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FIG. 4. Changing the tortuosity factor 
by crossing gaps of soil pores. Roots, rhizomorphs, and individual hyphae can reduce the by reducing the capillary length (Lc) compared with the column length (L), by providing linear units crossing soil pores. The two examples show these linear units. The left images are minirhizotron photos and the right images are from a program that identifies edges, showing the structure of the edges created by the roots and rhizomorphs. (A) shows a root stretching across a minirhizotron frame and (B) shows a rhizomorph. In both cases, the soil pores are outlined in small spherical objects, whereas the roots and fungal hyphae are linear units.
