e 



METHODS 



Root samples were taken in 1965 and 1966 merely to determine the relative amounts 

 of roots at different levels in the rhizosphere. Alternate layers 7.5 cm. thick were 

 taken from soil columns 20 cm. by 46 cm. (area 1 ft.^). All columns were sampled to a 

 depth of 67.5 cm., and two of them to the maximum rooting depth, which was 112 cm.- in 

 the columns sampled. (A few fine roots were seen to a depth of 135 cm. in one soil pit 

 on the site, and a lone dead herbaceous root, 3 mm. in diameter at the 183-cm. level, 

 was seen in another pit.) Roots were sieved from soil over a 6-mm. screen. Many of 

 the finer roots, dead and fragile, were lost through the screen. The roots retained 

 were separated from gravels by flotation in water, then rinsed on a No. 80 sieve, oven- 

 dried at 75° C. for 24 hr. , and weighed. 



In April 1970, when new top growth started to appear, we harvested the plant 

 material above the ground, and below the ground to a depth of 22.5 cm. The weight 

 of this material provides an estimate of the absolute amount of accumulated organic 

 matter above that depth. The total accumulation at greater depths can be extrapolated 

 from this estimate by using the earlier data. A wire 4.5 m. long, marked at 15-cm. 

 intervals, was stretched along the ground in each of three 1.5- by 6.0-m. plots. Using 

 a mapping frame as a guide, we mapped the plots freehand to shov\f each plant and wire. 

 All plant material, living, standing dead, and litter, was gathered from the plots, 

 separated by species, air-dried, and weighed. Weights were adjusted to an ovendry 

 basis. No attempt was made to separate living from dead wood. Atriplex and Eurotia 

 typically have much dead wood in the crowns unless they are young plants. Older living 

 stems are often alive only along one side; the major part of the wood of these structures 

 is dead and weathered. We estimate that no less than 60 percent of the wood of living 

 shrubs is dead; i.e., "attached litter." Of course, all herbaceous material from pre- 

 vious years was dead. 



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