Leonardo Hernandez-Espinoza NRES 641 Spring 2010

 Family Poaceae  Genus Bromus  Species Bromus tectorum

 Downy brome  Downychess  Cheat  Mormon oats  Junegrass

 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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 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

 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

 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 19 th century

 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

 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

 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 CO 2 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

 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

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

 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

 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

 Control biomass to control wildfires  Sheeps

 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 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 CO 2 will be different in a wet year and in dry year.  During a wet year, increased CO 2 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 CO 2