Highlight Morphological differences between seedlings of blue grama and crested wheatgrass show why plantings of blue grama fail while those of crested wheatgrass succeed. When both species are planted at a depth of 18 mm, crested wheatgrass initiates adventitious roots at the depth of planting and blue grama initiates adventitious roots at an average of only 2 mm below the soil surface. Adventitious roots of blue grama usually die in the harsh environment at this shallow depth. Blue grama (Bouteloua grucilis (H. B. K.) Lag.) is a dominant perennial grass on several million acres of the Great Plains. Nevertheless, if judgment regarding its adaptability to the Shortgrass Plains of Colorado were based on the results of seeding trials, it would be rated as not adapted (McGinnies et al., 1963; GP-6 Technical Committee, 1966). This paradox imposes two questions: 1. Why do blue grama seedings fail? 2. Does blue grama spread naturally by seed to unoccupied areas?

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Big sagebrush was controlled by rotobeating and spraying on both fair— and poor—condition ranges. A randomized block design was used with two replications of each treatment (untreated, sprayed, and rotobeaten). Data were taken from 10 permanent sampling units within each treatment plot. Numbers and crown cover of big sagebrush on treated range in fair condition changed little in 8 years after treatment. However, on poor—condition ranges sagebrush rapidly reoccupied mechanically treated areas. Some sagebrush increase occurred on sprayed poor—condition ranges, but brush numbers are strikingly lower than on rotobeaten plots. Herbage yields corrected to median—year precipitation varied considerably on untreated and treated plots, but herbage production was at least doubled, mostly from increaser—type species, on both sprayed and mechanically treated fair—condition range. On poor—condition ranges, herbage response was primarily from annuals with a marked trend toward an increasing amount of cheatgrass on treated plots. Soil moisture contents are generally greater on treated plots until the deep—rooted herbage species increase considerably. Soil temperatures are consistently lower on poor—condition, rotobeaten plots, and this difference is attributed to the insulating effect of the persistent woody residue on the soil surface.

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