TABLE 1.

Extrapolation of division-level diversity in four Arizona soils

Divisions	No. of divisions (variance)a
	Cosnino			Sunset Crater			All soils	Hot spring
	Interspace soil	Rhizosphere soil	Interspace + rhizosphere	Interspace soil	Rhizosphere soil	Interspace + rhizosphere
Observed	12	12	14	15	14	18	21	18
Estimated	20 (69.0)	14 (7.9)	16 (7.9)	16 (2.3)	17 (8.5)	20 (5.0)	24 (9.4)	38 (95.0)

^aVariance was calculated according to Chao (2) as follows: Var(S1) = b[(a/4b)⁴ + (a/b)³ + (a/2b)²], where a is the number of singleton species in a sample and b is the number of doubletons. Hot spring data are from reference 10.