Fig. 2 Experimental and fitted variograms of selected soil properties: (a) silt content (perennials), (b) clay content (annuals), (c) sand content (annuals), (d) organic C (annuals), (e) DEE/CHCl₃ (perennials, 1989), (f) CHCl₃/TEL (perennials, 1989), (g)CHCl₃/TEL (annuals, 1994), (h) DEE/CHCl₃ (annuals, 1994). DEE, CHCl₃, and TEL represent diethyl ether–, chloroform-, and total extractable lipids, respectively