The ubiquitous Cheatgrass

Leonardo Hernandez-EspinozaNRES 641Spring 2010

The Species

Family   Poaceae Genus   BromusSpecies  Bromus tectorum

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A.K.A

Downy brome Downychess Cheat Mormon oats Junegrass

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Description 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

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Phenology

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

Origin 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

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Origin

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

In the US 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

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The Success

Biology: Annual life form Self pollinated High seed output Ability to germinate over a wide range of

temperatures and soil conditions

The Success

Ecology: Flowering early in the season Fire Adaptation After fire:▪ Rapid utilization of the remaining available

water ▪ Rapid extend roots

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Engeeniering 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

Wide Range

The ability of cheatgrass of invading different ecotypesis 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

Economical Impacts

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

Ecological Impacts

Displacement of sagebrush (Artemisia) by cheatgrass has not only decreased the ecological value and the function of the ecosystem Effects to wildlife:

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Management

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.

Despite the widespread distribution of cheatgrass, not all the invaded areas become monocultures, and cheatgrass can exist in a mosaic of different densities

Management

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

Minimizing the losses

Control biomass to control wildfires Sheeps

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The future of the Invasion 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.

Climate Change

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.

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

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

The End!