Shrub Category Definition 



Small Under 12 inches high, small crown, 



one or a few stems. 



Medium 12 to 24 inches high (usually), 



well developed crown, one to 

 several stems. 



Large Over 24 inches high, large crown, 



several stems. 



Climate and Readily Available Soil Moisture 



Since climatic variations are thought to be responsible for much of the 

 natural variation exhibited by the plant communities studied, the most 

 important climatic factors were measured this year and will continue to be 

 measured in subsequent studies if possible. These factors are: precipitation, 

 temperature, and available soil moisture at various depths in the rooting zone. 



Precipitation was measured using a standard rain and snow gauge located at 



the Dreyer Ranch headquarters (NW 1/4, Sec. 36, T.21 N, R.45 E). This 



gauge, shielded by a wind screen, is located in a field over 50 yards from 



any objects that could affect measurements. Another rain gauge (wedge type) 



is located along Nelson Creek (north central portion of Sec. 25, T.20 N, R.44 E). 



A temperature-recording device is located on the north side of the Dreyer 



ranch house. 



Readily available soil moisture, defined as the difference between soil 

 moisture (as sampled) and the permanent wilting percentage (determined for 

 the soil at each sample site), has been determined for the following communities: 

 Arca/Agsm/Bogr, Agsp/Bogr-Cafi , Ansc, Bogr-Cafi/Stco, Stco-Agsm/Bogm, and 

 Bogr/Agsm, Readily available soil moisture was also determined for a wheat 

 field in Sec. 4, T.19 N, R.45 E. In both cases, the methods of Daubenmire 

 (1974) were used. Samples were taken in June, July, August, and September. 

 Since June samples were thought to have dried in transport, data for June have 

 been deleted. 



Vascular Plant Collections 



Vascular plant species not previously observed in the study area were 



collected and identified. Plant specimens were collected in May, August, 



and September 1981. A special attempt was made to locate Rorippa calycina 

 (Engelm.) Rydb. Var. calycina . 



