THE PRAIRIES. 



21 



prairies of southeastern Washington, where during 1914 the water- 

 content to a depth of 4 feet was reduced to the non-available point 

 (Weaver, 1915: 233-235). 



The available water-content in the loess soils supporting the sub- 

 climax prairie vegetation was not only higher but much more con- 

 stant. These data are shown in tables 4 and 5. Here also are included 

 determinations from an adjacent thicket of Corylus americana. A 

 comparison of these results is made on page 30. 



Table 4. — Available water-content in prairie and shrub communities near Peru, Nebraska, 

 during April to September 1917 and May 1918} 



The minus sign indicates water non-available for plant growth. 



Depth, to 6 inches. 

 Wilting coefficients: 

 Prairie 11.7; scrub 13.8. 



Depth, 6 to 12 inches. 

 Wilting coefficients: 

 Prairie 10.9; scrub 12.3. 



Depth, 1 to 2 feet. 

 Wilting coefficients: 

 Prairie 10.4; scrub 12.5. 



Depth, 2 to 3 feet. 

 Wilting coefficients: 

 Prairie 9.9; scrub 11.3. 



Date. 



Prairie. 



Scrub. 



Date. 



Prairie. 



Scrub. 



Date. 



Prairie. 



Scrub. 



Date. 



Prairie. 



Scrub. 



1917 







1917 







1917 







1917 







Apr. 5 

 May 15 

 June 30 



13.4 

 13.0 



21.4 

 14.7 



Apr. 5 

 May 15 

 June 30 



12.2 

 12.0 



18.0 

 14.1 



Apr. 5 

 May 15 

 June 30 



8.5 

 10.5 



12.1 

 11.7 



Apr. 5 

 May 15 

 June 30 



5.0 

 8.1 



8.0 



13.9 



20.8 



11.8 



17.1 



12.3 



13.1 



12.6 



12.9 



July 9 

 July 14 

 July 24 

 July 28 

 Aug. 6 

 Aug. 11 

 Aug. 18 

 Aug. 25 

 Sept. 8 

 Sept. 22 

 1918 



6.5 



3.9 



July 9 

 July 14 

 July 24 

 July 28 

 Aug. 6 

 Aug. 11 

 Aug. 18 

 Aug. 25 

 Sept. 8 

 Sept. 22 

 1918 



7.3 



7.4 



July 9 

 July 14 

 July 24 

 July 28 

 Aug. 6 

 Aug. 11 

 Aug. 18 

 Aug. 25 

 Sept. 8 

 Sept. 22 

 1918 







July 9 

 July 14 

 July 24 

 July 28 

 Aug. 6 

 Aug. 11 

 Aug. 18 

 Aug. 25 

 Sept. 8 

 Sept. 22 

 1918 







9.5 



11.5 



7.4 



5.2 











0.1 

 -1.4 

 4.0 

 8.4 



4.5 

 -1.7 



6.6 

 12.6 



2.5 

 0.4 

 -0.5 

 1.5 



3.4 

 -0.4 

 2.6 

 5.7 



3.1 

 2.1 

 -1.0 



3.0 

 1.2 

 0.7 



5.1 

 4.5 

 1.9 



5.5 

 4.4 

 2.4 



2.3 



7.6 



1.9 



1.5 











1.3 

 6.2 

 -1.2 



6.4 

 10.2 

 -1.6 



0.2 

 -0.8 

 -1.7 



1.8 

 2.4 

 0.5 



0.6 

 0.8 

 -1.0 



-0.1 

 -0.4 

 -0.7 



0.9 

 1.6 

 0.1 



1.2 

 -1.0 

 0.5 



May 16 



13.8 



16.3 



May 16 



15.0 



18.3 



May 16 



12.5 



16.5 



May 16 



12.7 



16.5 



The writer is indebted to Prof. F. C. Jean for the major portion of the data in these tables. 



The greater water-content of these mellow loess soils compared with 

 those of the prairie near Lincoln gives us a clue to the much more 

 luxuriant growth of certain prairie and shrub species. There is also a 

 great difference in depth of root-penetration, plants like Andropogon 

 furcatus and Brauneria pallida being much deeper-rooted in loess soil. 



However, vegetation is not only an expression of present conditions, 

 but also to a greater extent a record of conditions that have obtained 

 during a period of years, and the record is not likely to be altered 

 greatly in a year or two in which conditions may depart from the 

 normal. The preceding pages show that many prairie plants absorb 

 moisture well beyond a depth of 5 feet, while soil-moisture extends 

 many feet beyond the greatest root depth. In excavating root systems, 

 during September to December 1917, the soil below 5 feet was found 

 almost invariably to be quite moist. Some of the root systems were 

 excavated on bench-lands in the Salt Creek basin, where the alluvial 

 soils are somewhat different from those described. Such differences 

 were noted in discussing these species. 



