass
plant
– Decreasers - plants favored by grazing
animals; subject to decline when grazed
– Increasers - avoided by grazers;
abundance increases upon grazing
– Invaders - dominate overgrazed areas
ECOLOGY, continued
– Overgrazing:
• Too many animals for too long
• grasses replaced by woody plants and forbs
• reduces water and nutrients
• reduces litter, exposes soil
• more wind erosion
– Undergrazing:
• brown leaf and stem left to age (poor food quality)
• kills off (chokes) grasses and favors woody vegetation
• reduces water and nutrients
• reduced root mass leads to soil erosion
MANAGEMENT OF
RANGELANDS:
– Control amount of grazing
• periods of grazing and rest (deferred rotation)
• continuous grazing
• holistic grazing (6 paddock rotation)
– Control vegetation
• fire
• herbicides
MANAGEMENT OF
RANGELANDS, continued
– Control rodents and predators
• Rodent control:
– Controls don't last (temporary relief
– Ecology gives long-term solution
• Predator control:
– controls don't work (temporary relief)
– Ecology gives long-term solution
• Coyotes eat Rodents!!!
COYOTE PROBLEMS
– The federal government kills coyotes!
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'1080' in collars
cyanide in "coyote getter"
costs about $1,000 per coyote!
ineffective in reducing coyotes
– Other methods to deal with coyotes:
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fencing
guard dogs
good animal husbandry practices
Kansas model program only costs 5% of
nearby states' programs
NORTH AMERICAN GRASSLANDS:
– tall-grass prairie: southeastern edge
– mid-grass (mixed-grass) prairie: north and west of
tallgrass prairie
– short-grass prairie: western plains
– Palouse prairie: great basin country
– Valley grasslands: California's Central Valley
– Desert grasslands: Arizona and New Mexico and
Mexico
MORE ECOLOGY
– Most grasslands are subject to great variability in
temperature, precipitation, grazing, and fire, leading
to "multiple stable states" rather than one climax
community type
– Global warming and grasslands:
– may increase decomposition rate and thus increase
CO2 release (positive feedback)
– Grassland restoration is in progress
TEMPERATE AND
TROPICAL DESERTS
– Characteristics
• Hot vs. Cool deserts:
– temperatures below freezing may be rare or common
– What creates the desert environment?
• Rain shadow - mountains
• Cold upwelling - oceans
SPECIAL FEATURES OF
DESERT ECOSYSTEMS
– caliche - cement-like subsoil of calcium
carbonates
– desert pavement - hard, protective surface
layer
– cryptobiotic crust - algae, fungi, and lichens
form a fine organic tissue
• may take 200 years to reform if disturbed
DESERTS, ecological problems
– Desertification- drying of arid ecosystems
is a global concern
– Other Problems:
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Overgrazing by livestock
Competition with feral ungulates
ORV's
compact soil, disrupt surface
first pass does most of damage
– Reptiles, mammals, and birds are all reduced in
number of species and number of individuals per
species under heavy and very heavy ORV use*
» *Even moderate use cuts # species to <11
Effects of ORV’s on desert fauna
(Density per 2 ha plot)
Group
No use
Heavy
use
Very
heavy use
Reptiles
29-75
8-33
0-16
Mammals
22
11
3
Birds
4
2
0
# of species
(combined)
11-16
5-10*
1-7
*Even moderate use cuts # species to <11
Problems, continued
– Invasion of exotic plants:
• Annual grasses of genus Bromus that choke
out native plants after a rain, die, and carry fire
(native species evolved w/o fire)
• Salt cedar - shrub replacing willow and
cottonwood in riparian areas
• Deep-rooted, high transpiration: dries soil
• Carries fire; resprouts vigorously after fire,
outcompeting native species
• Beaver and deer do not feed on it
Problems, continued
– Global warming will increase
desertification
– Desert soils are a source of carbon in the
atmosphere; more desert surface and
weaker cryptobiotic crusts will add to the
greenhouse effect!
Management of arid/desert
systems:
– Need to limit use of ORV's
– California Desert Protection Act
• 1994 - upgraded several deserts to National
Parks, enlarged areas of protection, and
designated more "wilderness"