Transcript Bromus tectorum

Leonardo Hernandez-Espinoza
NRES 641
Spring 2010
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Family Poaceae
Genus Bromus
Species Bromus tectorum
http://dcnrnews.files.wordpress.com/2008/04/2008-04-03-cheatgrass.jpg
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Downy brome
Downychess
Cheat
Mormon oats
Junegrass
http://heritage.nv.gov/images/invasive/brtela80.jpg
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Between 5 and 40 cm high.
Spikelets tend to be sub-cylindric to somewhat
compressed.
Glumes may vary between short haired to
glabrous.
Lemma length is between 9 and 13 mm, and a
long awn between 8 and 18 mm.
Flowers are bisexual, generally with 3 stamens
and 2 stigmas, and once mature, yield an
achene-like grain.
Roots are fibrous, shallow and thin
http://plants.usda.gov/gallery/large/brte_004_lhp.jpg
http://content5.eol.org/content/
2008/10/07/01/47913_large.jpg
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Cheatgrass is a self pollinating winter annual
Germinates during the fall
Juveniles remain dormant during the winter,
resuming function in the late winter or early
spring.
Seeds mature by late spring or early summer
and quickly fall to the ground,
 Transported by wind or water
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Cheatgrass originated
in Eurasia and was
introduced into the
United States by the
late 1800s, and by the
late 1900s it was
already considered
one of the most
widely spread species
in many rangelands
http://www.unc.edu/depts/slavic/images/Caucasus_Cntrl_Asia0.jpg
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There still is debate on how the species was
first introduced into de US
Most likely as contamination in seed and
grains from Europe
The species may have been discarded Along
the railroads
It was purposely introduced at least once into
the western US as a forage alternative to the
overgrazed ranges in the late 19th century
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Widely distributed in the
US, below 2200m in
elevation.
From xeric to mesic
conditions
It requires large
quantities of sunlight
The best conditions for
development are in open
grasslands and the
foothills of the western
US
http://plants.usda.gov/maps/large/BR/BRTE.png
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Biology:
 Annual life form
 Self pollinated
 High seed output
 Ability to germinate over a wide range of
temperatures and soil conditions
Ecology:
 Flowering early in the season
 Fire Adaptation
 After fire:
▪ Rapid utilization of the remaining available water
▪ Rapid extend roots
http://www.scsv.nevada.edu/~susanb/jblog/archives/fire.gif
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Invasive SPP can increase their success by
modifying the environment to favor their
long term survival
Cheatgrass modifies the fire cycle by the
accumulation of fine fuel
Fire not only affects community composition
 modifies growing conditions
 community dynamics by reducing competition
and increasing nutrient availability
The ability of cheatgrass of invading different ecotypes
is the result of differences in the physiological behavior
of the species:
 Plants from arid steppe environments tend to have
lower specific leaf area, lower CO2 assimilation rates,
and lower optima temperature, than plants from
more mesic conditions.
 At the same time, plants from dry environments tend
to allocate more resources to flowering structures,
which can increase the odds of survival for the species
in such environments
 These differences may be selected for plant form dry
environment to be able to flower before the soil dries
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Infection of crops and hay fields, reducing the
yield of those crops.
The High biomass accumulation is a serious
threat because of the potential wildfire risk
However, in some limited cases, cheatgrass
may be a positive presence:
 Early in the spring when it provides an important
forage option in western US
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Displacement of sagebrush (Artemisia) by
cheatgrass has not only decreased the
ecological value and the function of the
ecosystem
 Effects to wildlife:
http://www.idahoconservation.org/images/sagegrouse_fws_web.jpg/image_preview
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The most important aspect of the cheatgrass
invasion is that once it becomes established,
it is very difficult to eradicate .
Therefore, cheatgrass management and
control options are very limited.
In legal terms, it is no longer considered an
invasive species.
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Despite the widespread distribution of
cheatgrass, not all the invaded areas become
monocultures, and cheatgrass can exist in a
mosaic of different densities
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A viable option for management of
cheatgrass is the use of native species with
lower nutrient requirements to outcompete
or reclaim areas previously invaded by
cheatgrass
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Control biomass to control wildfires
 Sheeps
http://www.wiids.co.uk/wp-content/uploads/2009/07/shaun-the-sheep-relaxed.jpg
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Environmental change could play an
important role in the future of the cheatgrass
invasion
 increased N deposition from anthropogenic
sources may open new areas for the invasion of
cheatgrass and other invasive species
 increase in frequency and intensity of
disturbances : new opportunities for the
establishment and spread of cheatgrass.
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Climate change is expected to modify
temperature and precipitation regimens. In
the case of the expected changes in
precipitation, these not only include changes
in the overall amount of precipitation but also
in the timing of rains.
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The amount of summer precipitation is
important for the germination and also
prediction of the presence of cheatgrass.
An increase in summer precipitation may
favor summer growing perennial and
therefore hinder cheatgrass invasion
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In the Mojave Desert, it has been observed
that plant responses to increased
atmospheric CO2 will be different in a wet
year and in dry year.
During a wet year, increased CO2 lead to
increased in biomass and density of different
plant species, including B. madritensis,
whereas during a dry year no difference was
observed between ambient and increased
CO2